Content:
Presentation type:
HS – Hydrological Sciences

EGU24-9079 | Orals | MAL23-HS | Henry Darcy Medal Lecture

A view into the richness of processes in porous media 

Alberto Guadagnini

Flow and transport scenarios taking place in porous media are characterized by a staggering range of physical, chemical, and biological processes. The dynamics associated with these are distributed across an astonishingly wide range of (spatial and temporal) scales, thus contributing to the challenges related to their observation and description. Direct observation and attempts to a quantitative characterization of these processes indicate that they are prone to multiple interpretations, as rendered through various conceptual and mathematical formulations and their parameterization. Even the outcomes of apparently straightforward models of flow (or chemical transport) can surprise us! As complexity related to the formulation and parametrization of processes and their feedbacks increases, so does the need to establish approaches enabling us to quantify the effect of various types of uncertainty on target quantities of interest. For example, tackling the often strong (spatial) heterogeneity of parameters embedded in a model and coping with our limited ability to describe all of the relevant details of the porous medium hosting processes of interest poses significant challenges. In this broad context, I will initiate a discussion about uncertainties related to process formulation and parametrization and the way they can propagate to model outputs such as, e.g., water availability, solute concentrations, source protection regions, or reaction rates. The discussion is set in a framework encompassing experimental studies, characterization of porous media heterogeneity, sensitivity analysis for model diagnosis, and stochastic inverse modeling. Sensitivity analyses approaches are tackled with a focus on their ability to identify the relative importance of processes (and associated parameters) embedded in a model and driving system behavior. The ensuing results are then employed to inform model calibration under uncertainty. All of these aspects are exemplified through the analysis of settings related to three distinct scales. These comprise a regional scale complex aquifer system subject to diverse forcings, a laboratory scale scenario involving dynamics of pharmaceuticals in a porous medium, and direct observations of processes acting at nanoscales and governing material fluxes associated with chemical weathering related to rock dissolution. While these systems are associated with very different scales (and processes), their analysis is unified through the use of stochastic approaches sharing common traits and leading to similar workflows for uncertainty quantification.

How to cite: Guadagnini, A.: A view into the richness of processes in porous media, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9079, https://doi.org/10.5194/egusphere-egu24-9079, 2024.

EGU24-6307 | Orals | MAL24-HS | John Dalton Medal Lecture

How far can we go in global flood inundation modelling? 

Paul Bates

Over the last fifteen years, hydrodynamic modelling has, like so many branches of hydrology, made the leap from local to global scales.  Where once we may have applied our models to single river reaches a few 10s of kilometres in length, we can now build and execute models at ~30m spatial resolution over the entire terrestrial land surface.  In turn, this has allowed us to address scientific and practical questions that were hitherto impossible to answer.  For example, global inundation modelling can help us understand and quantify large scale hydrological and biogeochemical cycles and many questions in flood risk management, for example decisions about future government spending on flood defences, analysing the solvency of flood insurance portfolios under extreme conditions, or determining climate change impacts, require predictions of flood risk at national, continental, or even global scales.

This paper therefore discusses the scientific developments that were needed to make this local-to-global transition possible and outlines what the latest generation of global inundation models now can (and cannot) do.  Finally, the paper looks at current limits to inundation modelling in terms of boundary conditions, flood defence data and model validation and considers the prospects for further improvements in model skill using the data from recently launched and forthcoming satellite missions such as SWOT and NISAR.

How to cite: Bates, P.: How far can we go in global flood inundation modelling?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6307, https://doi.org/10.5194/egusphere-egu24-6307, 2024.

Human-water feedbacks have been increasingly studied in the last decades, motivating the foundation of new disciplines such as socio-hydrology and, in general, enhanced interest toward conceptualization and modelling of the spatial and temporal dynamics of human-water systems. With anthropogenic activities being widely recognized as a major driver of global change and the human population being increasingly exposed to hydroclimatic extreme events, human systems are now at the forefront of the water cycle. Yet, human preferences, behaviors, and decisions in relation to water systems - including water usage dynamics, adoption of precautionary measures against climate extremes, and adaptation of urban landscapes - are often modelled based on behavioral or economic theories, or derived from small-scale samples. This often leads to heterogeneous results, which are often case-specific, or lack validation against real-world observations.

The availability of increasingly fine-resolution data from distributed sensors and databases (e.g., water consumption data from intelligent meters, flood insurance adoption records at the household level, and socio-demographic data) and earth observations (e.g., aerial and satellite imagery) provides us with an empirical basis to model heterogeneous individual and societal behavioral patterns, along with their determinants.

In my research, I strive to develop multi-disciplinary data-driven behavioral modelling approaches that bridge hydrologic/hydraulic sciences, informatics, economics, and systems engineering and harness information from multi-scale human data and earth observations and the power of data analytics and machine learning to better understand, model, and characterize human behaviors in coupled human-water systems. In this talk, I will first provide an overview of recent advances in descriptive behavioral modelling in human-water systems, with a focus on household-to-continental scale modelling of residential water consumption patterns and adoption of household flood insurance. Second, I will elaborate on modelling challenges that are motivating ongoing research related to machine learning-based behavioral models, including model explainability, data and computational requirements, generalization and scalability, and the influence of data resolution in time and space. Finally, I will discuss how developing descriptive models that learn human behaviors retrospectively can be used to inform forecasting tasks and formulate policy-relevant recommendations to shape future societal adaptation to climate change. Implications span from informing the design of feedback-based digital user engagement in pursuit of water conservation, to fostering proactive climate adaptation, addressing societal inequalities and heterogeneous water access and affordability conditions, or evaluating incentive programs and policies for sustainable urban development.

How to cite: Cominola, A.: Learning from the past to shape the future. Harnessing multi-scale human data and earth observations to foster sustainable water usage and societal adaptation to climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19445, https://doi.org/10.5194/egusphere-egu24-19445, 2024.

HS1.1 – Hydrology in Climate Change

EGU24-5377 | Orals | HS1.1.1

Modelling future water resources in interconnected water systems: are catchment scales relevant? 

Gemma Coxon, Anna Murgatroyd, Francesca Pianosi, Saskia Salwey, Doris Wendt, and Yanchen Zheng

Freshwater resources are increasingly under threat from climate change and increasing water demand. Catchment-scale hydrological models generate hydrological projections that underpin the management and sustainability of future water resources. Yet, water systems are increasingly interconnected across catchment boundaries through nationally strategic water supply schemes that aim to ensure a reliable supply of water in a changing climate.

In this presentation, we draw on a range of studies from across Great Britain to discuss the challenges and complexities of hydrological modelling for future water resources management from catchment to national scales. We focus on interconnected water systems including catchments impacted by (1) inter-catchment groundwater flows and (2) water transfers via reservoirs, abstractions and wastewater treatment plants. For the human-impacted catchments, we identify where and when representing human interactions are important for robust streamflow projections. As water systems become more interconnected in space and time, we highlight the need to move beyond the catchment scale for future water resources management.

How to cite: Coxon, G., Murgatroyd, A., Pianosi, F., Salwey, S., Wendt, D., and Zheng, Y.: Modelling future water resources in interconnected water systems: are catchment scales relevant?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5377, https://doi.org/10.5194/egusphere-egu24-5377, 2024.

EGU24-6684 | Orals | HS1.1.1 | Highlight

The (ir)relevance of plot- and hillslope scale processes for catchment runoff 

Ilja van Meerveld

Experimental field studies are crucial to understanding hydrological processes. Studies at the plot-, hillslope-, or small catchment-scales have helped us to understand how water flows toward the stream network of larger catchments. However, little of this detailed knowledge is used in hydrological models because the calibration of simple models already leads to good runoff simulations. Furthermore, not all hillslope locations contribute equally to catchment runoff and in some cases, hillslopes or specific hillslope locations may seem irrelevant for the catchment scale runoff response, at least until a certain threshold is crossed. It is essential to consider these thresholds because climate or land use change may cause them to be passed more frequently in the future, so models based on historic runoff data might no longer accurately predict the catchment runoff response. In this talk, I will provide examples of such thresholds and discuss the need to consider connectivity between landscape elements when interpreting the streamflow or stream chemistry response at the catchment scale. In doing so, I will highlight the need to understand hydrological processes at the plot and hillslope scales for predicting catchment-scale runoff, even if these processes may seem irrelevant at first.

How to cite: van Meerveld, I.: The (ir)relevance of plot- and hillslope scale processes for catchment runoff, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6684, https://doi.org/10.5194/egusphere-egu24-6684, 2024.

Contrary to widespread belief, it is well known since ancient Greece that rivers flow most of the time because they receive groundwater discharge. However, it is less widely known that rivers are losing their base flow because of aquifer overexploitation and, even less, the intimate link between ground and surface water processes. I review the processes that control water quality, from pore scale biofilms to hyporheic exchange, and runoff generation. While there is a broad understanding of these processes, I argue that the way they are represented in models is poor. As a result, water management and regulations tend to ignore them. Specifically, managed aquifer recharge is currently hindered by EU regulations. Yet, it remains the only practical management strategy to reverse groundwater (and, thus, the loss of river base flow and ecosystem services). I find it paradoxical that, while a lot of effort is devoted to global "accounting", we are deemphasizing the river basin scale, within which most water management relevant processes occur (ironically, the only management relevant trans-basin processes, i.e., the recycling of moisture, is equally ignored). I conclude for a renewal od the old call for close interaction between surface and groundwater hydrologists.

How to cite: Carrera, J.: From the pore to the catchment-scale: a discussion of groundwater processes and modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20252, https://doi.org/10.5194/egusphere-egu24-20252, 2024.

Groundwater is the largest accessible freshwater resource on earth and is critical for people and the environment. In many regions around the world, sectoral water demands exceed the availability of surface water and groundwater is being pumped. Irrigation stands out as the largest groundwater user worldwide, with ca. 40% of current irrigated agriculture relying on groundwater. In many heavily irrigated regions, groundwater abstractions surpass replenishment, resulting in often severely declining groundwater levels. This leads to groundwater depletion, reduced streamflow, drying of wells and springs, land subsidence, saltwater intrusion, and deteriorating surface water quality due to reduced pollutant dilution.

In the coming decades, global food demands will increase, driven by a growing world population and socio-economic development. A major challenge lies ahead in how to sustainably ensure sufficient regionally and globally available food. It is inevitable that agriculture will increasingly rely on groundwater to support the required increase in crop production, but the extent to which this groundwater can be extracted sustainably from a quantity and quality perspective is still largely unknown.

In this talk, the latest advances in our model development will be presented, focussing specifically on linking groundwater dynamics, surface water interactions, and crop production at both global and regional scales. A specific focus lies on connecting global and regional scales and approaches to better understand the impacts and trade-offs related to global change. In addition, attention will be given to the development of regionally relevant adaptation strategies for sustainable groundwater use worldwide. 

How to cite: de Graaf, I.: Navigating global challenges: development and application of a coupled groundwater and crop growth model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20946, https://doi.org/10.5194/egusphere-egu24-20946, 2024.

EGU24-618 | ECS | PICO | HS1.1.2

Climate Change Impact Assessment on Hydrological response of Tawa Basin for Sustainable Water Management  

Pragya Badika, Akash Singh Raghuvanshi, and Ankit Agarwal

Sustainable water resources planning and management is critical in fulfilling the demands of present and future generation in limiting environment. River basins plays a crucial role in balanced and responsible management strategies, as they frequently serve vital role in freshwater supply, irrigation, hydropower generation, industrialization and to support a balance ecosystem. In the era of climate change and adverse environmental impacts, it is required to prioritize assessment for sustainable development and management of river basins to ensure a resilient water system. In this study, the Tawa Basin has been selected which is one of the important tributary of Narmada Basin and has a paramount importance in irrigation and hydropower generation. From a hydrological standpoint, basin response to climate change is critical for analysing hydrological extremes and developing long-term plans and strategies for water-related activities and policies. The basin experiences significant rainfall fluctuation throughout the year, particularly during the monsoon season (June to September) which adversely influence the runoff generation in the basin and consequently, the likelihood of catastrophic occurrences. However, the hydrological response of Tawa basin to climate change has been rarely investigated under socio-economic pathways. Present work sought to evaluate the hydrological response of Tawa basin under changing climate using Coupled Model Inter-comparison Project (CMIP6) scenarios. In this study, a comparative assessment has been done with the application of two conceptual lumped hydrological model to ensure the robustness of the Hydrological model. For this, the MIKE 11 NAM and GR4J model has been set up for period of 2009 to 2021. The model is calibrated at the downstream of the Tawa reservoir using the water balance at reservoir scale. For climate change assessment, the latest CMIP6 outputs has been incorporated for two shared socio-economic pathways; SSP2-45 and SSP5-85 for near (2040-2060) and far (2070-2100) future. In addition, evaluation was performed using the individual and ensemble output of climate models to ensure the uncertainty in hydrological responses. The findings of this study are critical for understanding how climate change will alter the hydrology of the Tawa River Basin. This research might lead to the adoption of a strategic strategy for sustainable water resources and improved societal resilience to climate change in the Tawa River Basin.

How to cite: Badika, P., Raghuvanshi, A. S., and Agarwal, A.: Climate Change Impact Assessment on Hydrological response of Tawa Basin for Sustainable Water Management , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-618, https://doi.org/10.5194/egusphere-egu24-618, 2024.

EGU24-858 | ECS | PICO | HS1.1.2

Addressing Nonstationarity in Extreme Rainfall Patterns: A Case Study on Indian Cities 

Ankush Ankush, Narendra Kumar Goel, and Vinnarasi Rajendran

The evolving landscape of extreme rainfall patterns, triggered by climate change and global warming, introduces nonstationary behavior, challenging conventional hydrologic design assumptions rooted in stationarity. This study addresses this paradigm shift by modeling distribution parameters with covariates, utilizing a 70-year high-resolution IMD gridded dataset to extract and model extreme annual rainfall across diverse Indian cities. Drawing on previous research and goodness-of-fit tests that favor the Generalized Extreme Value (GEV) distribution for modeling extremes, the study incorporates various indices, including Nino3.4, dipole mode index, global and local temperature and time, to characterize nonstationarity in extreme annual rainfall, leveraging climate cycles and global warming trends. Performance assessment utilizes the Akaike information criterion and Likelihood ratio test, while quantile reliability is scrutinized through confidence intervals (CIs). The findings uncover widespread nonstationary trends in most grid points, resulting in broader CIs for estimated quantiles, return periods, and covariates in fitted models. Despite the broader confidence bands associated with nonstationary conditions, indicating higher uncertainty, the results affirm a nonstationary pattern in rainfall extremes. Consequently, the study underscores the imperative to develop nonstationary models that effectively capture these dynamic trends with reduced uncertainty.

How to cite: Ankush, A., Goel, N. K., and Rajendran, V.: Addressing Nonstationarity in Extreme Rainfall Patterns: A Case Study on Indian Cities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-858, https://doi.org/10.5194/egusphere-egu24-858, 2024.

In the Slovakia for assessment of climate change is used as references period hydrological years 1981 - 2010. Although the first observations in groundwater began in 1956, the monitoring network was not dense enough and the objects were not evenly distributed in Slovakia. Even the expansion of monitoring network in the 1970s was not enough to obtain longer, 30-year time series. Based on the new reference period 1991 - 2020 recommended by the World Meteorological Organization WMO, this period was also evaluated from the point of view of groundwater. The aim of the contribution was to compare reference periods 1981 – 2010 and 1991 - 2020 and their changes in the groundwater in Slovakia. These two reference periods were compared with each other based on the ratio values of long-term time series of minimum and average values of the groundwater level and springs yield. The new reference period 1991 - 2020 and period 1981 - 2010 were also evaluated by trend analysis using the non-parametric Mann-Kendall test. The Mann-Kendall statistical test was use to assess whether a set of data values is increasing or decreasing over time and whether the trend in either direction is statistically significant. The Mann-Kendall test does not assess the magnitude of change. The advantage of this test is, that it is not affected by the current distribution of the data and at the same time is less sensitive to extreme values in the time series.

                The long-term average values of the groundwater level and the springs yield for the period 1991 - 2020 compared to 1981 - 2010 were lower in the outer West and Northwest, in the Northern parts of Slovakia, in the region of central Slovakia, and in the Southeast and outer East. Based on the comparison of the long-term minimum values of the compared periods, the values were steady in compared to the previous period at most of the evaluated objects.

                When evaluating the trends of long-term averages for the period 1991 - 2022, significant decreases in the average groundwater level and springs yield were detected in the outer West and Northwest, in the strip from Northern to central Slovakia, in the North of Eastern Slovakia, and in the Southeast and outer east of the territory. When evaluating the trends of long-term minima for the period of hydrological years 1991 - 2022, the situation was similar to the evaluation of long-term averages.

                By comparing the period of 30 annual series 1991 - 2020 to the period 1981 - 2010 based on the evaluated ratio values, we did not notice significant deviations.

 

Keywords: groundwater, spring yield, references periods

How to cite: Kurejova Stojkovova, M. and Slivova, V.: Comparison of the reference periods of the hydrological years 1981 - 2010 and 1991 - 2020 in groundwater in Slovakia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1424, https://doi.org/10.5194/egusphere-egu24-1424, 2024.

EGU24-1920 | PICO | HS1.1.2 | Highlight

Future drought changes in Australia from multiple projections 

Anna Ukkola, Elisabeth Vogel, Steven Thomas, Ulrike Bende-Michl, Andy Pitman, and Gab Abramowitz

Australia suffers from frequent droughts but future drought changes have remained stubbornly uncertain over the continent, with CMIP projections indicating low model agreement across most regions. Here we constrain future changes in drought over Australia by combining a hierarchy of projections from coupled global and regional climate models and several offline hydrological models that are widely employed in Australia. We analyse changes across multiple types of droughts (meteorological, hydrological and agricultural) to understand robustness of trends across drought types. Using this multi-projections approach, we identify robust future increases in drought across key agricultural and densely populated regions that are consistent across different drought types. Our study demonstrates value in analysing multiple projections together to build confidence in future changes in other regions of the world where model uncertainty is high.

How to cite: Ukkola, A., Vogel, E., Thomas, S., Bende-Michl, U., Pitman, A., and Abramowitz, G.: Future drought changes in Australia from multiple projections, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1920, https://doi.org/10.5194/egusphere-egu24-1920, 2024.

The change of groundwater storage (GWS) on the Tibetan Plateau (TP) is vital for water resources management and regional sustainability, but its estimation has large uncertainty due to insufficient hydrological measurements and diverse future climate scenarios. Here, we employ high-resolution land surface modeling, advanced satellite observations, global climate model data, and deep learning to estimate GWS changes in the past and future. We find a 3.51±2.40 Gt yr-1 increase in GWS from 2002–2018, especially in exorheic basins, attributed to glacier melting. The GWS will persistently increase in the future, but the growth rate is slowing down (0.14 Gt yr-1 for 2079–2100). Increasing GWS is projected over most endorheic basins, which is associated with increasing precipitation and decreasing shortwave radiation. In contrast, decreasing GWS is projected over the headwaters of Amu Darya, Yangtze, and Yellow river basins. These insights have implications for sustainable water resource management in a changing climate.

How to cite: Wang, L. and Jia, B.: The slowdown of increasing groundwater storage in response to climate warming in the Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2331, https://doi.org/10.5194/egusphere-egu24-2331, 2024.

Large-scale revegetation presents a new set of challenges by augmenting water consumption in arid regions, despite its positive impact on ecosystems. In water-stressed areas, where precipitation is the primary source of water, extensive afforestation may disrupt the balance between water supply and demand. Consequently, it is crucial to assess the maximum extent of vegetation coverage and productivity that can be sustained by rainwater resources. Our study characterizes the sustainability of revegetation by determining the upper limit of the leaf area index (LAI) supported by rainwater resources. The research focuses on the Loess Plateau (LP), a region known for both large-scale vegetation restoration and severe water shortages. The upper limit on LAI is computed based on evapotranspiration (ET) supported by rainwater resources, utilizing an optimized Shuttleworth-Wallace (S-W) model that incorporates dynamic vegetation and carbon dioxide components. Carbon sequestration capacity and efficiency are compared between the maximum and actual vegetation scenarios using an analytical water use efficiency (WUE) model. Both models exhibit good performance and align with empirical observations. Results indicate that under the maximum vegetation scenario, the LAI is 11.5% higher than the actual scenario when vegetation on the LP is restored to its maximum level. The average gross primary productivity under the maximum vegetation scenario surpasses the actual scenario by 25.0%, with a 17.9% increase in ecosystem WUE. It is important to note that the maximum scenario represents a theoretical upper limit based on ideal assumptions. The findings emphasize that enhancing rainwater utilization efficiency can unlock the potential for sustainable vegetation restoration, improving its efficiency. This study provides valuable guidance and theoretical support for planning vegetation restoration in water-scarce regions.

How to cite: Zhang, B., Tian, L., and Li, Y.: Estimating the maximum vegetation coverage and productivity capacity supported by rainwater resources on the Loess Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2402, https://doi.org/10.5194/egusphere-egu24-2402, 2024.

EGU24-2953 | PICO | HS1.1.2

Intensified Structural Overshoot Aggravates Drought Impacts on Dryland Ecosystems 

Liu Liu, Yixuan Zhang, Yongming Cheng, Qiang An, and Shaozhong Kang

A favorable environment can induce vegetation overgrowth to exceed the ecosystem carrying capacity, exacerbating water resource depletion and increasing the risk of lagged effects on vegetation degradation. This phenomenon is defined as structural overshoot, which can lead to large-scale forest mortality and grassland deterioration. However, the current understanding of structural overshoot remains incomplete due to the complex time-varying interactions between vegetation and climate. Here, we used a dynamic learning algorithm to decompose the contributions of vegetation and climate to drought occurrence, trace the connection between antecedent and concurrent vegetation dynamics, thus effectively capturing structural overshoot. This study focused on the climate-sensitive hotspot in Northwest China drylands, where significant vegetation greening induced by a warming and wetting climate was detected during 1982–2015, leading to soil moisture deficit and aggravating vegetation degradation risks during droughts. We found that during this period, structural overshoot induced approximately 34.6% of the drought events, and lagged effects accounted for 16.7% of the vegetation degradation for these overshoot drought events. The occurrence of overshoot droughts exhibited an increasing trend over time, which was primarily driven by vegetation overgrowth followed by precipitation variation. Although the severity of overshoot and non-overshoot droughts were generally comparable in spatial distribution, the impact of overshoot droughts is still becoming increasingly obvious. Our results indicate that the expected intensified overshoot droughts cannot be ignored and emphasize the necessity of sustainable agroecosystem management strategies.

How to cite: Liu, L., Zhang, Y., Cheng, Y., An, Q., and Kang, S.: Intensified Structural Overshoot Aggravates Drought Impacts on Dryland Ecosystems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2953, https://doi.org/10.5194/egusphere-egu24-2953, 2024.

EGU24-3504 | ECS | PICO | HS1.1.2

Reversal of Precipitation Trend in Hothouse Climates 

Jiachen Liu, Jun Yang, Feng Ding, Gang Chen, and Yongyun Hu

Hydrologic cycle has wide impacts on the ecosystem, atmospheric circulation, ocean salinity and circulation, and carbon and nitrogen cycles. Under anthropogenic global warming, previous studies showed that the intensification of the hydrologic cycle is a robust feature. Whether this trend persists in hothouse climates, however, is unknown. Here we show that mean precipitation first increases with surface temperature, but it decreases with surface warming when the surface is hotter than ~320-330 K. This non-monotonic phenomenon is robust to the warming trigger, convection scheme, ocean dynamics, atmospheric mass, planetary rotation, gravity, and stellar spectrum. The weakening is because of the existence of an upper limitation of outgoing longwave emission and the continuously increasing shortwave absorption by H2O, and is consistent with the strong increase of atmospheric stratification and dramatic reduction of convective mass flux. Our results have wide implications for the climates and evolutions of Earth, Venus, and potentially habitable exoplanets.

How to cite: Liu, J., Yang, J., Ding, F., Chen, G., and Hu, Y.: Reversal of Precipitation Trend in Hothouse Climates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3504, https://doi.org/10.5194/egusphere-egu24-3504, 2024.

Changes in future climate are inevitable, strongly impacting water resources and their adaptation strategies. Northern Peru currently faces water scarcity issues, significantly limiting activities such as agriculture, a key economic and social pillar for the region. In addition, there are pronounced fluctuations in precipitation due to the effects of the El Niño phenomenon (ENSO), along with scarcity of information regarding various climatic variables in terms of quantity and quality, making it challenging to accurately account for the resources available for proper management.

Therefore, this research aims to, through cluster analysis, assess the importance of various variables such as elevation, precipitation, maximum and minimum temperature and stationarity index, for the period 1972-2015, in determining the hydrologically homogeneous regions currently present in the sub-basins of the northern region. Various multivariate cluster methods such as hierarchical clustering, partitioning around medoids (PAM), and K-means have been used for this purpose. To assess the validity of the analysis, Hopkins statistics and visual inspection methods were employed. Additionally, various validation tests, including internal and stability measures, were applied to evaluate the effectiveness of the cluster algorithm results. Alongside this analysis, a trend study of precipitation has been conducted, helping identify regions that may be experiencing changes in their rainfall patterns. This trend study was performed using the non-parametric Mann-Kendall test on the 49 stations located in the region. The same procedure was also applied to climate models with projections of precipitation and maximum and minimum temperatures up to the year of 2100 to understand the future behavior due to climate change.

Comparing hydrologically homogeneous regions and potential trend changes found between the current and future climate change situations would help identify potential areas where the analyzed climatic variables undergo significant changes. This would aid in identifying potential adaptation measures, since these variables are crucial for determining water availability.

How to cite: Chavez, A., Quevedo, V., Bravo, D., and Chapilliquen, D.: Evaluating the impact of climate change in Northern Peru by analyzing homogeneous regions based on different climate variables and precipitation trend changes., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3690, https://doi.org/10.5194/egusphere-egu24-3690, 2024.

Reservoirs have made significant contributions to human access and management of surface water resources, as well as to the production of clean energy, thus playing a vital role in alleviating the water crisis and decarbonizing energy systems through hydropower generation. The rapid growth in reservoir construction has led to an increase in the surface water area, consequently escalating evaporative water losses. As a crucial component of water cycle, most estimation methods for evapotranspiration focus on the land surface, with a relatively rough estimate of the significant evaporation loss from open surface water. Meanwhile, limited by the availability of reservoir geographic information and monthly area series data, there is still a lack of comprehensive and accurate estimation of reservoir evaporation losses. As the country with the largest number of dams in the world, it is necessary to accurately estimate China's surface water evaporation losses associated with its prosperous and developing dam construction. Here, we used the China Reservoir Dataset and LandSAT based Global Surface Water Dataset to reconstruct the monthly area series of 4874 reservoirs in China from 1984 to 2020, and further considering the heat storage of water bodies, the monthly evaporation losses of these reservoirs from 1988 to 2018 were estimated. The results indicate that the average annual evaporation volume of these 4874 reservoirs is 18.55 × 109 m3, equivalent to 31% of the total domestic water consumption of China (in 2021). During the research period, the evaporation rate shows a significant growth trend (p < 0.05, 0.15km3/year), attributed to the upward trend in evaporation rate (p < 0.05, 0.0046 mm/d/year) and total reservoir area (p < 0.05). The differences in economic development level and reservoir size result in significant spatial heterogeneity in the evaporation loss trend in different regions. The results can serve as a useful reference for water resources management and sustainable utilization.

How to cite: Zhu, Y. and Ye, A.: Estimation of Reservoir Evaporation Water Loss in Inland China over the Past 30 Years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3901, https://doi.org/10.5194/egusphere-egu24-3901, 2024.

EGU24-4014 | PICO | HS1.1.2 | Highlight

Mapping of climate to flood extremes in the European Alps: a multidisciplinary approach 

Alberto Viglione, Enrico Arnone, Susanna Corti, Olivia Ferguglia, Ignazio Giuntoli, Jost  von Hardenberg, Luca Lombardo, Paola Mazzoglio, and Elisa Palazzi

As our climate system climbs through its current warming path, temperature and precipitation are greatly affected also in their extremes and there is a general concern about the effects on river floods. While a wide body of literature on the detection of flood changes is available, the identification of their underlying causes (i.e. flood change attribution) is still debated. In this work, we aim at better understanding how floods of different kind are related to climate extremes (of precipitation and temperature) and how these extremes are related to large scale predictors (e.g. climate oscillations, teleconnections). The study area is the Greater Alpine Region, which is an ideal laboratory for analysing complex effects of climate on floods because of the interplay of heavy precipitation and snow processes in controlling flood generation, and also because the European Alps divide the Mediterranean and Continental Europe with different responses to climate oscillations. Through a novel integrated modeling chain, we aim at identifying the climate extreme indices that better relate to river floods, the large-scale climate phenomena controlling their dynamics, their expected modifications due to climate change and the associated uncertainties. The research plan of a multidisciplinary team of climatologists and hydrologists will be presented together with preliminary results. We believe that this research will strengthen our knowledge on flood risk in the future and contribute to improve existing methods for disaster risk assessment and management.

How to cite: Viglione, A., Arnone, E., Corti, S., Ferguglia, O., Giuntoli, I.,  von Hardenberg, J., Lombardo, L., Mazzoglio, P., and Palazzi, E.: Mapping of climate to flood extremes in the European Alps: a multidisciplinary approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4014, https://doi.org/10.5194/egusphere-egu24-4014, 2024.

Long-term extending cultivation activities resulted in the world’s worst soil erosion on the Chinese Loess Plateau. By converting cropland into vegetated land, the Grain for Green Project (GfGP)—the world’s largest investment revegetation project—effectively alleviates the soil erosion on the  Loess Plateau. However, during the GfGP implementation, the positive effect of cropland to the revegetation and soil erosion control has been underestimated to date, hindering a comprehensive evaluation to the effect of cropland on ecological restoration. Here, we evaluated the effect of the GfGP on soil erosion control across the  Loess Plateau, analyzed the dominant driver of the  Loess Plateau vegetation greening, and further identified the contributions of croplands to this world’s largest revegetation project. We found that the vegetation of the  Loess Plateau was significantly improved and its leaf area increased by 1.23 × 105 km2 after the implementation of the GfGP, which contributed 42% to the decrease of the  Loess Plateau soil loss. Among them, our results show that cropland contributed 39.3% to the increased leaf areas of the  Loess Plateau, higher than grassland (36.3%) and forestland (14.3%). With the reduction of agricultural area, the contribution of cropland to the increased leaf areas in the  Loess Plateau was still the largest, which was mainly due to the increase in cropland utilization intensity. This study highlights the significance of the GfGP in soil erosion control and revises our understanding of the role of cropland in ecological restoration and society development.

How to cite: Lan, X. and Liu, Z.: Land-use Intensity Reversed the Role of Cropland in Ecological Restoration over the World's Most Severe Soil Erosion Region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4397, https://doi.org/10.5194/egusphere-egu24-4397, 2024.

EGU24-5467 | ECS | PICO | HS1.1.2

The AAU Calibration and Data Assimilation (CDA) approach for improving large-scale hydrological models in a changing climate 

Maike Schumacher, Leire Retegui Schiettekatte, Fan Yang, and Ehsan Forootan

Extreme events such as floods and droughts are expected to become more frequent and intense due to the changing climate. However, it is still a challenge to monitor, understand, simulate, and anticipate the underlying hydrological processes. Large scale hydrological models and remote sensing observations (such as surface soil moisture from SMOS, SMAP and Sentinel, as well as total water storage changes (TWSC) from the GRACE and GRACE-FO gravity missions) provide a unique large-scale to global view on the changing hydrology. Sequential Calibration and Data Assimilation (CDA) provides opportunities to combine benefits from both, modelling and observing, and thus helps to improve our understanding of the impact of the climate change on water resources.

In this study, we present how the careful and consistent processing of GRACE/-FO data including a consistent estimation of the full error covariance matrix to represent the typical spatially correlated error structure supports the assimilation of satellite data into large-scale hydrological models. The first case study will tackle the question of selecting an appropriate multi-sensor data assimilation approach to combat the temporal and spatial resolution mismatch between data and model for high-dynamic frequencies. For this, daily GRACE data are assimilated for the Brahmaputra Basin that was subject to major floods, e.g., in 2004, 2007 and 2012. A reconstruction of these flood events allows a better understanding of the benefits and limitations of large-scale hydrological CDA in a changing climate. The second case study focuses on quantifying human-induced impacts on surface and groundwater storages under prolonged and intense droughts. Here, we assimilate two decades of monthly GRACE/-FO data for the Murray-Darling Basin, Australia, to better understand the impact of dry climatological conditions on our water resources.

How to cite: Schumacher, M., Retegui Schiettekatte, L., Yang, F., and Forootan, E.: The AAU Calibration and Data Assimilation (CDA) approach for improving large-scale hydrological models in a changing climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5467, https://doi.org/10.5194/egusphere-egu24-5467, 2024.

The impact of climate change and human activities poses significant challenges in the tropical region of Southeast Asia, specifically within the Mun-Chi River Basin, the largest tributary of the Mekong River in Thailand. The bias-corrected MPI-ESM1-2-LR, the most appropriate Global Climate Model (GCM) under the Coupled Model Intercomparison Project Phase 6 (CMIP6) for projecting Mun-Chi River flow, represent future climate variations in the basin. The analysis reveals forthcoming transformations in future land use, with cropland areas transitioning into forests and urban areas. The projected annual streamflow contributing to the Lower Mekong River is expected to increase by 1.14% to 3.49% in 2023-2035 and 1.84% to 4.26% in 2036-2050, with 67.17% attributed to climate change and 32.83% to land-use change. Temporal variations in the future flow regime reveal a wetter wet season and a drier dry season in this catchment. During the wet season, streamflow is projected to rise by 4.97% to 17.67% in 2023-2035 and 9.97% to 24.08% in 2036-2050. In contrast, the dry season is expected to experience a decrease of -2.69% to -9.15% in 2023-2035 and -6.28% to -17.10% in 2036-2050. These seasonal contrasts suggest a potential increase in extreme hydrological events, presenting challenges for efficient water resource management in this watershed and downstream countries. Consequently, effective water regulation and land-use policies are deemed crucial for sustainable management in the Mun-Chi River Basin.

How to cite: Inseeyong, N. and Xu, M.: Impacts of Climate and Land use Changes on Streamflow in the Mun-Chi River Basin, the Largest Tributary of the Mekong River, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6428, https://doi.org/10.5194/egusphere-egu24-6428, 2024.

The estimation of actual evapotranspiration (ET) using both rescaled and non-rescaled complementary relationship (CR) models has become a hotspot in the research on terrestrial ET. This study explores the relationship between these two CR models and improves the method for calculating xmin in rescaled CR models. The rescaled and non-rescaled CR models can be functionally interconvertible, i.e., the non-rescaled CR model enables the rescaled simulation of ET and the rescaled CR model can also conduct a non-rescaled simulation. The parameter b or c in the non-rescaled CR models plays a role similar to xmin in the rescaled models. Based on the data from 15 catchments in the Loess Plateau of China, we validate this relationship between the two CR models. Meanwhile, we evaluate the formulation for xmin proposed by Crago et al. (2016) (the Crago’s xmin values) and the results show that the range of variation for the Crago’s xmin values is smaller than that for the xmin values obtained by inverse method from the models (the inversed xmin values) in the interannual process. The inversed xmin values of RCR-C2016 are mostly larger than that of RCR-S2017, while the Crago’s xmin values are in between these two values. The empirical function for xmin is developed using the aridity index (AI) and normalized difference vegetation index (NDVI) as independent variables in the interannual fluctuations. On the mean annual scale, the empirical function for xmin is expressed only using the AI. Cross-validation results show that the rescaled CR models combined with xmin determined by the empirical functions can more accurately estimate ET and simulate its interannual and spatial changes. (Supported by Project 41971049 of NSFC)

How to cite: Mu, Z., Liu, W., Ma, N., Cheng, C., and Zhou, H.: Relations of rescaled to non-rescaled complementary models and improvement of evapotranspiration estimates by incorporating both climatic and land surface conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6983, https://doi.org/10.5194/egusphere-egu24-6983, 2024.

EGU24-7046 | PICO | HS1.1.2 | Highlight

Global models overestimate streamflow induced by rising CO2 

Haoshan Wei, Yongqiang Zhang, Changming Liu, and Qi Huang

The global streamflow plays a crucial role in the broader water cycle, intricately linked to human activities, ecology, and agriculture. The rise in atmospheric CO2 has complex effects on global streamflow. In addition to feedbacks to climate change, CO2 impacts on streamflow result from surface changes, including reduced streamflow induced by expanding vegetation and increased streamflow induced by reduced vegetation evapotranspiration due to stomatal closure. Global models, vital for policy planning, predict increased streamflow due to dominant positive impacts of elevated CO2. More than 10 out of 14 global dynamic vegetation models concluded that increased CO2 exacerbated runoff growth over the 1981-2020 period, especially in tropical and temperate regions. Yet, studying four decades of observed streamflow data, we find these models largely overestimate the increase in streamflow induced by elevated CO2, particularly in tropical forest (tropical) and cold forest (cold), pointing to an unexpectedly drier world.

How to cite: Wei, H., Zhang, Y., Liu, C., and Huang, Q.: Global models overestimate streamflow induced by rising CO2, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7046, https://doi.org/10.5194/egusphere-egu24-7046, 2024.

In order to compare the impacts of the choice of land surface model (LSM) parameterization schemes, meteorological forcing, and land surface parameters on land surface hydrological simulations, and explore to what extent the quality can be improved, a series of experiments with different LSMs, forcing datasets, and parameter datasets concerning soil texture and land cover were conducted. Six simulations are run for mainland China on 0.1o×0.1o grids from 1979 to 2008, and the simulated monthly soil moisture (SM), evapotranspiration (ET), and snow depth (SD) are then compared and assessed against observations. The results show that the meteorological forcing is the most important factor governing output. Beyond that, SM seems to be also very sensitive to soil texture information; SD is also very sensitive to snow parameterization scheme in the LSM. The Community Land Model version 4.5 (CLM4.5), driven by newly developed observation-based regional meteorological forcing and land surface parameters (referred to as CMFD_CLM4.5_NEW), significantly improved the simulations in most cases over mainland China and its eight basins. It increased the correlation coefficient values from 0.46 to 0.54 for the SM modeling and from 0.54 to 0.67 for the SD simulations, and it decreased the root-mean-square error (RMSE) from 0.093 to 0.085 for the SM simulation and reduced the normalized RMSE from 1.277 to 0.201 for the SD simulations. This study indicates that the offline LSM simulation using a refined LSM driven by newly developed observation-based regional meteorological forcing and land surface parameters can better model reginal land surface hydrological processes.

How to cite: Liu, J., Jia, B., and Xie, Z.: Elucidating Dominant Factors Affecting Land Surface Hydrological Simulations of the Community Land Model over China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7416, https://doi.org/10.5194/egusphere-egu24-7416, 2024.

The elevated CO2 concentration in the atmosphere has warmed the planet and modified the global precipitation pattern. Typical impact studies that investigate the regional hydrological response to climate change is based on the hydrological models forced by climate model projections. However, the physiological CO2 effects of plants that manifests as reduced transpiration via partially closed leaf stomata and enhanced photosynthesis is often overlooked in these impact studies. 
 
Here, the potential impact of the physiological CO2 effects on hydrological trends in France over the 21st century is assesed using the validated high-resolution Organising Carbon and Hydrology in Dynamic Ecosystems (ORCHIDEE) land surface model (Huang et al., 2023). The ORCHIDEE land surface model is forced with 4 regionalized climate projections narrowed from the CMIP5 ensemble projection under the RCP 8.5 scenario, with which we test the effect of two atmospheric CO2 conditions: a constant CO2 level of year 2005 and an increasing CO2 concentration of the RCP 8.5. 
 
We find that the physiological CO2 effects result in a decrease of evapotranspiration and an increase of total runoff over France for the 4 projections. Therefore, the physiological CO2 effects enhance the increasing trend of river discharges in wet projections and alleviate the decreasing trend of river discharges in dry projections over the 21st century. Despite the model uncertainties, our study confirms the important physiological CO2 effects on French water availaibility in the future, and this result likely holds at a broader scale.

How to cite: Huang, P. and Ducharne, A.: The impact of increasing atmosphere CO2 concentration on hydrological trends in France over the 21st century, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7788, https://doi.org/10.5194/egusphere-egu24-7788, 2024.

EGU24-7987 | ECS | PICO | HS1.1.2 | Highlight

Multi-decadal change in global rainfall interception and its drivers 

Feng Zhong, Shanhu Jiang, Akash Koppa, Liliang Ren, Yi Liu, Menghao Wang, and Diego G. Miralles

Rainfall interception loss (Ei) is one of the biggest unknowns in the global hydrological cycle. As a dynamic process, Ei depends on vegetation structure and canopy characteristics, but also on the precipitation and (micro)climatic conditions that determine the atmospheric demand for water. The spatial variability of these factors makes it difficult to reliably estimate Ei over large scales, and its sensitivity to non-stationary climate variability renders Ei trends highly uncertain. In this regard, process-based formulations accounting for key biophysical and climatic factors provide unique opportunities to examine the global patterns of Ei, as well as the driving mechanisms behind its variability.

Here we explore the estimates of Ei from the Global Land Evaporation Amsterdam Model (GLEAM v3; Martens et al., 2017), the Penman-Monteith-Leuning (PML v2; Zhang et al., 2019) model, and a recently proposed and validated global application constrained by a synthesis of global experimental data (Zhong et al., 2022). All three methods estimate long-term Ei based on Gash-type formulations (Valente et al., 1997; Van Dijk and Bruijnzeel, 2001). To reduce uncertainty, a multi-product approach is applied to examine the spatial-temporal trends in Ei. Moreover, we focus on a well-validated model (Zhong et al., 2022) to further isolate the relative contributions of precipitation, vegetation and evaporative demand to Ei variability. We find that Ei, described both in terms of the volume of evaporated water and as a percentage of precipitation, exhibits increasing trends globally. Contrasting regional changes are found, however, with a significant increase over Eurasia where the strongest vegetation greening occurs, and decreases over the Congo basin driven by a decline in precipitation. At decadal timescales, the increasing Ei is largely driven by global vegetation greening through an increase in the intercepting surface and storage capacity, while its inter-annual variations are mainly controlled by changes in precipitation. Moreover, the positive contribution of evaporative demand should not be overlooked, given the ubiquitous rise in global potential evaporation driven by atmospheric warming.

 

References

Martens, B., Miralles, D. G., Lievens, H., van der Schalie, R., de Jeu, R. A. M., Fernández-Prieto, D., Beck, H. E., Dorigo, W. A., and Verhoest, N. E. C.: GLEAM v3: satellite-based land evaporation and root-zone soil moisture, Geosci. Model Dev., 10, 1903– 1925, https://doi.org/10.5194/gmd-10-1903-2017, 2017.

Valente, F., David, J., and Gash, J.: Modelling interception loss for two sparse eucalypt and pine forests in central Portugal using reformulated Rutter and Gash analytical models, J. Hydrol., 190, 141–162, https://doi.org/10.1016/S0022-1694(96)03066-1, 1997.

Van Dijk, A. and Bruijnzeel, L.: Modelling rainfall interception by vegetation of variable density using an adapted analytical model. Part 1. Model description, J. Hydrol., 247, 230–238, https://doi.org/10.1016/S0022-1694(01)00392-4, 2001.

Zhang, Y., Kong, D., Gan, R., Chiew, F. H. S., McVicar, T. R., Zhang, Q., and Yang, Y.: Coupled estimation of 500m and 8day resolution global evapotranspiration and gross primary production in 2002–2017, Remote Sens. Environ., 222, 165–182, https://doi.org/10.1016/j.rse.2018.12.031, 2019.

Zhong, F., Jiang, S., van Dijk, A. I., Ren, L., Schellekens, J., and Miralles, D. G.: Revisiting large-scale interception patterns constrained by a synthesis of global experimental data, Hydrol. Earth Syst. Sci., 26(21), 5647-5667, https://doi.org/10.5194/hess-26-5647-2022, 2022.

How to cite: Zhong, F., Jiang, S., Koppa, A., Ren, L., Liu, Y., Wang, M., and Miralles, D. G.: Multi-decadal change in global rainfall interception and its drivers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7987, https://doi.org/10.5194/egusphere-egu24-7987, 2024.

EGU24-8134 | ECS | PICO | HS1.1.2 | Highlight

Predicting annual base flow index and its trends using a large sample of dataset across the globe 

Qi Huang, Jan Seibert, and Yongqiang Zhang

The Base-Flow Indices (BFI), indicating surface and groundwater interaction, play a significant role in the hydrological cycle. The values vary widely across the globe, and are expected to change in the context of a changing climate. Predicting global “natural” BFI is challenging due to limited observations reflecting natural impacts. This study aims to predict annual BFI and their trends for a compiled dataset of annual streamflow and meteorological data covering the period 1982-2020 for more than 2250 small unregulated catchments worldwide. BFI were derived using three digital filtering methods, resulting in a trend of -0.0009 ± 0.01 per decade over the last four decades. To predict annual BFI and their trends in ungauged catchments, a Random Forest Regression approach was employed, incorporating static attributes and meteorological time series data as model inputs. Five-fold cross-validation demonstrated the effectiveness of the Random Forest Regression in predicting both BFI and their trends. The Quantile Regression Forest method was utilized to quantify the uncertainty, achieving a relatively low range for both BFI and their trends. Soil conditions and maximum temperature emerged as the most crucial variables for predicting BFI, while temperature-related variables also proved essential for predicting the BFI trends. The goal is to extend the understanding of "natural" BFI and their trends in ungauged catchments, as the Random Forest Regression model was trained under unregulated conditions. This study offers the possibility to predict "natural" BFI and their trendsacross the globe. This could support water authorities in managing water resources, particularly concerning base flow.

How to cite: Huang, Q., Seibert, J., and Zhang, Y.: Predicting annual base flow index and its trends using a large sample of dataset across the globe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8134, https://doi.org/10.5194/egusphere-egu24-8134, 2024.

EGU24-9824 | ECS | PICO | HS1.1.2

The hydrometeorological ingredients needed to fill dry Saharan lakes 

Moshe Armon, Joëlle C. Rieder, Elad Dente, and Franziska Aemisegger

The Sahara desert was potentially much wetter and vegetated in the past during the warm African Humid Period. Although debated, this climatic shift is a possible scenario in a future warmer climate. The most prominent reported evidence for past green periods in the Sahara is the presence of paleo-lakes. Even today, Saharan desert lakes get filled from time to time. However, very little is known about these events due to the lack of available in-situ observations. In addition, the hydrometeorological conditions associated with these events have never been investigated in a dedicated climatological approach. This study proposes to fill this knowledge gap by investigating the meteorology of lake-filling episodes (LFEs) of Sebkha el Melah – a commonly dry lake in the northwestern Sahara. Heavy precipitation events (HPEs) and LFEs are identified using a combination of precipitation observations and lake volume estimates derived from remote sensing satellite imagery. Weather reanalysis data is used together with three-dimensional trajectory calculations to investigate the moisture sources and characteristics of weather systems that lead to HPEs and to assess the conditions necessary for producing LFEs. Results show that hundreds of HPEs occurred between 2000 and 2021, but only 6 LFEs eventuate. The runoff coefficient, i.e. the ratio between the increase in lake water volume during LFEs and precipitation volume during the HPEs that triggered the lake-filling, ranges five orders of magnitude and is much smaller than the figures often cited in the literature regarding this arid area. We find that LFEs are generated most frequently in autumn by the most intense HPEs, for which the key ingredients are (i) the formation of surface extratropical cyclones to the west of the Atlantic Sahara coastline in interplay with upper-level troughs and lows, (ii) moisture convergence from the tropics and the extratropical North Atlantic, (iii) a premoistening of the region upstream of the catchment over the Sahara through a recycling-domino-process, (iv) coupled or sequential lifting processes (e.g., orographic lifting and large-scale forcing), and (v) the stationarity of synoptic systems. Based on the insights gained into Saharan LFEs in the present-day climate, future studies will be able to better assess the mechanisms involved in the greening of the Sahara in the past and also in a warmer future.

How to cite: Armon, M., Rieder, J. C., Dente, E., and Aemisegger, F.: The hydrometeorological ingredients needed to fill dry Saharan lakes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9824, https://doi.org/10.5194/egusphere-egu24-9824, 2024.

EGU24-10051 | PICO | HS1.1.2 | Highlight

A survey of past and future changes in global river flow 

Lukas Gudmundsson, Manuela Brunner, Petra Döll, Etienne Fluet-Chouinard, Simon N. Gosling, Yukiko Hirabayashi, Hannes Müller Schmied, Louise Slater, Lina Stein, Conrad Wasko, Dai Yamazaki, and Xudong Zhou

River flow is an essential component of the global water cycle and arguably the best monitored variable in land hydrology. Both anthropogenic climate change as well as direct human influences on the terrestrial environment influence river flow at local to planetary scales. Here, we survey recent scientific advances in quantifying past trends and projecting future changes in global river flow, with focus on trends in flow volumes and seasonality. Previously published evidence of past changes is complemented by an analysis of changes in river flow using in-situ observations and river discharge estimates from a global re-analysis product. Available literature on future projections is accompanied by an analysis of Global Climate Model projections routed through the global river network.

Systematic patterns of past changes in river flow emerge at the regional to global scales, despite significant uncertainties and small-scale spatial variability. These uncertainties are related e.g. to differences in study periods, considered indicators of change, availability of in-situ observations, and uncertainties of model-based reconstructions. Some of the most pronounced changes in past river flow include increasing river flow in the northern high latitudes and robust decreasing trends in significant parts of central and south America, the Mediterranean region, the southern tip of Africa as well as central and southern Australia. In other world regions, available in-situ observations are sparse or there is conflicting evidence, meaning that trends are still uncertain. We further show systematic shifts in the river flow seasonality with a tendency for earlier streamflow and a dampened seasonal cycle in across many parts of the world likely to due to higher temperatures and earlier snowmelt, with later streamflow in the Mediterranean linked to changes in rainfall.

Climate model driven assessments of future changes in river flow suggest that total global discharge to the oceans may increase with global warming, albeit with large regional differences in the direction of change and substantial model uncertainty. Across several studies based on different model ensembles, there is consensus for increasing river flow in the northern high latitudes and some evidence for increasing river flow in tropical Africa, the Indian subcontinent and eastern and tropical Africa. Finally, we highlight regions in which past changes in river flow are consistent with future projections, which include but are not limited to increasing river flow in northern North America and northern Europe, as well as drying tendencies in the Mediterranean, the southern tip of Africa and Southern Australia. The consistency between model projections and historical trends in these regions gives confidence to future water management decisions, while disparities between historical trends and projections highlights regions where better understanding of the processes governing past and future change in river flow will be required moving forward.

How to cite: Gudmundsson, L., Brunner, M., Döll, P., Fluet-Chouinard, E., Gosling, S. N., Hirabayashi, Y., Müller Schmied, H., Slater, L., Stein, L., Wasko, C., Yamazaki, D., and Zhou, X.: A survey of past and future changes in global river flow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10051, https://doi.org/10.5194/egusphere-egu24-10051, 2024.

EGU24-10053 | ECS | PICO | HS1.1.2

Assessing impacts of vegetation changes on water availability in the upper Yellow River Basin, China 

Yan Wang, Guoqing Wang, Xiyuan Deng, and Yuli Ruan

Changes in vegetation are expected to influence terrestrial water and energy fluxes; however, the impacts of vegetation changes on water availability remain controversial. In this study, we applied the Community Land Model, version 4.5 (CLM4.5) coupled with the Variable Infiltration Capacity (VIC) hydrological parameterizations to the upper Yellow River Basin (UYRB), which is the most important water conservation area in the Yellow River Basin, to investigate the impacts of vegetation changes on water availability in the area. The results showed a pronounced greening trend in the UYRB from 1982 to 2018, resulting in increased evapotranspiration, decreased runoff, drier soil conditions, and decreased water yield. The water reduction effect of vegetation greening is more pronounced in water-limited areas than in energy-limited areas. This study highlights the diverse hydrological responses to vegetation changes under different climatic conditions and land cover types. It is crucial for ecological restoration policies in China to recognize these distinctions and their potential negative impacts on water availability, especially in water-limited regions.

How to cite: Wang, Y., Wang, G., Deng, X., and Ruan, Y.: Assessing impacts of vegetation changes on water availability in the upper Yellow River Basin, China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10053, https://doi.org/10.5194/egusphere-egu24-10053, 2024.

EGU24-10062 | ECS | PICO | HS1.1.2

Drivers of changes in catchment evapotranspiration in Central Europe over the past 40 years 

Doris Duethmann, Giulia Bruno, and Laurent Strohmenger

Understanding long-term changes in evapotranspiration and their drivers is crucial due to direct impacts on water availability. Increasing evapotranspiration rates can exacerbate droughts and jeopardise water availability, especially in the summer months with higher water demands. Uncertainties of multi-decadal variations in evapotranspiration at local to regional scale and their drivers are, however, still large. In this data-based study, we derive changes in evapotranspiration from the catchment water balance for a large number of catchments in Central Europe over 1982–2016. We further analyse changes in potential drivers including vegetation and land cover based on a remote-sensing derived vegetation index and a land cover product, water availability based on changes in seasonal precipitation and available energy and atmospheric demand based on changes in reference evapotranspiration. We find wide-spread increases in catchment evapotranspiration until about the year 2000 and only small changes with a decreasing tendency after 2000. The observed variations in regional evapotranspiration are significantly correlated with variations in precipitation, reference evapotranspiration and vegetation activity. High evapotranspiration around 2000 can be related to high values of reference evapotranspiration, precipitation and vegetation activity. Lower evapotranspiration in the early 1980s despite relatively high precipitation is linked to lower values of reference evapotranspiration and vegetation activity, while the halt of further evapotranspiration increases after 2000 despite high values of reference evapotranspiration may be explained by low precipitation. The study contributes to expand our knowledge on the drivers of changes in the water balance in Central Europe over recent decades, which is of great importance for water management in a changing climate.

How to cite: Duethmann, D., Bruno, G., and Strohmenger, L.: Drivers of changes in catchment evapotranspiration in Central Europe over the past 40 years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10062, https://doi.org/10.5194/egusphere-egu24-10062, 2024.

EGU24-11031 | PICO | HS1.1.2

Global Aridity Index and Potential Evapotranspiration Database: CIMP_6 Future Projections 

Antonio Trabucco, Donatella Spano, and Robert J Zomer

We present the recent release of the “Global Aridity Index and Potential Evapotranspiration Database: CIMP_6 Future Projections – v.1 (Future_Global_AI_PET)”, which provides very high-resolution (30 arc-seconds or about 1km at equator) global raster dataset of average monthly and annual potential evapotransipation (PET) and annual aridity index (AI) for two historical (1960-1990; 1970-2000) and two future (2021-2040; 2041-2060) time periods for each of 25 CIMP6 Earth System Models across four emission scenarios (SSP: 126, 245, 370, 585). Potential evapotranspiration (PET) characterizes the atmosphere's capacity to remove water through evapotranspiration (ET). Evaporation and transpiration processes collectively transfer water from the Earth's surface to the atmosphere with rates determined by solar radiation, air temperature, relative humidity (specifically, vapor pressure deficit), wind speed, as well as the distinctive traits of vegetation, or crops and the practices employed in their cultivation. Estimates of reference evapotranspiraton (ET0) have been widely used across diverse scientific fields and practical domains, with PET measurements and related indices playing a crucial role in agricultural and natural resource management with demonstrated utility on scales from individual farms to regional and global. The aridity index (AI), which describes the ratio of precipitation to PET provides an integrated measure to gauge moisture availability for plant growth, generally of specific reference crops or specific vegetation types, enabling both spatial and temporal comparisons. In an era of rapid environmental and climatic transformations, these metrics, along with their derived indices, assume a pivotal role as direct and critical measures, as well as predictive tools, for gauging the trajectory, direction, and extent of climatic variations and their ramifications for terrestrial, and particularly agricultural, ecosystems. This latest addition to the Global_AI_PET database also includes three averaged multi-model ensembles produced for each of the four emission scenarios: All Models:  includes all of the 25 ESM available; High Risk: includes 5 ESM which were identified as projecting the highest increases in temperature and significantly higher than the majority of estimates; Majority Consensus:  includes 20 ESM, that is, all of the available ESM minus the five ESM in the “High Risk” category.  Preliminary results based on CIMP6 ESM projections are provided showing significant change in global and regional trends for PET and aridity in the near- and medium-term, with implications for agriculture, biodiversity, watershed management, and water resources. The Future_Global_AI_PET Database is the latest and most recent addition to the Global PET_AI Database, which has provided PET and AI datasets using both the Hargreaves and Penman-Monteith equations, and has been available online since 2009, downloaded over 50,000 times, and with more than 2000 scholarly citations:

 https://figshare.com/articles/dataset/Global_Aridity_Index_and_Potential_Evapotranspiration_ET0_Climate_Database_v2/7504448/6)

How to cite: Trabucco, A., Spano, D., and Zomer, R. J.: Global Aridity Index and Potential Evapotranspiration Database: CIMP_6 Future Projections, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11031, https://doi.org/10.5194/egusphere-egu24-11031, 2024.

Heatwaves – short-term periods of anomalous warmth – can play an outsized role in shaping downstream water resources as they impact the timing and magnitude of snow and glacier melt.  Melt-driven runoff enhanced during spring heatwaves is particularly important as it can cause downstream flooding and damage.  It is well understood that heatwaves will become more frequent and more severe in the future due to climate change; however, it is not well understood how the hydrological response to heatwaves will change in the future.

Here, we quantify the streamflow response to heatwaves over the past century across Western Canada.  We investigate how such streamflow responses vary in space, time, by streamflow regime, and by hydroclimate conditions, and we present a simple mathematical framework to partition the responses into seasonal and heatwave-driven components.  We use freshet timing and winter snowfall as metrics that are expected to change under climate change, and we compare how streamflow responses to heatwaves differ between baseline historical years (later freshet and more snowfall) and future proxy years (earlier freshet and less snowfall). 

We find that in future proxy years, the streamflow response to spring heatwaves is diminished when seasonal streamflow is enhanced, indicating that peak streamflow during heatwaves does not necessarily increase under climate warming.  We also find that the proportion of spring streamflow generated by heatwaves is lessened relative to seasonal streamflow, and this proportion is diminished as the freshet progresses.

Our results contextualize how the streamflow responses to heatwaves have varied over the past century, to better understand how they may change in the future.  Importantly, our findings have implications for future heatwave-driven flooding in nival and glacial basins at both regional and global scales, and we present novel observational signals of change in heatwave-driven streamflow that can be further investigated by future modelling studies.

How to cite: Anderson, S. and Chartrand, S.: Spatiotemporal variability of heatwave-driven streamflow in nival and glacial basins: Future insights from a century of observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11575, https://doi.org/10.5194/egusphere-egu24-11575, 2024.

EGU24-13209 | ECS | PICO | HS1.1.2

Tree planting attenuates storm runoff response on the Chinese Loess Plateau 

Shaozhen Liu, Hansjörg Seybold, Ilja van Meerveld, Yunqiang Wang, and James W. Kirchner

Tree planting to mitigate climate change has become a popular topic in recent years. While it has been widely reported that tree planting reduces annual water yield, it is not clear how tree planting affects a catchment’s storm runoff response for events of different magnitudes. China’s “Grain for Green Program” almost doubled the vegetation cover on the Loess Plateau two decades ago, and thus represents a large-scale experiment revealing the impact of tree planting on hydrological processes. Here we show how the storm runoff response to rainfall has changed as a result of tree planting using five sub-catchments in a 26,000 km2 large basin that received different degrees of afforestation. Our dataset covers over 40 years of daily streamflows, allowing us to use new nonlinear Ensemble Rainfall-Runoff Analysis techniques to quantify the runoff response to rainfall events of different intensities. We find that after tree planting, the runoff response peak decreased up to 86%, proportional to the percentage increase in the Leaf Area Index (LAI). This attenuation of peak runoff is much larger than that of the decrease in average growing season runoff (59%). Surprisingly, the largest attenuation in peak runoff response occurs during high-intensity rainfall events rather than low-intensity rainfall events. This observation implies that the main mechanisms reducing runoff response cannot be increased canopy interception or soil moisture depletion, because these would be expected to have a larger effect on low-intensity events. Instead, we hypothesize that the main mechanisms are likely to be reductions in runoff-generating areas and increases in infiltration rates. Consistent with this hypothesis, low flows (i.e., Q95) do not decrease, but instead increase up to 25%, with the largest increases in low flows occurring in sub-catchments with the largest percentage increases in LAI. These findings highlight the positive effect of tree planting on reducing storm runoff peaks and increasing low flows, coincident with the reduction in annual water yield that has been widely reported in other studies. These substantial and persistent hydrological consequences of tree planting can inform future efforts at climate change mitigation through vegetation management.

How to cite: Liu, S., Seybold, H., van Meerveld, I., Wang, Y., and W. Kirchner, J.: Tree planting attenuates storm runoff response on the Chinese Loess Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13209, https://doi.org/10.5194/egusphere-egu24-13209, 2024.

EGU24-13611 | PICO | HS1.1.2

Hydrologic responses to climate change and implications for reservoirs in the source region of the Yangtze River 

Hongmei Xu, Pengcheng Qin, Zhihong Xia, Lüliu Liu, Qiuling Wang, and Chan Xiao

Understanding the hydrological impacts of climate change is essential for robust and sustainable water management. This study assessed the hydrologic impacts of climate change in the Jinshajiang River basin, the source region of the Yangtze River, using the historical observations and the future hydrologic simulations under two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5), deriving from a hydrological model. For the historical period, there is an increasing trend in precipitation, evapotranspiration, snowmelt, and consequently an increasing in streamflow in the upstream, whereas a decreased streamflow in the downstream catchment. For future scenarios, a warmer and wetter climate was projected for the basin throughout the 21st century, and correspondingly an overall increase in mean and extreme streamflow, with a larger magnitude in the far future than in the near future, and under SSP5-8.5 than SSP2-4.5. The projected remarkable increase in precipitation cause the transition in changing trend of streamflow compared with the historical period. The projected continuing decline in snowfall and snow water equivalent result in a significant advance and decrease in snowmelt, followed by an earlier and more concentrated peak streamflow in July, especially for the upstream catchment. Ultimately, reservoirs in the basin are expected to gain more inflows, however, with larger variability and more floods and hydrological droughts, which impose potential challenges on reservoir operations. These outcomes indicate the importance of adaptive water resources management in the melting water contributed basin to sustain and enhance its services under global warming.

How to cite: Xu, H., Qin, P., Xia, Z., Liu, L., Wang, Q., and Xiao, C.: Hydrologic responses to climate change and implications for reservoirs in the source region of the Yangtze River, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13611, https://doi.org/10.5194/egusphere-egu24-13611, 2024.

EGU24-13740 | ECS | PICO | HS1.1.2 | Highlight

Assessment of Land Surface Model's Evapotranspiration Response 

Yaoting Cai, Xingjie Lu, Zhongwang Wei, and Nan Wei

Biotic factors have been identified as one of the most important controls on evapotranspiration (ET) variation in the scenario of future climate change. Land surface models have developed sophisticated canopy processes to emphasize the importance of vegetation. However, as the vegetation processes become more and more complicated, the relative importance of biotic impact in comparison with abiotic impact on ET has not been well quantified. Failing to understand the relative importance between abiotic and biotic impact may result model bias in water cycle prediction. We collected satellite-based

ET dataset (GLEAM, CRv1, P-LSH), climate data, biotic factor estimates, and apply the variance decomposition analysis to quantify the relative importance between biotic and abiotic impacts. Then, we compared with the model counterpart, i.e. the ensemble means of LS3MIP and CMIP6. Variance decomposition analysis on ET dataset show that about 70% of the ET inter-annual variation is contributed from abiotic factors, such as vapor pressure deficit (VPD), net radiation, and precipitation, whereas only 30% of ET variance is explained by biotic factors, such as stomata conductance and leaf area index (LAI). The abiotic contributions of the models show great uncertainties, which range from 36% to 60%. Overall, the abiotic factor contributions of most models are significantly higher than satellite-based ET dataset. ET variation of grassland is mostly explained by abiotic factors, which is consistent between models and ET dataset. VPD and precipitation explained most of the ET variation in ET dataset, especially in high latitude, whereas stomata conductance and LAI explained most of the ET variation in LS3MIP and CMIP6 models in boreal forest. The model overestimates of abiotic contribution indicate more complicated canopy processes require better constraints. Climate change leading to increase in VPD and more frequent extreme precipitation potentially play more important role in future ET changes. More efforts, such as model parameterization, calibration, new process development, still need to be made by modelers to improve model meteorological feedback.

How to cite: Cai, Y., Lu, X., Wei, Z., and Wei, N.: Assessment of Land Surface Model's Evapotranspiration Response, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13740, https://doi.org/10.5194/egusphere-egu24-13740, 2024.

EGU24-13880 | ECS | PICO | HS1.1.2

Assessment of climate change impacts on Brazilian catchments using a regional deep learning approach 

André Almagro, Pedro Zamboni, and Paulo Tarso Oliveira

The potential impacts of climate change in catchment hydrology are still unknown in most of the world and it is not different in Brazil. Conducting an integrated analysis of catchments based on similarity groups allows us to extract conclusions and observations about the overall controls of hydrological behavior, but also considering the specific and distinctive characteristics of each of these groups. This approach enables us to identify and comprehend the primary features influencing hydrological behavior within each distinct group, increasing hydrologic predictability and knowledge of catchments’ functioning, which is essential to better understand the impacts of climate change. In this study, we investigate the possible shifts in Brazilian catchment hydrology behavior in response to a changing climate. Employing a regional approach of the Long Short-Term Memory (LSTM) to understand and predict streamflow across 735 catchments of six hydrologically similar groups in Brazil, we simulated streamflow throughout the 21st century. This simulation utilized a multi-model ensemble comprising 19 bias-corrected Global Climate Models (GCMs) from the sixth phase of the Coupled Model Intercomparison Project (CMIP6), driven by intermediate and high-emission scenarios (SSP245 and SSP585). Our results show that the regional LSTM outperforms the conventional hydrological modeling (NSE≈0.60), underscoring the reliability of deep learning to estimate streamflow with simplified input. Interestingly, we found that substantial variations in projected temperatures across scenarios do not necessarily correspond to significant differences in projected streamflow. Moreover, changes in precipitation and temperature may not exert proportional impacts on streamflow. Further, we will investigate the dynamics of transitions between catchment groups. This innovative approach to assess the impacts of climate change enhances the reliability of projected streamflow trajectories, a critical consideration given the uncertainties associated with CMIP6 models. Furthermore, this study holds potential utility in developing strategies to mitigate the impacts of climate change on Brazilian water resources.

How to cite: Almagro, A., Zamboni, P., and Oliveira, P. T.: Assessment of climate change impacts on Brazilian catchments using a regional deep learning approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13880, https://doi.org/10.5194/egusphere-egu24-13880, 2024.

Background

Both blue water and green water contribute to agricultural water scarcity, which is subjected to impacts of escalating climate extremes, e.g., precipitation and temperature extremes. However, an explicit quantification of the possible effects of compound climate extremes on agricultural water scarcity index (AWSI) under historical and future climate is absent and current research often overlooks how different spatial scales influence agricultural water scarcity.

Methods

We applied an integrated AWSI, which incorporates blue water and green water, to estimate agricultural water scarcity in provincial and basin scales in China, and to determine the association of AWSI with compound climate extremes over the historical period 1971–2010 and for future period 2031–2070.

Conclusions
Our results indicate a marked escalation in AWSI during dry years and periods of elevated temperatures, and precipitation significantly impacts AWSI more than temperature variations. In secondary basins, AWSI was about 25.7% higher than the long-term average during dry years, increasing to nearly 49% in exceptionally dry conditions. Comparatively, in tertiary basins, the increases were 27.7% and 55%, respectively. In years characterized by high temperatures, AWSI rose by approximately 6.8% (7.3% for tertiary basins) from the average, surging to around 19.1% (15.5% for tertiary basins) during extremely hot periods. Future climate change would further intensify AWSI and amplify the effects of climate extremes, particularly in Inner Mongolia with changes of AWSI over 200%. Southwestern China could also experience expanding agricultural water scarcity under future climate scenarios. Improving irrigation efficiency has potential to alleviate water scarcity by up to 30%. Moreover, it illustrates that AWSI assessment at the tertiary basin level could better capture the influence of climate extremes on AWSI compared to assessments at the secondary basin level. As a whole, the investigation offers an in-depth evaluation of the influence of compound precipitation and temperature extremes and research scale on water scarcity.

How to cite: Liu, J. and Liu, W.: Impacts of climate extremes on agricultural water scarcity under historical and future periods and the spatial scale effect, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14467, https://doi.org/10.5194/egusphere-egu24-14467, 2024.

EGU24-14546 | ECS | PICO | HS1.1.2

Intensified floods after mega forest fires in southeast Australia  

Zhenwu Xu, Yongqiang Zhang, and Günter Blöschl

Forest fires are commonly expected to exacerbate local flood hazards. Yet, it's not well-established if such an effect is evident across broader geographic regions concurrently, particularly when considering the compounded influences of forest fires and climate variability on floods. Here, we show that recent 2019–2020 mega forest fires in southeast Australia, characterized by unprecedented burned areas, have significantly increased the flood peak discharges in the ensuing two years. The impact varied regionally, being more pronounced in areas with winter-dominated and uniform rainfall patterns, while it was insignificant in regions with summer-dominated rainfall. This regional divergence in fire impacts can be attributed to the differences in burned areas and dominant flood generating mechanisms. Given the increasing influence of climate change on fire activities, people living in these fire-prone regions might face escalating risks of cascading flood hazards following fires in the future.

How to cite: Xu, Z., Zhang, Y., and Blöschl, G.: Intensified floods after mega forest fires in southeast Australia , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14546, https://doi.org/10.5194/egusphere-egu24-14546, 2024.

Affected by global climate change, the variations of snow cover and snowmelt runoff in the high cold region has raised an increasing concern. Snowmelt water is an important component of spring runoff in the Lancang River basin, and it is of great significance for the scientific operation of cascade hydropower stations in the Lancang River basin to master the variation law of snow cover in the upper reaches of the Lancang River and accurately simulate the snowmelt runoff process. Based on the remotely sensed snow cover data from 2000 to 2019, the Mann-Kendall trend test method was used to analyze the spatio-temporal variation of snow cover in the upper reaches of Lancang River. An snowmelt runoff model was established, and the PSO algorithm was introduced to determine the model parameters to simulate the snowmelt runoff process. The results show that the snow cover in the upper reaches of Lancang River showed no significant increase in spring, autumn and winter, and no significant decrease in summer. The average annual snow cover in spring, summer, autumn and winter was 0.16, 0.06, 0.13 and 0.17, respectively. The snow cover in the southwest and north of the Lancang River source area increased in all seasons, while the snow cover in the southeast area decreased. Among them, the increase of snow cover in the northwest reaches the largest in winter, up to 3%/a. The SRM model has good applicability in the upper reaches of the Lancang River, and the certainty coefficients of calibration period and verification period are 0.87 and 0.78, respectively, and the results have a certain implication for the simulation of snowmelt runoff in the alpine region.

How to cite: Zhang, J.: Evolution trend of snow cover and simulation of snowmelt runoff in upper reaches of Lancang River, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14558, https://doi.org/10.5194/egusphere-egu24-14558, 2024.

Detailed changes in land surface water fluxes under vegetation greening is unclear especially in different patterns of climate change and land-use change. A typical vegetation greening region located in Loess Plateau was selected as a studying area. Because of high spatial heterogeneous site conditions, similar spectral reflectance and shapes of different vegetation types, there is a low accuracy of land cover mapping in mixed regions of multiple vegetation types, thereby leading to a pronounced underestimate of land use change, such as grain for green project. Besides spectrum, topography, and some usually used features, a novel land cover mapping framework is constructed with evapotranspiration which vary dramatically in vegetation types. Generally, the classification accuracy of all kinds of land cover is above 90%, and improved by 5.4-15.3%, 0-15.7%, 3.0-20.4%, of cropland, forest and grassland, respectively. Then water fluxes including precipitation, evapotranspiration, soil moisture, and runoff were analyzed in nine different vegetation types, considering the three types of vegetation found in cropland, forest and grassland along with respective stable, loss, and gain states. The result indicated that the cropland returning and afforestation has successfully facilitated a positive regional water cycle. This finding is useful for supporting ecological restoration and future water resources management, and enhancing the carrying capacity and resilience of the region.

How to cite: Bao, Z., Wang, J., and Ruan, Y.: Characterization of land surface water flux under vegetation greening introduced by changes in climate and land-use, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14579, https://doi.org/10.5194/egusphere-egu24-14579, 2024.

In recent times, climate change leads to the occurrence of extreme weather phenomena such as heavy rainfall, severe drought, heatwaves, and cold spells. From the perspective of the watershed hydrologic cycle, these changes have resulted in adverse effects, including an increase in surface runoff, evapotranspiration, and a decrease in groundwater recharge. Coastal areas, in particular, have a greater reliance on groundwater compared to inland watershed, making water resources vulnerable to climate change. Therefore, in this study, the Soil and Water Assessment Tool (SWAT) was implemented for the An-Seong-cheon watershed (1,627 km2), which is adjacent to the coastal region in South Korea. The SWAT was calibrated and validated for runoff and evapotranspiration. The estimation of groundwater recharge was conducted based on the calibrated water balance components, the average recharge was calculated to be 21.2% for the study area. Subsequently, extreme climate change scenarios were selected, by examining the Shared Socioeconomic Pathway (SSP) scenarios derived from the Intergovernmental Panel on Climate Change's Assessment Report 6 (AR6). The extreme climate change scenarios will be applied to the SWAT model to project future changes in groundwater recharge. Ultimately, the purpose of study is to evaluate the climate change vulnerability of groundwater recharge based on land cover characteristics within the coastal watershed.

Key words: Coastal area, Climate Change, Groundwater recharge, Vulnerability Assessment, SWAT

Acknowledge

Research for this paper was carried out under the KICT Research Program (project no.20230166-001, Development of coastal groundwater management solution) funded by the Ministry of Science and ICT.

How to cite: Woo, S. Y., Chang, S. W., and Kim, M.: Vulnerability assessment of groundwater recharge under extreme climate change in coastal area watershed of South Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14589, https://doi.org/10.5194/egusphere-egu24-14589, 2024.

EGU24-15132 | ECS | PICO | HS1.1.2 | Highlight

Development of an integrated suite for estimating Intensity Duration Frequency curves in a climate change perspective  

Lisa Napolitano, Guido Rianna, Roberta Padulano, and Valentina Francalanci

This study introduces a comprehensive suite of methodologies for estimating Intensity Duration Frequency (IDF) curves, critical for engineering planning in the face of expected variations in extreme precipitations induced by climate change. Indeed, in recent years the climate proofing design of hydraulic infrastructures (e.g. sewage systems) arose increasing interest but, at the moment, there is a lack of clear understanding of the differences between approaches and the relative weight of the individual phases of the process on the final estimates (approaches to fit the statistical parameters, differences between simulation chains, variations induced by socio-economic scenarios driving climate models). To investigate such issue, four consolidated approaches to assess the potential variations induced by CC in IDF curves are compared: Padulano et al., 2018 [doi.org/10.1002/hyp.13449, QDM-CMCC], Hassanzadeh et al., 2019 [doi.org/10.1016/j.advwatres.2019.07.001; QQD], Alzahrani et al., 2022 [doi.org/10.1007/s11269-022-03265-3; EQM], Hassanzadeh et al., 2019 [doi.org/10.1016/j.advwatres.2019.07.001; SIM]. More specifically: QDM-CMCC combines a simple delta change with quantile delta mapping; the Quantile-Quantile downscaling (QQD) spatiotemporally downscales extreme rainfall quantiles through a parametric relationship; Equidistant Quantile Mapping (EQM) spatiotemporally downscales extreme rainfall quantiles using a two-step parametric procedure; Scale-Invariance Method (SIM) derives the distributions of short-duration local extreme rainfalls based on those of longer duration using the scaling relationships between non-central moments over different rainfall durations.

Precipitation values are provided by 14 climate simulation chains made available in the framework of the EURO‐CORDEX initiative; 1981-2010 is adopted as the current period while, as the future time horizon, 2036-2065 is adopted under three different Representative Concentration Pathways, RCP2.6, RCP4.5 and RCP8.5. As pilot case, the reference IDF curve adopted to design hydraulic infrastructures in the Ischia Island (30 km from Naples, Southern Italy) is used.

The investigation is aimed at exploring not only the spread among the findings returned by exploiting the different approaches in a real-world scenario but also to improve the understanding about how the theorical differences in the approaches can lead to very different estimates. Results show that the three main sources of uncertainty (statistical parameter fitting, climate modelling and RCP scenarios) play a comparable role inducing an increasingly evident spread as the return times increase.

Finally, it is worth noting that two libraries in R and Python for the four approaches, available upon request, have been developed to permit assessments over test cases in different precipitation regimes and by exploiting different climate simulation chains to replicate the findings achieved in the present investigation.

 

How to cite: Napolitano, L., Rianna, G., Padulano, R., and Francalanci, V.: Development of an integrated suite for estimating Intensity Duration Frequency curves in a climate change perspective , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15132, https://doi.org/10.5194/egusphere-egu24-15132, 2024.

This research focuses on the estimation of extreme precipitation quantiles using climate change scenario data from the 6th Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC). The study involved the analysis of precipitation data from 23 global climate models (GCMs), with a final selection of 10 models that best represented the characteristics of extreme precipitation in South Korea, based on statistical measures against observed rainfall data. Particularly, precipitation data from 71 observation points within the Chungju-Dam basin, a region of hydrological significance and susceptibility to extreme weather events, were collected for analyzing climate change impacts.

Furthermore, the study conducted the regional frequency analysis (index-flood method) to estimate rainfall quantiles, employing the Generalized Extreme Value (GEV) distribution and L-moment method for parameter estimation. The analysis resulted in the development of a multi-model ensemble (MME) incorporating the 10 selected GCMs and 4 Shared Socioeconomic Pathways (SSP) scenarios. This approach facilitated a comprehensive understanding of potential future climate changes, considering emission trajectories and socio-economic changes. Additionally, the study quantitatively evaluated the impact of climate change and associated uncertainties in the region, which is essential for devising adaptation and mitigation strategies in response to climate change conditions, particularly in areas susceptible to extreme weather events. This research provides valuable insights into the understanding of climate-induced extreme weather events and offers guidance for policymakers and environmental planners in preparing for the impacts of global climate change.

How to cite: Kim, S. and Heo, J.-H.: Assessment of extreme precipitation risks using multi-model climate projections: focusing on the Chungju-Dam basin in South Korea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16120, https://doi.org/10.5194/egusphere-egu24-16120, 2024.

EGU24-16155 | ECS | PICO | HS1.1.2 | Highlight

Effect of irrigation on joint evolution of water resources and hydroclimate variables under climate change 

Pedro Arboleda, Agnès Ducharne, Pierre Tiengou, and Frédérique Cheruy

Irrigation is one of the main human landscape management activity, and has seen a dramatic increase during the XXth century, with a direct local increasing effect on soil moisture (SM) and evapotranspiration (ET). To sustain the increase of ET, irrigation withdraws water from rivers and groundwater reservoirs. As a result, irrigation activities have a direct impact on water and energy balance, and drive the evolution of ET under the ongoing climate change in intensively irrigated regions. On the other hand, irrigation induces feedbacks from the atmosphere, that includes changes in precipitation patterns, air temperature cooling and changes in energy-related variables. Moreover, future climate change will complexify these interactions, and it is not clear what would be the future implications of irrigation activities in water resources management and key hydroclimate variables.

To assess the joint evolution of irrigation, water resources and hydroclimate variables, we use an irrigation scheme that was recently evaluated in ORCHIDEE, the land surface component of the IPSL climate model. This scheme calculates water demand based on a soil moisture deficit approach, and restrains water supply to water available in small and large rivers and in groundwater, considering the facility to access the water source and an environmental volume for ecosystems. To assess the effect of irrigation on water resources and climate, we use two transient coupled simulations at global scale, for the period 1950-2100, under SSP5-RCP8.5 scenario to have a strong climate change signal during the future period. One of the simulations runs with the irrigation scheme activated, while the second one runs without irrigation.

Preliminary results at global scale show that irrigation will increase under the chosen scenario, due to the prescribed increase of the irrigated surface from scenario SSP5-RCP8.5 and a warmer climate. This increase will counteract part of the increasing trend of groundwater storage and will complexify the evolution of river storage in irrigated areas. On the other hand, it will enhance the increase of ET at global scale. We will extend our analysis to water and energy-related variables, including key climate variables like precipitation and air temperature, at different seasons and regions. We will also focus our analysis in some intensively irrigated areas, to assess the causes of possible water supply shortages in irrigation activities. These results should help to understand future implications of irrigation in water resources management in irrigated areas, and also effects in non-irrigated zones via remote land-atmosphere feedbacks.

How to cite: Arboleda, P., Ducharne, A., Tiengou, P., and Cheruy, F.: Effect of irrigation on joint evolution of water resources and hydroclimate variables under climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16155, https://doi.org/10.5194/egusphere-egu24-16155, 2024.

EGU24-16654 | ECS | PICO | HS1.1.2

Understanding Changes in Iceland’s Streamflow Dynamics in Response to Climate Change 

Hörður Bragi Helgason, Andri Gunnarsson, Óli Grétar B. Sveinsson, and Bart Nijssen

Anthropogenic climate change is profoundly altering the hydrological cycle in high-latitude regions. Iceland, with its abundant hydrological and glaciological data, provides a unique opportunity to study the effects of climate change on streamflow in snow- and glacier melt dominated catchments. The country's reliance on hydropower, as the top electricity producer per capita globally, highlights the critical need for understanding these changes.

In Iceland, the average temperature has risen significantly in recent decades, outpacing the global warming trend. Despite this warming, increased precipitation has led to more extensive snow cover and depth in some regions. Glaciers have experienced a loss in area and mass, soil temperatures have risen, and vegetation has increased. However, the impacts of these environmental shifts on streamflow remain largely unexplored.

Our study utilizes the newly released LamaH-Ice dataset, encompassing streamflow observations from mainly undisturbed watersheds, atmospheric forcings from climate reanalyses and catchment characteristics, to investigate Iceland's streamflow dynamics changes over recent decades. We analyze annual, seasonal, and monthly streamflow volumes, spring freshet timing, and extreme flow events, correlating these changes with environmental conditions and catchment attributes.

The results suggest that streamflow regime alterations are influenced by multiple factors, including geographic location, topography, and river type. The findings offer crucial insights into Iceland's hydrological changes amid rapid climatic shifts, with broader implications for reservoir operations and water resource management. This study not only enhances our understanding of Icelandic hydrology but also contributes to global knowledge on climate-induced hydrological changes.

How to cite: Helgason, H. B., Gunnarsson, A., Sveinsson, Ó. G. B., and Nijssen, B.: Understanding Changes in Iceland’s Streamflow Dynamics in Response to Climate Change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16654, https://doi.org/10.5194/egusphere-egu24-16654, 2024.

In order to alleviate the problem of water scarcity, adapt to and mitigate the negative impact of climate change on water resources, large-scale infrastructure projects have been built worldwide. In addition to bringing huge social benefits, reservoirs may also affect meteorological conditions near the surface and mesoscale or weather scale processes. A high-quality meteorological dataset is an important foundation for understanding climate change. Considering the complexity of the underlying surface in the Three Gorges Reservoir region, this study uses CLDAS multi-source fusion grid meteorological data to study the characteristics of changes in the Three Gorges Reservoir before and after water storage. Select four elements: temperature, precipitation, wind speed, and relative humidity, and analyze the climate effects before and after the Three Gorges Reservoir from different time scales such as year, season, and day. Based on the analysis of CLDAS multi-source fusion data, it is shown that for the average temperature, after the water storage, except for the areas along the southern side of the Yangtze River where the temperature is lower than before the water storage, most other areas are higher. On an annual scale, there is not much difference in average temperature before and after water storage. The average temperature effect in the Three Gorges region after water storage varies at different time periods. During the subsidence period and high water level period, it shows an overall warming effect, with an average temperature increase of 0.1 ℃ and 0.3 ℃, respectively. However, during the flood season and water storage period, it shows a cooling effect, with an average temperature decrease of 0.2 ℃ and 0.9 ℃, respectively. The cooling effect is more pronounced during the water storage period. After water storage, it shows an increase in temperature during the day and a decrease in temperature at night. For annual precipitation, except for some areas in the east, northwest, and central regions where precipitation has decreased, most of the remaining areas of the Three Gorges generally have more precipitation than before the water storage. At the annual scale and different time periods, the precipitation in the Three Gorges area is higher after the water storage than before, and on the annual scale, the precipitation after the water storage increases by 8.8% compared to before the water storage; During the subsidence period, flood season, storage period, and high water level period, the precipitation after storage increased by 10.2%, 1.3%, 21.7%, and 32.2% respectively compared to before storage. The precipitation during the high water level period after storage changed the most, while the precipitation during the flood season changed the least.

How to cite: Wang, Q., Chen, X., and Li, W.: Assessment of Climate Effects in the Three Gorges Reservoir Based on Multi-source Fusion Data CLDAS, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17866, https://doi.org/10.5194/egusphere-egu24-17866, 2024.

The intensification of the water cycle over recent decades has produced changes in hydrologic extremes (floods and droughts) unevenly across the globe and the U.S. is not an exception. This has led to increased interest in coordination amongst federal agencies within the U.S. to improve readiness to respond to and mitigate the effects of these extreme events as well as for the U.S. to increase coordination with our international partners, as evidenced by a recent Quadrilateral Security Dialogue between the U.S., Japan, Australia, and India on extreme precipitation and its effects on water quality, inundation, and flooding. As the nation’s unbiased resource for land-surface information, the U.S. Geological Survey has responded by developing a set of interpretative studies and related datasets to understand changes in floods and droughts, the potential drivers of these changes, and strategies for updating frequency-based statistics for hydrological extremes. This presentation and discussion will highlight recent advancements in data and interpretation on hydrologic extremes as well as the detection of changes in, attribution of, and adjustment for observed changes.

How to cite: Archfield, S.:  U.S. Geological Survey datasets of hydrological extremes and their drivers to enhance security and improve understanding, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21007, https://doi.org/10.5194/egusphere-egu24-21007, 2024.

EGU24-21009 | ECS | PICO | HS1.1.2

Can Trend Tests Detect Changes in Design-Flood Quantiles under Changing Climate? 

Chandramauli Awasthi, Stacey A. Archfield, Brian J. Reich, and Sankarasubramanian Arumugam

To estimate design-flood quantiles, such as the 100-year flood, the observed annual maximum flood (AMF) series is fitted to a probability distribution and then the design flood quantile is estimated from the fitted distribution. This is because, in most cases, historical records are not long enough to observe rare, design-flood events. Changes in the AMF series, which are usually detected using simple trend tests (e.g., Mann-Kendall test (MKT)), are hypothesized to result in changes in  design-flood estimates. This hypothesis is tested by using an alternate framework to detect significant changes in design-flood between two periods – rather than changes in the AMF series – and then evaluated using synthetically generated AMF series from the Log-Pearson Type-3 (LP3) distribution due to changes in moments associated with flood distribution. Synthetic experiments show that the MKT does not consider changes in all three moments of the LP3 distribution and incorrectly detects changes in design-flood. We applied the framework on 31 river basins spread across the United States. Statistically significant changes in design-flood quantiles were observed even without a significant trend in the AMF series and basins with statistically significant trends did not necessarily exhibit statistically significant changes in design-flood. If changes to design-flood quantiles are of interest, this framework can be useful rather than simple trend tests on the AMF series which may or may not indicate changes in the design-flood quantiles have occurred. We are now extending the application of the developed framework to mixed population scenarios where floods are generated from more than one causal mechanism under the hypothesis that two more causal mechanisms result in statistically different design-flood quantile estimates at the same river.

How to cite: Awasthi, C., Archfield, S. A., Reich, B. J., and Arumugam, S.: Can Trend Tests Detect Changes in Design-Flood Quantiles under Changing Climate?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21009, https://doi.org/10.5194/egusphere-egu24-21009, 2024.

A representative example of how extreme rainfall events caused by climate change can be directly recognized is the increase of property damage due to urban flood. This surge in urban flood damage is not merely corresponding to an augmentation in probable rainfall depth but rather a result of urbanization with densely populated and concentrated flooding. Despite this circumstance, we have mostly revolved around increasing the return period, primarily focusing on the augmentation of probable rainfall depth to mitigate the flood damage by climate change. In terms of the temporal distribution of design rainfall, conventional methods such as the Huff method and alternating blocking method are still in use; however, they cannot accurately capture the real rainfall distribution. In this context, we investigate the viability of enhancing design standards by adjusting the temporal distribution of design rainfall without artificially inflating a return period for design. To achieve that, it is necessary to understand the impact of temporal rainfall distribution on the design flood.

We generate 449 dimensionless time-rainfall distributions for short-term(less than 6 hours) and 5,789 for long-term(6 hours or more) durations considering rainfall data from both meteorological observations by the Korea Meteorological Administration and d4PDF(Data for Policy Decision Making for Future) scenarios. Based on these distributions, total 25,860 hyetographs are synthesized for five rainfall durations. We repeatedly estimated the design flood using a rainfall-runoff model, revealing that the peak discharges varied up to 10 times depending on the time-rainfall distribution. Considering that increasing the return period from 50 years to 100 years generally results in only a 10% rise in probable rainfall depths, adjusting the temporal distribution of design rainfall provides a more adaptable approach to increasing design floods. These outcomes have the potential to broaden the perspective for applications of rainfall scenarios in data-based model or establishing the design flood standards.

 

Acknowledgement: This research was supported by a grant(2022-MOIS61-002(RS-2022-ND 634021)) of ‘Development Risk Prediction Technology of Storm and Flood for Climate Change based on Artificial Intelligence’ funded by Ministry of Interior and Safety(MOIS, Korea).

How to cite: Kim, J. and Hwang, S.: Considering temporal distribution of design rainfall for enhancing urban flood resilience in response to climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-45, https://doi.org/10.5194/egusphere-egu24-45, 2024.

EGU24-1677 | ECS | Orals | HS1.1.3

Evaluating the performance of Blue and Green Infrastructures in an urban area through a fine-scale water balance model 

Xuan Wu, Sotirios Moustakas, Nejc Bezak, Matej Radinja, Mark Bryan Alivio, Matjaž Mikoš, Michal Dohnal, Vojtech Bares, and Patrick Willems

Due to climate change and urbanization, increased extreme weather events and impervious urban surfaces have increased flood and drought risks. Blue and Green Infrastructures (BGIs) that can enhance stormwater management can help mitigate these negative effects. Nevertheless, the long-term performance of BGIs in an urban environment still requires further investigation. For this purpose, a fine-scale hydrological model and long-term water balance analysis are necessary. Accordingly, the first objective of this study is to develop a fine-scale water balance model that simulates runoff formation and propagation and incorporates BGIs. The second objective is to perform a long-term water balance analysis to determine the effectiveness of BGIs in mitigating urban floods and droughts.

The proposed water balance model is developed in Python. Model inputs include meteorological data such as rainfall and evapotranspiration, and catchment characteristics such as land use and pipe networks. This model divides the catchment into underground pipe reservoirs and surface reservoirs based on land use. All reservoirs are then connected by upstream and downstream relationships according to topological information. BGIs can be implemented by altering the properties of the reservoirs where they are proposed. To calculate the generated runoff, the continuous Soil Conservation Service Curve Number (SCS-CN) method is used in permeable reservoirs with infiltration capability, whereas the single-bucket approach is employed in impermeable reservoirs. The continuous CN method utilizes a dynamic CN and accounts for the recovery of initial abstraction between storms. In the single-bucket approach, all impermeable reservoirs are assumed to have inputs, outputs, and a certain amount of storage capacity. Rainfall and inflow from upstream reservoirs can be considered inputs, while discharge to downstream reservoirs and reuse for rain tanks can be considered outputs. These two rainfall-runoff calculation methods are validated by using monitoring data provided by the Czech Technical University in Prague and the University of Ljubljana, respectively, on green roofs and an urban park. After calculating runoff, the linear reservoir function is used as the runoff routing approach to simulate stormwater propagation according to reservoir connection relationships. Following the above processes, the water balance for the catchment can be analyzed, accounting for evapotranspiration, infiltration, reuse, overflow, and discharge at the catchment outlet.

The case study is done for the campus “Arenberg III” at the University of Leuven (KU Leuven) in Belgium. Three BGIs are proposed: permeable pavements, rain tanks and green roofs. Then five BGI scenarios are developed to evaluate the effectiveness of both single BGIs and combined BGIs: (1) campus without new BGIs, (2) every building has a green roof, (3) each building has a rain tank, (4) replacing impermeable parking lots with permeable pavements, and (5) all the BGIs listed above are implemented. The long-term water balance analysis is performed for the period 2010-2019. Initial results show that the combined BGIs scenario (5) yields the best results, as it can significantly reduce runoff and overflow, as well as provide substantial rainwater reuse and infiltration. Therefore, combining BGIs with different functions can be effective in mitigating both urban floods and droughts.

How to cite: Wu, X., Moustakas, S., Bezak, N., Radinja, M., Alivio, M. B., Mikoš, M., Dohnal, M., Bares, V., and Willems, P.: Evaluating the performance of Blue and Green Infrastructures in an urban area through a fine-scale water balance model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1677, https://doi.org/10.5194/egusphere-egu24-1677, 2024.

EGU24-2114 | ECS | Orals | HS1.1.3

Development of a water storage toolbox for surface-induced near-nature managed groundwater recharge 

Jan Stautzebach, Jörg Steidl, and Christoph Merz

Water stress is increasing in Northeast Germany due to climate change. New approaches for water management are needed to mitigate the impacts on the water resources. Therefore, our study deals with the development of a web-based toolbox to manage subsurface water storage by artificial groundwater recharge with focus on the lower catchment of the river Spree in the federal state of Brandenburg.

Our approach is based on a systematic combination of site selection criteria and spatial data on land use, soil, groundwater and potential water sources. The aim is to provide relevant information for the preliminary planning of managed groundwater recharge measures by authorities and water suppliers. This includes a wide range of project scales that can be covered by the tool. However, as necessary volumes for large scale recharge projects are unlikely to be found in concentrated form, small scale projects with low demand of infrastructure and energy, are of main concern. Considering surpluses from runoff and surface waters, also caused by extreme weather events, suitable locations for surface-induced recharge will be identified. Thereby, solutions with low environmental impact, like the use of natural depressions for recharge, are highlighted to the user. This will allow for a stabilization of the local water balance, induced by a large number of low impact measures.

Supported by additional modelling-based indications for implementation, efficiency and costs, as well as simplified site selection through a query system, the toolbox will offer an initial knowledge for such planning considerations.

How to cite: Stautzebach, J., Steidl, J., and Merz, C.: Development of a water storage toolbox for surface-induced near-nature managed groundwater recharge, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2114, https://doi.org/10.5194/egusphere-egu24-2114, 2024.

EGU24-2557 | ECS | Posters on site | HS1.1.3

Advancing water resource resilience through agroforestry 

Siham El Garroussi, Fredrik Wetterhall, Christopher Barnard, Francesca Di Giuseppe, and Cinzia Mazzetti

Future climate change is expected to exacerbate hydrological drought in many parts of Europe, making effective management of water resources more imperative to ensure groundwater sustainability. The EU biodiversity strategy for 2030 suggests a strategic target to turn at least 10% of the EU’s agricultural areas into high-diversity landscape features like hedges and trees. 
In this study, we investigate how afforestation would affect hydrological conditions in Europe under climate change, focusing on three scenarios: (1) an hypothetical extreme scenario transforming all agricultural land into forests under current climate, (2) a more realistic scenario aligning with the EU biodiversity strategy which envisages converting 10% of the land under current climate, and (3) a scenario involving the conversion of 10% of agricultural land into forests, but under a climate that is 2°C warmer. 
We use the LISFLOOD hydrological model setup across Europe at a spatial resolution of ~2km forced by gridded observed precipitation and temperature over a time period of 1991-2020 under the current climate scenario. The results were evaluated as changes in evapotranspiration, groundwater levels, and river discharge peaks. The findings from the afforestation scenario indicated a rise in evapotranspiration, higher groundwater levels, and diminished river flow peaks, suggesting an improvement in water sustainability as well as an increased resilience to flooding. This study highlights the hydrological benefits of strategic land use changes, offering key insights for European water resource management and policy formulation in the face of climate change.

How to cite: El Garroussi, S., Wetterhall, F., Barnard, C., Di Giuseppe, F., and Mazzetti, C.: Advancing water resource resilience through agroforestry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2557, https://doi.org/10.5194/egusphere-egu24-2557, 2024.

EGU24-4675 | ECS | Orals | HS1.1.3

Modelling the impact of beaver dams on hydrological extremes following the re-introduction of beavers in England  

Benjamin Jackson, Alan Puttock, Diego Panici, and Richard Brazier

The Eurasian beaver (Castor fiber) is being reintroduced to Great Britain after an absence of ~400 years. Beavers are well known for their considerable engineering capabilities. Given the right conditions, beavers construct dams, excavate channels and maintain wetlands. These changes have been demonstrated to have a significant impact upon hydrological extremes in the English environment. There is the potential for beaver re-introduction to have a transformative impact as a widespread nature-based solution (NBS). However, there is a need for policy and management relevant understanding at a national level.

Funded by the Environment Agency in England, the aim of this study was to use a modelling approach to be able to estimate how catchments in England may respond to extreme events following the re-introduction of beavers. To accomplish this, we have applied the 2D version of the hydraulic model HEC-RAS to sites across England. Sites were selected that had the potential for beavers to construct dams.

Beaver dams are represented within HEC-RAS by digitising a series of weirs intersected by culverts, allowing water to leak through the dam as well as overtopping the weir. To account for uncertainty in dam properties, we configured the model to simulate different configurations of dam height, as well as the “leakiness” of each dam.

Using the approach described, HEC-RAS was used to simulate the impact of hypothetical beaver dams on storm events of different magnitudes in addition to low flow scenarios. Results suggest that the impact of beaver dam sequences on hydrology is highly dependent on channel and floodplain topography.

We were then able to apply these results to produce an estimation of the impact of beavers on flow regimes at any river stretch in England. This was estimated for three scenarios with high, moderate and low presence of beavers across England. It is hoped that these modelling tools can be used to strategically determine where and how beavers may be able to provide a hydrological NBS and where supporting their wetland creation could be most valuable.

How to cite: Jackson, B., Puttock, A., Panici, D., and Brazier, R.: Modelling the impact of beaver dams on hydrological extremes following the re-introduction of beavers in England , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4675, https://doi.org/10.5194/egusphere-egu24-4675, 2024.

EGU24-5054 | Orals | HS1.1.3

Coupling stormwater protection and aquifer recharge 

Thomas Baumann and Lea Augustin

Stormwater in small catchments is a threat to agricultural land use and civilization. Increasing ambient temperatures increase the risks for severe rainfall and surface runoff and reduce the amount of groundwater recharge. At the same time, the demand for irrigation water is rising. This development calls for integrated strategies for stormwater protection and aquifer recharge.

In this contribution, we present a case study for a technical solution to infiltrate stormwater into the local aquifer. The site is located in an area well known for hop cultivation. The aquifers are located in tertiary sediments, which are covered with loess and are sometimes semi-confined. Hydraulic conductivities are in the 10-4 m/s range, and specific storage coefficients are between 10-6 (confined) and 0.2 (unconfined). Current stormwater protection plans include retention basins with a capacity of 5500 m³, not all of them fully functional, and flooding events were recorded two times per year. Demand for irrigation was 64 mm for the past five years, with peaks of 118 mm in 2022. Even if only the extreme rainfall events would be recharged into the aquifer, an area of 5-10 ha could be irrigated from the infiltrated water, assuming one extreme event. This is a significant amount of the area (15%) used for hop cultivation around the storage site.

Specific challenges at this site are the flood dynamics, the uncontrolled surface runoff, which brings a lot of fines, and the water quality with regard to fertilizers and pesticides. This requires small settling ponds or intermediate storage facilities and adsorbers. Most of the used products, however, have a medium to strong tendency to adsorb on organic carbon and even inorganic materials. The hydrogeological model indicates that the flood water can be infiltrated at high volumetric flow rates without risking upwelling groundwater tables. A detailed site investigation will be completed by mid-2024.

How to cite: Baumann, T. and Augustin, L.: Coupling stormwater protection and aquifer recharge, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5054, https://doi.org/10.5194/egusphere-egu24-5054, 2024.

EGU24-5105 | ECS | Orals | HS1.1.3

Revealing the role of Nature-based Solutions as drought adaptation strategies 

Claudia Bertini, Muhammad Haris Ali, Andreja Jonoski, Ioana Popescu, and Schalk Jan van Andel

Climate change has caused an increase in the frequency of hydrometeorological extremes world-wide, opening new challenges for decision makers and stakeholders in managing and regulating water. Among the adaptation strategies available, Nature-based Solutions (NBSs) gained increasing attention in recent years, because of their efficiency in reducing hydrometeorological risks while also providing additional benefits for biodiversity, landscape and society. Despite the ever-increasing interest for NBSs, many stakeholders still doubt their potential, as the quantitative effects of NBSs over long periods of time are still to be assessed.

In this research, we show how several types of NBSs, such as wetlands restoration, infiltration ponds, ditch blocking and others, can be used to adapt to drought conditions under the future climate projections. We use as a pilot case the transboundary Aa of Weerijs catchment, shared between Belgium and the Netherlands, which recently became drought-prone. We develop a fully distributed coupled MIKE SHE-MIKE 11 model to mimic the hydrological behaviour of the catchment in present (2010-2019) and future climate conditions (2050-2059, scenario KNMI ‘23). The same hydrological model is then used to test the effectiveness of different drought adaptation measures, based on single type or combinations of NBSs. To quantify the impacts of the chosen strategies to adapt to drought conditions and in consultation with some local stakeholders, we define a set of Key Performance Indicators (KPIs) that provide tangible results for stakeholders and decision makers. Finally, we show the results of the different adaptation strategies implemented on a web-app, which can be accessed and used by decision makers and stakeholders as an aid tool to select the best adaption strategy.

This research has been developed within the project EIFFEL (Revealing the role of GEOSS as the default digital portal for building climate change adaptation and mitigation applications, https://www.eiffel4climate.eu/), funded by European Union’s Horizon 2020 research and innovation programme under Grant Agreement Νο 101003518.

How to cite: Bertini, C., Ali, M. H., Jonoski, A., Popescu, I., and van Andel, S. J.: Revealing the role of Nature-based Solutions as drought adaptation strategies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5105, https://doi.org/10.5194/egusphere-egu24-5105, 2024.

EGU24-5423 | Posters on site | HS1.1.3

Enhancing groundwater recharge in face of hydrological extremes: assessment of stormwater managed aquifer recharge potential in Flemish drinking water protection zones (Belgium) 

Lara Speijer, Simon Six, Bas van der Grift, Gijsbert Cirkel, Goedele Verreydt, Jef Dams, and Marijke Huysmans

Flanders (Belgium) is expected to experience more severe drought and flooding events in face of climate change. Infiltration to increase groundwater recharge is therefore adopted as policy strategy to deal with both hydrological extremes. Stormwater provides an interesting water source for managed aquifer recharge, given the high urbanization and imperviousness level of the region. Furthermore, the historical ban on infiltration in groundwater protection zones for drinking water production has been removed to encourage infiltration practices. This could potentially enhance groundwater recharge in the groundwater abstraction zones, but concerns remain regarding the impacts on groundwater quality due to the potential contamination of stormwater with a wide range of pollutants originating from traffic, building materials, weed control and other more diffuse sources.

Therefore, tools need to be developed to weigh out benefits of groundwater replenishment relative to potential groundwater quality risks. This research aims to contribute to the knowledge on the hydrological aspects of this quantity-quality balancing exercise by investigating the potential of stormwater managed aquifer recharge to replenish the groundwater system in Flemish groundwater protection zones. For this, potential stormwater volumes that could supply managed aquifer recharge are calculated and compared to the actual groundwater recharge and pumping volumes for drinking water production to assess the significance of this practice in protection zones.

Results indicate a variable, but high stormwater infiltration potential in Flemish protection zones, providing up to 29% extra groundwater recharge in all protection zones combined. Furthermore, this practice could compensate up to 32% of abstracted phreatic drinking water volumes. Locally, the potential can be higher, reaching 100% in protection zones located in highly urbanized areas, including zones around the city of Leuven. Stormwater infiltration can therefore be considered as an important drought adaptation measure in Flemish protection zones, given the same order of magnitude of stormwater and pumping volumes in these areas. However, recent studies raise concern on the occurrence of organic micropollutants in stormwater and data in the Dutch and Flemish setting is insufficient. Therefore, additional research on occurrence and fate of these substances is needed.

How to cite: Speijer, L., Six, S., van der Grift, B., Cirkel, G., Verreydt, G., Dams, J., and Huysmans, M.: Enhancing groundwater recharge in face of hydrological extremes: assessment of stormwater managed aquifer recharge potential in Flemish drinking water protection zones (Belgium), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5423, https://doi.org/10.5194/egusphere-egu24-5423, 2024.

EGU24-5542 | ECS | Orals | HS1.1.3

Is drought protection possible without compromising flood protection? Estimating the maximum dual-use benefit of flood reservoirs in Southwest Germany 

Sarah Ho, Chantal Kipp, Hans Goeppert, Johannes Hoefer, Frank Seidel, and Uwe Ehret

As climate change drives intensification and increased frequency of hydrological extremes, the need to balance drought resilience and flood protection becomes critical for proper water resources management. Recent extreme droughts in the last decade in Germany have caused significant damages to ecosystems and human society, prompting renewed interest in sustainable water resources management. At the same time, protection from floods such as the catastrophic 2021 event in the Ahr Valley remain heavy in the public conscience. In the state of Baden-Württemberg in Southwestern Germany alone, over 600 small (< 1 million m3) to medium-sized (1-10 million m3) reservoirs are currently operated for flood protection. In this study, we investigate optimal reservoir operating (storage and release) rules in a dual flood-drought protection scheme for selected modeled flood reservoirs in Baden-Württemberg. Daily target releases for drought protection are proposed based on modeled inflows from the calibrated hydrological model LARSIM. In a first step, the reservoir operation is optimized in a scenario of perfect knowledge of the future by using  meteorological observations as artificial weather forecasts in LARSM. The results of different operating rules are then evaluated based on their adherence to the target releases and flood protection performance. Rulesets that result in worsened flood protection relative to the current (flood-only) operation were eliminated as potential operation schemes. Based on provisional results, we will present and discuss the maximum potential benefit of adapting and retrofitting existing flood reservoirs for drought water storage.

How to cite: Ho, S., Kipp, C., Goeppert, H., Hoefer, J., Seidel, F., and Ehret, U.: Is drought protection possible without compromising flood protection? Estimating the maximum dual-use benefit of flood reservoirs in Southwest Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5542, https://doi.org/10.5194/egusphere-egu24-5542, 2024.

EGU24-6391 | Orals | HS1.1.3

Enhancing Flood Resilience: Geomorphological Insights into Lowland Riverscapes for Nature-Based Solutions 

Inci Güneralp, Mahbub Hasan, Rakibul Ahasan, Billy Hales, and Anthony Filippi

Aimed at achieving environmentally and economically smart growth in lowland riverscapes in the face of exacerbating flood threats, the elements of natural riverscapes, such as floodplain landforms, riparian forests, and wetlands can provide solutions to flood risk reduction. Geomorphological knowledge is crucial to working effectively with river processes and landforms in addressing flood hazards. In addition to unique landforms and habitats that can support flood mitigation, landscape-level geomorphological characteristics, such as geomorphological heterogeneity and connectivity, can also impact the attenuation and retention of downstream fluxes of water, sediment, and other materials, and thus resistance and resilience to floods. In this study, we employ a geomorphological approach to delineate the natural elements of lowland riverscapes as geomorphological habitats to assess their susceptibility to floods and erosion/sedimentation as well as their capacity to alleviate the negative impacts of floods. To delineate geomorphological habitats, we utilize a range of classification approaches and geospatial data including LiDAR-derived digital terrain models, airborne and satellite images, raster/vector data on vegetation, soils, and land-cover land-use. We then quantify the diversity, heterogeneity, and connectivity of delineated habitats using landscape ecological approaches and in the context of flood impacts and mitigation. Our geomorphological approach to riverscape characterization provides new insights on fundamental knowledge of natural elements as geomorphological habitats and their interconnections and interdependencies. This new knowledge has a high potential for developing geomorphologically derived nature-based solutions to flood management and enhancing flood resilience of lowland riverscapes.

How to cite: Güneralp, I., Hasan, M., Ahasan, R., Hales, B., and Filippi, A.: Enhancing Flood Resilience: Geomorphological Insights into Lowland Riverscapes for Nature-Based Solutions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6391, https://doi.org/10.5194/egusphere-egu24-6391, 2024.

Water is an essential natural resource for human survival and development. In recent years, global climate change has led to noticeable shifts in rainfall patterns. In Taiwan, the gap between wet and dry years has gradually widened, and rainfall has become shorter in duration but more intense. This has increased the frequency of spring droughts in Taiwan. Hence, there is an urgent need to propose a new water utilization model.

The bucket model is employed to estimate parameters that are challenging to measure, while Bayesian networks are utilized to establish causal relationships among environmental factors. In addition, Bayesian Network is a systematic network based on conditional probability for constructing relationships between factors. It has been shown to capture crucial groundwater flow properties and uncertainties in groundwater systems. This study seeks to alter the previous management strategy, which prioritized the use of surface water during the rainy season. Consequently, two distinct theoretical models were established for comparison. Model 1 gives precedence to surface water usage, whereas Model 2 prioritizes groundwater usage. Compare the remaining water in surface and groundwater before the next rainy season. The results indicate that, under 'high' conditions, the capacity of groundwater and surface water in Model 2 will be 18% greater than in Model 1. This is attributed to groundwater resources flowing to the surface or serving as a source of submarine groundwater discharge due to saturated aquifers. Additionally, Bayesian networks were employed to conduct a sensitivity analysis of factors. The two most influential factors on the target node are rainfall and groundwater inflow and outflow from the outside area.

How to cite: Lai, C. C. and Lin, Y. C.: Conjunctive management strategies of groundwater and surface Water: a case study of meinong reservoir in Taiwan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7123, https://doi.org/10.5194/egusphere-egu24-7123, 2024.

EGU24-7837 | ECS | Orals | HS1.1.3

Study of Nature-Based Solutions for the Huang River Watershed 

Guan-Yu Lin, Kuo-Wei Liao, Pohsaun Lin, Kai-Lun Wei, and Tsungyu Hsieh

In response to the increasingly complex challenges faced by our environment and society, there's a paradigm shift in flood management practices within the field of hydraulic engineering. Traditional approaches using gray infrastructure are giving way to Nature-based Solutions (NbS), which prioritize sustainability and ecosystem-based approaches. Despite widespread discussions about NbS potential, there's a lack of a clear framework for its application and evaluation. This paper aims to apply Nature-based Solutions (NbS) measures for the Huang River Watershed, located in northern Taiwan. A clear process for planning and assessing the benefits of NbS is established while providing relevant case studies as demonstrations. The planning process thoroughly considers the opinions of stakeholders. To evaluate the effectiveness of the implemented measures, several methods such as hydraulic modeling using HEC-RAS 2D, ecosystem service assessment via Integrate Valuation of Ecosystem Services and Tradeoffs (InVEST), and flood risk analysis through reliability analysis are adopted. Results shown that the designed wetland can reduce the flooded area downstream of the Huang River by 9.86% for a 50-year flood and by 3.95% for a 2-year flood; the designed wetland will increase carbon storage by 75.74% and reduce soil erosion by 50.77%, while habitat quality will be maintained at a similar level and the probability of flooding reduces to 3%. By leveraging the above assessment methods, this study can bridge the gap between engineering and ecological conservation fields via demonstrating the benefits of NbS implementation. The outcomes of this research are intended to serve as a valuable reference for future studies and inform decision-making processes related to similar projects.

How to cite: Lin, G.-Y., Liao, K.-W., Lin, P., Wei, K.-L., and Hsieh, T.: Study of Nature-Based Solutions for the Huang River Watershed, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7837, https://doi.org/10.5194/egusphere-egu24-7837, 2024.

EGU24-9875 | ECS | Posters on site | HS1.1.3

Dewatering and Treatment of Domestic Sewage Sludge Using Constructed Reed Bed  

Tahra Al-Rashdi

Sultanate of Oman produces a high volume of wastewater on a daily basis. Since conventional / mechanical wastewater treatment methods are mostly used in the country, a respectively high volume of sludge by-product is also generated daily. Sludge is defined as a mixture of water, organic matter and inorganic matter resulting from the biological treatment of wastewater. Oman manages the generation of sludge by discharging about 84% of it in the landfills, especially the Sewage Treatment Plants (STPs) located outside the capital city of the country (Muscat Governorate), while about 16% of produced sludge is collected by Oman Water and Wastewater Services company and is further processed through composting to produce a fertilizer (‘Kala’ brand name).

For these reasons, revolutionary and cost-effective means and ways are needed to manage the sludge for environmentally friendly sound disposal and reuse. One of the promising and state-of-the-art sustainable technologies is the constructed wetland technology for dewatering and stabilization of sludge. The Sludge Treatment Wetland (STW) system depends on the type of substrate, type of plants and microbial communities that play an important role in the treatment and dewatering of the sludge. In addition, it contributes to the decentralized management of sludge, a parameter that is crucial for small and medium STPs.

This study focuses on the construction of STWs, i.e., vertical flow constructed wetland designed for sludge dewatering, using local common reed plants (Phragmites Australis) to treat activated sludge from Alseeb STP. A pilot scale experiment was conducted in an agricultural experiment station. This study is the first one in Oman and across the Arabic peninsula that tests the STW technology. The study consisted of 18 mesocosms tanks. Each tank has dimensions of 89 cm in height and 0.5 m² surface area. The freeboard in each tank was 54 cm above the top gravel layer. The units are filled with substrate media from top to bottom: 15 cm fine gravel (2-6 mm), 15 cm medium gravel (15-25 mm) 5 cm and drainage layer of cobbles (40-60mm). Two plastic tubes extending vertically with an open top are embedded in the bottom of each unit. The various units have different construction and operation parameters such as planted and unplanted beds (i.e., presence and absence of plants) and three different sludge loading rates (SLR; 75, 100, 125 kg/m²/year).

The results showed the dewatering efficiency reached 97% for the planted STWs compared to 91% for the unplanted beds. The total solids content in the dewatered sludge for the three SLRs (75, 100 and 125 m²/kg/year) were between 23 -56%, 16-57% and 11-42%, respectively. These first results demonstrate that a high total solid content in the dewatered sludge can be achieved even at a relatively high SLR of 100 m²/kg/year after almost 2 years of operation. This means that the dry content can be further increased in the final resting phase that is going to be applied before the emptying of the biosolids from the units.

How to cite: Al-Rashdi, T.: Dewatering and Treatment of Domestic Sewage Sludge Using Constructed Reed Bed , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9875, https://doi.org/10.5194/egusphere-egu24-9875, 2024.

Droughts are classified as the most expensive climate disasters as they leave long-term and chronic impacts on the ecosystem, agriculture, and human society. The frequency, intensity, and duration of drought events have shown a historical increase and are projected to escalate globally, continentally, and regionally in the future. Nature-based solutions (NBS) are highlighted as effective solutions to cope with the future impacts of these events. Until now, there has been a lack of a comprehensive suitability mapping framework that considers drought-specific criteria. To address this gap, a novel framework is introduced, targeting the identification of suitable areas for two drought-mitigating NBS types—detention basins and managed aquifer recharge—on a regional scale. 

This new framework incorporates diverse criteria to specifically address drought conditions. For example, by incorporating climate change scenarios for both surface and groundwater, it identifies suitable and sustainable locations capable of managing extreme drought events. Executed through Boolean logic at a regional scale in Flanders (Belgium), the framework's strict approach yields significant potential areas for detention basins (298.7 km²) and managed aquifer recharge (867.5 km²). Incorporating multi-criteria decision-making (MCDM) with the same criteria introduces a higher degree of flexibility for decision-makers. This approach shows a notable expansion across Flanders, varying with the level of suitability. The results underscore the highly suitable potential for detention basins (2840.2 km²) and managed aquifer recharge (2538,7 km²), emphasizing the adaptability and scalability of the framework for addressing drought in the region.

How to cite: De Trift, L. and Yimer, E. A.: Framework for identifying large-scale Nature-Based Solutions for drought mitigation: regional application in Flanders , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10085, https://doi.org/10.5194/egusphere-egu24-10085, 2024.

Combining flood dams with aquifer recharge may enhance water resource sustainability, flood protection and drought prevention. In an off-stream reservoir with a high seepage rate, some of the stored surface water can infiltrate into the aquifer. The recharged water can later supplement the water released from the reservoir to fulfill the requested water demand. In such cases, optimal reservoir management requires consideration of the leakage losses (aquifer recharge rate). In this study, a methodology, based on the combination of a calibrated numerical groundwater flow model (MODFLOW, Harbaugh et al., 2017) for simulating reservoir-aquifer interaction, and an optimization model, for the reservoir operation management considering surface/groundwater interactions is presented. The groundwater flow model was developed by means of the FREEWAT platform (Rossetto et al., 2018) and used to obtain a leakage function representing the reservoir's leakage loss to the aquifer in response to different water levels in the reservoir. The leakage function is embedded to the reservoir mass balance equation in the optimization model. The optimal policy was derived based on maximizing the reservoir's water yield while considering different constraints such as the water demand and storage constraints. The modeling method proposed in this study was applied to an off-stream artificial lake located atop an alluvial aquifer in the north-east of Iran. The reservoir was built to store the flood flows of the Bar river for water supply for domestic and industrial needs and with the secondary objective to intentionally recharge the aquifer. Based on the results, the distance between the total demand (12 Mm3/year) and optimal release from the reservoir (5.7 Mm3/year) could be largely supplied by groundwater via pumping wells while the aquifer recharge provided by the leakage is 7.26 Mm3/year. This study demonstrates that the possibility to move surface water to aquifers offers an opportunity to better manage water resources, increase water supply reliability and resiliency (Joodavi et al., 2020). Furthermore, the methodology presented can be tailored for application to any reservoir (artificial lake) system, enhancing its operational, planning, and management aspects. This allows for a precise evaluation of the impact of operational policies on lakebed seepage.

References

  • Rossetto, R., De Filippis, G., Borsi, I., Foglia, L., Cannata, M., Criollo, R., Vázquez-Suñé, E., 2018. Integrating free and open source tools and distributed modelling codes in GIS environment for data-based groundwater management. Environ. Model. Software 107. https://doi.org/10.1016/j.envsoft.2018.06.007
  • Harbaugh AW, Langevin CD, Hughes JD, Niswonger RN, Konikow LF, 2017. MODFLOW-2005 version 1.12.00, the U.S. Geological Survey modular groundwater model: U.S. Geological Survey Software Release, 03 February 2017, http://dx.doi.org/10.5066/F7RF5S7G
  • Joodavi A, Izady A, Karbasi Maroof MT, Majidi M, Rossetto R, 2020. Deriving optimal operational policies for off-stream man-made reservoir considering conjunctive use of surface- and groundwater at the Bar dam reservoir (Iran), Journal of Hydrology: Regional Studies. 31, 100725, https://doi.org/10.1016/j.ejrh.2020.100725

How to cite: Joodavi, A. and Rossetto, R.: Study on operation strategy for a multi-objective off-stream reservoir with large lakebed seepage to enhance climate resilience , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10272, https://doi.org/10.5194/egusphere-egu24-10272, 2024.

EGU24-11325 | ECS | Posters on site | HS1.1.3

Indicators for anthropogenic and natural water contributions to a small river 

Malina Ruck, Lea Augustin, and Thomas Baumann

River quality is expected to change significantly as a consequence of climate change. Extended drought periods and decreasing groundwater levels will lower the contribution of groundwater to receiving streams and heavy rain will cause excessive surface runoff effects. Constant sources, like discharge from wastewater treatment plants or industrial installations, will be diluted in largely different ratios. The overall hydrochemical dynamics will, therefore, likely increase. This affects flood management schemes and other potential uses of river water.

 

This study links trace substances (hydrochemistry, colloids) to the hydrological dynamics in the catchment. From this data the feasibility of infiltrating excess river water into a nearby aquifer (Flood-MAR) is assessed. The upper part of the study area is characterized by forests and meadows. There is a small village with one sewage treatment plant (1000 inhabitant equivalents) and a few hamlets. Additional emissions can be expected from surface runoff of one national road (deicing, tire abrasion, etc.).

 

The hydrochemical characteristics show a decrease in the main cations and anions during a flooding event. Nitrate concentrations were low in both cases. Although particle concentrations were increasing during the flooding event, the overall concentrations were still below our expectations. This indicates that the meadows behind the retention dam, which were partly flooded, served as a settling ponds and filters. During low water conditions, organic material and algae were dominant. Few calcite particles and silicates are indicative of the composition of the quaternary gravels that make up the aquifer.

 

The results confirm the risk assessment of the study area. The water quality during a flooding event met the legal thresholds set in the German Soil Protection Act, so infiltration into the downstream aquifer should be feasible.

How to cite: Ruck, M., Augustin, L., and Baumann, T.: Indicators for anthropogenic and natural water contributions to a small river, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11325, https://doi.org/10.5194/egusphere-egu24-11325, 2024.

EGU24-11339 | Orals | HS1.1.3

Co-benefit valuation of urban and peri-urban nature in high resolution on continental scale 

Roland Löwe, Martina Viti, Karsten Arnbjerg-Nielsen, and Jacob Ladenburg

Space is a highly valued asset in cities. This is a key reason why nature-based solutions (NBS) for water management are often perceived to be more expensive than traditional grey
solutions. Promoting NBS implementation requires methods for quantifying their non-market benefits that are widely accepted and easy-to-apply in early planning and brainstorming stages.

In this work, we develop a predictive metamodel for the total economic value of urban and peri-urban nature, based on 114 stated-preference valuation studies of nature in (peri-)urban areas and openly available geographic data from across the world. The dataset covers the entire range of NBS types with sizes from 0.5 to 900.000 ha. We employ a mixed-effects modelling approach and use a cross-validation procedure to determine which factors affect the willingness to pay for (peri-)urban nature. We consider the predictive performance of 8.4 million model permutations that consider different combinations of site properties and topographic and socio-economic characteristics of the surroundings as input.

We find that the total economic value is determined by the size of the nature areas and population densities in their surroundings. There is clear evidence for substitution effects where available nature areas reduce the willingness to pay for new nature. Beyond the dependency on area, there is little evidence for making distinctions between nature types. Economic values do depend on the average income at a site, but these variations are entirely captured by purchase power corrections. Our value estimates are aligned with related literature and range between 150 and 400,000 USD/ha/year. We have implemented our metamodel into a freely available Python program, which generates maps of the predicted values for any location in Europe in a spatial resolution of 100m.

How to cite: Löwe, R., Viti, M., Arnbjerg-Nielsen, K., and Ladenburg, J.: Co-benefit valuation of urban and peri-urban nature in high resolution on continental scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11339, https://doi.org/10.5194/egusphere-egu24-11339, 2024.

The implementation of Natural Flood Management (NFM) measures theoretically provides an opportunity to build resilience into flood risk management systems in a way that incorporates sustainable practices and holistic management of the landscape. However, there remains a lack of clear understanding of these solutions, and in practice this can hinder the uptake of NFM;  there is a need to expand the emerging evidence base in order to quantify and demonstrate their effectiveness in a range of catchment and storm event scenarios.

This study focuses on an NFM scheme implemented across a 22km2 rural, lowland catchment in Lincolnshire, UK. An additional 46,000m3 of storage has been created through the construction of five offline attenuation ponds and a number of field-edge swales alongside the channel network. Land management practices in this catchment have resulted in significant modifications to the hydrological processes through historical realignment and modification of the channel network, intensive agricultural practices and the installation of tile drainage beneath arable fields. The Swaton Eau catchment is located in a lowland area with an elevation range of less than 50m across the catchment. It is important to investigate how NFM features are expected to perform in catchments that are characterised by hydro-modifications and low gradients as there currently is a lack of research of this.

An array of monitoring has been installed across the catchment in a nested structure to gather empirical evidence on the performance of the NFM scheme both at a feature scale and at a wider sub-catchment and catchment scale. Water level sensors are located throughout the channel network to track the propagation of the peak flood level. Transects of soil moisture sensors are buried in the shallow sub-surface in chosen swales to monitor short time-scale movement of water through these features.

The first major test of the features occurred in October 2023 during Storm Babet and Storm Ciaran. Field evidence indicates that the flood wave was attenuated through the catchment with a less flashy catchment response observed compared to a pre-NFM event in 2012. Soil moisture data collected within the swales indicates that they are intercepting pathways of water through the catchment and preventing runoff entering the surface water drainage network.

How to cite: Lewis, C. and Pattison, I.: Understanding the role of natural flood management in a ‘not-so-natural’ catchment: field observations of an NFM scheme in rural, lowland Lincolnshire, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11525, https://doi.org/10.5194/egusphere-egu24-11525, 2024.

Groundwater is considered worldwide an important and resilient reserve of freshwater for human needs. The increasing demand, combined with climate change impacts, is leading to a remarkable quali-quantitative decay of water resource, especially in many megacities of the Global South, where the rapid urban growing pushed to environmental critical issues as the case of seawater intrusion for coastal aquifers. At the same time, the uncontrolled urbanization without a territorial planning favors the runoff and places ever greater areas in hydraulic danger, increasing the risk of flooding in currently inhabited areas. Dar es Salaam, in Sub-Saharan Africa, is one of these cases: a city of more than 4 million of inhabitants, with a population growth rate of about 5 per cent per year. A high dependence on natural resources ecosystems is mainly due to hybrid rural-urban livelihoods. The urban pressure on the aquifer caused a serious threat on water quality and quantity due to saline intrusion along the coastline, with depletion of groundwater levels and contamination of pumping wells. Moreover, the increasing risk of water scarcity and flooding due to climate change is threatening the local community, with an increasing need for adaptation measures. Catchment imperviousness of Mbezi River basin increased by 41% (2003-16), causing floods, erosion, land and marine pollution.

A new vision needs to integrate the groundwater management strategies, already proposed in the context of the “Adapting to Climate Change in Coastal Dar es Salaam” (ACC-DAR) project, with surface water management too. Aim of this feasibility study is to outline a strategy for a sustainable water management in the Dar Es Salaam territory, through the planning of MAR (Managed Aquifer Recharge) solutions in specific areas. This approach could be helpful to solve or, at least, mitigate the impact of both flooding and groundwater overexploitation in the area, allowing to support stakeholders and public government in implementing local policies and proposing a more sustainable use of the resource.

 

How to cite: De Filippi, F. M. and Sappa, G.: A new planning strategy for integrating surface water and groundwater management to face climate change impacts in the Dar Es Salaam Plain, Tanzania (Africa)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11760, https://doi.org/10.5194/egusphere-egu24-11760, 2024.

In Canada’s Western Boreal Plain, catchment runoff is typically low but spatially variable. Localized landscape soil and vegetation cover types, along with the hydrophysical properties of underlying glacial deposits and regional slopes, are important controls for the partitioning of precipitation into runoff, evapotranspiration, and soil water storage. Wetlands are abundant, covering up to 50% of the landscape, despite a regional sub-humid climate. Local topographic highs, including Stony Mountain, have been identified as water generation hotspots, with the goal of this research to evaluate the hydrology and importance of small headwater catchments on a local topographic high for water generation and availability in downgradient systems.

Hydrologic interactions between forestlands and adjacent wetlands were characterized and related to observations of small-scale (headwater) catchment runoff dynamics within the Stony Mountain Headwater Catchment Observatory (SMHCO) in northern Alberta, Canada. Catchment runoff efficiency, or runoff coefficients (i.e., the proportion of rainfall the is produced as runoff), were evaluated for 40 events across six wetland-dominated catchments ranging in size from <0.5 km2 to ~ 200 km2. Water table configurations indicated varying exchanges among forested hillslopes and adjacent wetland systems, with the magnitude of runoff response to rainfall events controlled largely by antecedent water table configurations. Small (<10 km2) headwater catchments demonstrated highly variable runoff efficiencies, ranging from 10 to 90% (average 35%). Larger meso-scale catchments (up to 200 km2) demonstrated lower runoff efficiency (average = 25%; range 10 to 40%). The higher catchment runoff efficiencies observed in smaller headwater catchments identifies these regions as highly productive regions for water generation on a per-unit area basis. Accordingly, the findings of this research demonstrates that smaller sub-catchments within headwater regions of larger catchments represent an important area for water supply and availability for down-gradient ecosystems and water courses.   

How to cite: Ketcheson, S. and Attema, J.: The importance of headwater catchments for water availability in the lower Athabasca River Basin, Canada., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11839, https://doi.org/10.5194/egusphere-egu24-11839, 2024.

EGU24-12100 | Posters virtual | HS1.1.3

Nature-based solutions for hydro-meteorological extremes in South Asian countries: Current practices, gaps, and opportunities  

Md Humayain Kabir, Md Arif Chowdhury, Md Nazmul Hossen, Shahpara Nawaz, Syed Labib Ul Islam, and Md Lokman Hossain

South Asian countries are highly susceptible to different forms of hydro-meteorological extremes (HMEs) like cyclones, storm surges, floods, erosion, sea level rise, etc., while changing patterns of climate variability also make the situations worse. Nature-based Solutions (NbS) in different forms, like mangrove forests, coral reefs, salt marshes, beach nourishment, reforestation and afforestation, wetland restoration, etc., can help to reduce the magnitude of impacts. This study was conducted in South Asia countries to understand the existing practices, challenges, and potentiality of NbS regarding HMEs. The findings of sea level rise-induced extreme events are summarized as follows: (a) Significance of coastal ecosystems in mitigating impacts of HMEs, (b) NbS approaches for coastal protection and restoration, (c) Co-benefits of NbS for coastal protection and restoration, (d) Coastal Protection and NbS: South Asia Perspective- (i) Current practices of NbS to protect the coastal region, (ii) Challenges to ensure NbS regarding coastal protection, and (iii) Potentiality of NbS to protect the coastal region.

Unusual rainfall patterns and their connection to landslides, along with the environmental and socioeconomic consequences and threats to vulnerable groups, are examined. We also delve into NbS interventions that stabilize slopes and prevent erosion-related events, emphasizing the significance of early warning systems, community-based strategies, and disaster preparedness measures to enhance resistance and resilience. Case studies from Chittagong Hill Tracts and Rohingya Camps in Bangladesh demonstrate the customization of NbS approaches to meet particular needs.

An in-depth analysis of diverse NbS approaches, including forest and floodplain restoration, construction of wetlands and green infrastructure, and several other solutions for urban flood prevention, is presented. The extent of their effectiveness and barriers to expanding NbS practices are discussed, encompassing a range of contexts from high-income urban areas to medium and low-income regions. The focus lies on the adaptability and potential impact of NbS in various contexts, providing valuable insights into their applicability. Barriers to large-scale implementation of NbS for urban flood prevention are elucidated, encompassing legislative, financial, and societal challenges that impede the integration of NbS in practice and policies, which hinder employing initiatives for a long-term national plan for NbS. Strategies to surmount these barriers are discussed, offering insights for stakeholders seeking to navigate the complexities of NbS integration. We conclude that although NbS can be considered a cost-effective and sustainable way to protect natural ecosystems and human properties, it needs more concentration to integrate into decision-making aspects from policy to practice perspectives.

How to cite: Kabir, M. H., Chowdhury, M. A., Hossen, M. N., Nawaz, S., Islam, S. L. U., and Hossain, M. L.: Nature-based solutions for hydro-meteorological extremes in South Asian countries: Current practices, gaps, and opportunities , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12100, https://doi.org/10.5194/egusphere-egu24-12100, 2024.

EGU24-14321 | ECS | Posters on site | HS1.1.3

Assessing habitat area changes from large-scale nature-based solutions 

Yared Abayneh Abebe, Samikshya Chhetri, Laddaporn Ruangpan, and Zoran Vojinovic

One of the benefits of nature-based solutions (NBS) is providing environmental benefits, which regulate and maintain ecosystem services and foster positive impacts on ecosystems. Environmental benefits of NBS include enhancing water quality, habitat changes, improving biodiversity and carbon sequestration and storage. In this research, we developed a method to assess changes in habitat areas using remote sensing data.

Since mapping habitats is a harder task, our method is based on mapping and detecting changes in land cover over a region and translating that to changes in habitat area. We employed the CORINE Land Cover (CLC) classes and EUNIS habitat classes, two commonly used classification systems for land cover and habitat types, respectively. To assess the change in habitat type and area before and after implementing NBS, the CLC Level III classes were transformed into EUNIS Level I habitat types. The CLC datasets of 2000 and 2018 were used as the land covers before and after implementing an NBS. We applied the method in Aarhus, Denmark, in two study areas called Egå Engsø and Lystrup. An artificial lake and wetland that covers an area of 115 hectares was implemented in 2006 in Egå, surrounded by 35 hectares of grazed meadows. The NBS in Lystrup includes basins, gullies and rainbeds. The purposes of the NBS are to reduce the flood risk from the river Egå and isolated storms, reduce the nitrogen supply to Aarhus Bay and improve the natural conditions in the area.

Results showed the conversion of a cultivated habitat to an inland surface water habitat. A bogs, mires and fens habitat had also emerged west of the wetland. In the southwest of the wetland, an agricultural habitat had changed to a complex habitat, and the south of the region was surrounded by an artificially dominated habitat. Finally, a complex habitat had changed to a constructed habitat in the southeast of the wetland. On the other hand, habitat changes had not altered significantly in Lystrup despite the implementations of NBS projects. It is also possible that NBS-induced modifications could not be recorded by the method as the area was a complex habitat characterized by a heterogeneous blend of different habitats. One limitation of this method could be that it is difficult to delineate changes within complex habitats. Additionally, the limitation arises from the translation of the land cover classes to habitat classification. However, the research offers a method to quantify one of the environmental benefits NBS generate to encourage decision-makers to implement and scale them up further.

How to cite: Abebe, Y. A., Chhetri, S., Ruangpan, L., and Vojinovic, Z.: Assessing habitat area changes from large-scale nature-based solutions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14321, https://doi.org/10.5194/egusphere-egu24-14321, 2024.

EGU24-16242 | Orals | HS1.1.3

Preliminary Assessment of Nature-Based Solutions Performance for Improving Irrigation Water Management Using the SWAT Model 

Vassilios Pisinaras, Konstantinos Babakos, Anna Chatzi, Dimitrios Malamataris, Vassiliki Kinigopoulou, Evangelos Hatzigiannakis, and Andreas Panagopoulos

Nature-based solutions (NBS) offer innovative and sustainable approaches to address irrigation water management challenges, since they can contribute significantly to enhancing water retention, reducing soil erosion, and optimizing water use efficiency. Within this framework, the Soil & Water Assessment Tool (SWAT) model was applied in the Pinios Hydrologic Observatory (PHO) in central Greece to quantify the impact of two NBSs on irrigation water use: a) effective soil water management through irrigation scheduling and b) increased soil water holding capacity through mulching and mowing. Encompassing an area of approximately 55 km2, PHO comprises forested and agricultural lands, predominantly cultivated with apples, followed by cherries and other orchards.

The SWAT model was applied in the PHO watershed for the period 2018-2022 and calibrated against soil water content with daily observed data obtained from soil moisture sensors installed both in forested and agricultural areas. A hybrid land use map, compiled by combining CORINE land cover and field-scale crop distribution, was utilized and the watershed was subdivided into 15 sub-watersheds and 696 Hydrologic Response Units (HRUs). Monitoring of actual irrigation water consumption in 10 orchards revealed an average of 670 mm per cultivation period. Simulation of irrigation scheduling using the SWAT model indicated a potential reduction of more than 20% in irrigation water consumption in the apple orchards.

Continuous cultivation for several decades, irrational irrigation and the excessive use of herbicides practiced in PHO affect soil health, potentially leading to soil organic content (SOC) depletion, microbial activity disruption, and overall soil fertility compromise. Augmenting SOC enhances soil water holding capacity, fostering improved moisture retention and resilience against drought conditions. Analysis of over 500 soil samples collected from orchards implementing mulching/mowing practices compared to those predominantly using herbicides revealed an average SOC 1.2% higher for soil depths of 0-10 cm and 0.6% higher for depths of 10-30 cm. This increase in SOC is estimated to potentially raise soil available water content by 2%, contributing to 3% more irrigation water savings when coupled with effective soil water management through irrigation scheduling. While this water-saving potential may not be high, it can contribute significantly to mitigating water scarcity during drought periods, whilst should SOC increase is achieved by mulching/mowing and no use of herbicides, soil erosion is prevented, soil aeriation is improved, natural pollinator population is increased and agrochemicals’ runoff potential is reduced.

 

Acknowledgements

This research was funded by PRIMA program supported by the European Union, grant number 2041 (LENSES—Leaning and Action Alliances for Nexus Environments in an Uncertain Future) (Call 2020 Section 1 Nexus IA).

How to cite: Pisinaras, V., Babakos, K., Chatzi, A., Malamataris, D., Kinigopoulou, V., Hatzigiannakis, E., and Panagopoulos, A.: Preliminary Assessment of Nature-Based Solutions Performance for Improving Irrigation Water Management Using the SWAT Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16242, https://doi.org/10.5194/egusphere-egu24-16242, 2024.

EGU24-17611 | Orals | HS1.1.3

When can rewetting of forested peatlands reduce extreme flows? 

Maria Elenius, Charlotta Pers, Sara Schützer, and Berit Arheimer

Historical drainage to improve agricultural and forestry practices has resulted in almost 1 million km of artificial channels in Sweden. This has reduced the storage of water in the landscape, and there are concerns related to the potential impacts on extreme flows, biodiversity, greenhouse gas emissions and nutrient outputs. A large national restoration program aims to rewet 100 000 hectares forested peatland. However, there is limited evidence in what the impacts will be.

Here, we implemented national information on ditches to the hydrological model HYPE and investigated the conditions at which removal of ditches in forested peatland could mitigate extreme flows under various conditions of the climate and local hydrology. We found that the impact on discharge at the level of 10 km2 sub-catchments or larger was small, mostly because only small fractions of the catchments consist of drained forested peatlands, meaning there is considerable mixing with other runoff. However, smaller streams with runoff primarily from the restored peatlands could have substantial impacts of restoration, which may be important for local biodiversity.

For instance, a modelling sensitivity study showed the minimum runoff per year from forested peatlands increased by up to about 15 % after removing ditches and the maximum runoff was reduced by up to about 25 %. Importantly, an increase in the minimum runoff was only obtained if the minimum groundwater level was low enough in relation to the depth of ditches. Similarly, a reduction of the largest yearly runoff required that ditches were not too deep.

If conditions were not favorable to mitigate extreme runoff, the opposite situation often occurred instead, with worse extremes. Therefore, although the impact on extreme flows was negligible at the level of 10 km2 catchments or larger, it is crucial to choose appropriate sites for restoration with respect to runoff extremes if there are sensitive smaller streams with runoff deriving mostly from the peatlands. The work presented here shows how this can be performed with the use of indicators for groundwater levels and ditch drainage prior to rewetting. Specifically, the minimum runoff is expected to increase only if the minimum groundwater level prior to rewetting is below the depth of ditches, or close to that depth. Reductions in the maximum runoff require ditches are not too deep, and large reductions cannot be expected if the groundwater level was already temporarily above the soil surface prior to rewetting, for example due to lateral inflow.

How to cite: Elenius, M., Pers, C., Schützer, S., and Arheimer, B.: When can rewetting of forested peatlands reduce extreme flows?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17611, https://doi.org/10.5194/egusphere-egu24-17611, 2024.

EGU24-17780 | Posters on site | HS1.1.3

High Enthalpy Shallow Geothermal Energy: The Anomaly 

Alejandro Gil, Juan Carlos Santamarta, Carlos Baquedano, Jorge Martínez León, Miguel Ángel Marazuela, Samanta Gasco Cavero, Jon Jimenez, Teresa Alonso Sánchez, Miguel Ángel Rey Ronco, José Ángel Sánchez-Navarro, Alicia Andreu Gallego, and Juan Miguel Tiscar Cervera

The SAGE4CAN project focuses on investigating the shallow geothermal potential of the Canary Islands. During the project execution in 2021, the Tajogaite volcanic eruption took place. This eruption resulted in the deposition of lava flows, totaling approximately 200 million cubic meters, with temperatures ranging between 400 and 900°C. Remarkably, these materials represent a shallow geothermal reservoir of exceptionally high enthalpy, deviating from conventional shallow geothermal reservoirs that typically maintain temperatures close to the annual atmospheric average.

This study presents the calculated results of harnessing geothermal energy from these deposits during the cooling period of the lava flows. The goal is to extract heat from the reservoir to generate both electricity and domestic hot water. The unique nature of this geothermal reservoir, characterized by its elevated temperatures, challenges the conventional understanding of shallow geothermal systems, offering an exceptional opportunity for sustainable energy utilization in the Canary Islands. Moreover, these findings provide a framework for redefining shallow geothermal potential, traditionally associated only with depth. While depth remains a crucial factor, our study highlights the exception that proves the rule, demonstrating that geothermal anomalies, such as the one observed here, contribute valuable insights to the broader understanding of shallow geothermal resources in the Canary Islands.

How to cite: Gil, A., Santamarta, J. C., Baquedano, C., Martínez León, J., Marazuela, M. Á., Gasco Cavero, S., Jimenez, J., Alonso Sánchez, T., Rey Ronco, M. Á., Sánchez-Navarro, J. Á., Andreu Gallego, A., and Tiscar Cervera, J. M.: High Enthalpy Shallow Geothermal Energy: The Anomaly, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17780, https://doi.org/10.5194/egusphere-egu24-17780, 2024.

Nature-based solutions have the capability to slow and store water during storm events, leading to the attenuation of flood peaks and the capturing of sediments and associated nutrients. These features can also provide important habitats for wildlife and pollinators. However, these features do take land that may be agriculturally productive and require maintenance, both factors mean that they have potentially significant ongoing costs. Therefore, it is important to ensure that they are effective and correctly located within the landscape. For all pressures, the location needs to be in a location where the problems are likely to originate. However, for flood waters, it is important to target locations that are likely to contribute to moving water out of the flood peak and into the receding limb of the hydrograph, rather than moving water from the rising limb into the peak. It is also important not to move water from the peak discharge of one community into the peak discharge of another. Therefore, careful analysis and planning are needed to ensure that the benefits from the nature-based solutions are maximised for all in the catchment.

 

The SCIMAP Toolkit provide an approach to assess the potential source area of flood waters, sediments, nutrients and FIOs and to ensure that the multiple benefits of the nature-based solution are realised. The toolkit uses a reduced complexity approach to map the generational of rapid runoff, the mobilisation of material and connectivity to the receiving waters. The SCIMAP-Flood module then considers the travel times to the impact points within the catchment, such as a community or key infrastructure.  This analysis is undertaken in a time-integrated way such that the potential benefits of a nature-based solution are optimised over a range of storms rather than fitting to the unique dynamics of a past event. The analysis is undertaken at landscape extent with sub-field detail, normally at a ground resolution of 1m with the catchment extent covering 1000s of km2.  This presentation shows the application of the SCIMAP approach to the spatial targeting of flood mitigation features and how these locations can co-deliver water quality benefits.

How to cite: Reaney, S.: Opportunity mapping for nature-based solutions for flood hazard reduction and water quality improvements with the SCIMAP toolkit, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18566, https://doi.org/10.5194/egusphere-egu24-18566, 2024.

EGU24-19873 | ECS | Orals | HS1.1.3

Advancing Climate Resilience in the Canary Islands: Insights from the NATALIE Project on Nature-Based Solutions 

Jorge Martínez León, Miguel Ángel Marazuela Calvo, Carlos Baquedano, Jon Jimenez, Samanta Gasco Cervero, Jesica Rodríguez-Martín, Juan Carlos Santamarta, and Alejandro García-Gil

Advancing Climate Resilience in the Canary Islands: Insights from the NATALIE Project on Nature-Based Solutions

 

Jorge Martínez León1, Carlos Baquedano1, Miguel Ángel Marazuela1, Jon Jimenez2, Samanta Gasco Cervero3 Jesica Rodríguez-Martín4, Juan Carlos Santamarta5 and Alejandro García-Gil1,

 

1Geological and Mining Institute of Spain (IGME), Spanish National Research Council (CSIC), Madrid, Spain (a.garcia@igme.es)

2Department of Earth Sciences, University of Zaragoza, Zaragoza, Spain

3Madrid Health Department, Madrid City Council, Spain.

4 Department of Techniques and Projects in Engineering and Architecture, University of La Laguna (ULL), Tenerife, Spain.

5Department of Agricultural and Environmental Engineering. University of La Laguna, Tenerife (Canary Islands), Spain

 

This communication outlines the research framework of the NATALIE project, emphasizing the application of Nature-Based Solutions (NBS) to address pressing climate change challenges across three distinct case studies in the Canary Islands—Gran Canaria, Tenerife, and Fuerteventura. The primary focus is on utilizing NBS as transformative measures to bolster resilience throughout the archipelago. Identified challenges encompass escalating extreme rainfall intensities leading to floods, uncontrolled runoff, water quality degradation from sewer overflows, desertification, and the management of groundwater bodies under future climate change scenarios.

 

The showcased activities include a series of NBS and Sustainable Urban Drainage Systems (SUDS) in Gran Canaria, with specific attention given to the Maspalomas lagoon. Tenerife's La Laguna case study highlights innovative NBS aimed at preventing flooding, presenting cost-effective alternatives for the construction of new drainage systems. Fuerteventura's initiative involves implementing natural treatment systems to combat nitrogen and pollutants, coupled with the utilization of regenerated water for restoring degraded wetlands. Furthermore, the research explores the monitoring of retention and infiltration capacities of traditional agricultural and rainwater storage systems.

 

The overarching goal of this research is to advocate for a comprehensive and diverse implementation of NBS, thereby contributing significantly to the resilience of the Canary Islands against the multifaceted impacts of climate change.

 

How to cite: Martínez León, J., Marazuela Calvo, M. Á., Baquedano, C., Jimenez, J., Gasco Cervero, S., Rodríguez-Martín, J., Carlos Santamarta, J., and García-Gil, A.: Advancing Climate Resilience in the Canary Islands: Insights from the NATALIE Project on Nature-Based Solutions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19873, https://doi.org/10.5194/egusphere-egu24-19873, 2024.

EGU24-21269 | Orals | HS1.1.3

Integrated and conjunctive Reservoir and Aquifer Management to improve water security in the Elqui Basin, Chile 

Marta Faneca Sànchez, Corine ten Velden, Felipe García Grez, Bernhard Becker, and Hans van Duijne

Reservoir operation and groundwater management, and specifically Managed Aquifer Recharge (MAR) are often tackled separately despite the common objective to store water when it is available and provide water when needed. Few studies focus on the conjunctive management of reservoirs and aquifers to optimize IWRM in basins. This work takes into consideration the combined management of reservoir operation and MAR for the Elqui Basin in the Coquimbo region, Chile and proposes a conceptual model for integrated modelling. The conceptual model captures the complexity of integrated management in terms of contributing processes, time and spatial scales, risks, data and models and proposes approaches for an integrated tool. The Elqui Basin is located in the northern part of Chile. The last decade it has been exposed to prolonged and severe droughts. This has posed enormous pressure on the already scarce water resources, causing overexploitation of groundwater resulting in drastic lowering of the groundwater table. To analyse optimization of water allocation in the basin (including reservoir management and MAR), in addition to the conceptual model, a real time control model (RTC-tools) is developed by coupling a hydrological model (WFLOW) and a groundwater model (iMODFLOW) to RTC-tools. The RTC-tools exercise shows when and how much water would be available to infiltrate through MAR, whilst also considering the water demand of the many different users in the basin. Preliminary results show that while infrastructure should be adapted to conduct and infiltrate water in the region, reservoir operation and water allocation could be optimized to make MAR possible.

How to cite: Faneca Sànchez, M., ten Velden, C., García Grez, F., Becker, B., and van Duijne, H.: Integrated and conjunctive Reservoir and Aquifer Management to improve water security in the Elqui Basin, Chile, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21269, https://doi.org/10.5194/egusphere-egu24-21269, 2024.

EGU24-21660 | ECS | Posters virtual | HS1.1.3

Stormwater trees in urban runoff management: Water balance of the SenseCity Experimental Device  

Hayath Zime Yerima, Martin Seidl, Marie-Christine Gromaire, Abdelkader Bensaoud, and Emmanuel Berthier

Faced with high levels of soil sealing combined with the effects of climate change, stormwater trees offer an adaptive solution for stormwater management. A stormwater tree is a street tree that has been designed to manage runoff from the adjacent pavement, while enhancing its development and various ecosystem services. It's a natured based solution for sustainable source control of runoff that's developing more and more, but whose operation is not yet completely mastered. The aim of the present study is to analyze and better understand the hydrologic functioning of such a device for a better application in the city, based on an experimental prototype, implemented in SenseCity, in Paris conurbation. SenseCity is a mini-city made up of a roadway and walls simulating a Canyon Street, with ball maples (Acer platanoide Globosum) planted on either side, one side of which is fed by runoff from 88m2 of pavement - these are the stormwater trees. The three stormwater trees are planted in a 1.6m-diameter reservoir with two main substrate layers, the first consisting of 20cm of Rainclean, a depollution filter providing temporary storage before infiltration into the deeper 60cm layer of topsoil. The runoff infiltrates through these two layers before reaching the clayey natural underground, where it can be exfiltrated to the soil and excess water can be collected in an underdrain. Various sensors were installed to study this system. These include inflow (Krohne Optiflux electromagnetic flowmeter), soil water content (Campbell SoilVue TDR probe), sap flow (Edaphic Implexx sensor) which allows to assess the evapotranspiration flux from the trees, outflow from the underdrain (Précis Mécanique 2x1-liter auger) and meteorological parameters. Most parameters are measured at 15-minute time steps.
The results obtained over one year (April 2022-March 2023) show exfiltration and transpiration rates on the system to represent respectively 53% and 27% of the inflow. Annual drainage accounts for around 19%. Exfiltration and transpiration are the main means of reducing runoff volumes. These different processes are not evenly distributed over the months. Transpiration rates are highest in summer, helping to cool the urban microclimate, while drainage and exfiltration is highest in winter. In summer, for example, transpiration rates were 41% and drainage 11%, while in winter transpiration was reduced to 5% and drainage increased to 32%.

How to cite: Zime Yerima, H., Seidl, M., Gromaire, M.-C., Bensaoud, A., and Berthier, E.: Stormwater trees in urban runoff management: Water balance of the SenseCity Experimental Device , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21660, https://doi.org/10.5194/egusphere-egu24-21660, 2024.

EGU24-1444 | ECS | Posters on site | HS1.1.7

Urban green space: global assessment of potential energy demand reduction in buildings 

Giacomo Falchetta and Enrica De Cian

Climate change impacts are increasingly felt, and a key hazard for human health is exposure to chronic and acute heat. Air conditioning is an effective indoor adaptation technology. However, it is widely regarded as a form of “maladaptation” due to its high energy intensity and the detrimental impact it has on urban outdoor temperatures and global greenhouse gas emissions. On the other hand, urban green space (UGS) is widely regarded as an effective green infrastructure with potential to mitigate the urban heat island effect. In this context, here we built on a global validated model based on street-level vegetation density, satellite imagery, and ancillary covariates to track UGS in a large sample of cities worldwide (Falchetta and Hammad, forthcoming) and derive a context-aware but generalized statistical linkage with buildings electricity consumption statistics. Based on the modelled relations, we derive future projection of the potential contribution of UGS expansions to energy demand reduction in buildings in different regions of the world. Our study advances the quantitative, globally relevant understanding of the intersection between climate change adaptation and mitigation, and the role of nature-based solutions to reduce the feedback impacts of adaptation while providing ecosystem service co-benefits.

How to cite: Falchetta, G. and De Cian, E.: Urban green space: global assessment of potential energy demand reduction in buildings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1444, https://doi.org/10.5194/egusphere-egu24-1444, 2024.

EGU24-6337 | Posters on site | HS1.1.7 | Highlight

Simulating the impact of ground-based façade greenery design on indoor heat stress reduction 

Yannick Dahm, Karin Hoffmann, Oliver Schinke, and Thomas Nehls

Vertical greenery (VG) reduces the indoor heat hazard. To take advantage of their cooling effects, the underlying key design factors have to be understood. However, the influence of plant species, building type, and VG design on the thermal advantages has received limited attention in current literature.
Therefore, heat fluxes and temperature profiles for different ground based VG designs in the temperate climate of Berlin, Germany, were analysed using a process-based model. Indoor temperature profiles were integrated, assuming that air conditioning (AC) had been installed. Cooling effects have been simulated for six parameterised plant species of varying ages, across three different building types, and alternated air gap and crop thickness.
The results were compared, quantifying the cooling potential and the possible energy savings. They differ between plant species and building types. The diurnal variation of the indoor temperature resulted in maximum savings during the night. Fallopia baldschuanica showed the highest energy savings of approximately 23%. Thereby, it was multiple times more energy efficient than a Humulus lupulus.
This illustrates the significance of selecting the appropriate VG plant species. Considering factors such as growth rates and potential harm to buildings, VG can be strategically optimzed.

How to cite: Dahm, Y., Hoffmann, K., Schinke, O., and Nehls, T.: Simulating the impact of ground-based façade greenery design on indoor heat stress reduction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6337, https://doi.org/10.5194/egusphere-egu24-6337, 2024.

EGU24-7729 | Posters on site | HS1.1.7

Evaluating Green Roof Heat Mitigation Potential in a Changing Climate 

Giovan Battista Cavadini and Lauren Cook

As the impacts of climate change intensify, bringing an increase in the frequency and magnitude of heat waves, the interest around urban heat mitigation strategies is rapidly growing worldwide. Green roofs, defined as roofing systems that incorporate a vegetated layer, have been proved to reduce urban heat, thanks to their evaporative cooling and lower heat storage than conventional roofs. Thus, they are expected to become increasingly important in the future, given their potential to counteract the projected temperature increases associated with climate change.

Numerous studies emphasize the urban heat mitigation potential of green roofs, yet accurate quantifications of their temperature reductions under future climate are currently lacking. For instance, under climate change, higher temperatures and longer dry periods are expected in central Europe, conditions that can negatively affect green roofs. Recently, microclimate models are gaining traction in evaluating the efficacy of heat mitigation strategies, facilitating the quantification of urban heat reductions under various climate conditions. However, despite their increasing use in the literature, microclimate models are rarely combined with climate projections, due to the complexity of downscaling interdependent weather variables such as precipitation, air temperature and global horizontal radiation. Consequently, the heat reduction potential of green roofs under future climates is largely unexplored, particularly in comparison to their observed performance under current climate. Additionally, it is unknown whether specific roof parameters could contribute to further enhancing heat mitigation, such as plant characteristics, irrigation schemes, or substrate depth.

This study aims to investigate the heat mitigation potential under climate change on a green roof in Mendrisio, Switzerland (characterized by hot, dry summers) using an open source microclimate model developed by Meili et al. (2020), Urban Tethys-Chloris (UT&C). This model was selected because of the fully coupled energy and water balance, and the incorporation of plant-specific characteristics. Continuous year-long monitoring of the green roof enabled to collect surface temperature using infrared sensors. These measurements were used to calibrate and validate the microclimate model. To account for climate change, coupled, sub-hourly, future projections of precipitation, air temperature, solar radiation, relative humidity, and wind speed were used as input to the validated microclimate model. These projections were derived from a convection resolving climate model (COSMO forced by MPI-M-MPI-ESM-LR at RCP 8.5, worst-case emissions scenario) run over the European domain at a 2.2-km, 6-minute resolution for a 10-year period that was bias corrected through quantile mapping. Lastly, variations in key parameters like substrate depth, vegetation type, and green roof irrigation schemes were explored to analyze their impact on urban heat mitigation under climate change.

Preliminary, manual calibration of the microclimate model resulted in a good predictive ability (r2 = 0.71), which will be further improved with automatic calibration. In a current climate, the green roof was able to reduce maximum surface temperatures in Summer by approximately 15°C, with respect to an adjacent concrete roof. Further expected results will evaluate potential temperatures reductions in a future climate and determine whether green roofs can counteract increasing temperatures by exploring a range of alternative designs.

How to cite: Cavadini, G. B. and Cook, L.: Evaluating Green Roof Heat Mitigation Potential in a Changing Climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7729, https://doi.org/10.5194/egusphere-egu24-7729, 2024.

EGU24-12889 | ECS | Posters on site | HS1.1.7 | Highlight

Rainfall temporal variability and rainwater harvesting efficiency: an analysis over the Italian territory.  

Matteo Carollo and Ilaria Butera

Rainwater harvesting for indoor uses could be a useful practice for a sustainable management of urban water. The realization of a rainwater harvesting system strictly depends on the costs and the required space so that an accurate design is necessary, especially in the tank sizing step. The volume of the tank is an important element of the system which impacts not only important environmental issues such as the volumes of saved potable water and the reduction of rainwater volumes to the sewerage system, but also the costs and the practical realization of the rainwater harvesting system. Nevertheless, while the professional world seeks solutions that are easy to apply (e.g. simplified sizing methods), from a scientific point of view several aspects are still to be clarified, among these the role of the temporal variability of rainfall in the tank sizing step, that is the object of the present study.

Rainfall temporal variability is quantified by the Coefficient of Variation (CV) of rainfall datasets. This analysis is carried out through numerical simulations and it is focused on the national Italian territory. Daily rainfall data of 3436 rainfall gauge stations located on the national Italian territory are considered and buildings with different catchment area and number of persons are taken into account. Our computations show that the majority of rainfall gauges in Italy has a rainfall CV in the 2.5-3.5 range, with higher values in the South and in the main islands. The role of the temporal variability of rainfall is clear: the same building in locations with the same mean annual rainfall depth, can require different tank sizes according to the rainfall coefficient of variation of the specific location. As an example, to reach the same water saving, a medium rise building located in Ascoli Satriano (CV=2.42) should be equipped with a tank size of 2700 litres, while in other locations which have the same mean annual rainfall depth but different CV, like Casale Monferrato (CV=3.41) and Muravera (CV=4.83), the required capacity is 3400 litres and 6800 litres, respectively. This underline the importance of taking into account the rainfall temporal variability in the tank sizing.

The analysis made use of non dimensional parameters, i.e. the storage fraction and the demand fraction, so that the results, obtained from different buildings over the Italian territory, are comparable, allowing in this way to build a unique graph that contains all information: the water demand, the mean annual rainfall depth and the rainfall coefficient of variation, as well as the number of inhabitants and the roof area of the building.

How to cite: Carollo, M. and Butera, I.: Rainfall temporal variability and rainwater harvesting efficiency: an analysis over the Italian territory. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12889, https://doi.org/10.5194/egusphere-egu24-12889, 2024.

EGU24-15912 | ECS | Posters on site | HS1.1.7

Modelling reference evapotranspiration of green walls (ET0vert) 

Karin A. Hoffmann, Rabea Saad, Björn Kluge, and Thomas Nehls

Green walls, facade greenery, living walls – vertical building greening as part of urban green infrastructure are measures for climate sensitive urban design, for water management and microclimate regulation. Strategic integration of green walls into local water and energy cycles requires prediction of evapotranspiration, considering the individual design, plant species, and building characteristics. Available models address horizontal surfaces but disregard vertical particularities and urban conditions, e.g., reduced direct radiation, spatial patterns of radiation on the wall due to building orientation and shading obstacles, and very heterogeneous wind fields that are influenced by rough surfaces, canyons, and adjacent wind barriers. We present a verticalization model, ET0vert, for the reference crop evapotranspiration ET0 (FAO) based on a sensitivity analysis. It comprises the adaptation of solar radiation and wind to the individual situations in front of a wall or facade. The accuracies of the model predictions are evaluated for (i) remote climate station data (horizontal reference plane), (ii) interpolated climate data (both horizontal and vertical reference plane) and (iii) on-site measured climate data (vertical reference plane, both not height-adapted and height-adapted) as input. We validate the model with data for a one-month reference period (25/07/2014 – 29/08/2014) from a weighable lysimeter with Fallopia baldschuanica greening of a 12 m high wall in Berlin, Germany.

Regarding individual meteorological input parameters, we found high relevance of both vapor pressure deficit (VPD) and solar radiation (RS) for the study area. Using VPD and RS, respectively, a linear model could explain 90 % and 85 % of daily ET0 variances. No such relationship could be detected for wind speed, but for maximum and minimum wind speed.

Compared to remote horizontal input data, verticalization of input data (RS and wind) reduced overestimations of ET from about 90 % to 14 % and 27 % for the daily and hourly resolution, respectively. If onsite climate data is available, deviations are reduced to 9 % and 5 % for the daily and hourly resolution. Height-adaptation of input data resulted in further improvements of the prediction accuracies (1 % and 2 % deviation for hourly and daily resolution).

We conclude that simply using remote horizontal climate data for calculating ET of green walls is not advisable. Instead, any input data, onsite measured or remote climate station data, should be verticalized and preferably height-adapted. The verticalized model predicts the hourly and daily evapotranspiration of green walls necessary for e.g., irrigation planning, building energy simulations or local climate modeling.

For more information: https://doi.org/10.5194/hess-2023-22

How to cite: Hoffmann, K. A., Saad, R., Kluge, B., and Nehls, T.: Modelling reference evapotranspiration of green walls (ET0vert), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15912, https://doi.org/10.5194/egusphere-egu24-15912, 2024.

EGU24-16430 | ECS | Posters on site | HS1.1.7

Assessing the microclimate conditions in urban green spaces and the effects of underlying driving factors in Switzerland 

Yuxin Yin, Gabriele Manoli, and Lauren Cook

Urbanization and climate change are leading to an increase in urban heat, posing a threat to human health and well-being. Urban green spaces (UGS), such as parks and gardens, have been recognized as an effective strategy for heat mitigation because they dissipate heat within their boundaries and in the surrounding areas. The magnitude of the cooling effect of UGS varies across locations and is affected by various factors, such as background climate, urban fabric, and vegetation properties. However, previous research studying the effect of UGS typically focused on specific case study areas and particular aspects of driving factors.

To do so, we integrate modeling, remote sensing datasets, and on-site measurements to assess the microclimate conditions of five different UGS (allotment gardens, public parks, private gardens, real estate yards, and ruderal sites.) in three Swiss cities with different biophysical conditions (Zurich, Geneva, and Lugano). Urban Tethys-Chloris (UT&C) model, a novel urban ecohydrological model with an explicit representation of urban canyon and vegetation properties, is applied to simulate the microclimate for each UGS and city. The models are validated using on-site measurements for air temperature, relative humidity, and surface temperature from July to October 2023. Preliminary results for Zurich show a good fit between simulation results and on-site measurements for both three variables, especially for air temperature and surface temperature with both R-squares larger than 0.8.

During the simulation period from June 21 to October 3, results will identify diurnal and daily patterns of microclimate conditions, including how different vegetation properties (i.e., height, canopy width, leaf area index, stomatal conductance) affect the microclimate. Subsequently, statistical regression will be employed to explore how the cooling effect of UGS is related to the distinct urban fabric and background conditions. Overall, the study will explain how various factors influence urban microclimate and provide insights on which factors will help to enhance the cooling effect in urban green space design.

How to cite: Yin, Y., Manoli, G., and Cook, L.: Assessing the microclimate conditions in urban green spaces and the effects of underlying driving factors in Switzerland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16430, https://doi.org/10.5194/egusphere-egu24-16430, 2024.

EGU24-17003 | Posters on site | HS1.1.7

Sustainable Water Consumption Strategies in a Changing Climate 

Christina Tsai, Yu-Kai Chiu, Ching-Hao Fu, and Yao-Wen Hsu

Water consumption is a fundamental global need.  Water production consumes lots of energy and emits plenty of greenhouse gases.  Determining the carbon footprint of water can offer various benefits. Reducing water use and conserving water can lead to lower energy consumption, lower carbon emissions, lower monthly water and energy costs, and less demand for water.  As carbon neutrality gradually prevails, low carbon emissions have become the future global trend and goal.  Therefore, it is crucial to understand the relationship between water consumption and carbon emissions.

As most countries struggle to reduce their carbon emissions in response to global warming, investments in water conservation, efficiency, and reuse are among the most cost-effective energy and carbon reduction strategies.  Urban water infrastructures have been demonstrated to contribute to global CO2 emissions significantly, and buildings account for a large portion of most urban water consumption.  Notably, while there is abundant rainfall in Taiwan, there appears to be a frequent water shortage crisis.  Such a crisis is aggravated by climate change because of the more unpredictable seasonal changes.  Climate change is linked to excessive anthropogenic carbon emissions. 

This study focuses on five types of buildings with various missions and usage on the National Taiwan University campus.  These infrastructures are typically deemed as having significant water consumption at National Taiwan University: (1) Residential buildings, (2) Experimental buildings, (3) Experimental farms, (4) the Department of Animal Science and (5) Lecture halls.  The specific objectives of this project are to uncover the nexus between thermal comfort and water consumption and the relationship between water consumption and hydro-meteorological and anthropogenic factors.

 

How to cite: Tsai, C., Chiu, Y.-K., Fu, C.-H., and Hsu, Y.-W.: Sustainable Water Consumption Strategies in a Changing Climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17003, https://doi.org/10.5194/egusphere-egu24-17003, 2024.

EGU24-376 | ECS | Posters virtual | HS1.1.10

Examining Landscape Ecological Dynamics Amid Climate Change in the GBM Delta Region of the Indian Sundarbans 

Anirban Mukhopadhyay, Indrajit Pal, Mashfiqus Salehin, Ahmed Ishtiaque Amin Chowdhury, Nilay Pramanick, Jyoti Prakash Hati, Subhajit Ghosh, Ayush Baskota, Subha Chakraborty, and Manas Sanyal

The GBM delta stands as one of the world's most densely populated areas, where human activities have profoundly reshaped the landscape amid the challenges posed by recurring climatic disasters. The region, prone to tropical cyclones and flooding, faces a future where these natural hazards are expected to intensify, making the understanding of landscape ecological dynamics imperative for effective environmental management. This study scrutinizes the transformations in land use and land cover (LULC) dynamics within the GBM delta spanning three decades through integrating remote sensing and geographic information systems (GIS). Leveraging Landsat TM and OLI data, the research aims to discern anthropogenic alterations in land use patterns over the study period. Grey-level co-occurrence matrix (GLCM) analysis on Landsat datasets facilitates the identification of land use changes, employing the Support Vector Machine (SVM) as the classifying algorithm. In tandem, the study will document the influence of climatic disasters, assessing the impacts of tropical cyclones and floods in the delta. Rainfall and temperature anomalies will be calculated, while flooded areas will be delineated using Sentinel-1 Synthetic Aperture Radar (SAR) data. Climatic anomalies will be detected by analyzing TRMM, PERSIAN, and MODIS datasets. This research aims to unveil the intricate dynamics of the GBM delta's landscape over time by comprehensively understanding the interplay between anthropogenic activities and climatic events. The insights garnered, including the interests and livelihood operations of local communities, will be instrumental in informing government policies geared towards mitigating the escalating impacts of climatic disasters in the GBM delta.

Key Words: Sundarbans, LULC, livelihood, GBM Delta, Policies.

How to cite: Mukhopadhyay, A., Pal, I., Salehin, M., Chowdhury, A. I. A., Pramanick, N., Hati, J. P., Ghosh, S., Baskota, A., Chakraborty, S., and Sanyal, M.: Examining Landscape Ecological Dynamics Amid Climate Change in the GBM Delta Region of the Indian Sundarbans, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-376, https://doi.org/10.5194/egusphere-egu24-376, 2024.

EGU24-512 | ECS | Orals | HS1.1.10 | Highlight

Policy implications to encourage the adoption of Nature-based Solutions in Vietnamese Mekong Delta (VMD). 

Sreejita Banerjee, Loc Huu Ho, and Indrajit Pal

Deltas are often densely populated and support much of the world’s fishes, forest products and agriculture. Protecting livelihoods and ecosystem services in deltas is therefore of global importance. The environmental degradation and the climate change are one of the multiple pressures experienced by deltas affecting the ecosystem services that pose risk in the livelihoods of the locals as well as the global population living in these areas. There is a need for new strategies for sustainable development to help deltas mitigate the effects of climate change as well as adapt to the changing conditions in a context of increasing uncertainty of hazards. Coastal areas of the Vietnamese Mekong Delta (VMD) are highly vulnerable due to land use changes and extreme climate hazards. This study will explore the specific aspects of deltas from a complexity-based approach, and analyse Nature-based Solutions as alternatives towards sustainable development in these areas. This examines Nature-based solutions (NbS) as a complementary or alternative approach to managing hazards in the Vietnamese Mekong Delta. We investigated the potential NbS as a complementary and sustainable method for mitigating the impacts of coastal disaster risks, mainly cyclones and floods. Finally, we address this gap by conducting a systematic literature review to assess the existence of policy instruments such as the Law on Natural Disaster Prevention and Mitigation (2009), Flood and Storm Prevention and Control (2000), Law on Dykes (2006), that adopt NbS and to evaluate the existence of specific examples of NbS.

How to cite: Banerjee, S., Ho, L. H., and Pal, I.: Policy implications to encourage the adoption of Nature-based Solutions in Vietnamese Mekong Delta (VMD)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-512, https://doi.org/10.5194/egusphere-egu24-512, 2024.

EGU24-684 | ECS | Orals | HS1.1.10

A Comprehensive Indicator Based Vulnerability Assessment Method for School Education System: A Case Study of Sundarban Delta, India 

Anushree Pal, Takuji W. Tsusaka, Mohana Sundaram, Mokbul Morshed Ahmad, and Thi Phuoc Lai Nguyen

ABSTRACT

Natural hazards significantly impact school education, particularly in developing countries owing to their low coping capacity to hazards. The world’s 10 percent of tropical cyclones are experienced by Indian coastlines, together with the high probability of extreme rainfall events often leading to flood hazards. A comprehensive literature review highlighted the needs for thorough research on the differential impacts of climatic hazards on Sundarbans school education system and its societal linkages for adaptation strategies, hence promoting the resilient community.

This research aims to explore the impacts of multiple hazards and associated disruptions in school education, and attempts to identify determinants of resilience of school education to multiple hazards. The study aims to formulate an indicator library for vulnerability assessment of school education in the deltaic region. The research comprises of the conceptual background of vulnerability assessment, the indicators for education systems in the delta, the methodology for indicator library, and the indicator library table for school education systems in a comprehensive way. The study aims at developing a comprehensive library of school vulnerability indicators that will academically contribute as a reference for future researchers in the field of school vulnerability assessment.

How to cite: Pal, A., Tsusaka, T. W., Sundaram, M., Ahmad, M. M., and Nguyen, T. P. L.: A Comprehensive Indicator Based Vulnerability Assessment Method for School Education System: A Case Study of Sundarban Delta, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-684, https://doi.org/10.5194/egusphere-egu24-684, 2024.

Climate change dominates the nexus between water resources management needed for farm farmland irrigation and food security insurance. The challenge increases when the population proliferates and the demand for food and water rises. This study will explore how climate change may affect food production and water use in the Nile Delta, Egypt, through higher temperatures and sea level rise. It also aims to investigate the best management practices (BMPs) that can be used to tackle these issues. In the Delta, where irrigated agriculture is practiced, sea level rise is a major potential impact of climate change since it significantly impacts the salinity of the water and soil. Furthermore, higher temperatures directly influence evapotranspiration, a crucial component of crop yields and water balance. To determine this interdisciplinary nexus between climate, water, and food, integrated hydro/hydrogeological and crop models will be created by calibrating and simulating the current baseline situation. For that purpose, a basic crop model will be merged with the coupled SWAT_MODFLOW hydro(geo)logical simulation software. Additionally, a range of forecasting scenarios will be run to represent the impact of multiple climate change scenarios. The outcomes of operated scenarios will be evaluated regarding socioeconomic and environmental aspects to support the decision-making process and define how far the BMPs can be implemented on ground in this study area.

How to cite: Gomaa, S., Fleskens, L., Carvalho Nunes, J., and Badr, M.: An Integrated Modelling Approach to Support Sustainable Water Resources Management and Climate Change Adaptation for Irrigated Agriculture in the Nile Delta, Egypt., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-693, https://doi.org/10.5194/egusphere-egu24-693, 2024.

Nutrient delivery and water yield are key ecosystem functions that impact food security. Climate and Land use Land cover (LULC) changes are the main driving factors that affect these water related ecosystem services. By recognizing the value of ecosystem services, the efforts to manage ecosystem services have increased. One such tool to help manage ecosystem services is the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, a new but powerful ecosystem service model. However, the InVEST model still requires testing in various geographic regions. This study assessed the performance of the InVEST water yield and nutrient delivery models in Siem Reap Province, Cambodia. The climate scenarios were projected using CMIP6 for two pathways namely SSP2-4.5 and SSP5-8.5. Past, Present, and future scenarios were developed for two InVEST models including Annual water yield (AWY) and Nutrient delivery ratio (NDR) to evaluate the impacts of Climate change and LULC. In the past and present, water yield dropped by 52-69% from 2018 to 2022, with nitrogen and phosphorus exports rising by 627 and 186 tons, respectively. In future scenarios, from SSP2-4.5 to SSP5-8.5, water yield in Near Future (NF) decreased by 6-8%, while in Mid Future (MF), it increased by 10-12%, and in Far Future (FF), it decreased by 1-2%. Future nutrient delivery showed minor changes, nitrogen exports dropped by 0.42 tons for NF and increased slightly by 3 tons for MF, also increasing by 2.4 tons for FF. Phosphorus exports decreased by 0.07 tons for NF and increased slightly by 0.8 tons for MF, with a 0.7-ton increase for FF in Siem Reap province. Climate change primarily impacts water yield, with LULC governing nutrient delivery. Expanding croplands and urban areas heighten pollutants and threaten food security, while diminishing forests and vegetation reduce water yield, intensifying challenges in securing a stable food supply in Siem reap province of Cambodia.

How to cite: Ahmed, F. and Loc, H. H.: Evaluation of Climate and Land Use Change impacts on ecosystem services that support Food Security in Siem Reap Province, Cambodia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3631, https://doi.org/10.5194/egusphere-egu24-3631, 2024.

EGU24-4213 | Orals | HS1.1.10 | Highlight

Preserving coastal agriculture: Nature-based solutions for the mitigation of soil salinization  

Paolo Tarolli, Edward Park, Jian Luo, and Roberta Masin

Soil salinization significantly threatens agriculture and food security, leading to profound soil degradation and desertification, negatively impacting ecosystems. The accumulation of excessive salts has negative effects on soil structure, fertility, plant growth, crop yield, and microorganisms. This phenomenon is attributed to natural factors, such as dry climates and high evaporation rates, and human-induced factors, including not optimal irrigation practices, inadequate drainage systems, and excessive fertilizer use. The increased frequency of weather extremes driven by climate change exacerbates this global issue, especially along coastal areas where millions of people live. Here, the sea-level rise, and recently also drought, are causing, especially in river deltas, a progressive land degradation, which negatively impacts the sustainable development of coastal agriculture. The lack of rainfall leads to scarce river discharge and consequently favours marine water inland flow intrusion. Anthropogenic activities (e.g., dams, mining) are exacerbating the phenomenon. Urgent mitigation strategies are therefore necessary. This study explores the potential of Nature-based Solutions (NbS) as sustainable and resilient response to soil salinization, offering benefits to agriculture through revitalizing ecosystem services. In detail, we addressed the challenges and limitations of implementing natural barriers, wetlands, buffer zones, conversion to aquaculture, straw incorporation, microbial-based solutions, organic fertilizers, and low impact water storage facilities. In detail, we should start re-introducing, where possible, wetlands through renaturalisation strategies, aiming to create a virtuous ecological equilibrium in agricultural landscapes. Indeed, wetlands can offer a natural barrier to saltwater intrusion. Soil remediation of degraded areas, especially for those interested in sand mining or oil refineries, is necessary to make soils more resilient and reestablish missed ecosystems. Agriculture must be sustainable and adopt conservation practices to keep and improve soil organic carbon content (SOC). Soils rich in SOC can retain more water and are more resilient; thus, they are more prepared for prolonged pressure given by water scarcity and soil salinization.

How to cite: Tarolli, P., Park, E., Luo, J., and Masin, R.: Preserving coastal agriculture: Nature-based solutions for the mitigation of soil salinization , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4213, https://doi.org/10.5194/egusphere-egu24-4213, 2024.

EGU24-5550 | Posters virtual | HS1.1.10

Salt intrusion monitoring in the Po River Delta branches (Italy)  

Mauro Del Longo, Elisa Comune, Alessandro Allodi, Giuseppe Ricciardi, Enrica Zenoni, Anna Gloria Angonese, Silvia Pigozzi, and Saverio Turolla

The Po River Delta is the outlet of the Po basin, the biggest catchment in Italy; it is composed of the  branches of Goro, Gnocca, Maistra, Tolle and Pila, spanning over a 700 km2 area, nowadays  inhabited by around 50.000.

Modeled by the human presence through channels, levees and other hydraulic infrastructures, this is a “young territory”, originated from the “Taglio di Porto Viro” done by the Republic of Venice, around 1600, in order to divert the Po river mouth southward and avoid silting of lagoon harbors.

Beyond its high natural, economic and cultural value, this area is exposed to multiple hazards related to floods and  storm surges, droughts, erosion, subsidence, water pollution and loss of biodiversity, exacerbated by soil consumption and climate change; one of the highest threats is the salinization of surface,  groundwater and soils, due to the increasing of duration and extension of salt intrusion from the Adriatic Sea (Enhance, 2016; Allodi, 2022).

Particularly during low flows, as in Summer 2022 (GDO, 2022), salt intrusion reduces fresh water availability  for drinking supply, agriculture and industry, as also for balancing habitat salinity and guaranteeing  ecological benefits.

For many years this fragile and dynamic context has been under systematic observation, related to salt intrusion as also to liquid discharges, solid transport, topography, hydrodynamics, tides and beach morphology (Visentini, 1940; Cati, 1981).

Within the current multi level-multi actor governance system, since 1995 the Emilia-Romagna Regional Agency for Prevention, Environment and Energy (Arpae) is involved in the integrated monitoring  of the Po River Delta, supporting  water protection and use, flood management and the general sustainability of human activities.

Through the Idro Meteo Climate  (SIMC) and the "Daphne" Oceanographic Structures, Arpae  collects river, delta and sea water level observations from telemetry networks and discharge measurements and salinity observations from field campaigns.

From these monitoring activities it is first possible to maintain stage-discharge equations, particularly at the Pontelagoscuro Station upstream the delta, and consequently to maintain the discharge repartition equations in the delta, depending not only on upstream discharge but also on  hydraulics of each branch and sea level conditions (Settin, 2012); secondly it is possible to support salt intrusion length assessment and estimation in each delta branch, mainly depending on river discharges, their repartition in each delta branch and sea levels conditions (Comune, Turolla, 2023).

Territorial knowledge and conservation, based on the integration of in situ monitoring and control, historical data,  other data sources (topography, groundwater, water quality), satellite products, models (including digital twins), artificial intelligence, uncertainties management and high computing capacities, may help better understand earth systems and better simulate future scenarios depending on climate, land use and  social changes.

Monitoring of the Po River Delta, is therefore indispensable for theoretical assessment, supporting from-short-to-long-term awareness, decision making and action by public institutions, private enterprises, associations and local community, in order to assuring sustainable and fair water uses and ecosystem services  in a vulnerable area exposed to increasing threats and at the same time rich in opportunities and beauty.

How to cite: Del Longo, M., Comune, E., Allodi, A., Ricciardi, G., Zenoni, E., Angonese, A. G., Pigozzi, S., and Turolla, S.: Salt intrusion monitoring in the Po River Delta branches (Italy) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5550, https://doi.org/10.5194/egusphere-egu24-5550, 2024.

EGU24-6453 | ECS | Posters on site | HS1.1.10 | Highlight

Seawater intrusion in coastal agricultural regions: a global review 

Aurora Ghiardelli, Eugenio Straffelini, Edward Park, Vincenzo D'Agostino, Roberta Masin, and Paolo Tarolli

Coastal agriculture is key in sustaining food production for the growing global population. Due to highly fertile soils and water availability, lowlands located in the proximity of river mouths often represent the backbone of coastal agricultural activities. However, over the past decades, anthropogenic-related processes are reducing yield increases. Climate change has rapidly become a major threat, with sea-level rise (SLR) and extreme weather events such as prolonged droughts and record-breaking temperatures. In addition, deltaic areas are often densely populated, and intense human activities undermine the resilience of coastal agro-environments. In this context, seawater intrusion (SWI) is one of the most damaging processes affecting agriculture through soil salinization and the depletion of irrigation water resources. This leads to crop damage, huge yield losses and permanent harm to soil fertility. Despite the relevance of the topic worldwide, to this date, there is a lack of global synthesis on the impact of SWI on coastal agriculture and an insufficient consideration of the phenomenon in local surveys. To fill this research gap, we present a systematic review of the global distribution and impact of SWI in coastal agriculture of river deltas, focusing on the main hotspots and prevalent drivers, related to climate change, natural processes, and local human activities such as dam construction, dredging or groundwater overexploitation. Moreover, the global study helps to highlight the areas where data is insufficient and compares patterns of SWI across different regions. Additionally, the study assesses the global distribution of rural regions potentially impacted by SWI and the main crops characterizing the economies of river deltas. Finally, we delve into the future implications of demographic growth and SLR projections in deltaic regions, discussing the possible scenarios of coastal agriculture regarding water management, agronomic practices, and relative sustainability.

How to cite: Ghiardelli, A., Straffelini, E., Park, E., D'Agostino, V., Masin, R., and Tarolli, P.: Seawater intrusion in coastal agricultural regions: a global review, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6453, https://doi.org/10.5194/egusphere-egu24-6453, 2024.

Concern for climate change impacts to the Vietnamese Mekong Delta is rapidly increasing due to the compound risks of a changing climate, environmental change and sensitivity and social-economic transformation. The Delta, located in the downstream section of the Mekong River is considered globally as one of the three most vulnerable deltas to climate change. Variations in precipitation, temperature changes, sea-level rise, progressive saline instructions, riverbank erosion, flooding and extreme weather events all aggravate the risk to the existing socio-ecological system.

Using Ben Tre Province as an in-depth case study, this paper develops a social vulnerability index (SVI) to understand the water hazards-modified by climate change in terms of their association between vulnerability, existing infrastructures and socio-economic patterns. A mix-method of qualitative and quantitative approaches was framed to procure and analyse data. This consisted of group discussions, individual surveys and key informant panel interview. Spatially mapped results of cluster analysis showed a strong spatial trend of SVI increasing from upstream to the downstream areas The multivariate regression model found linear correlations between the SVI and the proximity to the dike system and waterways. Additionally, the Moran’s I autocorrelation indicated the statistically significant difference between the SVI spatially of various household clusters. These findings contribute y to the understanding of the array of biophysical and socio-ecological impacts, their variability and their interlinkages.

How to cite: Phan, T., Van, T., Downes, N., and Thai, T.: Understanding Social Vulnerability to Climate Change-Modified Water Hazards in the Vietnamese Mekong Delta Coastal Zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8332, https://doi.org/10.5194/egusphere-egu24-8332, 2024.

EGU24-9307 | ECS | Orals | HS1.1.10

Combining Remote Sensing and On-site Observations to Explore Salinization Dynamics in the Po River Delta  

Aurora Ghiardelli, Eugenio Straffelini, Sara Cucchiaro, and Paolo Tarolli

Seawater intrusion (SWI) is an escalating concern in coastal regions globally, with alterations in weather patterns and sea-level rise emerging as pivotal factors contributing to the occurrence of SWI in both surface waters and groundwater. This phenomenon poses a significant risk to low-lying agricultural areas, leading to soil salinization with substantial adverse effects on soil quality and crop yields. In the Po River Delta, Italy's broadest agricultural region impacted by SWI, summer droughts play a pivotal role in driving SWI dynamics. Within this extensive lowland area, the deficiency in rainfall during the summer months reduces river flow, facilitating the inland movement of seawater. The escalating frequency of drought events and exceptionally high temperatures in recent summers, has highlighted the necessity for a thorough understanding of the impact of SWI on cropland, both on vegetation and soil, to detect any possible correlations between SWI, accumulation of salts and plant stress. The objective of this study is to combine multi-temporal remote sensing from satellite imagery, to monitor plant greening, with on-site observations of soil electrical conductivity (EC). Normalized Difference Vegetation Index (NDVI) maps for the summer period 2023 were elaborated from satellite data, classifying cropland with a machine-learning algorithm to filter bare soil and surface water from green vegetation. In the same time period, two experimental sites located in the delta region were periodically sampled with a Time Domain Reflectometry (TDR) probe to monitor soil temperature, moisture and EC. Soil samples were also collected and analyzed to measure EC of the water extracts. Although summer 2023 was not characterized by extreme drought, the combined results offered a quick method for identifying salinization trends within the delta cropland area, pinpointing the most susceptible areas both on a regional scale and on a local scale.

How to cite: Ghiardelli, A., Straffelini, E., Cucchiaro, S., and Tarolli, P.: Combining Remote Sensing and On-site Observations to Explore Salinization Dynamics in the Po River Delta , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9307, https://doi.org/10.5194/egusphere-egu24-9307, 2024.

EGU24-9392 | ECS | Orals | HS1.1.10 | Highlight

Identification of global hotspots for salinity vulnerability 

Md Feroz Islam, Judit Snethlage, Hester Biemans, Catharien Terwisscha van Scheltinga, and Ángel de Miguel García

Global food security is challenged by lack of fresh water availability and increasing salinity. Water and soil salinity have increased during the last few decades and are projected to increase in the future which will adversely effect the food security. Effect of climate change will exacerbate the situation. Previous researches have predominantly focused on the impact of either soil or water salinity on agriculture and food security. An assessment of combined impact of soil and water salinity at global scale is required. We have considered global datasets on soil and water salinity to locate areas with higher impact of salinity and combined indicators on climate, water availability, source of irrigation, cropping pattern, soil characteristics and level of salinity to identify regions with higher vulnerability to salinization. The impact of salinity on crop (wheat, rice and maize) yield was considered to produce a primary estimate of potential loss of food production. Combining soil and water salinity data indicate that currently the southeast and southwest coast of USA, southern part of Africa, southeast regions of Australia and coastal regions of Bangladesh are mostly impacted by salinity.  The MENA region, sub-saharan regions, large parts of Australia, southern Europe, southwestern coast of USA, eastern China, as well as the coast of Vietnam, GCC states, the eastern part of Indonesia, northern parts of India, coastal regions of Bangladesh and southeastern regions of Africa are identified as vulnerable regions for increasing salinity. The potential crop yield loss due to salinity is highest for Maize and lowest for Wheat.  Global cropping pattern shows that rice and maize are being cultivated more in salinity vulnerable areas than wheat, even though wheat is the most saline tolerant of the three. Identification of saline hotspot areas and regions vulnerable to increasing salinity will assist in development location specific of policies, regulation and adaptation strategies to counter the adverse impact of salinity in the future. More in depth analysis on Ganges-Brahmaputra-Meghna (GBM), Mekong and Nile delta will be carried out for regional verification of salinity hotspot and vulnerable location identification.

How to cite: Islam, M. F., Snethlage, J., Biemans, H., Terwisscha van Scheltinga, C., and de Miguel García, Á.: Identification of global hotspots for salinity vulnerability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9392, https://doi.org/10.5194/egusphere-egu24-9392, 2024.

EGU24-14750 | ECS | Posters virtual | HS1.1.10

Exploring disaster impacts on livelihoods in the Ganga Brahmaputra Meghna Delta communities in India 

Ayush Baskota, Indrajit Pal, and Anirban Mukhopadhyay

The Ganga Brahmaputra Meghna (GBM) delta, situated in India and Bangladesh, represents a densely populated and precarious area. Over 200 million residents face significant environmental threats, such as tropical cyclones, land subsidence, riverine flooding, coastal inundation, rising sea levels and storm surges, particularly affecting socio-economically marginalized communities with vulnerable livelihoods.

This paper investigates disaster impacts on local livelihoods in the GBM delta communities in West Bengal, India through a comprehensive household survey of 1236 respondents across Sandeshkali, Sagar, Hingalgunj, and Gosaba community blocks. The survey revealed a diverse distribution of hazard severity across the region; residents in Sagar and Hingalgunj blocks were primarily impacted by cyclones whereas Gosaba and Sandeshkali blocks were also impacted by flooding, inundation and land erosion. Furthermore, disasters have tremendous impact on the local economy, with respondents reporting a 50% decrease in income from their primary livelihood in the aftermath of a disaster. These impacts were found to be more profound in Sagar and Gosaba blocks, where people were more reliant on agriculture and farming, as compared to Sandeshkali where families were involved in diverse livelihoods. A significant proportion of disaster damages were attributed to salt-water intrusion in agricultural land and aquacultural ponds, followed by damages to critical infrastructure such as roads and power network and health-related issues in the aftermath of cyclonic events. The findings of this study demonstrate the diverse socio-economic scenario in the GBM delta, highlighting the importance of block and community specific risk management and livelihood strengthening programs.

How to cite: Baskota, A., Pal, I., and Mukhopadhyay, A.: Exploring disaster impacts on livelihoods in the Ganga Brahmaputra Meghna Delta communities in India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14750, https://doi.org/10.5194/egusphere-egu24-14750, 2024.

EGU24-17963 | Orals | HS1.1.10

Bridging Perspectives: Lessons from the Water Custodian approach 

Willem Van Deursen, Syeda Khushnuma Wasim, and Myisha Ahmad

Water management decision-making typically adopts either a top-down or a bottom-up approach. Presently, Bangladesh is exploring participatory planning, emphasizing consultations with local communities. This paper presents a framework for linking the top-down with the bottom-up approaches and discusses three case studies. The first one is about Tidal River Management in the South West Delta Bangladesh, and subsequently the framework is applied to Haor and Dhaka.

The livelihoods of communities in the South-West Delta face challenges due to environmental changes and socio-economic dynamics. Traditional approaches, inspired by Dutch polder development, have led to adverse effects such as increased salinity and drainage congestion. Local dissatisfaction with these solutions has manifested in events where farmers breach embankments to address these issues, while others turn to shrimp farming. A top-down approach to water management hampers effective communication and collaboration between experts and local communities.

The key challenge lies in managing the complex interactions among diverse stakeholders within the heterogeneous community. The Water Custodian framework aims to address this challenge by incorporating local community mapping into decision-making processes. The framework recognizes the diversity of stakeholders, including large landowners, subsistence farmers, and landless laborers, each with unique perspectives and incentives.

The primary objective of the framework is to enhance decision-making processes by incorporating humane elements, focusing on the inclusion of local communities and their vulnerability profiles. This involves developing a decision support process and tool to facilitate the inclusion of local knowledge and expertise in water management decision-making.

The approach is based on 'mental models' and 'life stories,' aiming to bridge geo-physical criteria with socio-economic and livelihood criteria. The Water Custodian framework uses fictional archetypal characters called Local Families, akin to personas in marketing and user interaction development, to represent different user groups. These personas help experts and decision-makers understand the diverse needs, experiences, behaviors, and goals of local communities. A serious board game is developed in which participants roleplay the various life-stories and have to prioritize the interventions based on their perspectives. The process is supported by a non-complex rapid impact assessment software, to provide rapid assessment of the scores obtained on the defined indicators.

The Water Custodian approach's adaptability to various contexts has been demonstrated by its application in the South-West Delta, the Haor region for integrated flood management, and for urban sustainability in Dhaka and Mumbai.  By using serious gaming for mapping and understanding the local context, the framework remains effective in addressing the unique challenges of each region.

Beyond its application in Bangladesh, the Water Custodian framework holds potential for various contexts worldwide. In natural resource management, it can be adapted to scenarios involving water resources, forests, or agricultural lands. The framework's inclusive approach can also find application in urban planning and development, disaster management, and educational initiatives.

In conclusion, the Water Custodian concept transcends geographic boundaries and application domains, serving as an anchor for inclusive and participatory approaches in decision-making.

How to cite: Van Deursen, W., Wasim, S. K., and Ahmad, M.: Bridging Perspectives: Lessons from the Water Custodian approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17963, https://doi.org/10.5194/egusphere-egu24-17963, 2024.

Riverbank erosion is one of the world’s major hazards in delta areas. The Mekong Delta of Asia is one among them which is facing many sediment-related issues, particularly riverbank erosion. Extreme flood events and sea level rise due to climate change increase the risk of riverbank and coastal erosion in the Mekong Delta. This study aims to assess riverbank stability using the BSTEM model, investigate the level of vulnerability of local communities to riverbank erosion and understand their adaptive strategies to cope with riverbank erosion problems. The study focuses on Kaoh Soutin (KS) and Ruessei Srok (RS) communes which are next to the Mekong River in the delta area of Cambodia. Linking with flow velocity and water level from the HEC-RAS  2D model, the BSTEM model was set up to examine riverbank stability at two locations in KS and two locations in RS. The study used soil samplings and the laboratory test to investigate critical shear stress and erodibility coefficient for the BSTEM model. The results indicate that river water level and groundwater level are crucial factors influencing the overall stability of the riverbank. Higher water levels result in increased confining pressure on the riverbank, leading to a higher factor of safety. Soil erosion also has significantly impacted the riverbank at the study location. The level of vulnerability in two communities was determined based on IPCC’s livelihood vulnerability index (LVI) and coping strategies were determined based on field survey questionnaires and focus groups interviewed. It is found that KS is slightly more vulnerable to riverbank erosion than RS, as indicated by LVI values of 0.49 and 0.46 for KS and RS, respectively. The Chi-square test was carried out to identify vulnerability indicators that are statistically different between KS and RS. The current adaptive strategies based on interviews include reducing expenses, resettlement, diversifying income sources, and seeking support from various entities, including local authorities, NGOs, and government interventions during riverbank erosion. Large-scale monitoring and modeling systems are necessary for developing early warning systems and identifying hotspots. Riverbank protections both infrastructure-and nature-based solutions and migration plans are required to support livelihood adaptation.

How to cite: Piman, T., Tha, T., and Ruangrassamee, P.: Modeling riverbank stability and assessing vulnerability and adaptive strategies on riverbank erosion in the Mekong Delta, Cambodia , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20488, https://doi.org/10.5194/egusphere-egu24-20488, 2024.

EGU24-21205 | ECS | Orals | HS1.1.10

Statistical associations of basin streamflow on sea surface salinity variability across major global deltas. 

Fahad Khan Khadim, Augusto Getirana, Rajat Bindlish, and Sujay Kumar

Sea surface salinity ( ) is a key parameter for the thermohaline circulation of global oceans, as well as the global hydrologic cycle. Near the deltas, inland streamflow through large catchments plays a crucial role in mediating salinity, which is vital for maintaining an agro-hydrological balance in the deltas. With recent remote sensing data sources providing both   and streamflow at global scales, we calculated the statistical associations of   with simulated basin streamflow ( ) at a monthly scale in 48 major deltas across the globe. The monthly   data was downloaded globally at   intervals from the SMAP RSS L3 products. The hourly streamflow data was extracted from HYMAP streamflow routing simulations (available at   spatial grids) within NASA’s LIS modeling framework. The streamflow data was spatiotemporally aggregated before performing the statistical analyses. We calculated the associations over different monthly-lags and plume distances and obtained the optimal correlations. The optimal correlation coefficients ( ) reveal strong anticorrelation phenomenon between   and   (  for seasonal data at 28 deltas, and   for de-seasoned data at 21 deltas). In addition to basin streamflow, we considered a number of sea surface climate forcings (precipitation, sea surface temperature, and wind speed) to perform similar statistical comparisons with  . The results revealed that   near the deltas are more influenced by basin streamflow in general. From a physical science perspective, we found consistent outcomes in the majority of deltas, with some irregularities in deltas with strong anthropogenic and management influences (e.g., deltas containing low forest cover and high reservoir areas). The anticorrelation phenomenon was more prominent in large deltas, specifically located near the tropical climates, which experience high streamflow and no ice-melting. We also found that the anticorrelations are more profound in river dominated deltas (e.g., deltas where the fluvial dominance ratio is greater than 1). The findings of this research will be useful for delta researchers aiming to devise global scale strategies amidst the rising threats of salinity intrusion.

How to cite: Khadim, F. K., Getirana, A., Bindlish, R., and Kumar, S.: Statistical associations of basin streamflow on sea surface salinity variability across major global deltas., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21205, https://doi.org/10.5194/egusphere-egu24-21205, 2024.

EGU24-482 | ECS | Posters on site | HS1.1.11

Predicting Global Change impacts on streamflow dynamics using distributed hydrological modeling in a data-scarce nested tropical catchment in West Africa. 

Albert Elikplim Agbenorhevi, Julian Klaus, Leonard Kofitse Amekudzi, Nelly Carine Kelome, Ernest Biney, and Ernestina Annan

Currently, the global water cycle is experiencing radical shifts and the associated global water crisis requires rapid action by stakeholders to mitigate adverse impacts on both human populations and ecosystems. This urgency in action is driven by the combined effect of Climate Change and Land-use land cover change (LULCC) and the associated challenges in securing clean water sources. The Global Change from climate change is making water scarcity worse in places that are water-stressed, causing more competition and even conflicts over water resources. Addressing the global water crisis is especially challenging in the data-scarce region of the Global South where the status of hydrological processes and water availability is poorly constrained. Here, progress in hydrological predictions through robust hydrological models remains on top of the research agenda. General for the Global South, and particularly for West Africa, is the limited hydrological process understanding of tropical catchments with accelerating land cover change. The focus of the research study seeks to address the following research questions:
•    How does climate change alter hydrological processes in tropical catchments and does this alter streamflow regimes across nested catchments? 
•    How does and what are the contribution of LULCC in spatial-temporal changes of streamflow in a nested catchment in addition to the alterations driven by climate change within a given West African region?
To address the questions above, we will rely on data from the Pra River Basin in West Africa. In the present study, we employed Google Earth Engine (GEE) and Random Forest Classifier (RFC) to assess a time-series spatio-temporal land-use/cover change and change detection of the Pra River Basin for the period 2007 to 2023. Focusing on five (5) LULCC classifications has become crucial to the region's unregulated large and small-scale mining activities. The use of the Normalised Difference Water Index (NDWI), and Modified NDWI (MNDWI), was effective in extracting water surface areas for the change detection and pressure on the Pra River Basin and dealing with the overestimation phenomenon. We next integrate the processed LULCC into an eco-hydrological model that is validated against observed and reanalysed streamflow at different stations, soil moisture, and groundwater data. Future work will consist of estimating the impact analysis of Global Change on streamflow using an ecohydrological model that will be driven with the downscaled climate scenarios from CMIP6 and time-series land use change scenarios. This multifaceted approach is novel to the scientific understanding of water resource dynamics in the face of Global Change in tropical systems.

How to cite: Agbenorhevi, A. E., Klaus, J., Amekudzi, L. K., Kelome, N. C., Biney, E., and Annan, E.: Predicting Global Change impacts on streamflow dynamics using distributed hydrological modeling in a data-scarce nested tropical catchment in West Africa., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-482, https://doi.org/10.5194/egusphere-egu24-482, 2024.

Food security is a major concern in the Lower Mekong River Basin, especially under the projected climate change conditions. The areas suitable for rice cultivation, the most important agricultural product in the basin, are expected to change drastically, with the most severe reduction in northeast Thailand. This study investigated the variations in the past ten years of three ecosystem services directly related to agricultural production in Nakhon Phanom, a mostly rural province in northeast Thailand. Using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) program, and historical and projected climate data up to 2050, we discovered significant variations in water yield, and nutrient and sediment delivery to streams that were strongly correlated with changes in local land use. Further variations can be expected in the future with significant differences observed between and rainy seasons. Sustainable adaptation strategies, such as nature-based solutions, are therefore highly recommended to safeguard and enhance food security within this region.

How to cite: Nguyen, H. M. and Ho, H. L.: Assessment and projection of food security related ecosystem services in Nakhon Phanom, northeastern Thailand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-612, https://doi.org/10.5194/egusphere-egu24-612, 2024.

EGU24-1478 | Posters on site | HS1.1.11

Assessment of drought prone areas in Slovakia according to the changes in the long-term mean discharges 

Katarina Jeneiova, Lotta Blaskovicova, Katarina Kotrikova, Zuzana Danacova, and Jana Poorova

The assessment of changes in the hydrological regime under the climate change uncertainty is especially important for the decision making processes as the hydrological design values, derived for a reference period, are directly used for decision making in many areas of water management, including drought management. Recent local studies confirmed that there are changes in hydrological regime of the last decades in comparison to the currently used reference period 1961-2000 in Slovakia. Therefore, the selection of the reference period for the design values is under revision. In the first step, long-term mean discharge observations from the state hydrological network with near natural regime were analysed. The newly proposed period 1991-2020 was compared to the reference period 1961-2000 and the deviations of long-term discharges in selected water-gauging stations were assessed. The newly proposed reference period was selected for the analysis, as it is recommended by the World Meteorological Organisation for the purpose of climate change monitoring and better comparability of climatological and hydrological characteristics. As the second step, maps of the drought prone areas were drawn according to the spatial distribution of the results. We hope that this analysis will serve as supporting material to help the decision makers in policy making process and toward more effective drought management in Slovakia.

How to cite: Jeneiova, K., Blaskovicova, L., Kotrikova, K., Danacova, Z., and Poorova, J.: Assessment of drought prone areas in Slovakia according to the changes in the long-term mean discharges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1478, https://doi.org/10.5194/egusphere-egu24-1478, 2024.

EGU24-1628 | Orals | HS1.1.11

The potential impact of climate tipping points on drinking water supply planning and management in Europe 

Peter van Thienen, Herbert ter Maat, and Sija Stofberg

In recent decades, substantial advancements have been achieved in state-of-the-art climate models, signifying commendable progress by the scientific community. These models have proven invaluable in comprehending and forecasting anthropogenic climate change. Nevertheless, their efficacy is limited when examining the intricate dynamics of tipping elements and their potential ramifications for overall climate stability. This limitation results in the absence of these tipping elements in widely adopted climate projections utilized by the drinking water industry to assess system resilience.

Despite the prevailing insufficiencies, there is a growing body of evidence indicating the existence and, conceivably, the imminent activation of certain tipping elements. The drinking water sector, characterized by its inherently slow-paced nature due to infrastructure designed for extended operational lifespans, faces a critical challenge. The rapid timescales associated with potential changes resulting from tipping element activations surpass the typical lifespan of drinking water infrastructure. Consequently, the water sector cannot afford to wait for scientific consensus to emerge.

This contribution asserts that climate tipping points pose a latent, underexplored, and potentially underestimated risk for the water sector. To address this concern, we introduce a straightforward model that explores potential magnitudes and timescales of abrupt climate changes linked to tipping element activations. Our investigation focuses on Europe, aiming to scrutinize the effects and consequences on drinking water supply. Specifically, we incorporate an assessment of the potential collapse of the Atlantic Meridional Overturning Circulation, deemed most pertinent for Europe based on projected effects, associated timescales, and implications for the water sector.

Our findings underscore the necessity of integrating tipping scenarios into the decision-making processes within the drinking water sector, given the profound uncertainty and far-reaching consequences associated with these events.

How to cite: van Thienen, P., ter Maat, H., and Stofberg, S.: The potential impact of climate tipping points on drinking water supply planning and management in Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1628, https://doi.org/10.5194/egusphere-egu24-1628, 2024.

EGU24-2135 | ECS | Posters on site | HS1.1.11

Assessment of Climate Change on Water Availability in Central Himalayas, Nepal 

Bipin Dahal, Insaf Aryal, Naba Raj Dhakal, and Suresh Marahatta

The Kaligandaki River Basin (KRB) in Nepal, as one of the Himalayan River Basins, is experiencing severe impacts of climate change on its water resources. In this study, future climate projections from downscaled CMIP6 GCM models were used to evaluate the potential effects of climate change on the hydrological regime of the KRB by developing a hydrological model soil and water assessment tool (SWAT). Multi-site validation approaches were used to address the high spatial heterogeneity of the basin. The performance of the model was excellent, achieving a consistently very good ranking throughout the study, as evidenced by calibration and validation results. Under the intermediate emission pathways SSP245 scenario, the average annual temperature in the basin is projected to increase by 1.5°C, with a maximum rise of 2.8°C during the pre-monsoon season in the far future. In the high emission pathways SSP585 scenario, the average annual temperature is projected to increase by 2.2°C, with a maximum rise of 4.3°C expected during the winter season in the far future. Precipitation is anticipated to increase across all future time windows, with higher magnitudes under the SSP585 scenario. The combined effect of temperature and precipitation increases is expected to increase the discharge of the river. Specifically, discharge is projected to increase by 6% (under SSP245) and 12% (under SSP585) for 2025-49, 14% (under SSP245) and 24% (under SSP585) for the 2050-74, and 23% (under SSP245) and 40% (under SSP585) for the 2075-99 timeframes. The projected changes indicate an overall increase in average annual discharge, with greater increases expected under the high-emission scenario. These findings highlight the significant influence of climate change on the water balance components and hydrological regime of the KRB.

 
Keywords: SWAT, Climate Change, Water Availability, Kaligandaki

How to cite: Dahal, B., Aryal, I., Dhakal, N. R., and Marahatta, S.: Assessment of Climate Change on Water Availability in Central Himalayas, Nepal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2135, https://doi.org/10.5194/egusphere-egu24-2135, 2024.

EGU24-2241 | ECS | Posters on site | HS1.1.11

Global vulnerable basins suffering social-ecological impacts of water scarcity 

Fubo Zhao and Yiping Wu

The UN water conference, convened in March 2023, calls for governing water and addressing climate change in tandem to co-achieve related sustainable development goals. However, the actual (water scarcity under current climate conditions) and potential (potential water scarcity under climate change) impacts of water scarcity on social-ecological impacts are rarely assessed. Herein, we developed a framework that integrates water scarcity and climate sensitivity to assess the socio-ecological vulnerability of global basins. We found that basins that already experience water scarcity are exhibit a disproportionate magnitude of climate sensitivity, which exacerbated the challenges associated with water resources management. We identified the vulnerable basins by integrating socio-ecological vulnerability and found that the most vulnerable basins are mainly located in developing countries. Therefore, the urgent international cooperation for reducing vulnerabilities of water scarcity is required. Measures involved in current Integrated Water Resources Management and Climate Change Adaptation may not be enough to alleviate the water crisis and to adapt to climate change in these vulnerable basins. We thus urge policy makers in regions suffering vulnerable water scarcity to integrate both approaches to manage water and climate in tandem and synergistically achieve related sustainable goals.

How to cite: Zhao, F. and Wu, Y.: Global vulnerable basins suffering social-ecological impacts of water scarcity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2241, https://doi.org/10.5194/egusphere-egu24-2241, 2024.

EGU24-2873 | ECS | Posters on site | HS1.1.11

Potential assessment of flood resource utilization based on the inflow flood identification model 

Jing Huang, Chao Tan, Xiaohong Chen, and Jiqing Li

The potential assessment of flood resource utilization is a prerequisite for the rational allocation of water resources and storage capacity in a watershed. In response to the increasingly uneven distribution of water resources in the context of climate change, an inflow flood identification model was established based on the Kolmogorov-Smirnov test, improved peak-over threshold method, and time-varying parameters with Poisson distribution model. A potential assessment method of flood resources utilization in reservoir groups was proposed based on constraints such as the comprehensive regulation and storage capacity of the watershed and water demand. The four cascaded reservoirs in the lower Jinsha River (Jinxia Four Reservoirs), namely Wudongde, Baihetan, Xiangjiaba, and Xiluodu, was used as a case study. The results show that: 1998 and 2002 are the consistency change points of the runoff seies from June to November at Xiangjiaba Hydrological Station. The main type of inflow flood is short-fat, and the 3-day flood volume is a key indicator of balanced comprehensive utilization benefits except for the flood peak. Jinxia Four Reservoirs are constrained by storage capacity, when encountering floods with a design standard of once-in-a-century or below, the potential utilization of flood resources is 37.27×108m3. It is recommended to continuously optimize the storage capacity by raising the water level to 952.26m, 806.77m, 576.31m, and 373.99m in sequence of Jinxia Four Reservoirs. This work aims to provide reference for the optimal allocation of water resources and storage capacity in the watershed.

How to cite: Huang, J., Tan, C., Chen, X., and Li, J.: Potential assessment of flood resource utilization based on the inflow flood identification model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2873, https://doi.org/10.5194/egusphere-egu24-2873, 2024.

EGU24-3204 | ECS | Orals | HS1.1.11

Sustainable water management in Southern Ecuador: water availability under climate change and adaptation strategies. 

Ana Ochoa-Sánchez, Patricio Crespo, Patrick Willems, Rolando Célleri, Pablo Guzmán, María Alvarado-Carrión, Johanna Ochoa, Jorge García, Santiago Núñez, Verónica Rodas, Rigoberto Guerrero, María Augusta Marín, and Gabriela Sánchez

Anthropogenic climate change together with non-climate drivers (e.g land use change) have affected natural and human systems in the Andean Mountain region. There is more evidence of changes in water systems, with decreasing water availability and increasing frequency and magnitude of extreme events (i.e. flooding and droughts). This region is especially vulnerable to climate change and faces challenges towards adaptation due to limited resources and policies. Therefore, we present an integrated water management (IWM) approach to secure water availability in a middle-size city in Southern Ecuador - Cuenca. The Andean city of Cuenca (~ 600 000 inhabitants, located at 2600 m a.s.l.) depends highly on precipitation and surface water from the highlands to ensure drinking water. Due to its complex orography, climate change projections are not yet available at an adequate resolution for local decision making and limited actions and plans towards adaptation are undertaken. Our IWM approach, then, involves two phases:

(1) Quantifying water availability projections. Statistical and dynamical downscaling techniques are used to quantify climate change projections at 1 km resolution for the study area, together with indicators useful for decision-makers. Discharge projections are quantified by using conceptual and distributed hydrological models. In parallel, water consumption is monitored and projected. Finally, we find water availability projections towards 2100.

(2) Constructing adaptation strategies. On the provision side, water management improvements are co-constructed with the local drinking water company (ETAPA EP), such as: evaluating old infrastructure (e.g. leaks control), proposing new green-blue and gray infrastructure. On the demand side, strategies to reduce water consumption are co-constructed and implemented within a pilot project that involves citizens from three neighbourhoods in Cuenca.

Our study involves a variety of actors and sectors (i.e. Ecuadorian and Belgian Universities, decision- and policy makers and citizens), enhancing capacity building of local governments and transferring knowledge among Universities and institutions, to plan and implement adaptation strategies through bottom-up approaches. We expect that our approach can be used in other middle-size cities, with similar challenges or complex orography conditions.

How to cite: Ochoa-Sánchez, A., Crespo, P., Willems, P., Célleri, R., Guzmán, P., Alvarado-Carrión, M., Ochoa, J., García, J., Núñez, S., Rodas, V., Guerrero, R., Marín, M. A., and Sánchez, G.: Sustainable water management in Southern Ecuador: water availability under climate change and adaptation strategies., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3204, https://doi.org/10.5194/egusphere-egu24-3204, 2024.

EGU24-4454 | ECS | Posters on site | HS1.1.11

Evaluating climate change impacts on the hydrology of Kamp catchment, Austria, under different shared social pathways (SSPs) 

Zryab Babker, Tim G. Reichenau, Morteza Zagar, and Karl Schneider

Climate change can severely affect water fluxes at the land surface and thereby water availability as well as floods and droughts leading to increased risks for man-environment systems. Understanding the impacts of climate change on future water resources at a catchment scale is essential for strategic planning and efficient integrated water resources management. In the frame of the DISTENDER project (EU Horizon-ID 101056836), climate change impacts upon several catchments in Europe are analyzed. A key goal of DISTENDER is to develop robust strategies for climate change adaptation. For the simulation of climate change impacts on water resources, the Soil and Water Assessment Tool (SWAT+) was selected for its accessibility, robustness, and transferability. Here we address the issue of effects of different climate models vs. shared socioeconomic pathways (SSPs) by driving SWAT with results of three models (CanESM5, EC-EARTH3, MPI-ESM1-2-HR) run of the updated Coupled Model Intercomparison Project Phase 6 (CMIP6) with four SSPs (SSPs 1-2.6, 2-4.5, 3-7.0, 5-8.5), respectively. The Kamp River in Lower Austria was selected as an example catchment because it is the longest river in the “Waldviertel” region, which has significant ecological, societal, and economic importance. The SWAT+ model was calibrated and validated at different locations in the catchment. Future climate change projections for the period 2021 to 2050 were obtained from CMIP6 and were statistically downscaled. Annual 3-day high runoff was used as a proxy for the extreme high runoff characteristics. Trends and variations of the water balance components were compared.

All climate models show an increase in average annual precipitation ranging from 5 % (MPI-ESM1-2-HR) to 17 % (CanESM5). In all climate models and SSPs, the 3-day high runoff at Stiefern gauge (near the catchment outlet) for 10, 50, and 100-year return periods is projected to increase. CanESM5 and EC-EARTH3 show the highest (54 %) and the lowest (13 %) increase in the 3-day high runoff for 10, and 100-year return periods respectively, variations across the SSPs range from 12 % (SSP1-2.6) to 77 % (SSP 5-8.5) for 100-year return periods. Changes in the average annual evapotranspiration across the different models range from 12 % to 18 %, and variations across the SSPs range from 14 % to 16 %. For all models, the average annual soil moisture in the catchment decreases significantly (5 % to 18 %), across SSPs the decrease ranges from 9 % to 13 %.

Our results indicate that the effects of choosing different models to reflect the changes in the runoff and average annual water balance components exceed the effects of different SSPs. Thus, decision-makers and planners should select a model according to their planning goal (i.e. use a model with extreme change to reflect the maximum potential risk). This research is intended to develop adaptation and mitigation strategies to reduce risks and vulnerabilities and to contribute to effective management of water resources in the catchment within the framework of the DISTENDER project.

 

Keywords: Climate change, CIMP6 Climate Model, SWAT+ model, Kamp catchment, Austria

How to cite: Babker, Z., G. Reichenau, T., Zagar, M., and Schneider, K.: Evaluating climate change impacts on the hydrology of Kamp catchment, Austria, under different shared social pathways (SSPs), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4454, https://doi.org/10.5194/egusphere-egu24-4454, 2024.

EGU24-5789 | ECS | Posters on site | HS1.1.11

Understanding the uncertainty in the climate and water resource availability interplay: a distributed analysis of the Italian territory 

Alessandro Amaranto, Leonardo Mancusi, and Giovanni Braca

As the tangible impacts of climate change continue to unfold, the imperative to assess and prepare for its repercussions on water resources becomes increasingly evident. This study addresses the urgent necessity to foresee future scenarios of surface water availability in Italy, recognizing the crucial role of water in sustaining ecosystems, agriculture, and human life. To unravel the intricate interplay between climate change and water availability, our methodology integrates the three representative concentration pathways (RCPs) from the Intergovernmental Panel on Climate Change with six regional circulation models. This combination projects future trajectories of temperature and precipitation. Utilizing the time-varying quantile mapping downscaling technique, we refine these trajectories for enhanced spatial and temporal resolution (1 km). These downscaled data feed into the water balance model BIGBANG, developed by the Italian Institute for Environmental Protection and Research (ISPRA), facilitating the generation of the spatiotemporal distributions of surface water availability across Italy. A probabilistic analysis offers a nuanced understanding of potential future water scenarios. Our findings highlight the profound influence of emission scenarios on water availability's future trajectory. Under maximum adaptation conditions (RCP 2.6), a relatively stable water availability pattern is projected through the century. Conversely, the business-as-usual scenario predicts a significant decrease of up to 50% in surface water availability, particularly in historically drought-prone southern regions of the country. These results underscore the critical importance of proactive adaptation measures to mitigate the potential impacts of climate change on Italy's water resources.

How to cite: Amaranto, A., Mancusi, L., and Braca, G.: Understanding the uncertainty in the climate and water resource availability interplay: a distributed analysis of the Italian territory, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5789, https://doi.org/10.5194/egusphere-egu24-5789, 2024.

The Murray-Darling Basin in south-eastern Australia is one of the world’s largest rivers, draining an area of just over 1 million square kilometres. The basin drains about one-seventh of the Australian land mass and is the 16th longest river in the world. However, being located on the driest continent on Earth, its discharge is relatively small, averaging just 767 m3/s, far smaller than the discharge from any other similarly sized river worldwide.

Despite the relative lack of water, the Murray-Darling Basin is one of the most significant agricultural areas in Australia. In 2008, the Murray-Darling Basin Authority was formed with a mandate to manage the basin in an integrated and sustainable manner. Water reform in the basin has been a world-first in terms of the scale of intervention, but it has led to numerous conflicts in terms of access to water. The ability to manage the basin adequately relies on appropriate research being carried out in order to determine how much water is currently available, where it is currently being used, and how water availability and use are likely to change into the future.

Climate change projections for the Murray-Darling Basin indicate a future that is likely to be hotter, with more frequent and intense droughts, accompanied by a reduction in cool season rainfall, particularly in the south of the Basin. As this is where the majority of runoff is generated, this is likely to lead to reductions in water availability, with a median reduction of around 20%.

The Murray-Darling Basin Plan was brought into force in 2012 and is due for review in 2026. CSIRO is carrying out hydroclimate research to assist policy makers to better understand the likely changes in water availability, and consequent adaptation options available to them. This presentation will summarise the likely climate change impacts on water availability and assess how best to deal with the uncertainties associated with these projections.

How to cite: Post, D.: Research informing policy to adapt to climate change: a case study from the Murray-Darling Basin, Australia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7034, https://doi.org/10.5194/egusphere-egu24-7034, 2024.

EGU24-7932 | ECS | Posters on site | HS1.1.11

Vegetation restoration potential in the drylands of China under water constraint 

Huiqing Lin and Yan Li

As an essential pathway for nature-based solutions, vegetation restoration can effectively absorb carbon sequestration and mitigate global warming. However, the excessive water consumption by vegetation expansion may create potential water conflicts between natural ecosystems and human systems, and even exacerbate local water shortages, especially in water-limited dryland regions. By evaluating water availability using multiple datasets, this study explored the vegetation restoration potential and the allowable vegetation conversion in China’s drylands under the constraint of water availability. We found that the additional water resources available for vegetation restoration in China’s drylands were 12 ± 114 mm (median ± SD) from 2003 to 2018 but it decreased over the period (-1.18mm/year). 43.3% of the dryland area had water deficits, after considering current vegetation and human water consumption. Under current water constraints, additional Gross primary productivity (GPP) that could be restored ranged from 8% to 12% depending on vegetation types (10.5% for forests, 11.6% for grasslands, 7.8% for irrigated crops, and 8.9% for rain-fed crops). In water surplus areas, primarily in the south and east of China’s drylands, most vegetation conversions toward higher-water-consumption types were allowed to occur. In water deficit areas, the west of drylands, even converting all the existing vegetation to less water-intensive types would not compensate for the water deficit in most regions, suggesting local vegetation may have exceeded the water-carrying capacity. Our research highlights the importance of the potential water constraint of vegetation restoration in drylands and provide a guidance for decision-making vegetation restoration while ensuring water sustainability. Next, we will explore the potential for vegetation restoration under different climate change scenarios (e.g., ssp126, ssp370, and ssp585).

 

How to cite: Lin, H. and Li, Y.: Vegetation restoration potential in the drylands of China under water constraint, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7932, https://doi.org/10.5194/egusphere-egu24-7932, 2024.

EGU24-8932 | ECS | Posters on site | HS1.1.11

Model Calibration and discharge simulations during extreme drought events for the Rhine River Basin using WRF-Hydro. 

MSc. Andrea Campoverde, PD. Dr.Uwe Ehret, Dr.Patrick Ludwig, and Prof. Dr. Joaquim Pinto

Recent drought events, leading to low water levels, have significantly affected navigation through the Rhine River and the transportation of goods. It has become imperative to analyze the conditions in which these events occurs to establish actions to prevent monetary losses. The main focus of this study is to test how well the hydrological model WRF-Hydro can capture extremely low water levels in the Rhine River basin. Using the meteorological reanalysis dataset ERA5 as forcing data for the model, we simulate the streamflow from January 2016 to December 2018, which includes the recent drought event in the Summer of 2018. Within the model, the calibration of various parameters allows the evaluation of the streamflow from WRF-Hydro to be contrasted with the daily observed values. The parameters influencing the amount of water routed across the basin are generally constant throughout the domain. Land use cover and terrain slope were used to create spatially distributed parameter values, avoiding the calibration process of testing a range of values and, therefore, reducing computational time. These promising results enables us to analyze recent and future drought events under different climate conditions.

How to cite: Campoverde, MSc. A., Ehret, PD. Dr. U., Ludwig, Dr. P., and Pinto, P. Dr. J.: Model Calibration and discharge simulations during extreme drought events for the Rhine River Basin using WRF-Hydro., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8932, https://doi.org/10.5194/egusphere-egu24-8932, 2024.

EGU24-9237 | ECS | Posters on site | HS1.1.11

A Graphical Representation of Climate Change Impacts with Associated Uncertainties 

Jose George and Athira Pavizham

Recent decades have seen increased occurrence of extreme climatic events, which have had devastating consequences, both in terms of loss of life and property. Proper understanding of the possible variations in climatic extremes is important in developing mitigation and adaptation plans. Climate change impact prediction employs a series of numerical models, each with their own limitations that contribute towards the overall uncertainty. Climate change impact prediction results are often not intuitive to a decision maker and the added complexities from uncertainties can complicate the policy making exercise. A clear and concise representation of the possible risks of climate change and the associated uncertainties needs to be developed to bridge the gap between the climate scientist and the policy maker. Here, a framework for graphical representation of regional climate risks in terms of hazards and vulnerabilities is developed. The uncertainties are quantified in terms of level of confidence as the result of an ensemble exercise. To help regional stakeholders relate to the prediction results, analysis of extremes is performed with respect to historical hazards in the region. Risk factors for climate extremes that happened in the past in the region are studied and the future risk for an event of same return period is compared to the historical risk. The methodology is validated in the Bharathapuzha catchment in Kerala, India, a catchment which is identified to be climate change hotspot. In terms of flood events, the risk of low intensity flood events is seen to be increasing in the catchment with high confidence, while high intensity flood events are seen to be predicted at low levels of confidence. The catchment is seen to be drying up with high intensity drought events being predicted at high confidence.  

How to cite: George, J. and Pavizham, A.: A Graphical Representation of Climate Change Impacts with Associated Uncertainties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9237, https://doi.org/10.5194/egusphere-egu24-9237, 2024.

Louisiana is a state in the United States of America that is experiencing the multiple challenges of climate change, extreme weather events (such as hurricanes), and human intervention impacts for flood protection. The marshland regions of lower Louisiana have been heavily impacted by human influence, since the state was originally formed and maintained by deposition of sediment carried from the Mississippi River. Not only has impact of human intervention impacted the sediment transport processes, but there has also been significant human development of levee systems and other flood protection structures in Louisiana’s coastal environment. Specifically after Hurricane Katrina, additional levee systems, environmental control structures, and floodgates were built in this marshland region. A few different design criteria are important to analyze for these systems, some of the more notable design criteria are flood protection, navigational safety for ships passing through floodgates, marshland protection, water quality, and system biology. In addition to monitoring human impacts, the US Army also seeks to understand how the system behaves under long-term climate change impacts.

While flood protection is a primary motivator for building these systems, it is important to ensure that structures built do not have adverse effects on the local wildlife or commercial/recreational opportunities for the locals in these areas. Adaptive Hydraulics (AdH) is a finite element based 2D shallow water equation solver that can be used to numerically evaluate these impacts. Another focus of this study is to analyze the indirect impacts of structures built since 2004. To ensure that everything built since then has not had major impacts on the local wildlife or commercial/recreation opportunities, AdH and PTM can also be used to gain insight into that impact. The numerical modelling portion is the author’s direct contribution to the project, though the overall project of developing Lower Louisiana, and its impact of that and climate change on the natural environment and local people will be discussed.

How to cite: Barreca, D.: Environmental Impacts of Developing Flood Protection Systems throughout a Marshland Ecosystem in Lower Louisiana: a Numerical Case Study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10709, https://doi.org/10.5194/egusphere-egu24-10709, 2024.

Climate change can pose a significant threat to water fluxes on terrestrial surfaces, impacting water availability, and increasing the risk for human-environment systems to floods and droughts. Understanding the repercussions of climate change on future water resources is imperative for effective integrated water resources management. As part of the DISTENDER project (EU Horizon-ID 101056836), we scrutinize the effects of climate change on diverse watersheds in Europe to develop strategies for climate change adaptation.
To simulate the impacts of climate change on water resources, we chose MIKE SHE for its spatially distributed and physically based modeling concept. Here we present the results of different climate models vs. SSPs on water balance components and runoff for the Ave River Basin in Northern Portugal.  MIKE SHE was calibrated and validated utilizing measured gauge runoff data from 1980 to 1986 and 1986 to 1990, respectively. For the various gauges, Nash-Sutcliffe efficiencies between 0.59 and 0.81 were achieved.
Statistically downscaled climate change projections for the period (2021-2050) from the Coupled Model Intercomparison Project Phase 6 (CMIP6) were used as input to MIKE SHE. We used three different climate models (CanESM5, EC-EARTH3, MPI-ESM1-2-HR) and four shared socioeconomic pathways (SSPs 1-2.6, 2-4.5, 3-7.0, 5-8.5) each. Hydrological variables were evaluated for each of the twelve-climate model runs in comparison to the reference period (1980-2010).  
All climate simulations show an increase in annual precipitation, except for CanESM5 SSP 3-7.0, MPI-ESM1-2-HR SSP 2-4.5, and MPI-ESM1-2-HR SSP 3-7.0. The precipitation increases range from 1 % to 24 %. This underscores the impacts of different SSPs and climate models on projected regional precipitation patterns and emphasizes their importance in comprehensive climate change assessments. 
In all scenarios, the projections indicate an increase in flood for different durations (1-day, 3-days) at all gauges across different return periods. The flood increase calculated for the three different climate models exhibits greater differences than the flood increase calculated for different SSPs across climate models. For example, in the Ave River, the range of the 100-year flood across SSPs varies from 81 m³/s (Min: 432m³/s, Max: 513 m³/s) for MPI-ESM1-2-HR to 225 m³/s (Min: 496 m³/s, Max: 721 m³/s) for EC-EARTH3. The corresponding range across models spans from 71 m³/s (Min: 425 m³/s, Max: 496 m³/s) for SSPs 3-7.0 to 213 m³/s (Min: 508 m³/s, Max: 721 m³/s) for SSPs 5-8.5. The 100-year flood (1-day duration) in the reference period value is 372 m³/s. In addition, the duration of low-flow events increases significantly for most climate scenarios. This increase in extreme events, which includes both, an increase in the volume of floods and an increase in the duration of droughts, emphasizes the need for proactive measures to address and adapt to the anticipated changes in hydrological patterns due to climate change.
However, our findings show that the selection of the climate model has a great impact on the hydrological variables. Decision-makers should carefully choose a climate model aligned with their planning objectives, considering the potential risk for robust planning.

Keywords: Climate change, CIMP6 Climate Model, MIKE-SHE, Ave catchment 

How to cite: Zargar, M., Reichenau, T. G., Babker, Z., and Schneider, K.: Assessing Climate Change Effects on Hydrology in the Ave catchment, Portugal: A Comparative Analysis of Various Shared Socioeconomic Pathways (SSPs), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11231, https://doi.org/10.5194/egusphere-egu24-11231, 2024.

EGU24-11834 | ECS | Posters on site | HS1.1.11

Climate change impact on the hydrological processes over an alpine basin: the Adige River 

Martin Morlot, Alison L. Kay, and Giuseppe Formetta

Hydrological extremes (drought and floods) have undeniable financial implications and are predicted to grow in the next years. Yet to understand their future local impacts it is necessary to understand the evolution of the governing hydrological processes. Such is the case for the Adige basin, an important basin in Italy, where understanding changing patterns of hydrological processes is crucial to optimally plan competing water uses, such as hydroelectric production and agricultural water allocation.

Euro-CORDEX models provide future climate projections throughout the region, for different emissions scenarios (RCP 2.6, 4.5, 8.5) and climate models (13). Upon the application of a downscaling and bias correction methodology against observed climate variables (i.e. air temperature and precipitation), a process-based semi-distributed digital twin of the Adige River basin is implemented. Hydrological process variables (snow, actual evapotranspiration, soil moisture and discharge) are obtained for the entire basin and the timespans of the different Euro-CORDEX models (1980-2005 for the historical baselines, 2005-2100 for the projections) at daily temporal scale and 5 km2 spatial resolution. The temporal and spatial patterns for discharges are evaluated through the average monthly values for 6 sub-catchments. Other process variables such as snow, actual-evapotranspiration (AET) and soil moisture (SM) are assessed against remote sensing datasets. The resulting climate and hydrological end of the century projections (2075-2100) are compared to historical baselines (1980-2005), to assess projected changes.

The digital-twin model is found to reproduce discharge patterns accurately, with an average KGE of 0.8, and provides a good fit for snow and AET, with average correlations of 0.95 and 0.96 respectively. A reasonable fit is found for SM, with an average correlation of 0.5. Careful assessment of the digital twin model through these variables ensures that it reproduces accurately historical local hydrological processes and increases confidence in the quantification of these variables under future projections.

The results of our study give regional policymakers insights into possible future scenarios and how these affect water resources and their potential impacts and adaptations on several economic sectors.

How to cite: Morlot, M., Kay, A. L., and Formetta, G.: Climate change impact on the hydrological processes over an alpine basin: the Adige River, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11834, https://doi.org/10.5194/egusphere-egu24-11834, 2024.

EGU24-11923 | ECS | Orals | HS1.1.11

Using water use models to project long-term trends of water supply and demand equilibriums under climate change: application to the French Loire River basin. 

Camille Debein, Victor Vermeil, Raphaël Lamouroux, Céline Monteil, Frédéric Hendrickx, Fabrice Zaoui, and René Samie

The French Loire River basin (81,000 km²) is characterized by a wide range of water uses (energy production, irrigation, drinking water supply, industrial processes, navigation, etc.). Recurring droughts and periods of low flow in the basin have emphasized the vulnerability of certain ecosystems and water uses in relation to the available resources. In addition, the prospect of global and local changes (climate change, changes in uses and territorial dynamics, etc.) added to evolutive environmental policies are expected to impact the availability of water resources in the upcoming years.

Within this evolving context of resource availability, we propose a quantified projection of future changes in the water supply-demand balance within the Loire River basin for two future timeframes, 2035-2065 (mid-term) and 2070-2099 (long-term), relative to the current climate (1976-2005). To achieve this, a modeling framework encompassing catchment-scale representations of climate, natural resource distribution, and primary water uses (energy, irrigation, drinking water supply, and industry) has been developed. Spatial and temporal heterogeneities are accounted for with a semi-distributed hydrological model [1] (using sub-catchment meshes of nearly 100 km2) and a daily time-step. This framework builds upon previous hydrological studies [2] and enables the representation of impacts on resource availability resulting from both natural and anthropogenic forcing variables.

Initially validated over the historical period (1976-2005) through comparison with national discharge monitoring networks and water use databases, this modeling chain was fed with data from four climate evolution trajectories taken from the Explore2 project that outline contrasting storylines of climate changes over the Loire basin. Simulation results reveal a decrease in water resources and an increase in global water demand, particularly in summer, correlating with increasing average air temperature and the relative reduction of precipitation. Evaluation of water stress indicators [3] suggests that tensions between water supply and demand will become increasingly frequent and more intense, particularly in summer.

This work emphasizes the interest of coupling water use modeling with hydrological simulations and advocates for evaluating the impact of changes in the territory (such as socio-economic or land use dynamics) on the resource.

Figure 1. Schematic representation of the modeling chain involved in quantifying the supply-demand balance.

(A) (B)

Figure 2. Spatial heterogeneity of the Blue Water Stress (A) and the Blue Water Scarcity (B) indicators [3] evaluated over the considered catchment area of the Loire River (august 2070-2099 for the “hot and humid” Explore2 climate trajectory, RCP 8.5).

 

References:

[1] Rouhier, L., Le Lay, M., Garavaglia, F., and Le Moine (2017). Impact of mesoscale spatial variability of climatic inputs and parameters on the hydrological response. Journal of Hydrology, 553, 13-25.

[2] Samie, R., Monteil, C., Arama, Y., Bouscasse, H., and Sauquet, E. (2014). La prospective territoriale, un outil de réflexion sur la gestion de l’eau du bassin de la Durance en 2050. Hydrology in a Changing World: Environmental and Human Dimensions, 221.

[3] Wang, Dan, Klaus Hubacek, Yuli Shan, Winnie Gerbens-Leenes, and Junguo Liu. (2021). "A Review of Water Stress and Water Footprint Accounting" Water 13, no. 2: 201.

How to cite: Debein, C., Vermeil, V., Lamouroux, R., Monteil, C., Hendrickx, F., Zaoui, F., and Samie, R.: Using water use models to project long-term trends of water supply and demand equilibriums under climate change: application to the French Loire River basin., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11923, https://doi.org/10.5194/egusphere-egu24-11923, 2024.

The rising costs and safety concerns associated with flood-induced infrastructure damages in Canada underscores the critical need for adapting design flood magnitudes to future climate change. Creager flood envelope curves, which serve as the upper bound/limit of observed extreme flows for different drainage areas within a specific region, are widely employed by practitioners to estimate design flood magnitudes, which in the case of most river-crossing highway bridges is considered as 75-year flood magnitude. A framework for adapting Creager curves to future changes in streamflow is proposed in this study. To this end, Creager curves, for the current 1951–2020 period, are developed using regional frequency analysis (RFA) on annual maximum daily mean streamflow, considering 417 observation stations, located in seven major Canadian river basins (i.e., Fraser, Nelson, Mackenzie, Yukon, Churchill, St Lawrence and St John). The Creager coefficient C, which is the main parameter that defines flood envelope curves for different regions, under the current climate, exhibits considerable variability, ranging from 1 to 45, across the studied river basins.

To adapt Creager curves for future changes, a correction factor, RC, defined as the ratio of future to current period C values is proposed. Two RFA approaches were employed to calculate the ratio using simulated streamflow data, derived using a cell-to-cell routing scheme, applied to an ensemble of five-member Regional Climate Model (RCM) GEM (Global Environmental Multiscale) simulated runoff for the current reference 1951–2020 and future 2021–2099 periods for the observation sites. The first RFA approach, considering only the GEM grid cells where the stations are located, suggests RC in the 0.3 to 1.6 range, with St John and St Lawrence River basins showing  values less than 1. The second approach, considering all GEM cells for a given region, produces comparable results but yields a wider range for RC and adds useful information in that RC values can also be established at ungauged locations, with RC values higher than 1.6 in various regions especially over western Canada. An evaluation of the level of confidence for RC , based on the GEM ensemble, reveal a higher level of confidence for most parts of the study domain. The second approach is likely to be a better choice for longer return periods considering the larger pooling of data. From a practical viewpoint, the proposed method for estimating future design floods is robust and transferrable to other basins but can benefit from using streamflow projections from other models for better quantification of uncertainty.

How to cite: Maria, D. and Sushama, L.: Flood envelope curves for the estimation of design flood magnitudes for highway bridges, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12009, https://doi.org/10.5194/egusphere-egu24-12009, 2024.

EGU24-14169 | ECS | Orals | HS1.1.11

Hydrokinetic resource assessment for the Canadian Arctic 

Koyena Bhattacharjee, Laxmi Sushama, and Julien Cousineau

Increasing renewable energy development has rekindled interest in hydrokinetic or in-stream river potential for power production using zero head turbines. This is also of interest for remote regions such as the Canadian Arctic where decentralized power production from renewable energy sources is an economically viable option in offsetting the high cost of diesel power production. However, one of the major obstacles is the absence of streamflow data at necessary spatial and temporal scales for these regions. This study estimates the hydrokinetic power potential for current-based systems in the rivers of the Canadian Arctic region, primarily Nunavut and adjoining regions, for the current and near-future periods, based on streamflow estimated using a routing scheme applied to runoff generated by ultra-high-resolution simulations of the Global Environmental Multiscale (GEM) model, for a high emission scenario. GEM simulation for current climate, validated against gridded and station observation data, suggest reasonable performance of the model, particularly streamflow-relevant variables such as precipitation, snow water equivalent, soil and air temperatures given improved representation of processes and surface heterogeneity due to the higher resolution. This is also reflected in the comparison of simulated streamflow characteristics with available observations from HYDAT.

Hydrokinetic power estimates over the study region show patterns similar to those of flow velocity as expected, with maximum hydropower being noted during the summer season for the central regions of Nunavut. Since the near-future period spans only till 2040, the changes in flow velocity and hydrokinetic power are minimal with an overall decrease of 2.5% for the southern and western regions of Nunavut and an increase of 2.5 to 5 % for some of the northernmost regions of Nunavut. The study further identifies ideal locations for the installation of hydrokinetic turbines for energy extraction, which require daily flow velocities above pre-defined thresholds, by considering indirectly also the impact of river ice on flow velocities. The results of this study provide useful information on hydrokinetic resources for the high-altitude regions of Canada by introducing a science-based approach and serve as a foundation for additional detailed investigations for site-specific studies to support the implementation of hydrokinetic energy conversion systems.

How to cite: Bhattacharjee, K., Sushama, L., and Cousineau, J.: Hydrokinetic resource assessment for the Canadian Arctic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14169, https://doi.org/10.5194/egusphere-egu24-14169, 2024.

EGU24-14318 | Orals | HS1.1.11

Balancing uncertainty when assessing climate change risk in large river basins: the case of the Murray Darling basin, Australia 

Andrew John, Avril Horne, Keirnan Fowler, Ranju Chapagain, and Rory Nathan

Climate change threatens water resources from local to global scales. However, there are significant challenges in assessing climate risk for large river basins, especially those with multiple jurisdictions and competing management objectives. Traditional methods follow a top-down approach, where the impacts of climate projections by climate models are simulated using hydrological and water resource models. While these methods can provide a detailed snapshot of how rivers are impacted under a small number of projected future climates, their computational burden, and challenges in linking water resource models owned by different jurisdictions mean it is difficult to robustly explore the implications of aleatory (from hydroclimate variability) and epistemic (from hydroclimate change) uncertainty. Unlike top-down approaches, bottom-up approaches can be used to better understand vulnerability under a range of possible future climate. Bottom-up approaches begin with a sensitivity analysis of important management objectives to multiple hydroclimate stressors. Unfortunately, bottom-up approaches are constrained when using complex system models in large river basins, as their methodologies typically require many times more simulations than top-down approaches.

The Murray Darling basin (MDB) is Australia’s most significant river basin. Irrigation in the basin supports over $30 billion (AUD) in agriculture and livelihoods for the 2.4 million residents. The MDB has significant environmental values, with RAMSAR wetlands, many endemic and threatened species, and it is the traditional land of over 50 first nations groups. We assessed the impacts of climate change on basin-wide inflows and key indicator sites using both top-down and bottom-up approaches. We stochastically generated multiple sequences of future hydroclimate conditions, which helps separate the influence of climate variability from climate change. We deliberately traded-off detail in our assessment by deriving simple functional relationships between sub-basin inflows and 21 key indicator sites using existing scenarios from the complex jurisdictional water resource models. This allowed us to assess far more replicates of stochastic data, more climate scenarios, and conduct a more rigorous stress test within the bottom-up framework than would normally be permitted using complex models.

The top-down approach provides a scenario-based assessment of likely conditions for water resources in the MDB, and spatially coherent projections of future inflows and river management metrics. The bottom-up approach provides more insight into spatial differences in sensitivity across the river catchments that make up the MDB, and can be used to both augment and help interpret outcomes from the top-down approach. The bottom-up approach also yields important thresholds in hydroclimate conditions which compromise basin-wide objectives (assessed through flow at the Murray River mouth which prevents the important lower lake system from becoming too saline). We consider top-down and bottom-up approaches to be complementary in assessing and adapting river systems to the impacts of climate change.

The simple methods used here are complementary with other more detailed impact models. The ease of undertaking simulations and computational efficiency means simple methods can filter down the range of possible conditions or stressors that contribute to uncertainty, allowing a more targeted set of simulations to be undertaken using detailed, but costly, water resource models.

How to cite: John, A., Horne, A., Fowler, K., Chapagain, R., and Nathan, R.: Balancing uncertainty when assessing climate change risk in large river basins: the case of the Murray Darling basin, Australia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14318, https://doi.org/10.5194/egusphere-egu24-14318, 2024.

EGU24-16678 | Posters on site | HS1.1.11

Using a detailed abstraction database to plan assessing current and future water resources availability in Scotland. 

David Haro Monteagudo, Shaini Naha, and Miriam Glendell

Scotland’s land and water resources are increasingly vulnerable to periods of droughts, impacting water users and the water environment. Abstractions from sectors with high water demands are forecasted to exacerbate the direct impacts of climate change by amplifying both the frequency and the duration of drought events. Previous studies that have assessed the potential future water scarcity in Scotland were limited by the lack of available data on actual abstractions. These studies assumed that all abstraction licences were used at their maximum (i.e., were based on worst case scenario); and did not account for public water supply abstractions. Therefore, there is a need for accessible data on timely, open, and detailed abstraction return values for all sectors to overcome these limitations to allow a more accurate assessment of the current state of Scotland’s water resources and their vulnerability to climate extremes. We have collated a database that comprises of abstracted daily volumes from different locations within the water bodies, for various sectors from Scottish Environmental Protection Agency and abstracted daily volumes for public water supply aggregated at the catchment level from Scottish Water. We then use these daily abstraction time series available for the common time 2018-2022, in conjunction with available daily river flow historical and future projections, to determine the available volume of water, per catchment, per day. This enables extracting the drought events, and drought characteristics such as frequency, duration, and intensity of droughts. This research will inform future water resources management in Scotland by identifying which regions and sectors may be subject to increased water scarcity pressures in the future.

How to cite: Haro Monteagudo, D., Naha, S., and Glendell, M.: Using a detailed abstraction database to plan assessing current and future water resources availability in Scotland., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16678, https://doi.org/10.5194/egusphere-egu24-16678, 2024.

EGU24-19003 | ECS | Posters on site | HS1.1.11

Land cover planning strategies and Water Use Optimization of a Mediterranean Basin Under Climate Change  

Serena Sirigu, Roberto Corona, Adriano Ruiu, Riccardo Zucca, and Nicola Montaldo

Over the past century, climate change has been affecting precipitation regimes across the world, and in the Mediterranean regions there is a persistent declining trend of precipitation and runoff decreases contributing to a desertification process with dramatic consequences for agricultural and water resources sustainability. Climate change projections point to an amplification of changes in global precipitation patterns and trends, with further drier trends for the Mediterranean area. These trends will have dramatic consequences on water resources for both managed (e.g., agricultural) and natural systems. In Mediterranean climates during the winter months much of the precipitation recharges sub-surface and surface reservoirs. In particular, in Mediterranean regions a strong decreasing trend of winter precipitation and an evident shift in how the precipitation is distributed across the winter and spring months is estimated. Considering that most of the runoff to surface reservoirs occurs in the winter months and that spring hydrologic response is likely to be influenced strongly by vegetation, these precipitation changes can be considered hydrologically important. Case study is the Flumendosa basin (Sardinia), which is one of the case studies of the ALTOS European project, characterized by a reservoir system that supplies water to the main city of Sardinia, Cagliari. Data are from 42 rain gauges stations (1922-2023 period) over the entire basin and data of runoff are available for the same period. In the Flumendosa reservoir system the average annual input from stream discharge in the latter part of the 20th century was less than half the historic average rate, while the precipitation over the Flumendosa basin decreased, but not at such a drastic rate as the discharge, suggesting a marked non-linear response of discharge to precipitation changes. We developed and calibrated a distributed hydrological model at basin scale which predicts runoff, soil water storage, evapotranspiration and grass and tree leaf area index (LAI). Hydrometeorological variables provided by the future climate scenarios predicted by Global Climate Model (CMPI-6 MPI-ESM1-2-LR downscaled) have been used as input in the model to predict soil water balance and vegetation dynamics under the future hydrometeorological landcover scenarios. The historical observations highlighted strong negative trends in precipitation series and number of wet days (examined using the Mann-Kendall trend test). The results from model application showed that tree dynamics are strongly influenced by the inter-annual variability of atmospheric forcing, with tree density changing according to seasonal rainfall. At the same time the tree dynamics affected the soil water balance. We demonstrated that future warmer scenarios would impact forest, which could be not able to adapt to the increasing droughts. In the Flumendosa basin future scenarios predict a reduction of the runoff, which is crucial for the dam reservoir recharge. The water resources system planning needs to carefully takes into account the effect of future climate change on water resources and vegetation dynamics.

How to cite: Sirigu, S., Corona, R., Ruiu, A., Zucca, R., and Montaldo, N.: Land cover planning strategies and Water Use Optimization of a Mediterranean Basin Under Climate Change , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19003, https://doi.org/10.5194/egusphere-egu24-19003, 2024.

HS1.2 – Innovative sensors and monitoring in hydrology

EGU24-7295 | ECS | Posters on site | HS1.2.1

Developing gravimetric water level meter 

YooSik Jeong, Ho Jeong Jo, Soo Jeong Park, and Oh Yoon Kong

According to Korean Statistical Information Service(KOSIS)’s data, the area of the Republic of Korea is 100,444 km2 and the area of Seoul, the capital city of Korea, is 605 km2, which is only 0.6 % of the area of Korea. However, the population of the Korea is 51.75 million, and that of Seoul is 9.39 million, accounting for a large 18 % of Korea. A large number of these densely populated cities are located in river basins. In most of time, water resources stored upstream are used as various purposes(drinking, industrial, and agricultural use) and drained downstream. During summer monsoon, however, rain that falls in the basin is discharged downstream as quickly as possible to prevent flooding. But heavy, concentrated rain caused by recent climate change often leads to capacity to exceed designed capacity. Moreover, inundation occurred due to neglect of neglect of drain pipe and street inlet and is becoming a serious social problem.

This study was conducted to observe the ‘flood level’ in the city, which is basic data for flood management. We already have the ability to accurately and conveniently measure the water level and transmit the data when flooding occurs at multiple point in the city. To monitor water levels in underpasses and areas where poor drainage is expected, rods on the centerline of roadway or border of the sidewalk are used. The prototype has been completed, and additional work is underway to miniaturize the built-in equipment(board, communication, and battery) and to extend battery duration. To maintain accuracy of measurement in the process of the miniaturization, it is important to secure enough distance between weight and outer case to minimize the surface tension effect. So it is necessary to understand the relationship between the weight-outer case distance and water level observation measurements. This relationship was confirmed through various weights and outer cases. As a result, the accuracy was found to be sufficient when a weight-outer case distance is about 9 mm or longer.

Acknowledgement : This research was support by a (2022-MOIS63-002) of Cooperative Research Method and Safety Management Technology in National Disaster funded by Ministry of Interior and Safety(MOIS, Korea).

How to cite: Jeong, Y., Jo, H. J., Park, S. J., and Kong, O. Y.: Developing gravimetric water level meter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7295, https://doi.org/10.5194/egusphere-egu24-7295, 2024.

EGU24-7444 | Posters on site | HS1.2.1

Development of Portable Weather Observation System 

Mi Eun Park and Yong Hee Lee

In the event of a large-scale forest fire, the Korea Meteorological Administration (KMA)’s weather observation vehicles are deployed to obtain weather information necessary for extinguishing the fire. However, due to the limited number of vehicles and the environment to enter the field, it is difficult to observe the point where the information is actually needed. Therefore, there is an urgent need to develop a weather observation system that is easy to transport and install in the field.

We developed a 'portable weather observation system' that can be easily utilized by anyone, even if the KMA does not support weather observation vehicles and their operators at the disaster site.

 - [Transport] Weight and size that can be easily carried by one adult in a suitcase (or backpack).
 - [Installation] Attached to a steel plate, such as the top of a vehicle without any additional components. If this is not possible, a tripod can be utilized for installation.
 - [Operation] Real-time storage, display, and transmission of observation data
 - [Information] Location of the observation site (latitude, longitude and altitude) and weather variables (temperature, humidity, atmospheric pressure, and wind direction*∙wind speed) of the observation site.
  * Corrected regardless of the system's installation orientation

The prototype consists of a weather observation sensor, two GPS antennas, a tripod, a data processing/storage/display unit, and a power supply unit, and the total weight of the components including the suitcase (10 kg) is 20 kg. The weather observation sensor used is the Vaisala WXT-536, which can observe weather variables. Two GPS antennas were used to determine the location of the sites and correct the wind direction observed by the sensor. The system can be directly utilized by the Korea Forest Service (KFS) and the National Fire Agency (NFA) for initial extinguishment of wildfires.

By applying weather observation data transmitted in real-time from the field to numerical forecasting models, the KMA can provide more accurate weather forecasts back to the field. In the future, we plan to improve the prototype by utilizing an inexpensive sensor and lightweight and long-lasting batteries to reduce the cost and weight as well as increase the operating time.

How to cite: Park, M. E. and Lee, Y. H.: Development of Portable Weather Observation System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7444, https://doi.org/10.5194/egusphere-egu24-7444, 2024.

EGU24-11069 | ECS | Posters on site | HS1.2.1

Lake SkyWater - a portable optical buoy for easily measuring water-leaving radiance in lakes based on the skylight-blocked approach (SBA) 

Arthur Coqué, Tiphaine Peroux, Guillaume Morin, and Thierry Tormos

Spaceborne optical sensors are a useful tool for monitoring water quality in oceans, lakes and rivers on a large scale, at high frequency and at relatively low costs. Based on water colour algorithms, many key biogeochemical parameters are operationally estimated from satellite data (e.g. chlorophyll-a concentration). Calibrating and validating these algorithms requires a huge collection of high-quality in situ radiometric data, such as the water-leaving radiance Lw (or the remote sensing reflectance Rrs), necessitating high-level expertise and expensive material.

One of the most robust methods to measure Lw is the skylight-blocked approach (SBA), which allows Lw to be measured directly at the air-water interface. Compared with the conventionnal “above-water” method, the measurement is not contaminated by light reflected from the surface (including both sky- and sun-glint), thanks to the use of a cone-shaped screen attached to the downward-facing radiance sensor (which measures Lw) that fully blocks all downward radiance at the air-water interface.

Our open-source system “Lake SkyWater” was designed around the idea of making in situ radiometry measurements in lakes user-friendly and affordable, while retaining the accuracy and robustness required for scientific and operational purposes. We have created a semi-autonomous buoy that implements the SBA method. Lake SkyWater is low-cost (<1 k€, excluding the cost of the two radiometers), lightweight, and easy to transport and deploy. Our new device addresses one of the main ongoing issues with the SBA protocol: the issue with the radiance sensor measuring water being in the direct sun shadow of the deployment platform.

Our device consists of two commercially available radiometers that use the MODBUS RTU protocol (e.g., TriOS RAMSES G2) controlled by open-source TinkerForge modules and mounted to a rotating platform attached on top of an inner-tube (the buoy). Everything has been optimised for maximal portability (allowing it to be taken on a commercial flight): 1) the buoy is inflatable and 2) the structure is made of lightweight anodised aluminium profiles and PETG 3D-printed parts, and can be disassembled and transported in a suitcase/bag (the longest part measures 745x40x20 mm). The buoy’s position, its absolute orientation as well as its tilt are recorded (thanks to the embedded GNSS receiver and the 9-DOF IMU), and the solar azimuth angle is derived from the buoy’s positioning data. This enables the system to calculate the motor adjustments needed to keep the radiance sensor on the sunny side of the instrument. Our device hosts its own WiFi network and can be controlled wirelessly over a mobile phone, tablet or PC. Additionally, the radiometric buoy can be transformed into a fully autonomous monitoring system by plugging in a Raspberry Pi to act as a data logger.

Lake SkyWater was designed in the context of my PhD thesis dedicated to the calibration and validation of water colour algorithms for Petit-Saut Reservoir in French Guyana.

How to cite: Coqué, A., Peroux, T., Morin, G., and Tormos, T.: Lake SkyWater - a portable optical buoy for easily measuring water-leaving radiance in lakes based on the skylight-blocked approach (SBA), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11069, https://doi.org/10.5194/egusphere-egu24-11069, 2024.

EGU24-11187 | ECS | Posters on site | HS1.2.1 | Highlight

DISCO: a low-cost Device-Instrumented Secchi disk for water Clarity Observations 

Gaia Donini and Sebastiano Piccolroaz

Water clarity regulates light penetration in aquatic environments, influencing both physical and biological dynamics. Its influence extends to heat transfer within the water column, shaping the thermal structure of lakes. Photosynthetically Active Radiation (PAR) in the euphotic zone is the source of energy for light-dependent organisms, which are crucial for ecological balance. The ability to accurately assess water clarity is therefore important in several aquatic science contexts, ranging from data analysis and process interpretation to modelling. Common metrics used to quantify water quality include the vertical attenuation coefficient Kd,PAR, a measure of light penetration, and the Secchi depth (ZSD), a measure of water visibility. The enduring simplicity and cost effectiveness of the Secchi disk has made it a global standard for measuring water clarity for almost two centuries. In contrast, Kd,PAR is typically determined using expensive instruments designed to measure light in the PAR range. This discrepancy highlights the need for innovative yet cost-effective methods that integrate both types of measurements. In this contribution, we present DISCO, a low-cost instrument that combines the standard and globally used Secchi disk with light attenuation measurement supported by light sensors. DISCO retains the traditional shape of a Secchi disk but is equipped with light-dependent resistors (LDRs), which are used as light sensors both looking up and down. In addition to the LDRs, the disk is also equipped with low-cost temperature and pressure sensors, all connected to an ArduinoUNO board. After calibrating the sensors against commercial instruments, DISCO was tested in two mountain lakes together with high-resolution PAR, temperature and pressure sensors used as a benchmark. The results show that the proposed low-cost instrument is able to reproduce the shape of the light profiles with proper quantification of the light attenuation coefficients. Its affordable cost and ease of construction and use is expected to increase the ability to make measurements in locations where expensive instruments are not available, thereby extending the coverage of water clarity monitoring sites. This in turn has potential implications for wider in-situ calibration of remote sensing products. The prototype of DISCO will be shown at the poster session.

How to cite: Donini, G. and Piccolroaz, S.: DISCO: a low-cost Device-Instrumented Secchi disk for water Clarity Observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11187, https://doi.org/10.5194/egusphere-egu24-11187, 2024.

EGU24-15584 | Posters on site | HS1.2.1

Leveraging inland radar altimetry over rivers with low cost GNSS reflectometry 

Roelof Rietbroek, Zeleke K. Challa, Michael Kizza, Modathir Zaroug, Tom Kanyike, and Calvince Wara

The monitoring of surface water levels in lakes and rivers is essential for adequate water resource management and timely responding to extreme events. Monitoring an entity as large as the Nile river comes with significant challenges. The cross-boundary nature of the Nile, complicates its management due to different jurisdictions and interests, furthermore there are logistical challenges related to accessibility and site safety.

Radar altimetry has the potential to offer remotely sensed water heights, but still requires expert knowledge and site-specific trial and error. Generating in-situ records of water level heights is therefore invaluable activity both for monitoring and validation purposes.

Low-cost Global Navigations Satellite Systems (GNSS) interferometric reflectometry promises a low-cost solution for monitoring water heights, and devices can be locally constructed using off the shelf components which are now widely available. Furthermore, the development of internet of things (IoT) networks in Africa is moving forward and creates opportunities for remotely controlled measurement stations.

Here, we present our activities on designing and deploying low-cost GNSS-R receivers on the shores of Lake Victoria. We show several designs based on raspberry Pi’s and a low-power version based on the Actinius Icarus platform (zephyr based). We further explore possibilities to apply on-board processing of GNSS signal to noise ratio series, which will pave the way for using low bandwidth networks.

How to cite: Rietbroek, R., K. Challa, Z., Kizza, M., Zaroug, M., Kanyike, T., and Wara, C.: Leveraging inland radar altimetry over rivers with low cost GNSS reflectometry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15584, https://doi.org/10.5194/egusphere-egu24-15584, 2024.

EGU24-16629 | Posters on site | HS1.2.1

SETIER Project: An open source flowmeter for monitoring flow rates output of waste water treatment 

Arnold Imig, Hélène Guyard, Stephanie Prost-boucle, Valerie Quatela, Sylvain Moreau, Julien Sudre, and Rémi Clément

Different types of sensors are used continuously or intermittently in urban water management systems. They are primarily useful for monitoring and controlling medium to large treatment plants, allowing the recording of physical parameters such as inflow and/or outflow rates or the temperature of the facilities (Murphy et al., 2015). Additionally, continuously measured parameters include those specifically used to monitor physico-chemical processes throughout the treatment: electrical conductivity, pH, turbidity, redox potential, or dissolved oxygen in the basins, as well as insufflated air flow rates. For smaller-scale stations (< 2,000 EH), water quality monitoring is often more limited, frequently confined to batch counting or using malfunction sensors (for instance, effluent overflow).Furthermore, taking the example of reed bed filters (RBF), which are primarily advantageous for operators due to their operational simplicity, the use of sensors could be seen as complicating this system primarily intended for rural areas (Rao et al., 2013). The costs of purchasing and maintaining measurement chains may appear excessively high depending on the parameters used, an opinion shared by municipalities and operators whose financial resources are increasingly constrained (Prost-Boucle et al., 2022). The issue of sensor costs is particularly significant for smaller stations, significantly impacting operational budgets. It is also worth noting the difficulty in repairing and maintaining these solutions, often regarded as black boxes for users, requiring complete upgrades at regular intervals. As part of the Setier project, we have developed a series of Open-hardware tools for the management and monitoring of wastewater treatment plants. The objective of our presentation will be to showcase an open-source ultrasonic flowmeter. This flowmeter allows monitoring variations in Venturi channels, encompassing heights from 0 to 1 meter. It offers a 1mm resolution, and all design elements are shared online. The uniqueness of our system lies in its requirement for no component soldering like “Lego”. The flowmeter is programmable via the Arduino IDE. As for data collection, it is done using a smartphone through a web server embedded in the Arduino MKR1010 Wifi board. Our presentation will highlight the first measurement results from a 6-month wastewater treatment plant.

 

Murphy, K., Heery, B., Sullivan, T., Zhang, D., Paludetti, L., Lau, K.T., Diamond, D., Costa, E., O׳Connor, N., Regan, F., 2015. A low-cost autonomous optical sensor for water quality monitoring. Talanta 132, 520–527. https://doi.org/10.1016/J.TALANTA.2014.09.045

Prost-Boucle, S., Kamgan Nzeufo, H., Bardo, T., Moreau, S., Guyard, H., Duwig, C., Kim, B., Dubois, V., Gillot, S., Clement, R., 2022. Capteurs bon marché et centrales d’acquisition DIY pour les eaux usées : le projet Setier: Low-cost sensors and datalogger open hardware for wastewaters: Setier project. TSM 35–44. https://doi.org/10.36904/tsm/202201035

Rao, A.S., Marshall, S., Gubbi, J., Palaniswami, M., Sinnott, R., Pettigrovet, V., 2013. Design of low-cost autonomous water quality monitoring system. Presented at the 2013 International Conference on Advances in Computing, Communications and Informatics (ICACCI), pp. 14–19. https://doi.org/10.1109/ICACCI.2013.6637139

How to cite: Imig, A., Guyard, H., Prost-boucle, S., Quatela, V., Moreau, S., Sudre, J., and Clément, R.: SETIER Project: An open source flowmeter for monitoring flow rates output of waste water treatment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16629, https://doi.org/10.5194/egusphere-egu24-16629, 2024.

EGU24-18913 | ECS | Posters on site | HS1.2.1

A low-cost multi-sensor platform for monitoring real-time hydrological and biogeochemical dynamics across land-stream interfaces 

Lluís Gómez Gener, Antoine Wiedmer, and Lluís Camarero Galindo

The recognition of global change impacts on catchments and the waters they drain emphasizes the need to better understand and predict both hydrological and biogeochemical dynamics at the terrestrial-aquatic interface. To achieve this great endeavor, a key priority is to substantially increase the number of multi-annual time series, covering a broad range of river types and filling existing geographical gaps (e.g., low-income regions in/and remote areas). However, commercial multi-sensor solutions are not affordable to everyone. The multi-sensor platform consists of a STM32 micro-controller board combined with a data logger module, and a set of sensors to measure hydro-chemical properties both at different depths in soils (adjacent to the streams) as well as within streams: temperature, water level, moisture, electrical conductivity, turbidity, dissolved O2 and CO2. The monitoring system is also equipped with a wireless communication capability using LoRa network technologies. To make our project as accessible as possible, we have designed, built, and programmed the multi-sensor adopting the Open Source Hardware and Software philosophy. Through the complete processes of pre-calibration and in situ measurement, the preliminary results illustrate that the proposed multi-sensor system can provide long-term, high-frequency hydrological and biogeochemical data across land-stream interfaces while keeping the balance of costs and accuracy.

How to cite: Gómez Gener, L., Wiedmer, A., and Camarero Galindo, L.: A low-cost multi-sensor platform for monitoring real-time hydrological and biogeochemical dynamics across land-stream interfaces, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18913, https://doi.org/10.5194/egusphere-egu24-18913, 2024.

EGU24-19085 | ECS | Posters on site | HS1.2.1

Rainfall Intensity Estimation Based on Raindrops Sound: Leveraging the Convolutional Neural Network for Analyzing Spectrogram 

Seunghyun Hwang, Jinwook Lee, Jongyun Byun, Kihong Park, and Changhyun Jun

In this study, we propose a novel approach for precipitation measurement based on rainfall acoustics, utilizing an effective rainfall acoustic collection device with low-cost IoT sensors housed in waterproof enclosure. Here, rainfall acoustics refer to the sound generated when raindrops fall and collide with surfaces such as the ground or canopy. Even at the same rainfall intensity, depending on the medium with which raindrops collide, acoustics with different frequency characteristics may occur. In this research, an acoustic collection device, combining a Raspberry Pi and a condenser microphone, was inserted into a waterproof enclosure and deployed in a rainfall environment to collect rainfall acoustics. This approach not only controls the medium of rainfall acoustics but also effectively blocks ambient noise and water, ensuring consistent characteristics of rainfall acoustics regardless of the installation environment. The collected rainfall acoustics were segmented into 10-second intervals, and spectrograms in the frequency domain were extracted by applying Short-Time Fourier Transform for each segment. Finally, using the extracted spectrogram as input data, a rainfall intensity estimation model based on a convolutional neural network was developed and other precision rainfall observation instruments (e.g., PARSIVEL, Pluvio², etc.) were considered collectively for the validation of the developed rainfall intensity estimation model. Acoustic-based rainfall observation enables the establishment of a dense observation network using low-cost devices. Leveraging the high temporal resolution of acoustic data, extremely short observation periods for rainfall can be achieved. This methodology presents an opportunity for cost-effective and high-spatiotemporal-resolution rainfall observation, overcoming the limitations of traditional methods.

Keywords: Acoustic Sensing, Rainfall Acoustics, Precipitation, Convolutional Neural Network

Acknowledgement

This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. RS-2023-00250239) and in part by the Korea Meteorological Administration Research and Development Program under Grant RS-2023-00243008.

This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No.NRF-2022R1A4A3032838).

How to cite: Hwang, S., Lee, J., Byun, J., Park, K., and Jun, C.: Rainfall Intensity Estimation Based on Raindrops Sound: Leveraging the Convolutional Neural Network for Analyzing Spectrogram, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19085, https://doi.org/10.5194/egusphere-egu24-19085, 2024.

EGU24-19610 | ECS | Posters on site | HS1.2.1

Open-hardware-based data logger platform for independently operating outdoor instrumentation 

Jannis Weimar and Markus Köhli

Open hardware-based microcontrollers, especially the Arduino platform, have become a comparably easy-to-use tool for rapid prototyping, stand-alone systems and implementing creative solutions. Such devices in combination with dedicated frontend electronics, external sensors and modems can offer low cost alternatives for student projects and independently operating small scale instrumentation. The capabilities of sensor-to-sensor communication can be extended to data taking and signal analysis at decent rates. Low-cost approaches to environmental monitoring will be critical for developing the evidence base needed to better understand the climate system, specifically in our case for understanding the water cycle. Off-the-shelf-components-based, internet-connected devices are easy to monitor and maintain, low risk and capable of extensive deployment to address the challenge of geographical variability and can address user- and site-specific demands. We present our project of a data logger platform "nCollector" based on an Arduino DUE, including data storage on SD cards, serial data transmission via USB, RS485, SDI-12, telemetry via GSM (4G), Nb-IoT and LoRa including its power supply and a minimal user interface. For outdoor instrumentation we specifically designed a solution with a low power demand of 0.2 W in order to realize 24/7 operation under harsh conditions with medium sized PV panels and batteries. With our presentation we want to provide a model case for other researchers to take inspiration from, share our experience with building and deploying over 100 systems all over Europe and help engaging the community to enhance their own instrumentation and data taking. 

How to cite: Weimar, J. and Köhli, M.: Open-hardware-based data logger platform for independently operating outdoor instrumentation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19610, https://doi.org/10.5194/egusphere-egu24-19610, 2024.

EGU24-2305 | Posters on site | HS1.2.5

Pedotransfer functions and their impact on water dynamics simulation and yield prediction 

Pablo Rosso, Kurt-Christian Kersebaum, Janis Groh, Horst Gerke, Kurt Heil, and Robin Gebbers

The dynamics of water availability for plant growth is particularly important for crop productivity simulation. Critical for the prediction of crop growth and development is the accurate simulation of soil moisture variation time. Soil capacity-based models assume that the vertical movement of water in the soil is mostly controlled by the intrinsic soil water retention capacities (WRCs), mainly field capacity (FC) and wilting point (WP). However, FC and WP are difficult to measure directly. Pedotransfer functions (PTFs) have been developed to determine these parameters from basic, more readily available soil attributes such as texture and soil organic carbon content. Functional evaluation, a procedure to assess the appropriateness of a PTF, entails testing the sensitivity of the different PTFs to model’s target simulation outcomes. This study constitutes an attempt to quantify and understand the impact of different PTFs on crop yield in a soil capacity-based model.

Six PTFs were used in the crop model HERMES to test their ability to simulate soil water dynamics and to determine their effect on yield simulation. This study, carried out in Germany, included three sandy soil sites in Brandenburg and a silty soil site in Bavaria. Five lysimeters at a site in Brandenburg provided a complete record for assessing the performance of PTFs. Measured soil texture and organic carbon were used as inputs in HERMES, which by applying the PTFs under study, produced the corresponding estimates of WRPs used for soil water dynamic simulations and yield predictions. Soil water records were statistically compared with model outputs to assess the accuracy of each PTF-based simulation. Differences in yield predictions were measured to estimate the sensitivity of the crop model to the PTFs tested.

Not a single PTF performed best in all sites. PTFs by Batjes and Rosetta were the best performers at the three Brandenburg sites. At Duernast, Bavaria, all PTFs resulted in higher errors than at the other sites. At this site, the measured soil water content maxima during the rainy months appeared very variable from year to year, which was unexpected if assumed that the maxima should stay around FC and be fairly constant. In general, HERMES simulations followed the trends in measured soil water dynamics regardless of the PTF applied, whereas differences between PTFs appear on the magnitude of the water maxima during the winter months. This shows that the accuracy of PTFs largely depended on their ability to correctly estimate FC. The highest variability in yield prediction for the different PTFs was observed in the three Brandenburg sites, which also corresponded with higher differences in FC estimation. A closer look at the sandy sites, and simulations with a synthetic soil database showed that differences in yield simulation between PTFs increased proportionally with soil sand percent. This points out at the empirical nature of PTFs and the care that needs to be taken when applied in new situations.

How to cite: Rosso, P., Kersebaum, K.-C., Groh, J., Gerke, H., Heil, K., and Gebbers, R.: Pedotransfer functions and their impact on water dynamics simulation and yield prediction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2305, https://doi.org/10.5194/egusphere-egu24-2305, 2024.

Nitrate pollution of groundwater is still an issue of concern at many drinking water wells located in the Swiss lowlands, where agricultural areas are the main pollution source. Extensification measures (e.g. conversion of arable land to extensive grassland, reduction of vegetable/potato areas in favor of cereals) are generally considered to be effective to reduce nitrate leaching to groundwater. However, these measures are also associated with large losses in agricultural productivity and can thus only be implemented on small focused areas within contribution zones of drinking water wells. It is hypothesized here that the trade-offs between agricultural production and groundwater protection can better be managed if more nuanced mitigation strategies are implemented at a broader scale. Such strategies would target at an improved synchrony between plant nitrogen demands and soil nutrient availabilities (e.g. by inclusion of cover crops and optimizing crop rotations, through reduced soil management and demand-driven fertilization practices). Since evaluating the effects of such strategies is anything but trivial given the high complexity of the process interactions and the strong influence of climatic variability, it is the aim of this work to train a mechanistic field scale model that simulates soil water and nutrient dynamics at a field scale in response to soil, climate and management drivers (DAISY model). The calibration builds on an extensive dataset from the lysimeter station Zurich Reckenholz including detailed data since 2009 on nitrate leaching, seepage water generation, soil moisture, water tension, soil temperature, and crop yields for a series of different experiments including non-inversion tillage, cover cropping as well as different fertilization types and amounts. The calibration strategy and selected calibration/validation results will be presented and discussed in context with implications for model applications.

How to cite: Holzkämper, A.: Managing the trade-off between agricultural productivity and groundwater protection in Switzerland – a model-approach based on long-term lysimeter data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2703, https://doi.org/10.5194/egusphere-egu24-2703, 2024.

EGU24-2783 | ECS | Posters on site | HS1.2.5

Critical Soil Moisture Content Estimated from Lysimeter Time Series for Different Soil, Vegetation and Weather conditions 

Xiao Lu, Jannis Groh, Thomas Pütz, Alexander Graf, Mathieu Javaux, Harry Vereecken, and Harrie-Jan Hendricks Franssen

Evapotranspiration (ET) is a crucial terrestrial ecosystem process that links water, energy, and carbon cycles. ET can be limited by either energy or water availability. The transition between water- and energy-limited regimes is associated with the soil moisture content, and can be postulated as the soil moisture content reaching a threshold, denoted as critical soil moisture (θcrit). Knowledge of θcrit is important for improving land surface, hydrological and crop models and predicting hydroclimate extremes such as droughts and heatwaves. However, the quantification of θcrit and the factors that impact θcrit are still not well understood. Here we used precise lysimeter observations to quantify θcrit by analyzing the relationship between soil moisture content and evaporative fraction (EF), as well as the relationship between soil moisture content and the actual ET/ potential ET ratio during drydowns. We estimated θcrit not only at the surface layer using in situ soil moisture measurements at 10 cm depth, but also for the root zone using vertically integrated in situ soil moisture (0–50 cm) observations. We estimated θcrit across various soil textures (e.g., sandy loam, silty loam, clay loam), vegetation types (grass, crop), as well as weather conditions from western and eastern Germany (spatial distances: 10 ~ 600 km). Especially, with some lysimeters that were taken from their original environment and translocated to other regions, we can identify the shift of θcrit with the same soil and vegetation but under different weather conditions, which can provide implication on changes of θcrit under global warming. We would expect a dependence of θcrit on soil texture and weather condition. We found for example that at the same site with the same crop rotation on the lysimeters but different soils, the sandy loamy soil experienced a lower θcrit (approximate 0.15 m3/m3) than the silty loamy soil (approximate 0.17 m3/m3), indicating that the higher content of sand would lead to the lower θcrit. In addition, an increase in θcrit was observed when the lysimeter was translocated from a site with a lower potential ET to a site with a higher potential ET.

How to cite: Lu, X., Groh, J., Pütz, T., Graf, A., Javaux, M., Vereecken, H., and Hendricks Franssen, H.-J.: Critical Soil Moisture Content Estimated from Lysimeter Time Series for Different Soil, Vegetation and Weather conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2783, https://doi.org/10.5194/egusphere-egu24-2783, 2024.

EGU24-3404 | ECS | Orals | HS1.2.5

Effects of changes in climatic conditions on soil water storage patterns 

Annelie Ehrhardt, Jannis Groh, and Horst H. Gerke

The soil water storage (SWS) defines crop productivity of a soil and varies under differing climatic conditions. Pattern identification and quantification of these variations remains difficult due to the non-linear behaviour of SWS changes over time.

We hypothesize that these patterns can be revealed by applying wavelet analysis to an eight-year time series of SWS, precipitation (P) and actual evapotranspiration (ETa) in similar soils of lysimeters in a colder and drier location and a warmer and wetter location within Germany. Correlations between SWS, P and ETa at these sites might reveal the influence of altered climatic conditions but also from subsequent wet and dry years on SWS changes.

We found that wet and dry years exerted influence on SWS changes by leading to faster or slower response times of SWS changes to precipitation in respect to normal years. This might be explained by a higher soil water content and the related higher soil hydraulic conductivity. Time shifts in correlations between ETa and SWS became smaller at the wetter and warmer site over time in comparison to the cooler and drier site where they stayed constant. This could be attributed to an earlier onset of the vegetation period over the years and thus to an earlier ETa peak every year and reflects the direct impact of changing climate on soil water budget parameters. 

How to cite: Ehrhardt, A., Groh, J., and Gerke, H. H.: Effects of changes in climatic conditions on soil water storage patterns, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3404, https://doi.org/10.5194/egusphere-egu24-3404, 2024.

EGU24-9112 | Posters on site | HS1.2.5

Investigating herbicide transport and fate in vegetated lysimeters with numerical modeling and stable carbon isotopes 

Arno Rein, Anne Imig, Lea Augustin, Jannis Groh, Thomas Pütz, Martin Elsner, and Florian Einsiedl

The application of pesticides can induce severe impacts to the vadose zone, groundwater, and their ecosystems. A study was carried out on two lysimeters located in Wielenbach, Germany. Different soil textures were considered within the soil cores, consisting of sandy gravel and clayey sandy silt. The lysimeters were vegetated with maize, and four different herbicides were applied according to common agricultural practice. Over a period of 4.5 years, concentrations of the herbicides and selected metabolites were monitored in the lysimeter drainage. In addition, stable carbon isotopes (δ13C) were analyzed for investigating biodegradation influences of two of the applied herbicides.

In a first step, we characterized unsaturated flow in the lysimeters based on stable water isotope measurements (δ2H and δ18O) combined with modeling. Different setups within the numerical model HYDRUS-1D were compared, including single and dual porosity approaches. Then, the unsaturated flow models were extended for describing reactive transport of the herbicides, and simulations were interpreted in combination with measured δ13C values. 

At the end of the observations, 0.9 to 15.9% of the applied herbicides (up to 20.9% for herbicides plus metabolites) were recovered in lysimeter drainage. Some metabolites were observed to accumulate in drainage, and biodegradation was indicated by small isotopic shifts in δ13C to less negative values in the leached herbicides. In the later sampling campaign (7.5 months after herbicide application), a higher increase in δ13C (less negative values) compared to earlier sampling (19 days after application) points towards stronger biodegradation. This can be explained by a higher biodegradation potential when the infiltrated water and the herbicides were affected by longer mean transit times in the unsaturated zone.

Observations were reproduced by modeling, where the overall dynamics of herbicide concentration in the lysimeter drainage could be covered well by the model setups. The concentration peaks were partly associated with heavy precipitation, which in turn indicates that the transport was influenced by preferential flow. Limitations were found for describing preferential flow events by using single and dual porosity models, as some concentration peaks were over- or underestimated. The use of δ13C for compound-specific isotope analysis allowed obtaining some evidence on biodegradation of the two herbicides in the unsaturated zone, which was also validated with the model results. 

How to cite: Rein, A., Imig, A., Augustin, L., Groh, J., Pütz, T., Elsner, M., and Einsiedl, F.: Investigating herbicide transport and fate in vegetated lysimeters with numerical modeling and stable carbon isotopes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9112, https://doi.org/10.5194/egusphere-egu24-9112, 2024.

The ongoing global concern regarding climate change necessitates innovative approaches to understand its complex dynamics. This presentation outlines the evolution of lysimeters and ecotrons, culminating in the development of a cutting-edge platform designed for comprehensive research on climate change parameters in both laboratory and field environments.

Lysimeters, traditionally employed to measure water movement and nutrient transport in soil, have undergone significant advancements. Enhanced instrumentation and sensor integration now allow for precise monitoring of multiple environmental factors, including soil moisture, temperature, and gas exchange. These improvements enable researchers to simulate and analyze various climate change scenarios in a controlled laboratory setting.

Simultaneously, ecotrons, specialized chambers designed to replicate natural ecosystems, have evolved to provide a more realistic representation of climate interactions. By incorporating advanced technologies such as remote sensing, automated data acquisition, and controlled environmental conditions, ecotrons now offer a holistic approach to studying the impact of climate change on ecosystems.

The integration of lysimeters under natural conditions and ecotrons into a unified platform represents a paradigm shift in climate change research. This new platform facilitates a seamless transition between controlled laboratory experiments and real-world field studies, allowing for a more comprehensive understanding of the intricate relationships between climate change parameters.

Researchers can now explore the effects of elevated temperatures, altered precipitation patterns, and increased greenhouse gas concentrations on soil health, plant growth, and ecosystem dynamics with unprecedented precision. The platform's adaptability and versatility make it a valuable tool for addressing urgent questions related to climate change impact mitigation and adaptation strategies.

In conclusion, the fusion of outdoor lysimeters and indoor ecotrons into a unified platform signifies a milestone in climate change research. This innovative approach provides researchers with a powerful tool to investigate and address the complex challenges posed by climate change, fostering a more sustainable and resilient future.

How to cite: Reth, S.: Advancements in Lysimeters and Ecotrons: A Novel Platform for Investigating Climate Change Parameters in Laboratory and Field Settings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9489, https://doi.org/10.5194/egusphere-egu24-9489, 2024.

EGU24-9685 | ECS | Orals | HS1.2.5 | Highlight

The need for realistic experimental setups in controlled environments: insights from a two-year ecotron experiment on earthworms’ impact on ecosystem H2O, CO2 and N2O dynamics 

Joana Sauze, Oswaldo Forey, Clément Piel, Emmanuel S. Gritti, Sébastien Devidal, Abdelaziz Faez, Olivier Ravel, Yvan Capowiez, Damien Landais, Jacques Roy, and Alexandru Milcu

Recent studies have highlighted the potential role of earthworms in modulating soil greenhouse gas (GHG) emissions, yet the complexity of natural ecosystems and the lack of high-resolution temporal data have limited our understanding. To bridge this gap, a two-year experiment was undertaken in a controlled ecotron setting, utilizing large-scale lysimeters (5 square meters in area and 1.5 meters in soil depth) in the Macrocosms experimental platform of the Montpellier European Ecotron (CNRS). This study aimed to provide an understanding of the impact of earthworms (specifically endogeic and anecic ecotypes) on water and greenhouse gas emissions in a realistically simulated agricultural ecosystem undergoing a three-crop rotation.

We employed continuous, high-frequency monitoring to measure ecosystem-level exchanges of CO2, N2O, and H2O. While temporary increases in CO2 fluxes were noted in earthworm-inhabited replicates, the cumulative data over the entire study period did not demonstrate a significant increase in CO2 emissions. Interestingly, the presence of endogeic earthworms was correlated with a notable reduction in N2O emissions during wheat cultivation (by 44.6%), although this effect did not persist throughout the entire experimental timeline. Additionally, while earthworms had an impact on water infiltration along the soil profile, no consistent patterns were observed in terms of ecosystem evapotranspiration or water use efficiency (WUE) changes attributable to earthworm activity.

Our findings provide critical insights into the role of earthworms in terrestrial GHG dynamics, particularly in agricultural settings. Contrary to prevailing assumptions, this study suggests that earthworm activity does not lead to a significant increase in greenhouse gas emissions over a period of two years under conditions that closely emulate agricultural environments. These results underscore the importance of conducting long-term, high-resolution studies in realistically simulated ecosystems to better comprehend the intricate relationships between soil biota and greenhouse gas emissions.

How to cite: Sauze, J., Forey, O., Piel, C., Gritti, E. S., Devidal, S., Faez, A., Ravel, O., Capowiez, Y., Landais, D., Roy, J., and Milcu, A.: The need for realistic experimental setups in controlled environments: insights from a two-year ecotron experiment on earthworms’ impact on ecosystem H2O, CO2 and N2O dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9685, https://doi.org/10.5194/egusphere-egu24-9685, 2024.

EGU24-11233 | Orals | HS1.2.5 | Highlight

Influence of climate and land management on water, carbon and nitrogen cycling in grasslands of the pre-alpine region of southern Germany 

Ralf Kiese, Marcus Schlingmann, Katrin Schneider, Sophie Reinermann, Anne Schucknecht, Jincheng Han, Thomas Koellner, Carolin Boos, and Michael Dannenmann

Pre-alpine grasslands provide important economic value through forage for milk and meat production. Grassland soils also support ecosystem services such as carbon and nitrogen storage, water retention, erosion control and biodiversity. These functions are currently threatened by climate change, which is likely to accelerate in the coming decades. In addition to climate change, management decisions such as mowing and fertilisation frequency have a major impact on grassland yields, biodiversity and soil C and N dynamics. In this presentation we will summarise results from long-term monitoring of control and translocated grassland soil monoliths (1m2; 1.4m height) as operated in TERENO and studied in detail in the SUSALPS project.

From 2012, moderate climate change (plus 2°C) has increased grassland productivity, unless water stress has reversed the temperature stimulating effect. However, this increase in plant growth is only possible because increased N mineralisation rates under climate change allow increased N demand to be met. As plant N uptake is already in the range of total N fertilisation rates under current climate conditions, N losses to the environment, such as microbial N2O emissions and nitrate leaching from montane grassland soils, are comparatively low. If other ecosystem N losses such as NH3 and N2 emissions are considered, it becomes clear that even under the present climatic conditions substantial N has to be provided by mineralisation of soil organic N, indicating soil N (and C) mining. As the latter is associated with negative effects on soil fertility/productivity, C sequestration and GHG exchange, as well as filtering functions to protect water bodies, this trend poses risks to key soil functions in the long term. The detailed investigations from long-term monitoring sites were essential for testing a process-based model (LandscapeDNDC), which was used together with remote sensing information for spatial and temporal upscaling of the results.

How to cite: Kiese, R., Schlingmann, M., Schneider, K., Reinermann, S., Schucknecht, A., Han, J., Koellner, T., Boos, C., and Dannenmann, M.: Influence of climate and land management on water, carbon and nitrogen cycling in grasslands of the pre-alpine region of southern Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11233, https://doi.org/10.5194/egusphere-egu24-11233, 2024.

EGU24-11711 | Orals | HS1.2.5

The Deep Soil Ecotron – A Facility to Explore, Model, and Sense Deep Soil 

Zachary Kayler, Michael Strickland, David Williams, Rodrigo Vargas, Zeli Tan, Caley Gasch, Susan Crow, and Noah Fierer

The Deep Soil Ecotron will give researchers the unparalleled ability to investigate and experiment with deep soils while complementing established ecotrons across the globe. This facility, composed of twenty-four, highly instrumented ecounits, will allow for soil profiles up to three meters in depth to be repeatedly sampled and continuously monitored. This facility will be the first modern ecotron facility in the United States and as such will provide research infrastructure that this country currently lacks. The Deep Soil Ecotron will enable researchers to address the following four broad research needs using approaches and instrumentation that have been unattainable under more common field and laboratory experiments. First, the Deep Soil Ecotron will reveal how deep soil communities and processes affect and interact with surface soils to influence whole ecosystems. Second, the Deep Soil Ecotron will allow researchers to determine how deep soils and associated vegetation respond to global and land-use change, such as increasing soil temperature and agricultural management practices. Third, information gained from the Deep Soil Ecotron will be integrated into earth system models to improve model representation of soil carbon cycling. Fourth, the Deep Soil Ecotron will provide a testbed for the development of sensors for the in-situ monitoring of deep soils. This presentation will provide an overview of the Deep Soil Ecotron's design, capacity, and preliminary research agenda.

How to cite: Kayler, Z., Strickland, M., Williams, D., Vargas, R., Tan, Z., Gasch, C., Crow, S., and Fierer, N.: The Deep Soil Ecotron – A Facility to Explore, Model, and Sense Deep Soil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11711, https://doi.org/10.5194/egusphere-egu24-11711, 2024.

EGU24-12759 | Orals | HS1.2.5

Enhanced understanding of water cycling processes of dwarf shrubs using high-precision lysimeters and climate manipulations 

Georg Leitinger, Elena Tello-García, Lucía Laorden-Camacho, Lisa Ambrosi, Karl Grigulis, Bello Mouhamadou, Christiane Gallet, Ursula Peintner, Ulrike Tappeiner, and Sandra Lavorel

Throughout European mountains, changes in livestock production systems since the 1950s have resulted in the gradual segregation between more accessible, flatter, and productive grasslands with intensified fodder production, and more remote, steeper, and less productive meadows used for extensive grazing, and some abandoned. After cessation of grazing in subalpine grasslands, secondary succession promotes the gradual colonization of species and functionally diverse herbaceous communities by shrubs. Although shrub encroachment is considered a ‘Plant Functional Type transformation’, our knowledge about the impact of climate change on shrub encroached ecosystems is still limited. Mechanistic analyses of alpine grassland responses to drought have focused on carbon fluxes, and a few studies have targeted components of the ecosystem water budget or nutrient cycling. However, these studies are focused on herbaceous functional groups, and shrubs are usually neglected. Moreover, despite the prevalence of this original climate change driver in mountains, snow manipulations are still rare.

To improve understanding of nitrogen and water cycling processes of shrubs with expected increased drought and advanced snowmelt, small high-precision lysimeters (SFL®, Meter Group AG, Munich, Germany) were used to analyze the effects and mechanisms of climate change on shrub species. In a garden experiment in the LTSER-site Stubai Valley (970 m a.s.l.), Tyrol Austria, two congeneric shrubs contrasting a deciduous (Vaccinium myrtillus) and evergreen (Vaccinium vitis-idaea) were planted into 16 lysimeters. In a split-plot design of 3.5m x 3.5m each, two plots were subject to either (1) control, (2) earlier snowmelt, or (3) summer drought treatments.

The manipulative experiments indicate that a shortening of the period with snow cover at the end of winter affects soil freezing and hence, soil nitrogen (N) and carbon (C) availability. Results further highlight the interacting effects of climate manipulations on key plant traits, and their consequences for N- and water availability. Furthermore, summer drought seems to additionally affect biogeochemical cycling and evapotranspiration for both investigated shrub types. This study's results reveal the importance of addressing the impact of shrub encroachment not only from a land management perspective but also to increasingly raise awareness about climate change effects on shrubs. Moreover, it provides valuable insights into challenges and chances of growing shrubs in lysimeters, being a promising approach for future climate impact studies. The study was conducted as part of the LUCSES project, ANR-FWF (ANR-20-CE91-0009 and FWF-I 4969-B).

How to cite: Leitinger, G., Tello-García, E., Laorden-Camacho, L., Ambrosi, L., Grigulis, K., Mouhamadou, B., Gallet, C., Peintner, U., Tappeiner, U., and Lavorel, S.: Enhanced understanding of water cycling processes of dwarf shrubs using high-precision lysimeters and climate manipulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12759, https://doi.org/10.5194/egusphere-egu24-12759, 2024.

EGU24-14816 | ECS | Posters on site | HS1.2.5

Can we bring alpine climate into ecotrons? 

Harald Crepaz, Johannes Klotz, Marco Cavalli, Ulrike Tappeiner, and Georg Niedrist

Climate change is advancing at an unprecedented pace, impacting terrestrial ecosystems, particularly those in alpine regions. Consequently, there is a growing need to comprehend the associated impacts, underlying mechanisms, and implications. Long-term monitoring may face challenges in capturing the effects of accelerated climate change, and in-situ experiments in remote alpine areas often grapple with logistical constraints. Furthermore, attributing vegetative responses to specific manipulated variables proves challenging, especially under extreme alpine conditions such as low atmospheric pressure, low temperatures, or high radiation levels.

Using a specially designed ecotron called 'TerraXcube' (Bozen, Italy), we investigated the feasibility of realistically reproducing harsh alpine conditions and explored the interactions among various parameters. For our measurements, we equipped the chamber with temperature and relative humidity probes, a spectrometer, barometer, and anemometer positioned at different heights within the chamber. We tested the spatial and temporal homogeneity of the variables— atmospheric pressure, temperature, relative humidity (RH), and radiation—independently, as well as their interactions over time and in space, by simulating various realistic alpine climatic scenarios.

The measurements, conducted between -20°C and +25°C with relative humidity ranging from 10% to 95%, yielded satisfactory results. Over several hours, the largest difference at a specific position was 0.6°C and 4.3% RH, while the maximum difference between two sensors simultaneously was 1°C and 7% RH. At a height of 170 cm, the LED system emitted radiation at an intensity of 1,002 W/m² within the wavelength range of 280 to 900 nm; however, with a sharp decrease in intensity from the light source. The photosynthetically active radiation (PAR) at the chamber's center reached 1,883 μmol·m−2·s−1, achieving 77% of the potential annual maximum measured at 2,400 m a.s.l. This enables us to replicate the PAR level for 97% of the days throughout the year. Despite the high light intensity, the heating effect of the LED system was limited to a maximum of 2°C in the upper 40cm of the chamber. Pressure manipulation, with the highest technical demand, nonetheless resulted in high temporal homogeneity up to 4,000m a.s.l., corresponding to 618.9 mbar.

In conclusion, the results emphasize the potential and utility of ecotrons in simulating a suitable climate for alpine ecological experiments. However, as in many ecotrons, it is crucial to acknowledge that minor island effects and irregularities are inevitable. Even more sophisticated parameters such as wind effects or pollinator function are currently not sufficiently addressed. A combined in- and outdoor usage of mobile field lysimeters might be a further step to bridge this gap between experimental results obtained in ecotrons and in the field.

How to cite: Crepaz, H., Klotz, J., Cavalli, M., Tappeiner, U., and Niedrist, G.: Can we bring alpine climate into ecotrons?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14816, https://doi.org/10.5194/egusphere-egu24-14816, 2024.

EGU24-15212 | ECS | Posters on site | HS1.2.5

Effects of land use change on dry heathland soil moisture in a changing climate 

René Shaeffer, Francois Rineau, and Nadia Soudzilovskaia

Conversion of natural and semi-natural systems to agricultural use is one of the largest conservation
challenges of our time. As the world’s population continue to grow at unprecedented rates,
multinational organizations like the United Nations and its subsidiary the Food and Agriculture
Organization call for higher crop production and the expansion of existing agriculture to ensure future
food security, especially in the face of changing climate. However, these efforts will most likely endanger
numerous landscapes of historical and cultural value, including those found in northwest Europe. How
these possible changes in land use may alter the functions of these ecosystems and the associated
services they provide are questions that need to be answered before any policy decisions can be made.


Using a state-of-the-art ecotron facility, we compared soil moisture profiles between an intact dry
heathland system and heathland soils that had been cleared for cereal agriculture, both of which were
subjected to climate conditions projected for the year 2070, in line with the IPCC RCP8.5. After
continuously monitoring moisture changes in the top 1.5 meters of soil for three years, we found that
there are significant differences between the two modes of land use. Soils used for cereal crops were
significantly drier (up to >60%) in the upper 10-20cm than intact heathland soils, and significantly wetter
(up to >500%) at the lowest soil levels (140cm). This redistribution of moisture within the soil column
under different land use schemes can have serious implications for overall ecosystem functioning,
particularly with regard to potentially mitigating heathland soils’ ability to store and capture carbon and
exacerbating detrimental soil-climate feedbacks under agricultural use.

How to cite: Shaeffer, R., Rineau, F., and Soudzilovskaia, N.: Effects of land use change on dry heathland soil moisture in a changing climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15212, https://doi.org/10.5194/egusphere-egu24-15212, 2024.

EGU24-15321 | ECS | Posters on site | HS1.2.5

A practical approach to link lysimeter and large-scale measurement systems. 

Gunther Liebhard, Peter Strauss, Peter Cepuder, and Reinhard Nolz

An accurate and reliable measurement system is essential for analysing transport processes within the soil-plant-atmosphere continuum and for calibrating and validating ecosystem or hydrological models. Weighing lysimeters are very suitable tools for these purposes, as they are the most direct tools to reliably and precisely measure water mass balance components such as rainfall and non-rainfall water inputs, evapotranspiration, and percolation at the system boundaries. Investigating the ecosystem by use of lysimeters is more or less limited to point measurements, though. Approaches are therefore required to link lysimeter mesurements to the landscape scale. We present our experimental approach to link point and large-scale parameter assessment at an experimental station in Groß-Enzersdorf, Austria. In particular, we use soil water content data across the soil profiles from capacitance sensors and t-test statistics to check the representativeness of the conditions in the lysimeter body with the surrounding field and to assess soil hydraulic properties for numerical modeling of water fluxes. Based on this, we transfer measurement data with high measurement accuracy and temporal resolution from the lysimeter scale to the large-scale measurement systems such as eddy covariance, scintillometry, or isotope hydrology. On the other hand, we are able to incorporate parameters from areal measurements and from measurements using disturbed and undisturbed soil samples into the lysimeter measurement system.

How to cite: Liebhard, G., Strauss, P., Cepuder, P., and Nolz, R.: A practical approach to link lysimeter and large-scale measurement systems., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15321, https://doi.org/10.5194/egusphere-egu24-15321, 2024.

EGU24-15370 | Posters on site | HS1.2.5

What you do not know, and what you should know about lysimeter experiments 

Thomas Puetz, Horst H. Gerke, Nicolas Brueggemann, Harry Vereecken, and Jannis Groh

For many studies in the fields of soil, hydrology, agriculture, ecology, meteorology, and environmental sciences and across disciplines, conventional field experiments are inadequate because the variables cannot be measured properly or controlled experimentally. In the soil-plant-atmosphere continuum, lysimeters can be used as an integrative experimental approach that enables precise measurements of water and matter fluxes in combination with field crops. The term lysimeter basically refers to two different types of experimental equipment. Porous suction cups, as well as containers/vessels filled with soil substrates or other materials, are termed lysimeters. Lysimeters are vessels of various sizes filled with ecosystem compartments, taking a holistic approach as each compartment interacts dynamically within the biosphere.

Lysimeter experiments are carried out in a wide variety of designs. To optimize the scientific exploitation of lysimeter data, various prerequisites should be met. The complexity of lysimeter experiments will be explained in more detail, the advantages of lysimeters, but also the restrictions and limitations will be examined in more detail. We would like to suggest some hints, norms, and rules for conducting lysimeter experiments that can optimize and increase the benefit and profit of lysimeter experiments. Special attention is paid to the important technical details that can significantly influence the quality of lysimeter measurements. The latest technical developments are also briefly presented.

How to cite: Puetz, T., Gerke, H. H., Brueggemann, N., Vereecken, H., and Groh, J.: What you do not know, and what you should know about lysimeter experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15370, https://doi.org/10.5194/egusphere-egu24-15370, 2024.

EGU24-16315 | Posters on site | HS1.2.5

Aluminum fate in forest soils developed from magmatic and metamorphic rock of mid-mountain areas in Germany 

Roukaya Eid, Katharina Lehmann, Karin Eusterhues, and Kai Totsche

Climate and land use change affect weathering and pedogenesis with potential consequences for the fate of Al-bearing minerals and the potential export of Aluminum to groundwater resources. These changes might result in strong acidification, originally known for “acid rain” affecting these areas until the second but last decade of the past century. To explore the fate of Al in areas now affected by climate and land use change, we investigated two sites of different geology in North-Bavaria. Site 1 is located on granitic rocks under a reforested 6-year-old Norway spruce forest. Site 2 is a hilltop site located on metamorphic rocks under a 60-80-year-old spruce forest. Soil samples (< 2mm) and clay fractions were analyzed by hydrochemical and spectroscopic techniques. Zero tension controlled lysimeter and automated tension controlled lysimeters were installed for monitoring the soil solution volume and composition at the topsoil-subsoil and the subsoil-regolith boundary. Monitoring started in June 2018. Since then, 85 sampling campaigns have been completed that amounted to 1500 individual lysimeter samples. Analysis comprised among others EC, pH, elemental composition major anions and cations, and carbon sum parameters (DOC, TOC, DIC, TIC).

Recent climate at the sites differs markedly from the 1961-1990 period, indicating a transient climate at the sites. Mean soil pH ranged from 3.2 to 4.7 at both sites and was comparable to values published in 1995 by Franken et al. (3.4 to 4.2). Thus, recent soil pH is as low as used to be under the conditions of strong acid precipitation of the last century. Soils developed from magmatic rock showed higher contents of variable Al phases than those developed from metamorphic rocks.

At both sites pyrophosphate extractable Al is the dominant Al pool accounting 19.4% of total Al in site 1(14.1 g/kg in Bs horizon), and 6.9% of total Al in site 2 (4.9 g/kg in Bs horizon).

Noteworthy, hydrological summer was more important for seepage generation than the hydrologic winter: Roughly 68% of the total annual seepage volume was found in the hydrological summer. As a result, the TOC flux from the subsoil in summer is 35.66 ± 20 mg/year, and only 13.88 ± 13.8 mg/year in winter. Similarly, the Al flux in summer is 1.02 ± 0.7 mg/year and only 0.43 ± 0.4 mg/year in winter.

Variation partitioning analysis showed that the seasonal variation and the difference between topsoil and subsoil combined explained less than 5 % of the particle-related soil solution properties ((pH, ∑LMWO, TOC, Al and Si(mg/L)) and less than 1% of the hydrochemical properties (TIC, Cl, SO42−, Ca, Mg, Na (mg/L)). Difference between the two sites explained 13.84% and 6.48% of the two sets, respectively and the sampling year explained 4.52% and 4.74%. We conclude that the Al system at our sites is controlled by climatic conditions and site properties (lithology, slope, vegetation..). There are no indications that the released Al is immobilized in any secondary immobile Al-phase in the subsoil or downstream, pointing to the potential transport of Al and other unwanted substances to the aquifers.

How to cite: Eid, R., Lehmann, K., Eusterhues, K., and Totsche, K.: Aluminum fate in forest soils developed from magmatic and metamorphic rock of mid-mountain areas in Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16315, https://doi.org/10.5194/egusphere-egu24-16315, 2024.

EGU24-20671 | Posters on site | HS1.2.5 | Highlight

Effect of climate change on functioning of natural and agricultural ecosystems: an ecotron study 

Francois Rineau and Nadejda Soudzilovskaia and the Ecotron consortium team

Ecotrons represent enclosed systems in which macrocosms are subjected to controlled environmental conditions, and their responses are closely monitored at a high frequency. This makes them particularly well-suited for investigating the impact of climate change on ecosystem functioning. In this presentation, we demonstrate the utilization of the UHasselt ecotron to examine the effects of climate change on two distinct ecosystems: a natural heathland and an agricultural pear orchard.

We delve into the results obtained thus far, covering aspects such as carbon balance, water balance, greenhouse gas emissions, soil water nutrients, plant biomass, phenology, soil microbial communities, and soil fauna. Additionally, we explore the strengths and limitations associated with ecotron-based approaches. The presentation concludes by identifying future challenges in this field.

How to cite: Rineau, F. and Soudzilovskaia, N. and the Ecotron consortium team: Effect of climate change on functioning of natural and agricultural ecosystems: an ecotron study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20671, https://doi.org/10.5194/egusphere-egu24-20671, 2024.

EGU24-20967 | Orals | HS1.2.5

Determining the soil water balance at a large-scale lysimetric facility with 60 years of uninterrupted data comprising a grassland basin, oak/beech and a pine basin 

Marcel Gaj, Stephan Costabel, Michèle Erlach, Julia Frank, Viktoriya Tarasyuk, Stephan Peth, and Vera Schimetzek

The research facility St. Arnold presented here consists of three individual lysimeters with an area of 400m² and 3.5m depth each. They are similar in soil types but differ in vegetation cover. This unique setup allows the direct comparison of the water balance of grassland, oak/beech forest and pine forest under the same climatic and topographic boundary conditions. The later site were cut after a significant storm occurred in 2007. Since a pioneer forest developed. 

The data collection of precipitation, groundwater recharge, temperature, humidity and sunshine duration started in 1964. In addition, stem diameter at certain trees has been determined once a year.  All data until 1997 were collected manually. After that automated collection of hydro climatic data were established and transmitted directly into the database of LANUV. From the data, evaporation rates were calculated with Penman-Montheith. More recently in October 2023 undisturbed soil cores where collected and analyses for their saturated and unsaturated hydraulic conductivity. In addition, the investigation of the water balance has been done with HYDRUS 3D.

The data shows significant trends. Further, it can be observed how storm damage and/ or clear-cut of forested areas impact the soil water balance.  The long-term average of the period 1965 to 2007 showed, the grassland basin turns more than half of its annual incoming precipitation into leachate and only 36% into evaporation while the deciduous forest exhibits a ratio of 36% leachate and 56% for evapotranspiration. The evergreen coniferous forest shows the highest evaporation rate 65% and the lowest leachate rate with 26%. (Harsch et al., 2009)

An upgrade of the entire facility with state of the art measurements devices is in progress. This will initiated with a geophysical survey in the beginning of 2024 along with the installation of soil moisture and tensiometer sensors. Depending on funding permanent and long term geophysical measurements and stable isotope analysis will be conducted all data will be available open source. We welcome collaborators for joint research at the facility.

 Harsch, N., Brandenburg, M., & Klemm, O. (2009). Large-scale lysimeter site St. Arnold, Germany: analysis of 40 years of precipitation, leachate and evapotranspiration. Hydrology and earth system sciences13(3), 305-317.

How to cite: Gaj, M., Costabel, S., Erlach, M., Frank, J., Tarasyuk, V., Peth, S., and Schimetzek, V.: Determining the soil water balance at a large-scale lysimetric facility with 60 years of uninterrupted data comprising a grassland basin, oak/beech and a pine basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20967, https://doi.org/10.5194/egusphere-egu24-20967, 2024.

EGU24-21932 | Orals | HS1.2.5

Heat transport model simulations of Lysimeter/Ecotron systems 

Gernot Klammler, Janja Vrzel, and Hans Kupfersberger

Soil temperature plays a central role in the complex processes in the vadose zone, particularly in connection with water and solute transport. As a major thermal factor, soil temperature influences not only the physical properties of the soil, but also the biochemical reactions responsible for the transport of water and solutes. The variation of soil temperature can have significant effects on the mobility of nutrients and pollutants and thus plays a key role in understanding and controlling important soil processes.

Ecotrons in combination with weighable lysimeters are generally able to investigate complex ecological processes (e.g. evapotranspiration, nutrient dynamics) under controlled conditions. However, the requirement for this is that the temperature control of the soil column can be simulated with sufficient accuracy over the entire height and cross-section. Furthermore, it must also be ensured that the required rates of temperature change in the soil column, which can vary depending on the scientific question, can be simulated.

In the course of the abstract submitted here, we would like to present the results of 3D heat transport model simulation for selected examples, which contribute to the optimization of the technical design of Lysimeter/Ecotron systems (e.g. with regard to insulation thickness, heat exchanger area, required inlet temperature in the heat exchanger, etc.).

How to cite: Klammler, G., Vrzel, J., and Kupfersberger, H.: Heat transport model simulations of Lysimeter/Ecotron systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21932, https://doi.org/10.5194/egusphere-egu24-21932, 2024.

HS1.3 – Cross-cutting hydrological sessions

EGU24-1500 | ECS | Posters on site | HS1.3.1

Reclaimed wastewater or surface water use in irrigation: Delineating potential fate and impacts of pharmaceuticals  

Anwesha Mukhopadhyay, Sonali Banerjee, Sonam Jha, Saibal Ghosh, Pradip Bhattacharyya, and Abhijit Mukherjee

The depletion of groundwater storage is being acknowledged as a progressively severe global issue. Around 69% of the total groundwater abstracted is used in the agricultural sector. Hence, it is imperative that we refrain from excessive abstraction of groundwater for irrigation and instead focus on utilizing surface water or reclaimed wastewater. However, these alternate sources can be contaminated with certain emerging contaminants (EOCs) that might raise concern in the future. Hence, this study aims to investigate the effect of surface water or reclaimed wastewater irrigation on rice (Oryza sativa), a water-intensive staple grain in the Asian region. A field experiment was carried out on rice, in which they were subjected to irrigation with water spiked with three commonly detected pharmaceuticals in the environment, namely sulfamethoxazole (SMX), carbamazepine (CBZ), and ibuprofen (IBP). The crops were irrigated at regular intervals for ten times throughout the growing period with three different pharmaceutical doses (0.5g), medium (1g), and high (5g). The control set was irrigated with uncontaminated water. Post-harvest agronomical analysis suggests that the grain yield remained unaffected by contaminant addition, whereas the straw yield was increased by up to 25%, 29% and 33% for SMX, CBZ, and IBP, respectively. The contaminant concentration in the rice grains was found to be greater than the limit of detection (LOD) for all the contaminants at different doses but was not > LOQ for some of them. The health quotient (HQ) for SMX and IBRU was <0.1, signifying lower risk, while for CAR, it ranged from 0.1 to 1, indicating medium risk. Overall, irrigation with reclaimed wastewater or surface water can be detrimental only if higher concentrations of certain pharmaceuticals, like CAR, are present. However, further studies are required as far as metabolites are concerned. Hence, this study will help in determining appropriate concentration thresholds for pharmaceuticals present in surface water or reclaimed wastewater that are considered safe for agricultural purposes.

How to cite: Mukhopadhyay, A., Banerjee, S., Jha, S., Ghosh, S., Bhattacharyya, P., and Mukherjee, A.: Reclaimed wastewater or surface water use in irrigation: Delineating potential fate and impacts of pharmaceuticals , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1500, https://doi.org/10.5194/egusphere-egu24-1500, 2024.

Comprehending runoff generation processes remains a formidable challenge for hydrologists. This study advocates for a comparative examination of these processes across global experimental watersheds. As part of the HELPING decadal initiative, a dedicated working group has been established. Embracing a Darwinian methodology, our objective is to synthesize information through comparative studies across a diverse array of local ecosystems, with the aim of cultivating a global perspective and formulating overarching theories.

We warmly welcome and invite research groups managing experimental watersheds worldwide to actively participate in this collaborative effort. The working group is designed to achieve the following objectives:

1) Compile datasets for experimental watersheds globally, maximizing the utilization of available information.

2) Identify both similarities and differences in watershed characteristics and processes across diverse experimental sites.

3) Develop a more quantitative framework to discern dominant processes within specific watersheds, thereby contributing to a profound understanding of hydrological dynamics.

By bringing together researchers and research groups from across the globe, this collaborative initiative seeks to transcend geographical boundaries and foster a holistic understanding of runoff generation processes.

How to cite: Tian, F. and Cui, Z.: Exploring Runoff Generation Processes: A Global Comparative Study of Experimental Watersheds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2274, https://doi.org/10.5194/egusphere-egu24-2274, 2024.

EGU24-2412 | Posters on site | HS1.3.1

Development of Watershed Simulator and Its Application in China 

Jun Xia, Junguo Liu, Dunxian She, Liangsheng Shi, Sidong Zeng, Lei Zou, Yanjun Zhang, and Chen Hu

The river basin is a fundamental natural unit interlinked with water, soil, air, ecology, and society, serving as a water management system for local communities. The River Basin Simulator (RBS) operates as a simulation system driven by datasets and hydrological knowledge, utilizing the technology of a digital twin basin. This paper addresses the initiative of WG1.14, specifically the Development & Application of River Basin Simulators, under Theme 1 of the HELPING program for IAHS, encompassing the goals and work plan of WG1.14. The development and applications of RBS in China, including the Yangtze River Simulator and its practical applications, are presented.

Through RBS development, it can play a pivotal role in supporting the integration of natural hydrology with socio-hydrology, thereby fostering sustainable development. The initiative of WG1.14 has the potential to promote the development of tools for the digital twin basin, building a bridge from Change (Panta Rhei) to Solution (HELPING). This includes understanding hydrological processes, utilizing advanced hydrological models, and the practical application of socio-hydrology insights, supporting Theme 1 of HELPING with global and local interaction.

How to cite: Xia, J., Liu, J., She, D., Shi, L., Zeng, S., Zou, L., Zhang, Y., and Hu, C.: Development of Watershed Simulator and Its Application in China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2412, https://doi.org/10.5194/egusphere-egu24-2412, 2024.

EGU24-3020 | Posters on site | HS1.3.1

Obtaining holistic solutions for wet extremes and flooding in the Awash basin, Ethiopia   

Meron Teferi Taye, Ellen Dyer, Mengistu Dessalegn, and Katrina Charles

The Awash basin of Ethiopia experiences frequent climate extremes-related disasters. Climate change is contributing to frequent flooding in different parts of the basin. This study explores the drivers of extreme rainfall, the multi-causality and consequences of flooding, governance, and policy implications using a combination of interdisciplinary approaches. The multi-dimensional perspective includes analysis of hydroclimatic variables at the basin level including global drivers, flood characterization, and understanding of affected communities at different parts of the basin through examining the experiences of different water and land users. The study covered urban and rural areas, small-scale agricultural, and pastoral or agropastoral catchments. To obtain diversified perspectives consultation with various basin stakeholders was conducted. By considering the 2020 extreme wet season the study aims to contribute to future management practices that might adapt to extremes and associated floods. The results show that recent rainfall extreme during the summer of 2020 occurred in unusual parts of the basin. Compared to the 1981-2010 baseline the lower part of the basin had a rainfall anomaly of more than 50%. Moreover, antecedent rainfall conditions during April-June contributed to saturating the soils as the months before July were wetter than the base period on average by 62%. The soil moisture content conditions were wetter than average from 10 to 40% in these antecedent months. Unusual rainfall in terms of location, magnitude, and timing is the major cause of flooding in the cases of 2020.  First, the western part of the lower basin received higher rainfall than normal earlier in the season. Then, in the later part of the season, the upper basin received high rainfall that increased the amount of water in upstream rivers which contributed to the massive flooding in the lower basin. This characterizes the 2020 flood occurrences by early onset and delayed recession. The extreme rainfall collided with weak La Nina and positive Western Indian Ocean as global drivers. There are other contributing factors that exacerbate the cause and impacts of flooding on communities. This includes challenges in river morphology, flood forecasting, reservoir management, and differences between private investors and local vulnerable communities in managing extreme cases. For instance, the Awash River broke off its normal course during 2020 extreme rainfall. Uncontrolled water diversion by farmers for irrigation created new water pathways. Low quality of engineering structures e.g., dikes failed to prevent extreme floods. Land use changes, such as urbanization and deforestation increased erosion and blocked drainage ways. Lack of coordination among institutions, weak collective action and governance aspects are exacerbating factors of climate extreme impacts on vulnerable communities. A holistic approach to solving the devastating impact of climate extremes provides better understanding of the multi-causality and multi-dimensionality of water-related risks, to support implementation of adaptive management and coordination approaches in monitoring human-physical systems interactions across sectors.

How to cite: Taye, M. T., Dyer, E., Dessalegn, M., and Charles, K.: Obtaining holistic solutions for wet extremes and flooding in the Awash basin, Ethiopia  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3020, https://doi.org/10.5194/egusphere-egu24-3020, 2024.

EGU24-4773 | ECS | Orals | HS1.3.1 | Highlight

HELPING: Co-creating and communicating water solutions in a globally changing world 

Adeyemi Olusola, Giulio Castelli, and Natalie Ceperley

The current IAHS decade is dedicated to "Hydrology Engaging Local People IN one Global world" (HELPING). One of the core mandates of HELPING, as captured under Theme 3, emphasizes the co-creation of water knowledge and communication. Even though co-creation is not novel, especially within a participatory framework, defining and providing boundaries has been challenging when viewed through a hydrological lens. Our ongoing discussions and meetings have focused on understanding the uniqueness of this Theme and how best we can HELP to utilize diverse communication instruments IN one Global world. For Theme 3, we intend to answer questions such as: (a) How best can we co-create hydrological knowledge (indigenous/traditional and evidence-based) between people and disciplines? (b) How can we improve and increase the visibility of the hydrological decade? (c) How can we provide water solutions through the active engagement of Local People? Some answers to these questions lie in focusing on bottom-up approaches to solve the water crisis in a globally changing world. We acknowledge the fluidities in HELPING regarding the co-creation of water knowledge, which underscores the recognition of variability and complexity within this endeavour. As such, we intend to be diverse in our approach by amplifying silent voices that may have been overlooked, also with a decolonial perspective, and engaging other perspectives from other disciplines, such as but not limited to social sciences and humanities, specifically those whose work intersects sociohydrology, hydro-sociology, hydropolitics and hydronarratives. 

 

How to cite: Olusola, A., Castelli, G., and Ceperley, N.: HELPING: Co-creating and communicating water solutions in a globally changing world, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4773, https://doi.org/10.5194/egusphere-egu24-4773, 2024.

EGU24-5911 | ECS | Orals | HS1.3.1 | Highlight

REHYDRATE - an international HELPING working group to REtrieve historical HYDRologic dATa and Estimates 

Miriam Bertola and Paola Mazzoglio and the HELPING REHYDRATE working group

Historical hydrological observations are often stored in printed documents and volumes of archives worldwide. This makes them practically inaccessible and unusable for modern hydrological studies as well as puts them at risk of permanent loss due to the deterioration of their medium. In addition to the intrinsic value of rescuing past observations, having access to historical data is essential for understanding better the complexity and changes in the hydrological cycle and its extremes.

Several data rescue initiatives exist, but the efforts are highly fragmented in space and time. Current tools for data digitization include optical character recognition (OCR) software and manual transcription. The latter is often carried out through participatory citizen science projects. The use of OCR software is cheap and fast, but it still requires a considerable amount of manual work due to the diversity of the documents, and its accuracy is, to date, not always acceptable. Manual transcription is more accurate, but extremely resource-intensive. For these reasons, there is a general need for better and less costly methods for hydrological data rescue. New tools are becoming available, and new technologies are developing rapidly. 

In response to these challenges, the REHYDRATE Working Group has been proposed as part of the IAHS HELPING Science for Water Solutions decade in summer 2023 (https://iahs.info/uploads/HELPING/WG%20Proposal%20REHYDRATE.pdf). The Working Group aims to connect scientists engaged in data rescue, fostering a collaborative community to exchange knowledge, experiences, and best practices in hydrological data rescue and digitization. The ultimate objective is to promote and facilitate hydrologic data digitization initiatives and to ensure their accessibility through open-access repositories.

Approximately 80 scientists from diverse geographical regions have joined the Working Group at the time of writing this abstract. Initial meetings were organized in late 2023, and the group is currently working towards its first short-term objective: conducting a comprehensive state-of-the-art assessment of methods, initiatives, and articles related to the digitization of historical hydrological data.

How to cite: Bertola, M. and Mazzoglio, P. and the HELPING REHYDRATE working group: REHYDRATE - an international HELPING working group to REtrieve historical HYDRologic dATa and Estimates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5911, https://doi.org/10.5194/egusphere-egu24-5911, 2024.

EGU24-13108 | Orals | HS1.3.1

Building a community of practice to produce hydrological evidence: the iMHEA example 

Wouter Buytaert and the iMHEA network

The IAHS HELPING decade aims to foster a stronger connection and interaction between scientists, practitioners, policy makers, and end-users towards the goal of global water security. This is a formidable challenge. Despite increasing and highly valuable efforts of scientists to reach out beyond their own discipline and working environment, the ultimate goal of co-creating actionable knowledge is still a long way off in most contexts. Establishing communities of practice has been posited as an approach to creating inter- and transdisciplinary environments that enable cross-learning, pooling of expertise, and collaborative working towards a common goal. However, establishing such communities of practice is very hard, and the conditions and driving factors that allow them to emerge and be productive are poorly understood. It is therefore informative to analyse existing case studies to gain a better understanding of how they can be created and made sustainable. Here I analyse the case of the Initiative for the Hydrological Monitoring of Andean Ecosystems (iMHEA), which is a grassroots initiative that emerged 15 years ago as a collaborative attempt to generate a solid scientific evidence base to support water management in the upper Andes.

It started as a small network of 4 partners operating 6 catchments in Ecuador and Peru, using a common monitoring protocol. Since then, it has grown into a network of 22 partners, monitoring 51 catchments at 24 sites along the Andes. Partners represent academia, civil society, and local, regional, and national governments. Originally focused on sharing technical expertise, iMHEA has evolved into a more holistic knowledge co-creation community with a strong focus on community involvement, knowledge exchange, and supporting decision making at various levels.

We attribute the success of iMHEA to several factors, of which we believe the following are key. The members’ ability to raise funding, both at the start and at various stages of its development has certainly been a major factor. At the same time, its nature as an informal network has allowed it grow organically and bridge periods of very limited resource availability. Another identified factor is the clear common goal and mission statement, which gave it a clear sense of purpose, direction, and transparency for existing and future members. Lastly, the active approach to multidirectional knowledge exchange, allowed it to create value for all its members, creating a strong motivation to participate and contribute actively.

How to cite: Buytaert, W. and the iMHEA network: Building a community of practice to produce hydrological evidence: the iMHEA example, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13108, https://doi.org/10.5194/egusphere-egu24-13108, 2024.

EGU24-13368 | ECS | Orals | HS1.3.1

From Local Success to Global Solutions: Tenets for Effective Groundwater Governance 

Maria Elena Orduna Alegria, Sam Zipper, James J. Butler Jr, Bill Golden, Blake B. Wilson, Burke W. Griggs, Chung-Yi Lin, David J. Yu, Donald O. Whittemore, Geoffrey C. Bohling, Hoon C. Shin, Jillian M. Deines, Jonah J. Allen, Landon T. Marston, Matthew R. Sanderson, Nathan P. Hendricks, Qiuyun Yu, Stephen Lauer, and Steven M. Smith

Groundwater depletion driven by intensive pumping for irrigated agriculture poses a global threat to economies, food security, and ecosystems. Addressing this issue requires pumping reductions, but their implementation is a wicked problem due to interlinked hydrological, social, and economic factors. Our study inspired the working group "Effective Aquifer Governance for Agriculture," aiming to contribute to the HELPING decade's goals by understanding local socio-hydrological processes and promoting recognition in the implementation of general policies at the local level.

This interdisciplinary study explores the success of the Sheridan 6 Local Enhanced Management Area (SD-6 LEMA) in the US High Plains Aquifer—a rare example of effective collective action in agricultural-groundwater systems. In its first decade, SD-6 LEMA exceeded reduction goals, reducing depletion rates by over 50% without significantly impacting net income. By analyzing hydrologic, climatic, economic, and social data from the SD-6 LEMA and the presence of Ostrom Design Principles in the SD-6 LEMA conservation program, we identified transferable governance tenets applicable to groundwater-dependent regions. These include multi-year allocations for flexibility, regulatory oversight to support irrigators' plans, and a strong scientific foundation for monitoring the agricultural-groundwater system. Furthermore, we identified key actors (government, scientific community, resource users) responsible for each tenet and emphasized interdisciplinary collaboration (hydrologic, economic, social) and data availability necessary for each tenet. The success of the SD-6 LEMA underscores the pivotal role played by collaborative institutional crafting and evidence-based decision-making in legitimizing groundwater governance rules, enhancing rule compliance, and promoting overall effectiveness.

Our presented tenets provide a framework for groundwater conservation efforts worldwide, addressing the global challenge of groundwater depletion while minimizing economic and social impacts. Addressing the scale mismatch between global drivers of depletion and local communities requires future studies and socio-hydrological modeling approaches. Our working group will utilize these approaches to bridge the gap, linking hydrological, agricultural, and socio-economic modeling tools into a comprehensive framework. By doing so, we aim to help achieve sustainable groundwater management, mitigating the global challenge of depletion while promoting economic and social resilience.

How to cite: Orduna Alegria, M. E., Zipper, S., Butler Jr, J. J., Golden, B., Wilson, B. B., Griggs, B. W., Lin, C.-Y., Yu, D. J., Whittemore, D. O., Bohling, G. C., Shin, H. C., Deines, J. M., Allen, J. J., Marston, L. T., Sanderson, M. R., Hendricks, N. P., Yu, Q., Lauer, S., and Smith, S. M.: From Local Success to Global Solutions: Tenets for Effective Groundwater Governance, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13368, https://doi.org/10.5194/egusphere-egu24-13368, 2024.

EGU24-14824 | Posters on site | HS1.3.1 | Highlight

Setting up the new Scientific Decade of IAHS: Science for Solutions with HELPING 

Berit Arheimer, Christophe Cudennec, Salvatore Grimaldi, and Günter Blöschl

IAHS has proudly and successfully coordinated two subsequent Scientific Decades, which, amongst other things, set a research agenda worldwide through collaborative forces; and IAHS now set up the third one. The overall aim with a Scientific Decade is to accumulate knowledge and streamline the efforts so that coherent engagement, sharing and focus accelerate scientific methodologies and synthesise understanding of a specific hydrological problem or phenomenon. It stimulates vivid discussions between young and senior scientists globally.

The first IAHS Scientific Decade (2003–2012), entitled Prediction in Ungauged Basins (PUB), was implemented with the primary aim of reducing uncertainty in hydrological predictions.

The second IAHS Scientific Decade (2013–2022) of IAHS, entitled “Panta Rhei – Everything Flows”, was dedicated to research activities on change in hydrology and society, investigating their co-evolution.

The third IAHS Scientific Decade (2023-2032) is and will be dedicated to local solutions under the global water crisis. The short name is HELPING, which stands for Hydrology Engaging Local People IN one Global world. The vision is to solve fundamental water-related environmental and societal problems by engaging with other disciplines and local stakeholders. We envisage that this will contribute in realising the sustainable development goals of Agenda 2030 of the United Nations. Hence, HELPING has the ambition and great potential to become a vehicle for putting science in action, with strong co-creation and open science dimensions, in local contexts and through the epistemic added value of networking.

This presentation will describe the first year of the decade and the collaborative process in the IAHS community, which lead to the HELPING vision and set-up in 25 working groups under 3 Themes.

Read more and join the working groups:

https://iahs.info/Initiatives/Topic-for-the-Next-IAHS-decade/Forms-and-forums/ 

How to cite: Arheimer, B., Cudennec, C., Grimaldi, S., and Blöschl, G.: Setting up the new Scientific Decade of IAHS: Science for Solutions with HELPING, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14824, https://doi.org/10.5194/egusphere-egu24-14824, 2024.

Currently, to explore spatial and temporal pattern of hydrological elements is not a difficult job as there are so many easy-use models and more and more open-source datasets ready to be downloaded. However, most research so far pays more attention to providing what it looks like. Less is for why. For those for why, there have been lots of attribution studies, but more mathematical results, few for guiding the practice. Deep explanation and evaluation for practices in hydrological Changes (DEEPHY) is yet the weak links in hydrological study. In the following decade, DEEPHY becomes one of the important foci of International Association of Hydrological Sciences (IAHS) with DEEPHY as the name of one of its HELPING decadal program’s working groups from 2023 to 2033, initiated at IUGG2023 in Berlin in July, 2023 (https://iahs.info/Initiatives/Topic-for-the-Next-IAHS-decade/helping-working-groups/). The main approaches of DEEPHY include working hard to monitor hydrological system long-termly, fully making use of large-sample data from multiple sources, careful designing the evaluation tools and focusing more on the practical applications. Short term result of DEPPHY will explain out more mechanisms and explore out deeper drivers behind the spatial and temporal pattern of hydrological elements. In the long-term, DEEPHY will acquire deeper understanding of hydrological changes evaluated based on the casual relationship with mechanisms and drivers being well explained. Ultimately, a better decision on how to administrate the hydrological change will be given to guide people to better adapt to the hydrological changes and be more resilient to the hydrological changes. This study will display how these possible approaches can help us to achieve the goal(s) of DEEPHY, and finally establish balances between science and practice and serve the people at different conditions worldwide to be collaborated better.

 

How to cite: Liu, S. and Mo, X.: Why we need DEEPHY (Deep Explanation & Evaluation for Practices in Hydrological Changes)  ?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14832, https://doi.org/10.5194/egusphere-egu24-14832, 2024.

EGU24-15283 | Posters on site | HS1.3.1

HydroSOS: Knitting local and global hydrological status and outlooks systems together for seamless water resources assessment  

Katie Facer-Childs, Lucy Barker, Harry Dixon, Alan Jenkins, Sulagna Mishra, Luis Roberto Silva Vara, Dominique Berod, Hwirin Kim, Jim Nelson, Riley Hales, Rachel Huber, and Angelica Gutierrez

Many hydroclimate services exist across the world at different scales. However, these services all use different categorisation schemes, different presentation styles, and are hosted across countless different websites. The Hydrological Status and Outlook System (HydroSOS) is a World Meteorological Organization initiative uniting, or “knitting”, hydrological status and sub-seasonal to seasonal outlooks products across scales in a consistent framework, weaving seamless services for water resources assessment.

HydroSOS extends beyond uniting existing services, also building capacity where services do not currently exist. It provides essential guidance and frameworks enabling the assessment of hydrological status for different variables. Additionally, HydroSOS is reviewing methods of producing useful hydrological forecasts in data sparse regions using statistical methods, or hydrological models, with and without real-time meteorological forecast inputs. Working in collaboration with the GEOGloWS initiative, global scale services are being improved with bias correction using machine learning and local scale data.

This fiber-art poster presents the HydroSOS initiative, its progress, and calls for ideas and collaborations on how we can knit hydroclimate services together to make the best fabric for water resources management.

How to cite: Facer-Childs, K., Barker, L., Dixon, H., Jenkins, A., Mishra, S., Silva Vara, L. R., Berod, D., Kim, H., Nelson, J., Hales, R., Huber, R., and Gutierrez, A.: HydroSOS: Knitting local and global hydrological status and outlooks systems together for seamless water resources assessment , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15283, https://doi.org/10.5194/egusphere-egu24-15283, 2024.

The new scientific decade (2023-2032) of the International Association of Hydrological Sciences (IAHS) aims at searching for sustainable solutions to undesired water conditions - may it be too little, too much or too polluted. Theme 1 of the decade “Global and local interactions” is focused on the science to accelerate hydrological understanding of hydrological processes at local and global scales, how they interact, and how they and their interactions affect water resources in the local context. It recognizes the interconnectedness of processes across scales and the need to understand local variability in the context of large-scale processes and changes. This theme is being implemented via 14 Working Groups (WG) which span a range of topics including retrieving historical data, urban water issues, water quality under global change, soil moisture variability across scales, aquifer governance for agriculture, and drought in mountain regions. As such there are significant opportunities to make progress on a wide range of scientific questions over the next decade. This talk summarizes the overarching objectives of Theme 1, including the goals for advances in scientific understanding, the potential outcomes and products (e.g. datasets, methods, case studies) and goals for community activities (e.g. synthesis, collaboration, recognition of local context). We also highlight the opportunities for the Theme, including the potential to develop generalized frameworks and approaches for understanding cross-scale interactions and identifying emergent properties, as well as challenges in driving forward a diverse set of WG activities globally to provide more than the sum of the parts.

How to cite: Sheffield, J.: Global and local interactions of hydrological processes – challenges and opportunities for Theme 1 of the IAHS Science for Solutions scientific decade, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18611, https://doi.org/10.5194/egusphere-egu24-18611, 2024.

The IAHS’ scientific decades are unique as international scientific initiatives in the hydrological community, linking researchers from around the globe, from different professional backgrounds, and at different career stages. The current HELPING - Science for Solutions decade in particular aims to address the current water crises by synthesising hydrological knowledge, establishing links between local and global processes, applying cross-cutting methods, and providing science-based decision support. This approach aims to involve not just hydrologists worldwide, but also practitioners, decision-makers, and a broader general public. Given these objectives, (science) communication is paramount. It is also the main focus of a dedicated HELPING Working Group. 

This study aims to analyse which internal and external communication approaches can be harnessed to support the success of an international scientific initiative like HELPING, both through streamlining internal workflows between participants, and through providing a coherent, easily digestible message to an external public. It strives to assess communication lessons learned from previous IAHS scientific decades - Predictions in Ungauged Basins (PUB) and Panta Rhei - while also taking into account the changes in communication technology since the launch of the first decade in 2003. Subsequently, it casts the net wider and analyses successful communication and diffusion approaches used by similar scientific initiatives launched recently at different scales. 

On a meta level, the different approaches needed for internal and external HELPING communication are assessed. What strategies can be leveraged to raise awareness for the scientific decade within the hydrological community, especially among researchers in locations and at career stages where they would typically not be highly involved? What tools can be harnessed to communicate the aims and achievements of HELPING to a wider public and to encourage interactions and participation? And, ultimately, what workflows are needed to assess the progress and impact of the HELPING decade itself, and to track all the initiatives and research by individual hydrologists carried out under its banner? 

Keywords: science communication, IAHS, scientific decades

How to cite: Payne, T. and Orieschnig, C.: (Science) Communication is Key - Analysing and Adapting Outreach Approaches and Internal Workflows to Support HELPING as a Major International Scientific Initiative., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19045, https://doi.org/10.5194/egusphere-egu24-19045, 2024.

EGU24-20150 | Orals | HS1.3.1

Hydrologic Design: Solutions and Communication 

Elena Volpi, Svenja Fischer, Eleonora Dallan, Salvatore Grimaldi, Aldo Fiori, Krzysztof Kochanek, and Cristina Prieto

Hydrologic design is one of the key tasks of hydrologists and most important for the majority of stakeholders, authorities and practitioners. Generally, hydrologic design consists of the dimensioning of hydro-structures in order to fulfill a pre-specified purpose related to water, e.g. flood protection or water supply. Hydrologic design, therefore, is a key element also for engineering activities beyond the hydrological application, and therefore must be communicated to the interested parties in an appropriate and comprehensive way.

In this context, the “Hydrologic Design: Solutions and Communications” working group aims at:

1- development of novel, goal-oriented procedures for the design of hydrologic solutions for the societal problems (e.g. extremes like floods and droughts, water management, control of water contamination etc.), bringing the best of the available methods;

2- development of novel methods to improve the understanding, characterization, quantification and reduction of uncertainty in hydrology, which will be able to extrapolate the results to data-scarce regions, ungauged catchments or beyond the observation range. The usage of available information from local sources will be improved, by combining different sources of information;

3- advances towards more reliable predictions by innovating the combination of the knowledge from deterministic models, probabilistic models and artificial intelligence methods, as well as, analyzing the predicted problem from different angles.

We plan to involve the stakeholders into the whole process of acquisition, modeling and/or concluding. Altogether, this will result in a simplified communication of hydrological design and the corresponding uncertainty to stakeholders, local people and authorities and, hence, strengthen the connection between science and practice.

How to cite: Volpi, E., Fischer, S., Dallan, E., Grimaldi, S., Fiori, A., Kochanek, K., and Prieto, C.: Hydrologic Design: Solutions and Communication, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20150, https://doi.org/10.5194/egusphere-egu24-20150, 2024.

EGU24-21088 | ECS | Orals | HS1.3.1 | Highlight

On promoting education and community adaptation in Global South’s studies populating the Digital Water Globe: the DREAMS project for the HELPING Science Decade 

Denise Taffarello, Danielle Bressiani, Adelaide Nardocci, Susana Dias, Dirce Maria Lobo Marchioni, Suzana Gico Montenegro, Marcos Roberto Benso, Gabriel Marinho e Silva, Veber Afonso Figueiredo Costa, Nilo Nascimento, Wilson dos Santos Fernandes, Jose Antonio Marengo, Jamil Anache, and Eduardo Mario Mendiondo

We present a contribution to promote education and community adaptation from a Global South’s case-study to populate the Digital Water Globe. From a NSFC-FAPESP project ‘Flash DRought Event evolution chAracteristics and the response Mechanism to climate change considering the Spatial correlations (DREAMS)', we discuss lessons for the IAHS HELPING Decade. DREAMS aims to respond to “science-for-policy" and “education-for-action” questions around Sustainable Development Goals of what adaptation pathways are feasible to cope with human-water impacts under change. DREAMS is organized into Research Methods of Drought resilience through Community-based Adaptation (CbA), Ecosystem-based Adaptation (EbA), Nature-based Solutions (NbS) and Participatory Action Research (PAR). DREAMS seeks for enhancing local case studies for the IAHS/Digital Water Globe with the multidimensional impacts of flash droughts addressed to SDGs nexuses of poverty, health, education, sanitation, economy and climate action. Here we discuss a DREAMS-CbA initiative in the headwaters of the Corumbataí river basin (PCJ River Basin Committee, MG-SP, Brazil) for building community knowledge of climate change and pro-environmental behaviours adapted into both new climate activism and teachers’ curriculum. In 2023, DREAMS started CbA strategies in different education levels for tradeoffs for drought’s duration, namely: in the primary schools, with teachers and pupils of local schools at the headwaters of selected river basins; in higher education, through the community-adapted curricula.  In primary schools, with a CbA strategy based on educational methods of Science, Technology, Society and Environment (“CTSA, Ciência, Tecnologia, Sociedade, Ambiente” , in Portuguese), the DREAMS’  researchers conducted the local project “Árvores da Amizade e Água: Preservar para não faltar!” (Friendship Trees and Water: Preservation and Conservation) with environmental education and climate-adaptation in the PCJ river basins’ headwaters with teachers, staff and pupils of the public school EMEF Profa Zezé Salles, Analândia-SP (Taffarello, 2023). DREAMS’ communication and open science literacy are expanded by:  a new UNESCO Chair; the USP Center for Education and Research on Disasters (http://www.ceped.eesc.usp.br/); the Braz. Water Resources Assoc. Technical Commission on Education, and three Braz. Inst. of Sci. & Tech., INCTs, of “Climate Change-Phase 2”(CEMADEN), “Food Insecurity (FSP/USP)” and “Nat. Observatory for Water Security & Adaptive Mgmt”, ONSEAdapta (UFPE, https://onseadapta.org). With Panta Rhei groups, and during the 100-year drought of Amazon river, DREAMS promotes archetypes of the Coevolution of the Amazon-Sanitation-Hygiene Paradox. DREAMS’ future work envisages more local examples for DWG, i.e. river basins of Yangtze (China), São Francisco (Brazil), Amazon and Parana (transboundary). References: Mendiondo, E M (2023) Flash DRought Event evolution chAracteristics and response Mechanism to climate change considering Spatial correlations, FAPESP 2022/08468-0, https://bv.fapesp.br/en/auxilios/111385/flash-drought-event-evolution-characteristics-and-the-response-mechanism-to-climate-change-consideri/; Taffarello, D (2023) “Árvores da amizade e Água: preservar para não faltar!”, CTSA Adaptation to Climate Change Impacts in Analândia-SP, EMEF Profa Zezé Salles, Environmental Education Project, Report.

How to cite: Taffarello, D., Bressiani, D., Nardocci, A., Dias, S., Marchioni, D. M. L., Montenegro, S. G., Benso, M. R., Marinho e Silva, G., Costa, V. A. F., Nascimento, N., dos Santos Fernandes, W., Marengo, J. A., Anache, J., and Mendiondo, E. M.: On promoting education and community adaptation in Global South’s studies populating the Digital Water Globe: the DREAMS project for the HELPING Science Decade, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21088, https://doi.org/10.5194/egusphere-egu24-21088, 2024.

Water security is impacted by complex inter-related drivers from within and beyond the hydrological system. The demands to address challenges to energy security, food security, climate security, and biodiversity security through various just-transitions all have implications for water security but this dimension is rarely considered in the different solution spaces. Increasing water risks from many drivers including climate change are also challenging the possibilities of these transitions to deliver safe, sustainable and just solutions. 

There is thus a critical need for water research to support insight, innovations, and tradeoffs, that include variables and drivers beyond those of hydrological systems. To bring impact on the ground, researchers need to develop framings, methods, and models that work across traditional siloes to deliver evidence, technical innovations and policy solutions that deliver in the local environmental, social, economic, and political contexts. 

Following this framing, a case study from the Middle East North Africa will be given on joined up research across many disciplinary boundaries to deliver insight and solutions to manage drought risk in Morocco and Jordan. Global and local interactions playing out in these locations demand new water thinking and ideas are put forward on how to achieve this. The approaches used draw on a plethora of methods, data and approaches from development in agricultural water management, through seasonal precipitation forecasting, and policy and planning through to understand the drivers to internal displacement of people through the threat multiplier effects of droughts. 

How to cite: McDonnell, R.: Multiple competing securities and transitions impact future water resource solutions: the importance of integrated approaches to frame, investigate and build resilient water futures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21346, https://doi.org/10.5194/egusphere-egu24-21346, 2024.

EGU24-22254 | Orals | HS1.3.1

Overview of the Theme 2 of IAHS HELPING: Holistic Solutions for Water Security  

Ana Mijic, Claudia Teutschbein, David Finger, Junguo Liu, Kristian Foerster, Marthe Wens, Nejc Bezak, Santosh Palmate, Shiv Nishad, and Stefan Krause

The term "water security" denotes the sustainable availability and access to clean and safe water for diverse purposes, ensuring the well-being of individuals, communities, and ecosystems. Despite numerous proposed solutions from the scientific community to address water security challenges, a genuinely holistic, systems-level approach is still lacking. The research conducted under Theme 2 of the new IAHS HELPING decade is grounded in the premise that holistic solutions for water security necessitate an integrated approach. This involves understanding the potential and challenges associated with mitigation methods for floods, droughts, and water quality/pollution, as well as being aware of the sectorial nexus of problems and solutions. Nature-based solutions (NBS) are also considered for sustainable water management. The theme brings together seven working groups (WGs) focusing on methods and applications for characterising droughts in the Anthropocene, providing near-term water availability forecasts, and conducting water systems analysis using integrated tools and participatory engagement. Additionally, these WGs address interactions between water, energy, health, and ecological systems, with the aim of advancing ecological restoration and the implementation of NBS. This talk will present a high-level overview of the WGs, showcase preliminary findings, and discuss the potential for integrating insights and methods from multiple work streams into a comprehensive framework for water security solutions.

How to cite: Mijic, A., Teutschbein, C., Finger, D., Liu, J., Foerster, K., Wens, M., Bezak, N., Palmate, S., Nishad, S., and Krause, S.: Overview of the Theme 2 of IAHS HELPING: Holistic Solutions for Water Security , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22254, https://doi.org/10.5194/egusphere-egu24-22254, 2024.

For hydrological modeling in snow-free catchments, precipitation (P) and potential evapotranspiration (Epot) are the two key input time series. There are different methods to observe, calculate and interpolate these time series. In the Australian large sample data set for hydrological modeling (CAMELS-AUS, Catchment Attributes and Meteorology for Large-sample Studies)  with data for 222 catchments, two different time series for P and seven different time series for Epot are provided. Here, we address the open question of which data should be used as input to an hydrological model.

Our basic assumption is that the most suitable combination of P and Epot is the one that results in the best model performances in terms of runoff simulations. For this we first tested the differences between the different input time series. Secondly, we conducted a thorough comparison of the 14 possible combinations of P and Epot time series. First analyses show that the differences between the two P time series are relatively minor, whereas the seven Epot time series differ more substantially from each other, especially in terms of seasonality and magnitude. Despite these differences, preliminary modeling results show that for the majority of the catchments there is no significant difference in model performance between the model calibrations carried out for each of the 14 different P/Epot combinations, suggesting that the model has a certain capability to compensate for differences in the input data by adapting its (soil) parameters. However, for some of the catchments there is a clear trend between the mean Epot and the corresponding model performance. Characterizing and further investigating these catchments can help to gain insight in the impact of different input data on the model performance, as well as to provide general recommendations that can help the user of a hydrological model to make an informed choice when it comes to the selection of the input data.

How to cite: Niu, J., Vis, M., and Seibert, J.: Evaluation of different precipitation and potential evapotranspiration time series for hydrological modeling in Australian catchments , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1022, https://doi.org/10.5194/egusphere-egu24-1022, 2024.

EGU24-1038 | ECS | Orals | HS1.3.3

How to avoid unreliable formulas for time of concentration in ungauged basins 

Giulia Evangelista, Ross Woods, and Pierluigi Claps

Estimating design flood hydrographs in ungauged basins requires the determination of hydrological response parameters. These parameters are derived from relationships that often lack a solid foundation in the specific physical characteristics of the basin. Among the parameters subject to greater uncertainty, the characteristic time of the IUH function certainly stands out. Indirect methods for estimating this parameter involve the use of empirical or analytical formulas and, in the engineering practice, the use of one or more formulas is often justified on heuristic grounds, lacking solid scientific considerations to guide the choice towards the most appropriate formulation.

Here, we propose a methodological approach to provide support in choosing a robust formulation for estimating basin flood response time. We have selected 35 formulas from the literature, all containing parameters related to the basin's length and slope. After verifying the real meaning of the input parameters and units required by the formulations in the original articles where they were published, the structure of the formulas considered has been analyzed in dimensional terms, using a reasoning scheme consistent with the hydraulic relations of resistance formulas. In this way, 17 hydraulically consistent formulas have been identified.

At this stage, we point out the advantage of comparing the formulas in terms of equivalent average flow velocity rather than in terms of observed travel times. Starting from the celerities obtained as the ratio between the length of the basin's drainage path and the response times provided by each formula and using the morphology of the river network of 135 basins in northwestern Italy, we compared the variability of estimated mean travel velocities. In line with literature observations, which highlight a slight increase in mean velocities with basin size, some formulas are deemed physically inconsistent, while 5 of them were identified as hydraulically robust and consistent with empirical observations. These formulas are Chow (1962), NERC (1975), SCS (1954), McEnroe and Zhao (1999), and Watt and Chow (1985).

The results obtained analytically identify the relationships between the exponents of length and slope in each formula and those governing empirical relationships between lengths and slopes of main river reaches in the basins. These relationships allow us to identify the range of values for the exponents of length and slope in the formulas for the characteristic time for which velocity estimates increase with the basin area. Based on these relationships, it is also possible to provide a guideline for the calibration of new formulations.

How to cite: Evangelista, G., Woods, R., and Claps, P.: How to avoid unreliable formulas for time of concentration in ungauged basins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1038, https://doi.org/10.5194/egusphere-egu24-1038, 2024.

EGU24-3415 | ECS | Orals | HS1.3.3

Event-type-based Multi-dimensional Diagnostics of Process Limitations in Hydrological Models 

Zhenyu Wang, Larisa Tarasova, and Ralf Merz

Shifts in generation processes of streamflow events driven by advancing climate change are raising concerns about the adaptability of conceptual hydrological models to changing hydrological systems. Using 30-year streamflow data across 395 German catchments, we evaluate the performance of a conceptual rainfall-runoff model for three distinct streamflow event types: events associated with snow and icy conditions (Snow-or-Ice), rainfall on dry soils (Rain-on-Dry), or wet soils (Rain-on-Wet). We focus on a two-dimensional evaluation of the timing and magnitude of streamflow events using the Series-Distance approach (Seibert et al., 2016) while also diagnosing the impact of inherent process limitations on model performance using random forest. The results reveal that the modelled streamflow consistently exhibits time delays and underestimations of magnitude for all types of events. Specifically, the Rain-on-Dry are associated with the most considerable delays, while underestimation of streamflow is the largest for Snow-or-Ice events. Given the statistically significant increasing trends in the occurrence of Rain-on-Dry events across 78.8% of catchments (Mann-Kendall test, p < 0.05), it can be assumed that the timing errors might further deteriorate in the future, compromising the reliability of the model-based early-warning systems for future flood events. Additionally, the errors vary across different hydrograph components (rising limbs, peaks, and recessions) for each type of streamflow event. Peaks are the most underestimated component in all events. Further diagnostics of the links between errors and drivers identifies the pre-event errors are the most important factors of timing and magnitude errors during the events. The process limitation in the model (e.g., groundwater recharge and fast runoff process) and properties of the events themselves (e.g., duration and peak discharge of events) cause the error heterogeneity among the events and exacerbate the errors in peaks of the events. Therefore, our study highlights the critical need for further improvement of process representation in hydrological models and more accurate simulation of pre-event conditions in order to address emerging challenges posed by changing hydrological systems.

Seibert, S. P., Ehret, U., & Zehe, E. (2016). Disentangling timing and amplitude errors in streamflow simulations. Hydrology and Earth System Sciences, 20(9), 3745-3763.

How to cite: Wang, Z., Tarasova, L., and Merz, R.: Event-type-based Multi-dimensional Diagnostics of Process Limitations in Hydrological Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3415, https://doi.org/10.5194/egusphere-egu24-3415, 2024.

EGU24-3454 | ECS | Posters on site | HS1.3.3

Benchmarking model performance in complex human-water systems. 

Saskia Salwey, Francesca Pianosi, Gemma Coxon, and Hannah Bloomfield

Human activities must now be considered as an integral part of the water cycle. Consequently, the integration of human-water interactions into hydrological modelling is essential for the large-scale simulation of flow. However, whilst the last decade has seen substantial advancements in the guidance available for modelers on how best to benchmark and evaluate flow simulations in natural catchments, there is little discussion surrounding how these practices may differ in more complex, human-impacted catchments.

Here we discuss some of the key issues in benchmarking model performance in human-impacted catchments and demonstrate these using a large-sample of reservoir-impacted catchments across Great Britain. We find that evaluation metrics designed for natural systems do not always translate to those impacted by human activity, where reservoir-impacted flow timeseries can have a substantially different distribution. In light of the new parameters and model assumptions associated with representing human activities within the natural water cycle, we suggest that the integration of uncertainty quantification and sensitivity analysis (UQ and SA) for robust model evaluation is particularly important. We discuss the need for clear accessible workflows for the application of UQ and SA in the evaluation of complex and large-scale water resource system modelling.

How to cite: Salwey, S., Pianosi, F., Coxon, G., and Bloomfield, H.: Benchmarking model performance in complex human-water systems., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3454, https://doi.org/10.5194/egusphere-egu24-3454, 2024.

EGU24-3940 | ECS | Orals | HS1.3.3

Effects of Conceptual Model Structure Uncertainties on Actual Evapotranspiration Simulation 

Shuyue Wu, Yuting Yang, and Jianshi Zhao

Understanding the structural uncertainties within current conceptual hydrological models is crucial, as an appropriate model structure is essential for achieving accurate and reliable hydrological simulations. The development and evaluation of conceptual models have primarily focused on replicating streamflow dynamics, with less attention given to other important processes, such as the conversion from potential evapotranspiration (PET) to actual evapotranspiration (AET). This study assesses the performance of 33 existing conceptual model structures in simulating 8-day-scale AET across 671 catchments in the United States. These models are calibrated using both daily streamflow data and 8-day remote-sensing AET data. While most models demonstrate comparable performance in streamflow simulations, significant differences are observed in their performance in AET simulations. None of these models can consistently performs well in AET simulations across all 671 catchments, indicating that the “one-model-fits-all” assumption is not applicable. The performance of most models is found to be related to one or more catchment attributes. The most relevant catchment features are climatic, vegetation and topographical characteristics, including climatic aridity, precipitation seasonality, fraction of precipitation falling as snow, green vegetation fraction and catchment mean slope. In contrast to the “one-model-fits-all” assumption, catchments with distinct climatic, vegetation and/or topographical conditions require different ways to represent the AET process. Specifically, most models tend to underestimate AET in humid catchments where the majority of rainfall occurs in winter, except those account for interception evaporation. Additionally, models that explicitly include a vegetation transpiration component tend to perform better in catchments with denser vegetation cover. This work highlights the structure uncertainties related to AET simulations and may help model structure selections in a way to reasonably represent AET process.

How to cite: Wu, S., Yang, Y., and Zhao, J.: Effects of Conceptual Model Structure Uncertainties on Actual Evapotranspiration Simulation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3940, https://doi.org/10.5194/egusphere-egu24-3940, 2024.

EGU24-7238 | Orals | HS1.3.3

Neglecting hydrological errors can severely impact predictions of water resource system performance  

Mark Thyer, David McInerney, Dmitri Kavetski, Seth Westra, Holger Maier, Margaret Shanafield, Barry Croke, Hoshin Gupta, Bree Bennett, and Michael Leonard

Risk-based decision making for water resource systems often relies on streamflow predictions from hydrological models. These predictions are integral for estimating the frequency of high consequence extreme events, such as floods and droughts. However, streamflow predictions are known to have errors due to various factors such as incomplete hydrological understanding, parameter misspecification, and uncertain data. Despite these errors being well known, they are frequently neglected when undertaking risk-based decision-making. This paper demonstrates that neglecting hydrological errors can impact on drought risk estimation for high stakes decisions with potentially severe consequences for water resource system performance. A generic framework is introduced to evaluate the impact of hydrological errors for a wide range of water resource system properties. This framework is applied in two Australian case study catchments, where we use a stochastic rainfall model, the GR4J hydrological model, a residual error model, and a simplified reservoir storage model to estimate water resource performance metrics (risk and yield). The results underscore the impact of neglecting hydrological errors on decision-making. In one case study catchment, the yield was over-estimated by ~15%-55%, resulting in the (actual) risk of running out of water being ~2-30 times larger than reservoir design. The magnitude of these errors in water resource performance metrics is striking, especially considering that the streamflow predictions appear reasonable based on typical performance metrics (e.g., NSE of ~0.7). The errors in performance metrics stem from the complex propagation of hydrological errors through the water resource system modelling chain. By accounting for critically important hydrological errors we can mitigate highly erroneous risk estimates and improve decision-making related to water resource management

How to cite: Thyer, M., McInerney, D., Kavetski, D., Westra, S., Maier, H., Shanafield, M., Croke, B., Gupta, H., Bennett, B., and Leonard, M.: Neglecting hydrological errors can severely impact predictions of water resource system performance , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7238, https://doi.org/10.5194/egusphere-egu24-7238, 2024.

EGU24-10546 | ECS | Orals | HS1.3.3

Towards a better understanding of the hybrid modelling methodology for streamflow prediction 

Antoine Degenne, François Bourgin, Charles Perrin, and Vazken Andréassian

The use of machine learning (ML) methods in rainfall-runoff modelling has apparently led to better prediction, but there are some concerns about the interpretability of these models. The emergence of hybrid modelling, which couples the data driven approach with the classical physics-based conceptual approach, has shown promise in enhancing both interpretability and accuracy. ML models and conceptual models each come with their own modelling practices and habits. To develop a hybrid approach, it is necessary to consider them.

While some of the steps in these modelling chains are similar (for instance the selection of the right metric during the calibration or learning step), others are more specifics, such as the optimization of the hyper-parameters of ML models. Furthermore, the hybrid approach comes with specific methodological challenges that emerge when coupling the two different types of models. For instance, depending on the choice made by the modeller, the parameters of the conceptual model are either trained with the ML model parameters or calibrated separately by a non-ML method.

There is a need to better understand the variety of hybrid approaches and to estimate the impact of their methodological choices. This work is based on a literature review and on large-sample modelling experiments with hybridizations of two classical models running at different time steps: the monthly GR2M model and the daily GR4J model. 

How to cite: Degenne, A., Bourgin, F., Perrin, C., and Andréassian, V.: Towards a better understanding of the hybrid modelling methodology for streamflow prediction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10546, https://doi.org/10.5194/egusphere-egu24-10546, 2024.

EGU24-10629 | ECS | Posters on site | HS1.3.3

Quality Assurance in Conceptual Hydrologic Models: Developing functional validation tests for ensuring model quality and robustness 

Florian Bucher, Corina Hauffe, Diana Spieler, and Niels Schuetze

Currently, the quality assurance of conceptual hydrological models is primarily based on calibration and validation procedures, such as the validation tests proposed by Klemeš [1986]. These procedures provide insufficient testing of the underlying assumptions of a model structure and their correctness and credibility for specific purposes. While we assume the models we use are implemented physically correct, actual “crash tests” (Andréassian et al. [2009]) or quality assurance procedures do not exist.

This study therefore focuses on the development of a standardized quality assurance procedure for conceptual hydrologic models. A so called functional test scheme is proposed that complements existing calibration and validation procedures. Hereby, expected and unexpected model setups and parameterizations are tested and the model response is evaluated. The applied functional approach involves self-generated time series with synthetic climate data and a synthetic catchment to systematically test individual processes and procedures. We developed a line of test series for the modular modelling framework RAVEN, where several iterative test runs with changing model setups and parameterizations have been conducted in order to gain further insights into the correctness and plausibility of the implemented approaches and equations. We developed an R package that enables the almost automated execution of the repetitive processes in the test application for the RAVEN-based models.

Preliminary results revealed some minor and major problems of model functioning, sometimes related to simple reasons like unclear information in the model documentation. For example, showed the testing that the slope correction for different slope angles is not applied on manually entered PET data, while the documentation does not explicitly mention that slope angles are only affecting internally generated PET data. The conducted experiments prove the potential of readily developed functional tests and provide a basis for further developments in this regard.

How to cite: Bucher, F., Hauffe, C., Spieler, D., and Schuetze, N.: Quality Assurance in Conceptual Hydrologic Models: Developing functional validation tests for ensuring model quality and robustness, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10629, https://doi.org/10.5194/egusphere-egu24-10629, 2024.

EGU24-13157 | Orals | HS1.3.3

10 years of eWaterCycle: from prototype-forecast to platform for Open and FAIR hydrology 

Rolf Hut, Niels Drost, Nick van de Giesen, Peter Kalverla, Stefan Verhoeven, Bart Schilperoort, and Jerom Aerts

Over the last decade our answer to the question: “but what is eWaterCycle?” has changed considerably. In 2014 we presented the first iteration of eWaterCycle: we showed that it was feasible to build a real time hydrological forecasting system that ran an ensemble of global models, forced with weather forecasts, assimilating satellite observations at every timestep, all from pre-existing openly available components.

In the light of the discussion in the hydrological community on reproducible science [Hutton, 2016] we build the next iteration of eWaterCycle: a platform that allows everyone to use commonly available hydrological models. Years (and a pandemic) later this platform is now openly available [Hut, 2022]. The vision behind the platform is to take as much as possible the computer-related headaches of running other people’s models away to let hydrologists focus on the hydrology. Furthermore, eWaterCycle is ‘FAIR by Design’: it should be easy to make any analysis done by eWaterCycle adhere to the FAIR principals. Using eWaterCycle MSc students have been able to do the type of research that previously was done by a PhD and PhDs have done the type of research that previously would require a whole team of people. Large Sample hydrology studies, Model coupling and climate change impact studies have all been done using eWaterCycle.

Adding one’s own model to the platform, however, still required considerable effort which limited the uptake by the broader hydrological community. That’s why recently we released v2.0 of eWaterCycle which fixes this: it is now significantly easier to add models to eWaterCycle!

Looking forward, among other things we will be:

  • Making teaching material on hydrological modelling available as Open Educational Resources through eWaterCycle [funded project]
  • Adding data assimilation as a module to eWaterCycle [funded project]
  • Add easy access to Large Sample Hydrology datasets (camels / caravan) [looking for students]
  • Study the impact of climate change on all catchments of the world, using many different hydrological models [looking for students]
  • Connect or host eWaterCycle on the infrastructure currently being developed for Destination Earth (DestinE) [looking for funds and collaborations]

In this presentation I will reflect on the achievements of the last decade, highlight the scientific results generated with eWaterCycle and look forward to the next decade.

 

Hutton, C., T. Wagener, J. Freer, D. Han, C. Duffy, and B. Arheimer (2016), Most computational hydrology is not reproducible, so is it really science?, Water Resour. Res., 52, 7548–7555, doi:10.1002/2016WR019285.

Hut, R., Drost, N., van de Giesen, N., van Werkhoven, B., Abdollahi, B., Aerts, J., Albers, T., Alidoost, F., Andela, B., Camphuijsen, J., Dzigan, Y., van Haren, R., Hutton, E., Kalverla, P., van Meersbergen, M., van den Oord, G., Pelupessy, I., Smeets, S., Verhoeven, S., de Vos, M., and Weel, B.: The eWaterCycle platform for open and FAIR hydrological collaboration, Geosci. Model Dev., 15, 5371–5390, https://doi.org/10.5194/gmd-15-5371-2022, 2022.

How to cite: Hut, R., Drost, N., van de Giesen, N., Kalverla, P., Verhoeven, S., Schilperoort, B., and Aerts, J.: 10 years of eWaterCycle: from prototype-forecast to platform for Open and FAIR hydrology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13157, https://doi.org/10.5194/egusphere-egu24-13157, 2024.

EGU24-14444 | Orals | HS1.3.3

Land surface hydrological modeling: do we really need complex model formulations? 

Philippe Ackerer, David Luttenauer, Aronne Dell'Oca, Alberto Guadagnini, and Sylvain Weill

Land Surface Models (LSM) grounded on physically-based mathematical models for energy and water balance can be characterized by various levels of complexity, especially when they integrate numerous processes. Diverse mathematical models (i.e., sub-models) can sometimes be formulated for some processes, due to different assumptions made during the system conceptualization stage. Therefore, running LSMs require (i) selection of a set of processes and related mathematical formulations that will be used and (ii) estimation of the corresponding parameters. A convenient way to guide model (and parameter) choice is to rely on global sensitivity analysis. In this work, we analyze sensitivity of 3 common hydrological outputs (evaporation, transpiration, and groundwater recharge fluxes) to models and parameters involved in typical LSMs. The global sensitivity analysis relies on random (Monte Carlo) sampling of values of parameters associated with each of the different formulations considered for the sub-models embedded in the LSM. This enables us to quantify the relative importance of process formulation and ensuing parameters. Three diverse indices based on (i) the whole (sample) probability density function (pdf) of the model output (Borgonovo et al., 2011) and (ii) the first and second moment of the pdf (corresponding to the moment-based sensitivity indices introduced by Dell’Oca et al. (2017)) are used. The joint use of these metrics is exemplified upon relying on realistic field conditions (in terms of, e.g., climate, vegetation, and soil type) associated with two watersheds in the Vosges region (France). Results show that sensitivity analysis plays a crucial role in identifying sub-models and parameters that contribute significantly to the uncertainty of model outputs. It is found that the main characteristics of the soil comprising the litter layer and root zone play an important role in the evaluation of the evaporation and groundwater recharge fluxes. As such, our results strengthen the need for targeted studies on the characterization of flow in these layers.

 

Borgonovo et al., https://doi.org/10.1111/j.1539-6924.2010.01519.x, 2011.

Dell’Oca et al., https://doi.org/10.5194/hess-21-6219-2017.

 

How to cite: Ackerer, P., Luttenauer, D., Dell'Oca, A., Guadagnini, A., and Weill, S.: Land surface hydrological modeling: do we really need complex model formulations?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14444, https://doi.org/10.5194/egusphere-egu24-14444, 2024.

EGU24-14555 | Orals | HS1.3.3

Innovating the calibration of a national-scale integrated hydrological model 

Raphael Schneider, Lars Troldborg, Anker Lajer Højberg, Maria Ondracek, David Terpager Christiansen, and Simon Stisen

The National Hydrological Model for Denmark (DK-model) is a distributed, integrated hydrological model coupling 3D groundwater flow to descriptions of root zone processes, overland flow and river routing, including anthropogenic interference with the hydrological cycle. It covers all of Denmark (~43,000km2) at 500m and 100m grid scale. Its constant development over the last three decades has both been driven by research projects and projects for public authorities. It is being used for various tasks such as water resource assessments, climate change impact assessments, hydrological real-time monitoring and nutrient transport studies.

Recently, we endeavored novel ways to calibrate and parameterize the DK-model. The model is placed on the edge between research interest and practical applications, with a demand for adequately representing various aspects of the hydrological cycle across the entirety of the model domain. In combination with its large-scale distributed nature and high computational demand, conventional (groundwater) model optimization techniques are challenged: The complex nature and versatile applications of the DK-model require suitable parametrization schemes and inclusion of diverse calibration and evaluation data, beyond conventional groundwater head observations and streamflow. This also leads to trade-offs between the multiple objective functions. Hence, we moved beyond previously used single solution, gradient-based optimization algorithms.

The Pareto Archived Dynamically Dimensioned Search (PADDS) algorithm allows us to use a global parameter optimization, effective even at a few hundred model runs. Another major advantage of PADDS is that it does not require the a-priori weighting of objective function groups – instead, it explores the tradeoffs (pareto front) between the different objective function groups, allowing weighting after gaining knowledge about tradeoffs during the optimization process. Also, all solutions explored during the optimization are stored and remain open to analysis after finished optimization. This not only sheds light on tradeoffs between different objective functions in a unique manner, but also supports understanding of parameter sensitivity and uncertainty in a manner which otherwise is hard to achieve due to computational constraints.

Moreover, we included evapotranspiration patterns from satellite products as well as a machine learning based estimate of artificial drain flow as novel spatial data in the model evaluation. This helps us constraining some of the model processes crucial for e.g. nutrient transport, but otherwise poorly constrained by conventional data such as streamflow (305 stations) and groundwater heads (24,000 wells) covering practically the entire model domain.

We explored the benefits of this optimization setup applied to the DK-model, advancing not only the calibration process itself, but also our understanding of model process representation and performance.

How to cite: Schneider, R., Troldborg, L., Højberg, A. L., Ondracek, M., Christiansen, D. T., and Stisen, S.: Innovating the calibration of a national-scale integrated hydrological model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14555, https://doi.org/10.5194/egusphere-egu24-14555, 2024.

EGU24-15352 | ECS | Posters on site | HS1.3.3

eWaterCycle V2: enabling Hydrology as a Service (HaaS)  

Peter Kalverla, Bart Schilperoort, Stefan Verhoeven, Niels Drost, and Rolf Hut

2024 marks the 10th anniversary of presenting eWaterCycle at EGU [i]. Over the past decade, we've been building a platform capable of running global hydrological simulations, that democratizes research, and fosters reproducibility [ii]. We've built various libraries, added models, and glued them together. Our efforts culminated in the release of eWaterCycle V1 in 2021[iii].  

For eWaterCycle V1 we initially targeted users of hydrological models, enabling researchers and students to do experiments that they would not have been able to do before. While this narrow focus was great for designing the core functionality of the platform, the process for adding or upgrading supported models was still tedious. Model developers had to make changes to the core of eWaterCycle whenever they updated their model.  

To address this, we have recently released a new version of the eWaterCycle Python package that connects all components of the platform. In V2, compatibility with existing models is facilitated through a plugin structure. In contrast to eWaterCycle V1, plugins are small, simple, and self-contained, and can easily be maintained by the model owners. This structure also facilitates gradual adoption of standards until the compatibility layer becomes obsolete.

Another improvement in eWaterCycle V2 is that it is now possible to run certain BMI models without containers. The use without containers, on the other hand, enables new use cases for purposes like education. While we recognize that this facilitates the development process, we still emphasize the use of containers for sharing and reproducibility.

The changes in V2 make eWaterCycle simpler and more robust and facilitate a better governance structure for developing and maintaining the platform and contributed models, enabling what we envision for “Hydrology as a Service”: infrastructure providers host instances of the eWaterCycle platform, model developers can register their model to make it available on these platforms, and researchers can access and use them. 

[i] https://ui.adsabs.harvard.edu/abs/2014EGUGA..16.6291V
[ii] https://doi.org/10.1002/2017WR020665

[iii] https://doi.org/10.5194/gmd-15-5371-2022
 

How to cite: Kalverla, P., Schilperoort, B., Verhoeven, S., Drost, N., and Hut, R.: eWaterCycle V2: enabling Hydrology as a Service (HaaS) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15352, https://doi.org/10.5194/egusphere-egu24-15352, 2024.

EGU24-15853 | ECS | Posters on site | HS1.3.3

Can we quantify the impact of the modeler on the model? 

Leon Frederik De Vos, Karan Mahajan, and Nils Rüther

Hydrological and hydraulic models are historically different disciplines and work on different scales.   The recent increase in computational resources allows for the two models to be combined into one model having one holistic approach. This removes the bottleneck of the data linkage between the two disciplines.

In this study, we apply the two-dimensional module of the open-source software openTELEMAC-MASCARET with the included SCS-CN method on an ungauged catchment in central Germany with an area of around 58 km². The catchment is part of the Main River tributary. We describe the excessive data preprocessing of the building and land use data, and the topography to sufficiently represent the small-scale stream geometry. This preprocessing is subjective in selecting different thresholds, such as the degree of mesh refinement in the streams and the foreland, or a minimum size for buildings to be represented in the model. Additionally, the SCS-CN method is highly sensitive to the model results, as small changes in the CN-values already significantly alter the total volume of water in the model. We collect the different sources of subjectivity and uncertainty and rank them based on the impact on the model results. The results will lead to a better view of the potential of combined hydrological-hydraulic models.

How to cite: De Vos, L. F., Mahajan, K., and Rüther, N.: Can we quantify the impact of the modeler on the model?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15853, https://doi.org/10.5194/egusphere-egu24-15853, 2024.

EGU24-16172 | Orals | HS1.3.3

What are the best strategies for managing a single extreme flood event in hydrological model evaluation? – Insights from the extreme flood 2021 in Western Germany 

Li Han, Björn Guse, Viet Dung Nguyen, Oldrich Rakovec, Husain Najafi, Xiaoxiang Guan, Sergiy Vorogushyn, Luis Samaniego, and Bruno Merz

Extraordinary floods like the one in July 2021 have induced catastrophic consequences on both societal and economic domains. Robust model simulations are crucial for mitigating the adverse effects of such extreme events on human life. However, accurately reproducing and predicting exceptional floods remain a challenge in particular when only one such flood extreme is available in the reference record period. This single flood could be included either in calibration and evaluation period. In both cases, extreme events are missing in the other period. To analyze how to best handle a single extreme flood, we present a framework for calibrating and evaluating the mesoscale Hydrologic Model (mHM) using the July 2021 flood in western Germany as a case study. Hereby, we tested the effect of including the extreme 2021 flood in calibration or evaluation periods.

Our study shows that including the exceptional 2021 flood event in model calibration proves crucial for accurately reproducing high streamflow. Without including the 2021 flood in the calibration period, the model cannot learn how to reproduce extreme floods. Our findings reveal that employing the modified weighted Nash-Sutcliffe Efficiency (wNSE) as the objective function significantly improves mHM's performance in capturing flood peaks. This leads to a notable reduction from -35% to -7.8% in the difference between the simulated and observed/reconstructed peaks as demonstrated for the catchment outlet. The hydrological model performance was validated spatially for an independent set of gauges. Spatial validation is necessary for assessing model performance when only one exceptional historical event is available. In conclusion, our framework provides valuable insights into improving hydrologic modeling accuracy, emphasizing the importance of specific calibration strategies and spatial validation in capturing exceptional flood events.

How to cite: Han, L., Guse, B., Nguyen, V. D., Rakovec, O., Najafi, H., Guan, X., Vorogushyn, S., Samaniego, L., and Merz, B.: What are the best strategies for managing a single extreme flood event in hydrological model evaluation? – Insights from the extreme flood 2021 in Western Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16172, https://doi.org/10.5194/egusphere-egu24-16172, 2024.

EGU24-16542 | Posters on site | HS1.3.3

Promoting Open and Transparent Hydrologic Modeling: Workflows, Tools and Self-Contained Modules 

Wouter Knoben, Martyn Clark, Louise Arnal, Shervan Gharari, Kasra Keshavarz, Hongli Liu, Alain Pietroniro, Kevin Shook, Ray Spiteri, Tricia Stadnyk, and Andy Wood

Configuring process-based hydrologic models can be a cumbersome task, especially for larger domains. In the past model inputs (data), configuration and analysis code, as well as the source code of the models themselves were only rarely openly available. More recently, the hydrology community is moving toward a more open culture, focused on shareable data, tools and code. Here we present various recent open-source advances along the entire modeling chain. These include:

  • Workflows for model configuration of large-domain hydrologic models, data-driven seasonal streamflow forecasting and forcing data processing;
  • Tools for the remapping of forcing variables from one set of spatial elements to another;
  • Tools for adjusting and correcting baseline geofabrics for internal consistency and efficient routing;
  • Computationally frugal sensitivity analysis methods;
  • Independent hydrologic process modules for specific geographic landscape features and routing through reservoirs;
  • Improved numerical methods for model solving and parallelization.

These tools are publicly available with the specific aim to make them useful to others. During this PICO, we welcome discussion about the tools, as well as general discussion about the opportunities and pitfalls surrounding open-source science.

How to cite: Knoben, W., Clark, M., Arnal, L., Gharari, S., Keshavarz, K., Liu, H., Pietroniro, A., Shook, K., Spiteri, R., Stadnyk, T., and Wood, A.: Promoting Open and Transparent Hydrologic Modeling: Workflows, Tools and Self-Contained Modules, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16542, https://doi.org/10.5194/egusphere-egu24-16542, 2024.

EGU24-16855 | Posters on site | HS1.3.3

Improving process understanding using multi-criteria model comparison for different catchments 

Björn Guse, Anna Herzog, Tobias Houska, Diana Spieler, Stephan Thober, Maria Staudinger, Paul Wagner, Doris Düthmann, Ralf Loritz, Uwe Ehret, Jens Kiesel, Sebastian Müller, Lieke Melsen, Sandra Pool, Larisa Tarasova, Juliane Mai, Thorsten Wagener, Doerthe Tetzlaff, and Nicola Fohrer and the other members of the DFG scientific network IMPRO

Hydrological models differ in the way how hydrological processes are implemented. A rigorous comparison of different hydrological model structures is needed to disentangle the link between similarities and differences in process representations and simulated hydrological processes, states and fluxes. A major challenge in model comparison is to identify effects of individual processes. To move a step in this direction, we developed controlled experiments and compared three hydrological models (HBV, mHM, SWAT+) in nine German catchments (400-3000 km²) along an elevation gradient. We aim at presenting a framework for a consistent comparison of process representations in model structures consisting of three steps:

(1) A model comparison protocol was developed for a detailed comparison of process representations in model structures. Consistency was achieved by using the same input data for all models. By grouping the processes in a standardized way, differences and similarities between the models were identified.

(2) To investigate the dominant model components, a daily parameter sensitivity analysis was carried out for the three models with different hydrological variables as target variables (e.g. actual evapotranspiration, soil moisture, snow and discharge). The dominant model parameters and associated processes vary more between the models than between the catchments. This also applies to the temporal variability of the parameter sensitivity.

(3) The model performance was analysed for a set of different performance criteria. The optimal parameter values differ greatly depending on which performance criteria were selected. This is in particular true for soil and evapotranspiration parameters. Typical patterns can be derived between catchments of different landscapes.

The joint analysis of these three methodological steps demonstrates the benefit of a detailed process analysis in model structures for a better understanding of suitable process representations. Therefore, it shows the potentials for improving model structures.

How to cite: Guse, B., Herzog, A., Houska, T., Spieler, D., Thober, S., Staudinger, M., Wagner, P., Düthmann, D., Loritz, R., Ehret, U., Kiesel, J., Müller, S., Melsen, L., Pool, S., Tarasova, L., Mai, J., Wagener, T., Tetzlaff, D., and Fohrer, N. and the other members of the DFG scientific network IMPRO: Improving process understanding using multi-criteria model comparison for different catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16855, https://doi.org/10.5194/egusphere-egu24-16855, 2024.

EGU24-17094 | ECS | Posters on site | HS1.3.3

How can we improve the correctness and plausibility of our hydrological models? 

Corina Hauffe, Diana Spieler, Clara Brandes, Sofie Pahner, and Niels Schütze

Using hydrological models is a common task for almost all hydrologists. Sometimes there is enough time to conduct a comparison study before selecting a model or we use the model we already know. But do we really know “our” model? Do we test all processes and approaches implemented prior to the model application? Usually we assume that the models are working correctly and by doing so we strongly rely on the developers willingness and capability to provide a mathematically and physically well tested hydrological model.

We believe that more effort is needed to ensure the quality assurance of models. This topic is yet underdeveloped in hydrology. We argue that our models should pass a standardized quality test in which they proof physical robustness and hydrologic plausibility. The commonly used split-sample test (Klemes, 1986) for an area of interest during the model validation may not be the best option to test for model quality. Attempts to increase standardization, transparency, and model quality have already been made e.g. by introducing the good modelling practice (van Waveren et al., 1999) and the FAIR principles (Wilkinson et al., 2016).

Nevertheless, there is still much potential to improve the quality assurance of models. We suggest a framework consisting of (1) the usage of synthetic input data and catchment properties, (2) a standardized test scheme, and (3) a set of diagnostics to evaluate the model results. The current study focuses on the development of the test scheme, which includes global behaviour tests, robustness tests, and additional tests.

Applying these tests serves different purposes: (1) detecting model limitations, (2) finding unintended feedback processes, (3) wrong or hydrological implausible responses, and (4) hidden or fixed parameters of a model. This kind of functional validation already proofed to be useful. A case study for the model ArcEGMO revealed several findings, e.g. fixed parameters, undocumented process implementations for lake evaporation and an unintended model response in the calculation of the groundwater recharge. Therefore, we believe that standardized tests would improve our model understanding, model usage and the trust in the model results.

 

Klemeš: Operational testing of hydrological simulation models, Hydrological Sciences Journal, 31, 13–24, https://doi.org/10.1080/02626668609491024, 1986.

van Waveren et al.: Good Modelling Practice Handbook, Tech. report, Dutch Dept. of Public Works, Institute for Inland Water Management and Waste Water Treatment, https://www.researchgate.net/publication/233864541_Good_Modelling_Practice_Handbook, 1999.

Wilkinson et al.: The FAIR Guiding Principles for scientific data management and stewardship, Scientific Data, https://doi.org/10.1038/sdata.2016.18, 2016.

How to cite: Hauffe, C., Spieler, D., Brandes, C., Pahner, S., and Schütze, N.: How can we improve the correctness and plausibility of our hydrological models?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17094, https://doi.org/10.5194/egusphere-egu24-17094, 2024.

EGU24-18765 | ECS | Posters on site | HS1.3.3

A questionnaire-based review on the role of hydrological models in operational drought management: Insights from the Netherlands 

Marleen Lam, Liduin Bos-Burgering, Lieke Melsen, Pieter van Oel, Miriam Coenders, Ruud Bartholomeus, Petra Hellegers, and Ryan Teuling

The recent report from the Joint Research Centre (JRC) of the European Commission emphasizes a growing impact of drought on the whole of Europe, worsened by climate change. Even in temperate climates such as the Netherlands, the impact of droughts is on the rise. Drought can be divided into three stages: meteorological drought, soil moisture drought, and hydrological drought. These stages often coincide with specific policy phases that require different approaches. In the Netherlands, these policy phases are Phase 0 (focused on drought adaptation), Phase 1 (addressing impending water scarcity), Phase 2 (managing actual water shortages), and Phase 3 (dealing with an area-wide crisis). Each phase involves a shift in organizational management. Phase 0 and, to some extent, Phase 1 focus on strategic development for drought, while operational management is important from Phase 1 through Phase 3 as the drought progresses. Decision-making in these phases is often supported by specialized tools, with hydrological numerical models often playing a key role, either embedded in monitoring dashboards or directly used by water managers. This research aims to uncover the role of hydrological models as decision-support tools across different drought phases. In this way, this study wants to contribute to the development of effective decision-support tools for drought management as drought is expected to increase in frequency and intensity. The Netherlands is chosen as a case study because of the novelty of drought events, the prevalence of model-based water management systems, and regional variations in water management practices. The primary research methods include a survey and interviews. 

How to cite: Lam, M., Bos-Burgering, L., Melsen, L., van Oel, P., Coenders, M., Bartholomeus, R., Hellegers, P., and Teuling, R.: A questionnaire-based review on the role of hydrological models in operational drought management: Insights from the Netherlands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18765, https://doi.org/10.5194/egusphere-egu24-18765, 2024.

EGU24-19142 | ECS | Posters on site | HS1.3.3

A flexible modelling framework for model creation based on perceptual understanding in integrated human-water systems 

Robin Maes-Prior, Barnaby Dobson, and Ana Mijic

Perceptual and conceptual modelling has been used historically by hydrologists to develop models rooted in a physical reality. As human activity increases and intertwines with the natural world, hydrological systems cannot be treated in isolation, particularly in urbanised areas. We argue that expanding our models and modelling approaches to consider interactions with water infrastructure can help us to identify the dominant processes and interactions within coupled human-water systems (CHWS) and guide our modelling processes towards models that produce results for the right reasons. We develop a three-level perceptual modelling approach that maps CHWS complexity in a systemic way. Perceptual models are representations of a system of interest based on stakeholder’s understandings and rooted in reality (e.g. visualised as a cross-section of the system with processes mapped on). Conceptual models are representations that break down the perceptual model to a component and state level (e.g. visualised as buckets and flows). From these definitions the framework was created to construct a computational model from an initial understanding of the region of interest. This framework prioritises engagement of different stakeholders at key junctions in the model making process, as well as providing a clear roadmap of modelling decisions. We applied this modelling approach for the Mogden Wastewater Catchment in North West London. The Mogden case study captures the interaction between surface water, groundwater and the sewer network, giving insight into the understudied field of sewer infiltration/exfiltration, highlighting the framework’s ability to better understand impact and behaviour of complicated flow paths. The case study highlights how this framework allows for the identification of interactions between human activity and the urban water system, producing models which are rooted in reality. The case study further revealed the benefit of flexible models, such as the implemented WSIMOD, for this framework, capturing diverse system perceptions and adaptability to include dominant processes.

How to cite: Maes-Prior, R., Dobson, B., and Mijic, A.: A flexible modelling framework for model creation based on perceptual understanding in integrated human-water systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19142, https://doi.org/10.5194/egusphere-egu24-19142, 2024.

EGU24-131 | ECS | Orals | HS1.3.5

A plastic tipping point: The influence of biofouling on the settling orientation of plastics. 

James Lofty, Pablo Ouro, and Catherine Wilson

The settling velocity of a plastic particle is a crucial descriptor for plastic transport in rivers. When a plastic particle is introduced into the riverine environment, the plastic’ surface provides a medium that enables the attachment, accumulation and growth of microorganisms, known as biofouling. While the settling velocity has been extensively studied for pristine plastics, the influence of biofouling on settling velocity and transport dynamics of plastics needs to be fully understood. Biofouling can alter a plastic particle's size, shape, weight, and buoyancy, potentially leading to an increase in settling velocity of up to 130% compared to the same pristine plastic. However, the effect of an uneven particle weight distribution, caused by heterogeneous biofilm growth, on the plastic’s settling orientation, vertical trajectory and subsequent settling velocity has yet to be investigated.

 

This study aims to quantify the impact of biofouling on the settling orientation of a plastic particle and describe its subsequent effect on settling velocity and pattern. To achieve this, we conducted experiments using a synchronised multi-camera setup and a three-dimensional particle reconstruction to characterise particle trajectories and settling orientations. Two sets of the same negatively buoyant PTFE plastic fragments and spheres were tested, namely: i) pristine plastics, and ii) plastics subjected to biofilm colonisation in laboratory conditions. The tested plastics were fragments in sizes 1 x 10 x 10 mm and 1 x 20 x 10 mm, as well as spheres with a diameter of 5 mm. These experiments will have significant implications for the description of the settling velocity of plastics which will aid in informing future field campaigns aimed at quantifying riverine plastic transport.

How to cite: Lofty, J., Ouro, P., and Wilson, C.: A plastic tipping point: The influence of biofouling on the settling orientation of plastics., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-131, https://doi.org/10.5194/egusphere-egu24-131, 2024.

EGU24-494 | Orals | HS1.3.5

In-situ and real-time detection of micro/nanoplastics in water: Combining laboratory experiments and modelling studies for plastic life cycle analysis 

Zi Wang, Devendra Pal, Abolghasem Pilechi, Maïline Fok Cheung, and Parisa Ariya

Maritime micro/nanoplastic research provides valuable insights into oceanic plastic waste remediation. Yet, there is a notable disparity, with micro/nanoplastic research in freshwater being ~ 85% less extensive than that in seawater. Observational studies suggest that over 1000 rivers contribute to ~ 80% of the global riverine plastic input into the oceans. Understanding the presence of micro/nanoplastics in freshwater systems is essential for unraveling the global micro/nanoplastic cycle.

In our laboratory, a cutting-edge nano-digital inline holographic microscope (nano-DIHM) was developed for real-time and in-situ micro- and nanoplastic research, including physicochemical characteristics, coatings, and dynamic behaviours in freshwater systems. The nano-DIHM data revealed distinct intensity and optical phase patterns of various types of single particles and clusters of micro/nanoplastics (PE, PP, PS, PET, PVC, and PUR), along with other organics (oleic acid), inorganics (magnetite), and biological materials (phytoplankton). We further incorporated a deep neural network functionality to nano-DIHM for rapid micro/nanoplastic detection in real-environmental waters. With its 4D (3D + time) tracking capability, we utilized nano-DIHM to measure the sedimentation (settling and floating) velocity of plastics in two size categories in water. The experimental results were subsequently integrated into a numerical model (CaMPSim-3D) developed at the National Research Council Canada to simulate the transport of plastic particles in Canadian rivers. Complementary modelling results demonstrated distinct distribution and accumulation patterns of macro-, micro-, and nanoplastic particles in aquatic systems, establishing nano-DIHM a powerful approach for plastic life-cycle analysis.

How to cite: Wang, Z., Pal, D., Pilechi, A., Fok Cheung, M., and Ariya, P.: In-situ and real-time detection of micro/nanoplastics in water: Combining laboratory experiments and modelling studies for plastic life cycle analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-494, https://doi.org/10.5194/egusphere-egu24-494, 2024.

EGU24-850 | ECS | Posters on site | HS1.3.5

Review and analysis of atrazine adsorption on different microplastics in aqueous solution.  

Bishwatma Biswas and Sudha Goel

Microplastics (MPs) are ubiquitous in all kinds of water matrices. The different properties of MPs facilitate their role as carriers of emerging contaminants like pesticides, pharmaceuticals, PFAS and surfactants. Hydrophobic pesticides have a high tendency to be adsorbed on non-polar substances such as MPs. The widespread use of atrazine has caused it to be omnipresent in the environment, leading to their concurrent presence with MPs. The partitioning and fate of atrazine sorbed MPs are governed by various environmental conditions and physicochemical characteristics of different matrices. The interaction of MPs with pesticides enables MPs to serve as vectors for the transport of pesticides in aquatic media. In this work, the sorption of atrazine on polyethylene MPs was investigated in batch adsorption studies. The characterization of MPs was conducted using FTIR, SEM and XRD. By examining the characteristics of MPs and atrazine, an adsorption mechanism is proposed. The sorption of atrazine on PS was mainly governed by van der Waals forces and pore-filling mechanism. The effect of contact time on the adsorption of ATZ on PS was examined. Contact time was used to compare the results of different experiments as it is necessary to establish an equilibrium time that can be used in all the experiments. It was found that the pseudo-second order model was a better fit than pseudo first order-model based on the highest R2 values obtained. Finally, the effects of salinity and pH were also measured and found to be relatively limited. The results of this study prove that MPs can act as carriers of pesticides like atrazine in aqueous medium.

How to cite: Biswas, B. and Goel, S.: Review and analysis of atrazine adsorption on different microplastics in aqueous solution. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-850, https://doi.org/10.5194/egusphere-egu24-850, 2024.

EGU24-1077 | ECS | Posters on site | HS1.3.5

Microplastics from surgical masks: A piggy-back ride for sulfamethoxazole in the sea 

Anuja Joseph, Bishwatma Biswas, and Sudha Goel

Microplastics can act as carriers for several organic pollutants like poly aromatic hydrocarbons, pesticides, polychlorinated biphenyls, and other persistent pharmaceutical pollutants. It is important to be noted that pharmaceuticals are bio-active substances, structurally modified to induce pharmacological changes in living organisms. These pharmaceuticals pose a threat to the ecosystem and the organisms living in it when not treated effectively. Antibiotic residues may enter the aquatic environment through effluents from sewage treatment plants, application in aquaculture, and other riverine inputs. The transport of one such antibiotic, Sulfamethoxazole (SMX), with the aid of microplastics was investigated in this study.

Surgical masks are made up of polypropylene fibers and they tend to degrade faster in the air as compared to sea-water when exposed to sunlight. Surgical masks are used for medical and personal care purposes and are often disposed of irresponsibly. In this study, the sorption mechanism of SMX onto the mask fibers was observed. The optimum adsorption capacity was analyzed for the microplastics. The effects of pH, salinity, microplastic dose, and SMX concentration were observed. Kinetic models were used to identify the sorption behavior and mechanism. The sorption pattern was then fitted onto linear and Freundlich isotherms. The van Der Waal interactions were probably responsible for the interaction between SMX (hydrophilic) and microplastics (hydrophobic). The results indicate that the microplastics can adsorb up to 15 % of the SMX concentration, when in seawater. The adsorption and desorption of SMX aided by the microplastics from the surgical masks can be interpreted into a transport model for SMX. Thus, this study confirms that aged microplastics when left near the seashore, gradually enter the aquatic ecosystem and act as carriers for pharmaceuticals like SMX. The ability of microplastics to desorb a certain amount of adsorbed contaminant can lead to major health concerns, as the organisms may consume the same, causing complications to health.

How to cite: Joseph, A., Biswas, B., and Goel, S.: Microplastics from surgical masks: A piggy-back ride for sulfamethoxazole in the sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1077, https://doi.org/10.5194/egusphere-egu24-1077, 2024.

In the environment, plastics are exposed to weathering processes such as mechanical cutting and abrasion, chemical and biological degradation, as well as UV radiation and heat. These processes breakdown larger plastics into smaller pieces and alter the physical and chemical properties of plastics. Most environment micro- and nano-plastics are generated via weathering of larger plastics. Micro- and nano-plastics are often more mobile, bioavailable, and toxic than their larger counterparts due to their smaller size. As a result, contamination of micro- and nano-plastics has become an increasing concern. Although many laboratory studies have been conducted on micro- and nano-plastics to understand their behavior in the environment, most studies were conducted using synthesized, mono-dispersed, polystyrene micro-spheres as surrogate for micro- and nano-plastics in the environment. The polystyrene micro-spheres, however, do not represent well the complex and diverse composition, size, shape, and other physiochemical properties of real-world micro- and nano-plastics. The objective of our research is to fill the gap by studying the micro- and nano-plastics released from macro-plastics including polystyrene (PS), high-density and low-density polyethylene (HDPE and LDPE), polypropylene (PP), and nylon under laboratory-controlled conditions. Plastic sheets or pellets were cut into small pieces, mixed with nano-pure water, heated, and filtered through 1 um membrane to collect fine plastics. Some macro-plastics were also “weathered” using UV radiation or high temperature. Particle concentration measurement showed that substantial quantities of fine plastics (~ 5*10^9 particles/mL) were released from PP and LDPE macro-plastics, moderate quantities were released from PS macro-plastics (~5*10^8 particles/mL), and practically no fine plastics were released from nylon or HDPE. SEM results indicated the fine plastic particles were of irregular shape and poly-dispersed with a size-range of ~100 to 400 nm, while the polystyrene micro-spheres were of spherical shape with a uniform diameter of 100 nm. Zeta-potential of LDPE fine plastics in 3 mM NaCl solution at pH 5 was ~-42 mV, more negative than those of polystyrene micro-spheres (~-25 mV). This study highlights the distinct properties of manufactured polystyrene micro-spheres and fine plastics released from macro-plastics. Results from our study suggest fine plastics released from macro-plastics may better represents the properties of micro- and nano-plastics in the environment.

How to cite: Cheng, T. and Saliminasab, S.: Release and characterization of micro- and nano-plastic particles from different types of macro-plastics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1433, https://doi.org/10.5194/egusphere-egu24-1433, 2024.

EGU24-1720 | Orals | HS1.3.5

Quantifying microplastic residence times in lakes using mesocosm experiments and 1D random walk model 

Hassan Elagami, Sven Frei, Jan-Pascal Boos, Gabriele Trommer, and Benjamin S. Gilfedder

Microplastic residence time in lakes is governed by complex and interrelated processes. In this work, we have used a series of in-lake mesocosm experiments combined with random walk modeling to understand microplastic residence times in the lake water column. Three size ranges of green fluorescent microplastic (1-5, 28-48, and 53-63 µm) were added to a 12m deep mesocosm and detected using fluorescence detectors. Experiments were conducted over one year capturing thermal stratification in summer as well as lake turnover in autumn. The measured residence times in summer ranged between ~1 and 24 days and depended mainly on particle size. The modeled residence time for the smallest particles (>200d) was considerably longer than the measured residence times in the mesocosm (~24d). This could be due to interactions between the small microplastic particles and existing particles in the lake. In contrast, during lake turnover large Rayleigh numbers showed that instabilities in the water column likely led to turbulent convective mixing and rapid sinking within the mesocosm.

How to cite: Elagami, H., Frei, S., Boos, J.-P., Trommer, G., and Gilfedder, B. S.: Quantifying microplastic residence times in lakes using mesocosm experiments and 1D random walk model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1720, https://doi.org/10.5194/egusphere-egu24-1720, 2024.

EGU24-3025 | ECS | Posters on site | HS1.3.5

The effects of streambed movement and particle size on microplastic deposition 

Verena Levy Sturm, Silvia Gobrecht, and Shai Arnon

Microplastic (MP) is ubiquitously found in aquatic environments and poses a significant environmental challenge. However, what controls MP deposition and burial in river networks is unclear, especially when sediments are in motion. This study addresses this gap by examining the impact of streambed motion and particle size on microplastic deposition in sandy streambeds. Experiments were conducted in a stainless-steel flume (650 cm x 20 cm) filled with 25 cm of silica sand (D50 = 0.6 mm) and water (depth = 12 cm). A centrifugal pump circulated the water and maintained a stream water velocity of 0.53 m/s. Polypropylene (PP) fibers at lengths of 25 μm, 100 μm, 200 μm, and 2000 μm, and carboxylated Polystyrene (PS) microspheres (diameter of 0.5 μm, 1 μm, and 5 μm) were added to the stream water and their concentration in the water was measured over three days. The deposition of the MP was inferred from the decline of MP in the streamwater. A control experiment was conducted by repeating the same experiments but without sediments. The flow in the flume generated ripples, which move at a speed of approximately 4 m/h. Bed motion dominated the exchange flux of streamwater and particles with the sediments. MP concentrations declined rapidly in the first two hours after the addition due to the exchange that led to a mixing of streamwater with particle-free pore water. After the relatively fast initial decline in MP, further reduction in MP concentrations in the water occurred due to deposition. Different deposition dynamics were observed for fibers and microspheres. Buried MP particles were partly resuspended during the scouring of the ripples during their movement. It was found that  PP fibers 25 μm and 0.5 μm spheres were more mobile in the sediment than longer fibers and larger spheres, respectively. We explain their higher deposition than larger particles by a potential advective movement through the porous media, leading to their transport below the scour zone. PP fibers ≥ 100 μm were immobile within the sediment, and thus, their deposition was only due to burial by the ripple motion. Our results highlight the significant influence of moving sediments on MP and the importance of considering MP size for catchment-scale modeling to predict MP fluxes to oceans. Deposition locations are also likely to be affected by bed motions and thus should be considered when developing effective sampling strategies.

How to cite: Levy Sturm, V., Gobrecht, S., and Arnon, S.: The effects of streambed movement and particle size on microplastic deposition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3025, https://doi.org/10.5194/egusphere-egu24-3025, 2024.

MP of all sizes and densities have been found deposited in streambeds. Several delivery processes were proposed to explain these observations, especially their dynamics, because most information was based on discrete sampling. Only a few studies have attempted to use a wide range of particle sizes to understand how MP moves in streams and rivers. At the same time, no experiments were conducted during bed motion due to the complexity of running such experiments. This study aimed to quantify the effect of streambed motion on the deposition and accumulation of MP in streambed sediments. We used a numerical model that predicts the flow and transport of particles in a moving streambed to quantify MP deposition. The model was run for streamwater velocities of 0.1- 0.5 m s-1 and median grain sizes of 0.15, 0.3, 0.45, and 0.6 mm. Streambed morphodynamics were estimated from empirical relationships. The flow conditions and sediment types resulted in ripple formation with celerities between 0-2000 cm hr-1. MP propensity to become trapped in porous media was simulated using a filtration coefficient. Various filtration coefficients (0.1-1 [1/cm]) were used in the simulations to predict the fate of particles in the sediment. The maximum deposition efficiency and deposition depth were found for sediment with high hydraulic conductivity and slow-moving stream water velocity conditions. Also, we found that the exchange of water and particles due to sediment motion leads to burial and potentially long-term deposition of MPs that initially were not expected to enter the bed due to size exclusion. However, increasing celerity reduces the depth of MP deposition in the streambed and reduces deposition efficiency due to resuspension. The burial of MP beneath the moving fraction of the bed provides a mechanism for long-term accumulation and may explain resuspension events characterized by high MP loads during floods. The modeling results could also assist in developing strategies for streambed sampling since a horizontal layer of particle deposit is expected to form below the moving fraction of the bed.

How to cite: Peleg, E., Teitelbaum, Y., and Arnon, S.: Understanding how sediment movement affects microplastic deposition in sandy streambeds: A modeling study., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3545, https://doi.org/10.5194/egusphere-egu24-3545, 2024.

Microplastics (MPs) are a major pollutant of the modern world, being dubbed “the lead of our generation”. Even though their potential danger to life on Earth is understood, their transport in water bodies remains an area with open questions, specifically their transport in rivers and streams. Such contaminants can be divided into three categories: spherical, irregular and fiber MPs. While research has been done on the fluvial transport of spherical MPs and their interaction with the hyporheic zone, the transport mechanisms that govern Microplastic Fibers (MPFs) are still unknown. State of the art models suggest a marked difference between the transport and settling of MPFs compared to spherical and irregular MPs, thus the need to confirm these models in a laboratory setting. The difference between the fluvial transport of spherical MPs, irregular MPs and MPFs is thereby researched here. Similarly sized fluorescent MPs and MPFs will be compared in an experimental flume, continuously logging the concentration in the water head and that in the hyporheic zone at the flume interface.

How to cite: La Capra, M. and Frei, S.: Comparing the interaction of differently shaped Microplastics with the Hyporheic zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3779, https://doi.org/10.5194/egusphere-egu24-3779, 2024.

EGU24-6625 | ECS | Orals | HS1.3.5

Bedforms effect on microplastics deposits erosion  

Arianna Varrani, Massimo Guerrero, Magdalena Mrokowska, and Paweł M. Rowiński

Transport processes involving both microplastics (MPs) and natural sediments are being marginally studied, for the high complexity of the system and the many factors requiring attention. Still, it is of high importance to understand the interactions between natural sediments and MPs transport, especially at the water-bed interface, a critical area for rivers’ ecology and biodiversity. To bridge this gap, we carried out flume (15-m long, 1.0-m wide and with 0.27 m water depth) experiments to study the interactions of a small bedform and a deposit of compact MPs. The compact-shaped MPs, consisting of Polyamide 6 particles with equivalent sphere diameter around 2.9 mm, were released at a low flow rate (around 20 l/s corresponding to a mean velocity of 0.1 m/s), for which deposit formed at the lee side of a 2-cm high and approximately 0.7-m long sand dune. A sudden increase of flow rate was then applied (up to 60 l/s corresponding to a mean velocity of 0.3 m/s), forcing erosion of the MPs. Measurements included velocity profiles and turbulent measurements via Acoustic Doppler instrumentation, videos and underwater photos of the small bedform. From Doppler measurements the mean flow characteristics were derived, as well as fluctuating terms of the velocity components up to 50Hz. Using Structure from Motion, a 3D model of the bedform and the MPs deposit was constructed. The erosional behaviour of deposited MPs was derived by estimating the total volume mobilised from the deposit by difference (prior and post erosion) via DEM. The MPs’ removal efficiency was then estimated, in three cases of MPs’ deposit initial volumes.  

How to cite: Varrani, A., Guerrero, M., Mrokowska, M., and Rowiński, P. M.: Bedforms effect on microplastics deposits erosion , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6625, https://doi.org/10.5194/egusphere-egu24-6625, 2024.

EGU24-6714 | ECS | Posters on site | HS1.3.5

Integrating Numerical Modeling and Fieldwork for Understanding Land-to-Ocean Litter Transport: A Comprehensive Review 

Nazife Oruc Baci, Félix Santiago-Collazo, and Jenna R Jambeck

The global issue of marine litter pollution, mainly from land-based sources, has gained significant attention in recent years due to its profound environmental and socio-economic impacts. Environmental impacts pose a significant threat to marine ecosystems, harming marine life through ingestion and entanglement, disrupting habitats, and even introducing harmful chemicals into the food chain. Socio-economically, it affects coastal communities and industries by reducing tourism revenues, damaging fisheries, and increasing cleanup costs, thereby undermining livelihoods and the overall well-being of communities. Furthermore, long-term consequences include potential economic burdens related to public health issues and the need for more extensive waste management systems. This review is a comprehensive overview of the state-of-the-art numerical modeling of land-to-ocean litter transport. It underscores the significance of an integrated approach in addressing this pressing environmental challenge. The focus of this study is exploring the evolving landscape of numerical modeling techniques in the context of hydrodynamics and the significance of fieldwork in enhancing their accuracy in litter transport. Numerical modeling techniques have emerged as powerful tools for simulating complex hydrodynamic processes responsible for litter movement in aquatic environments. For example, Particle Tracing Models (PTMs) have gained prominence in recent years as an effective approach for simulating the trajectory of individual litter particles in aquatic systems by considering various environmental factors, such as currents, tides, and winds. These models enable researchers to assess various scenarios, identify key drivers of litter transport, and develop targeted strategies for litter management and remediation by aiding in predicting their dispersion patterns and arrival locations. However, their effectiveness is significantly enhanced when informed and validated by real-world field data. Fieldwork complements numerical models by providing crucial data for model validation and calibration. It also offers a unique perspective on the real-world challenges and dynamics of land-to-ocean litter transport. Moreover, fieldwork helps identify hotspots of litter accumulation, assess the composition and sources of litter, and understand the influence of local conditions on transport pathways. By combining these approaches, researchers can accurately represent litter transport processes, ultimately aiding in effective litter management and policy development.

How to cite: Oruc Baci, N., Santiago-Collazo, F., and Jambeck, J. R.: Integrating Numerical Modeling and Fieldwork for Understanding Land-to-Ocean Litter Transport: A Comprehensive Review, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6714, https://doi.org/10.5194/egusphere-egu24-6714, 2024.

EGU24-8159 | ECS | Posters on site | HS1.3.5

Low-intrusive colour-enhanced pattern coating of plastics for fluid-mechanics laboratory experiments 

Daniel Valero, Stefan Felder, Frank Seidel, Antonio Moreno-Rodenas, and Mário J. Franca

Plastic transport experiments have been conducted under laboratory conditions over the past five-year period. The primary objective of these experiments is to obtain physical insights into the interactions among fluids, plastics, and solids. These insights aim to facilitate the upscaling of findings to riverine or maritime environments for predictive purposes. Despite the significant progress, challenges persist, notably in tracking plastic particles, potentially employing multi-camera setups. Traditional imaging methods, such as contrast-based detection or moving-object algorithms (based on selected computer vision or background differentiation techniques), can encounter several limitations. For instance, samples with low contrast relative to the background are more susceptible to errors, and the slow movement of samples can yield weaker signals compared to fluctuating light reflections in the area of interest. Additionally, 3D tracking can introduce compounded errors across multiple cameras, leading to amplified errors.

In response to these difficulties, our research introduces a novel colour-based contrast enhancement technique, based on a multi-colour water-proof coating for plastic samples. Our protocol leads to coating added masses remaining below 1%, while facilitating the precise detection of transparent and deformable plastics. We present the current limitations in detectability, including light dependency, and discuss the potential advancements enabled by our proposed methodology.

How to cite: Valero, D., Felder, S., Seidel, F., Moreno-Rodenas, A., and Franca, M. J.: Low-intrusive colour-enhanced pattern coating of plastics for fluid-mechanics laboratory experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8159, https://doi.org/10.5194/egusphere-egu24-8159, 2024.

EGU24-8538 | ECS | Posters on site | HS1.3.5

Modelling the transport of microplastics in the Gironde estuary: Sensitivity to physical processes and their parameterizations 

Betty John Kaimathuruthy, Isabel Jalon Rojas, and Damien Sous

Studying microplastic transport in estuaries is challenging due to the dynamic interplay between river and ocean, compounded by the diverse properties exhibited by these particles. Lagrangian particle-tracking numerical modelling is a relevant tool for investigating microplastic transport dynamics, dispersion patterns, and vertical distribution. However, these models oversimplify the parametrizations of crucial estuarine processes by ignoring the effect of varying water density or vertical diffusion coefficients. In this study, we implement a hydrodynamic and improved particle tracking model in the macrotidal Gironde estuary (SW France) to explore the relative importance of different physical processes (time-space varying vertical diffusivity and water density, beaching-refloating, bottom resuspension) and provide a better understanding of microplastic dispersion and potential trapping. The simulated particle trajectories and density distributions from our findings indicate a limited influence of the spatio-temporal variability of vertical turbulence on floating particles, with a notable impact observed for settling particles, showing its significance in particle resuspension. Despite the time-space-varying water density, the effect on the transport patterns of both floating and settling microplastics is relatively lower, while the phenomenon of beaching-refloating increases the particle's residence time within the upper estuary. The higher river discharge during the spring season flushes floating particles downstream, with a portion reaching the open sea, while settling particles persist within the estuary during both seasons. Notably, denser microplastic particles tend to accumulate in the upper estuary region during summer, where the estuarine turbidity maxima have been identified.

How to cite: Kaimathuruthy, B. J., Jalon Rojas, I., and Sous, D.: Modelling the transport of microplastics in the Gironde estuary: Sensitivity to physical processes and their parameterizations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8538, https://doi.org/10.5194/egusphere-egu24-8538, 2024.

In the last decade mismanaged plastic waste, specifically microplastics (1-5000 µm) have gained significant scientific and public interest with research from numerous disciplines highlighting the ubiquitous nature and potential harm microplastics can exert on both human and ecosystem health. Microplastics can now be found in all of Earth’s environmental compartments. Although a large level of knowledge has been obtained highlighting the sources (wastewater treatment plants, urban areas, agricultural fields etc), sinks (oceans, lakes, rivers, ground water, etc) and transport routes (rivers, air currents, ground water etc) of microplastics in the environment, our understanding of the processes that drive flux between systems is still limited. This is especially true in systems where environmental loading and activation events are less predictable, such as those found in diffuse source dominated catchments. Previous studies have highlighted storm events as significant drivers of microplastic flux in such catchments. However, little research has been conducted examining how microplastic concentrations, loading and characteristics change over the course of a storm hydrograph and also how the hydrometeorological conditions before and during an event interact with the microplastic supply dynamics.

This study aims to address this gap. In June 2022 a single light storm event (<2.5 mm/day) was sampled after a 10-day dry period (<0.2 mm/day) within a peri urban, headwater catchment located within Birmingham, UK. In total 34 surface water samples were collected covering discharge before, during and after the captured event. For each sample 100 L of surface water was collected from the main flow path of the Bourne Brook river and filtered through a 64 µm sieve. Collected particles were treated with H2O2 (30%) and Fenton to remove organics and stained with Nile red to aid quantification and characterisation of potential microplastics using fluorescent microscopy. Furthermore, >20% of the potential microplastics identified were analysed using Raman spectroscopy for polymer classification. Additionally, in-situ loggers collected level (to infer discharge, concentration and loading) and turbidity data. During baseflow (discharge = 58 to 99 L/s) immediately before the event, microplastic concentrations ranged from 0.01 to 0.17 MP/L (n = 7). In contrast, during the event microplastic concentrations ranged from 0.13 MP/L (discharge = 91 L/s) the statistically defined start of the storm hydrograph to 1.69 MP/L (discharge = 401 L/s), with microplastic concentrations being significantly higher in the ascending limb of the storm hydrograph than the descending limb. Hysteresis analysis indicated source limitation (Clockwise hysteric loop and hysteresis index >1 (2.05)) with microplastic concentration peaking before peak discharge suggesting microplastic supply depletion. Furthermore, it was estimated that during the sampled portion of the storm event (around 8 hours) about six million microplastic particles were exported from the catchment. In contrast, microplastic export during baseflow ranged from around 28,000 to around 368,000 particles for the same time frame, indicating the significance of such events when calculating annual MP flux. This study demonstrates how microplastic concentrations and characteristics change over the course of a single storm event, providing a mechanistic understanding of how hydrometeorological conditions interact with microplastic supply dynamics.

How to cite: Haverson, L., Mignanelli, L., Schneidewind, U., and Krause, S.: High frequency sampling during a storm hydrograph offers insights into the possible transport and source activation dynamics of microplastics within a peri urban stream. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8895, https://doi.org/10.5194/egusphere-egu24-8895, 2024.

EGU24-8953 | ECS | Posters on site | HS1.3.5

Subsurface transport of microplastics in riverine sediment: Impacts of different rain events and particle density 

Jaswant Singh, Reza Dehbandi, Neeraj Chauhan, Uwe Schneidewind, Lee Haverson, Brijesh K Yadav, and Stefan Krause

Microplastics (MPs) have emerged as a growing concern, posing potential risks to both marine and terrestrial environments. While surface soils are recognised as a primary sink for these particles, the vertical mobility of MPs in the subsurface remains uncertain due to a lack of comprehensive scientific data. Here, we conducted column experiments to study the transport behaviour of MPs through and retention in subsurface sediment. Two types of pre-stained MPs (median size 50.4 µm) with densities greater than (polystyrene) and smaller than (polyethylene) water were added to the top of large (110 cm) wet-packed fine gravel columns - the most common gravel found in the subsurface zone of the riverine environment. The concentration of deposited MPs was 50,000 particles per kilogram of sediment, derived from an extensive literature survey of polluted sites. Various scenarios, including continuous rain, wet-dry cycles, and dry conditions (characterised by a single rain event followed by a subsequent drying period), were implemented to simulate diverse rain events. 20 mL of water samples were systematically collected at specified intervals from different ports of the column at depths of 30, 50 and 70 cm. Additionally, continuous effluent collection took place at the bottom port (90 cm), which was connected to a pump that maintained a controlled flux at around 4.6 mL/min. At the end of the experiment, gravel samples were methodically collected from discrete sediment layers within the columns (0–5 cm (top of the source layer), 5–10 cm (source layer), 10–30 cm, 30–50 cm, 50–70 cm, 70–90 cm) to quantify the MP mass retained in the column. Results showed that the smallest PS-MPs with a continuous flow system exhibit the highest potential for transport due to higher density and less hydrophobicity compared to PE. With increasing rain events, MPs in the source sediment layer decreased, while MPs concentrations in deeper column layers increased significantly. Furthermore, an intriguing observation indicates that as these MPs undergo more wet-dry cycles, their penetration depth substantially increases. The results indicate that sediment may not only act as a sink for MPs but also as a possible entry point to subsurface receptors such as subterranean fauna and aquifers. This research underscores the intricate dynamics of MPs in sediment and raises awareness regarding the potential environmental consequences.

 

Keywords: Microplastics, Transport, Raining events, Density, Hydrophobicity

 

How to cite: Singh, J., Dehbandi, R., Chauhan, N., Schneidewind, U., Haverson, L., Yadav, B. K., and Krause, S.: Subsurface transport of microplastics in riverine sediment: Impacts of different rain events and particle density, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8953, https://doi.org/10.5194/egusphere-egu24-8953, 2024.

EGU24-9356 | Posters on site | HS1.3.5

Controls on microplastic breakdown due to abrasion in gravel bed rivers 

Annie Ockelford, Xuxu Wu, and Daniel Parsons

Microplastic contamination of river sediments has been found to be pervasive at the global scale however, the physical controls governing the storage, remobilization and pathways of transfer in fluvial sediments remain largely unknown. The properties that make plastics useful - strength, flexibility, durability and resistance to degradation - also make their transport through the environment difficult to predict. Specifically, the risk profile associated with microplastic transfer is dynamic because their physical and chemical properties change over time as they persist in, or move through, the environment. For example, mechanical breakdown, due to abrasion, likely decreases the size of microplastic particles, increases their surface roughness and surface area to volume ratio, and influences the diversity and abundance of the microbial taxa that colonise them. However, the processes controlling the mechanical breakdown of plastic particles rivers by abrasion is poorly understood, particularly in gravel bed rivers where there are a range of grain sizes present with the bed sediment. Here we report a series of experiments designed to explicitly quantify the influence of sediment grain size on microplastic degradation and understand how this varies by microplastic type.

Four sediment beds ((i) 0.8mm uniform sand; (ii)10mm uniform gravel; (iii) 20mm uniform gravel and (iv) bimodal sand gravel mix D50 14mm)) were seeded with either Nylon pellets (d= 1.2 g/cm3), Polycarbonate fragments (d=1.2 g/cm3) or Nylon fibres (d = 1.15g/cm3) at 0.005% concentration by mass. The sediment and plastic were placed into a cement mixer with 20L of water and tumbled for 100 hours. During each experiment, the cement mixer was periodically stopped and a sample removed to assess microplastic abrasion.

Results indicate that fibres are abraded to the greatest degree in comparison to beads and fragments.  Results also indicate a clear relationship with sediment size where microplastic fragmentation rates increase with river sediment grain size. In all plastic types surface complexity increases with time which has implications for the ability of the plastics to potentially host microbial taxa.   

How to cite: Ockelford, A., Wu, X., and Parsons, D.: Controls on microplastic breakdown due to abrasion in gravel bed rivers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9356, https://doi.org/10.5194/egusphere-egu24-9356, 2024.

EGU24-10148 | ECS | Posters on site | HS1.3.5

A simple model for beaching and resuspension of plastic debris 

Jenny Margareta Mørk, Tor Nordam, and Øyvind Breivik

When modelling the transport of plastics in the marine environment it is common to use a Lagrangian modelling framework. The movement of the particles is governed primarily by advective and diffusive transport, but the plastics are also subjected to a number of other physical, chemical, and biological processes that affect their fate. For transport in coastal regions, one of the more important processes is the interaction between particles and the shoreline.

Currently, there is no consensus on how to handle shoreline interactions in particle tracking models, and many resort to over-simplified descriptions such as considering a particle to be permanently beached at the position where it first hits land, or not allowing for beaching of debris at all. However, it is well-known that a lot of floating marine litter ends up on beaches, and mark-recapture studies of plastic on beaches around the world show that there can be considerable turnover in the litter on a beach. Furthermore, these studies show that both beaching and resuspension rates vary both over different beaches, and over different seasons at the same beach, indicating that these processes depend on several different factors, such as wind and wave conditions, beach morphology, and likely also the shape, size, and density of the object. Thus, in order to accurately predict the accumulation sites for floating plastic debris in coastal regions, more care should be put into modelling shoreline interactions.

Here we investigate a toy model for beaching of floating plastic debris, implemented in an idealised Lagrangian framework with analytically defined current, spatially constant wind and diffusivity, and a domain bounded on one edge by a straight, homogeneous shoreline. We implement different strategies for handling the beaching and resuspension of debris and compare the resulting distribution of particles. There is currently insufficient experimental data on the extent to which the different factors affect the beaching and resuspension processes for different kinds of plastic objects, so the purpose of this work is not to reproduce actual conditions, but rather to investigate the effect of the choice of beaching and resuspension strategies on the simulation results. We investigate e.g. a simple resuspension model where particles have an average lifetime on the beach, as well as a wave-based model where the beaching and resuspension is affected by randomly generated wave heights. 

How to cite: Mørk, J. M., Nordam, T., and Breivik, Ø.: A simple model for beaching and resuspension of plastic debris, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10148, https://doi.org/10.5194/egusphere-egu24-10148, 2024.

EGU24-10392 | ECS | Orals | HS1.3.5

Green barriers to plastic transport in rivers: an indoor study 

Giovanni Di Lollo, Luca Gallitelli, Claudia Adduce, Maria Rita Maggi, Beatrice Trombetta, and Massimiliano Scalici

Every day, millions of tons of plastic debris are poured into rivers from industrial and civil waste or due to social carelessness and transported to the ocean. Here they decompose into small fragments, compromising the health and growth of fauna and flora that ingest or absorb them. In recent years the idea of using vegetation to trap and extract plastic waste has developed to limit this phenomenon. The aim of this work is to experimentally quantify the ability of aquatic vegetation in trap plastic and understand whether different biotic factors, hydraulic conditions or debris type influence it. Three of the most abundant macrophytes in European and Asian rivers are tested in this study, Myriophyllum spicatum, Potamogeton crispus and Phragmites australis. Natural samples of vegetation, taken along the Tiber, Ninfa-Sisto and Aniene rivers, are positioned into a recirculating flume, where the flow rate and the water depth can be varied. Once stationary flow conditions are reached, a known quantity of polystyrene fragments of different sizes (macroplastics, mesoplastics and microplastics) is added in the upstream part of the channel. The ratio between the fragments retained in the green barrier and the total added during the experiment defines the species' capacity to retain plastics. A change in seasonality, simulated by changing the water depth and the number of stolons inserted into the flume, is tested and its effects on the trapping efficiency is analysed. Three plant’s densities and two water depths are tested for each species. All three plant species show to effectively retain large and medium-sized plastic debris. Only the Myriophyllum spicatum, whose needle-like leaves form a denser network than the other two species, is also found to be efficient in retaining microplastics. The density of the area occupied by vegetation affects the number of trapped fragments, which increases for all species as the number of inserted stolons increases. The change in water depth has no significant impact on the results obtained. In conclusion, the three macrophyte species analyzed in this work can be used to create a barrier to the transport of plastics from rivers to oceans. A more complex structure of the vegetation allows the trapping of microplastics. A larger density of the area occupied by vegetation induces larger trapping efficiency, while hydraulic conditions appear to have no significant influence for the values tested in this study.

How to cite: Di Lollo, G., Gallitelli, L., Adduce, C., Maggi, M. R., Trombetta, B., and Scalici, M.: Green barriers to plastic transport in rivers: an indoor study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10392, https://doi.org/10.5194/egusphere-egu24-10392, 2024.

EGU24-10484 | Orals | HS1.3.5

Measurements of spinning and tumbling rates of micro-plastic fibres 

Vlad Giurgiu, Giuseppe Carlo Alp Caridi, Marco De Paoli, and Alfredo Soldati

We perform measurements to assess the influence of the wall-normal position of micro-
plastic fibres on their spinning and tumbling rates in wall-bounded turbulence. The exper-
iments are carried out in a turbulent water channel at a Shear Reynolds number of 720.
The used fibres are curved, 1.2mm long, and 10μm in diameter (aspect ratio 120). Their
length ranges between 4 and 12 Kolmogorov length scales. In the generated flow condi-
tions they are inertial-less, neutrally buoyant, and undeformable. We observe their motion
with six high-speed cameras focused in the near-wall region and channel centre. We employ
and improve upon an established methodology involving the tomographic reconstruction of
each fibre and subsequent tracking. Leveraging their curved shape, we uniquely identify the
temporal evolution of their orientation, enabling measurements of spinning and tumbling
rates. We discuss the uncertainty on the rotation rates based on their shape and angular
displacement between time-steps. Analysis of converged statistics revealed that the mean
and mean square spinning are higher than tumbling rates at both channel centre and near-
wall region. These results are novel, considering that previous experiments are restricted to
measurements of rotation rates of longer straight fibres in homogeneous isotropic turbulence
or to tumbling rates only.

How to cite: Giurgiu, V., Caridi, G. C. A., De Paoli, M., and Soldati, A.: Measurements of spinning and tumbling rates of micro-plastic fibres, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10484, https://doi.org/10.5194/egusphere-egu24-10484, 2024.

EGU24-12122 | Orals | HS1.3.5

Bioswales as potential sinks for tyre wear particle pollution 

Sophie Comer-Warner, John Scott, Jim Best, Keith Carr, and Stefan Krause

Microplastics are known to be ubiquitous throughout the Earth’s ecosystems, with plastics found everywhere from terrestrial soils to deep ocean trenches. Much of the research to date has focussed on microplastics typically found in, for example, plastics bags, disposable utensils and food containers, with a large focus on marine microplastics. Recently, tyres have been identified as major sources of microplastics to the environment, due to the synthetic rubber they contain. Currently, estimates of the tyre microplastic burden in the environment suggest up to a third of marine microplastics and a third of terrestrial microplastics are tyre wear particles. Despite an increase in tyre wear research we still lack knowledge and understanding of the fate, transport and dynamics of tyre wear particles in the environment. Here, we investigate the role of green infrastructure, specifically bioswales, on the fate of tyre wear from road runoff. We present data from bioswales constructed in 2010, which were subsequently sampled in 2011, 2015 and 2023, providing a temporal record of tyre wear in the bioswales. We analysed samples from two bioswales (wet versus dry) to determine if there is an advantage of different bioswale designs to act as a sink of tyre wear particles. Samples were taken within the bioswale from upstream of the culvert inflow pipe, at various points down the bioswale and upstream of the bioswale outflow. These sampling sites were selected to provide information on potential transport through the bioswale, including whether bioswales are acting as sinks for tyre wear particles and if areas of preferential settling upstream of check dams produce increased rates of settling and trapping of tyre wear particles compared to other areas. The total mass of styrene-butadiene rubber and natural rubber in the samples was analysed using pyrolysis-gas chromatography-mass spectrometry, particle count, size and morphology were determined using optical microscopy. This study aims to determine whether bioswales can be used to effectively remediate tyre wear pollution from road runoff and the best design for this potential storage.

How to cite: Comer-Warner, S., Scott, J., Best, J., Carr, K., and Krause, S.: Bioswales as potential sinks for tyre wear particle pollution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12122, https://doi.org/10.5194/egusphere-egu24-12122, 2024.

EGU24-12168 | ECS | Orals | HS1.3.5

Investigating the deposition behavior of different polystyrene nanoplastics onto mineral surfaces using QCM-D 

Sascha Müller, Edith Hammer, Tommy Cedervall, and Nathalie Tufenkji

Nanoplastic, as primary or secondary plastics, emerges as a contaminant across all environmental compartments. In terrestrial settings, the vadose zone is considered a plastic sink. Yet, leaching into deeper saturated subsurface areas and groundwater may occur via preferential flow paths, changing hydro-chemical conditions, or direct infiltration in low lying or recharge areas. Understanding transport and deposition behavior of nanoplastics in aquifer settings is crucial as it i) is expected to deviate from that of engineered nanoparticles (ENPs) due to its more complex physical and chemical properties, and ii) to be able to develop and inform numerical models to upscale nanoplastic contaminant transport when e.g., exploring groundwater resources.  Quartz-crystal microbalance with dissipation monitoring (QCM-D) was used to investigate the deposition behavior of various model polystyrene nanoparticles onto two of the most abundant mineral species on Earth: quartz and kaolinite under various chemical settings.Three types of polystyrene of ~ 100 nm were used herein: A non-functionalized spherical polystyrene (PLAIN), a spherical carboxyl functionalized polystyrene (CARBO) and a hexagonal secondary polystyrene (GRIND) produced by mechanical grinding of larger polystyrene beads. Furthermore, divalent ion concentrations in terrestrial environments are inducing larger effects on nanoplastic processes than monovalent ions and therefore only the effect of increasing Ca2+ concentration in solution was tested. Moreover, natural organic matter (NOM) in terrestrial environments is usually degraded with depth, thus its presence in saturated groundwater can be negligible, yet to consider even low concentrations, we also tested the effect of technical grade humic acid as a model NOM.   We found that deposition behavior differs between various particles and mineral surfaces as well as with Ca2+ concentration. For quartz surfaces, non-spherical particles showed the highest deposition rates, while with the increasing mineral complexity (kaolinite), this effect diminished, and other factors gained more importance. Kaolinite surfaces showed the highest deposition rates among all particle types. This suggests the involvement of surface charge driven processes, where positive Al-OH sites of the kaolinite more effectively attract negatively charged nanoplastics as compared to negatively charged quartz. Increasing the ionic strength increased the deposition behavior until a peak deposition observed at 15 mM Ca2+ due to a gradual charge decrease of particles and minerals. Beyond 15 mM, deposition decreases as a result of reduced particle stability, and consequently lowered convective-diffusive transport to the mineral surface. Surprisingly, highly carboxylated CARBO particles showed a large increase in deposition on kaolinite irrespective of Ca2+ concentration. This may be explained by the importance of Al-OH sites, which bind -COOH groups more effectively than Si-O sites.  Adding 1mg/L humic acid at 15 mM Ca2+ reduced the deposition behavior significantly at both mineral surfaces. Our results highlight important processes between nanoplastics and mineral surfaces and thereby also important impacts in understanding nanoplastic transport in subsurface terrestrial environments. Charge driven processes dominate in simple mineral settings (quartz), while with increasing mineral complexity, chemical processes and specific ion binding interactions will dominate nanoplastic deposition and transport.

How to cite: Müller, S., Hammer, E., Cedervall, T., and Tufenkji, N.: Investigating the deposition behavior of different polystyrene nanoplastics onto mineral surfaces using QCM-D, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12168, https://doi.org/10.5194/egusphere-egu24-12168, 2024.

Microplastics (MPs) and nanoplastics (NPs) have gained considerable attention as emerging contaminants that can pose potential risks to subsurface environments due to their widespread presence and persistence in the environment. They can act as carriers for other contaminants, such as heavy metals, by adsorbing onto their surfaces, potentially increasing their mobility and consequently causing toxicity to organisms and human health. MPs and NPs can enter groundwater through landfill leachate, agricultural mulches, and wastewater effluent. However, MPs’ and NPs’ behavior in porous media with complicated components has not been thoroughly examined. Therefore, further research is essential to identify the key factors such as aggregation (particles attaching to each other) and deposition (particles attaching to a transport medium), that may influence MPs' and NPs' behavior, fate, and transport mechanisms in soils and groundwater.

The purpose of our research is to investigate how plastic particle properties, pore water chemistry, as well as characteristics of the medium would influence the aggregation and deposition of MPs and NPs.

This study focuses on the attachment of low-density polyethylene micro- and nano-plastics (LDPE) released from macro-plastic pellets and synthesized polystyrene micro-spheres to quartz sand under controlled laboratory conditions. Batch experiments were performed to study the aggregation and deposition of LDPE and synthesized polystyrene micro-spheres onto quartz sand that allow for precise control over environmental variables, facilitating the observation of microplastic-sand interactions in varying background solutions. The influence of two common salts, sodium chloride (NaCl) and calcium chloride (CaCl2), on the attachment process is systematically investigated. The results from our experiments indicated that similar to polystyrene micro-spheres, the LDPE particles did not adsorb to quartz sand at pH 5 in 3 mM NaCl solution, while a substantial amount of LDPE adsorbed to quartz sand in 1 mM CaCl2 at pH 5. This could be attributed to the less negative zeta potential of LDPE (~-25 mV) and polystyrene micro-spheres (~-17 mV) in 1mM CaCl2 background solution as a result of lower electrostatic repulsion between particles.

Results from these experiments provide insights into the complex mechanisms governing MPs' and NPs' behavior in aquatic environments, aiding in the development of strategies to mitigate their impact on ecosystems.

How to cite: Saliminasab, S. and Cheng, T.: Deposition of synthetic polystyrene and low-density polyethylene to quartz sand in different background solutions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13565, https://doi.org/10.5194/egusphere-egu24-13565, 2024.

EGU24-17435 | ECS | Orals | HS1.3.5

UV-weathering affects heteroaggregation and subsequent sedimentation of polystyrene microplastic particles with ferrihydrite 

Johanna Schmidtmann, Hannah Weishäupl, Luisa Hopp, and Stefan Peiffer

Microplastic (MP) particles are ubiquitous in aquatic environments. There they interact with naturally occurring particles and colloids. Processes like aggregation affect not only MP surface properties but also removal from the water column. Additionally, MP particles are exposed to UV radiation, which alters their surface properties and thus their interactions with environmental particles. We studied heteroaggregation and subsequent sedimentation of 1 µm polystyrene (PS) (pristine and UV-weathered) with ferrihydrite, an iron (oxy)hydroxide commonly found in nature. Pristine PS particles were highly negatively charged at pH 3-11. After reaction with ferrihydrite, at neutral pH values, strong heteroaggregation with ferrihydrite caused sedimentation of almost all PS particles. At acidic pH, negatively charged PS particles were coated with positively charged ferrihydrite leading to charge reversal. UV-weathering of PS led to lower negative surface charge, and particle size decreased with increasing weathering time. These changes in surface properties and particle size resulted in differences in aggregation behavior with ferrihydrite. With increasing weathering time, the isoelectric point (pHIEP) of samples with PS and ferrihydrite shifted from slightly alkaline pH to pH 3-4. Furthermore, we observed aggregation and subsequent sedimentation of weathered PS and ferrihydrite for larger pH ranges (3-7) compared to pristine PS. We attribute this to the fact that zeta potential values of the mixture of weathered PS and ferrihydrite were rather low in this pH range. Thus, particle repulsion was low, leading to aggregation. Overall, UV-weathering but also interactions of MP with environmental particles cause changes of MP surface properties, which influence its environmental behavior in water and contribute to removal from the water column.

How to cite: Schmidtmann, J., Weishäupl, H., Hopp, L., and Peiffer, S.: UV-weathering affects heteroaggregation and subsequent sedimentation of polystyrene microplastic particles with ferrihydrite, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17435, https://doi.org/10.5194/egusphere-egu24-17435, 2024.

EGU24-18284 | ECS | Posters on site | HS1.3.5

SWAT (Shoreline plastics in Waves and Tides) 

Ralph Stevenson-Jones, Tor Nordam, Raymond Nepstad, Frode Leirvik, Jenny Margareta Mørk, Shraddha Mehta, and Arsalan Mostaani

The understanding of processes governing the distribution of plastics pollution on beaches is currently an underdeveloped field of study but one with huge potential impact. Current models for plastics transport in the marine environment tend to use very simplified descriptions of the plastics-shoreline interaction. However, the stranding process is clearly a very important component of a model, both due to the direct interest in plastics on beaches and because of the impact on the overall transport due to beaching and resuspension.  Hence, experimental lab data and comparisons with observed beach litter is necessary for further understanding and model development for processes governing the distribution of plastics accumulation.

Here we investigate the mechanisms controlling the accumulation of plastic pollution upon an artificial beach.  Weakly buoyant plastic “nurdles” are placed within a linear wave flume with a sloping sandy beach. The water level is changed to emulate tides, and randomly generated waves are sent towards the beach. The distribution of particulates is imaged using a downward facing camera above the beach.  Image analysis is then used to determine the varying concentration of plastics, as a function of time, over varying wave and tide conditions.

How to cite: Stevenson-Jones, R., Nordam, T., Nepstad, R., Leirvik, F., Mørk, J. M., Mehta, S., and Mostaani, A.: SWAT (Shoreline plastics in Waves and Tides), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18284, https://doi.org/10.5194/egusphere-egu24-18284, 2024.

EGU24-20181 | Orals | HS1.3.5

Microplastic transport in rivers and their hyporheic zone – combining modeling and experiment 

Jan Fleckenstein, Franz Dichgans, Jan-Pascal Boos, Ben Gilfedder, and Sven Frei

Microplastic (MP) pollution in the aquatic environment has become a problem of growing concern due to potential adverse effects on aquatic organisms and ecosystems. While MP transport and fate in marine systems has been researched to quite some extent relatively little is known about the transport mechanisms of MP particles in terrestrial surface waters and in saturated porous media like in groundwater or the hyporheic zone (HZ).

We investigated the transport and fate of small (1, 3 and 10 μm diameter) polystyrene MP particles in a rippled, sandy stream bed (D50 = 1.04 mm) using CFD simulations calibrated to a set of flume experiments. A novel detection system for fluorescent MP particles (Boos et al. 2021) was used to track and quantify particle movement in the turbulent open water and in the hyporheic sediments in the laboratory flume following a pulse injection of MP particles into the surface water compartment. A new, integrated CFD simulation scheme within the OpenFOAM suite of CFD solvers was implemented for the flume system for a seamless simulation of water flow and particle transport in the open water and in the hyporheic sediments (Dichgans et al. 2023). Additionally we simulated the transport and fate of a range of “virtual” particles in the open water for different channel geometries using a Lagrangian approach.

Simulations show that 1 μm MP particles are transported through the HZ like a solute, following the typical hyporheic flow cells below the bedforms. Transport and particle progression through the HZ could be adequately described with an advection-dispersion equation. Larger 10 µm MP particles instead showed retarded transport through the HZ, while retardation increased with travel distance in the sediments. Our results indicate that advective pumping across the streambed interface can transport very small MP particles through the HZ, while larger particles are increasingly retained. Distinct flow structures in the open water are found to be decisive for the fate of MP particles in the river channel.

References:

Dichgans, F., Boos, J.P., Ahmadi, P., Frei, S., Fleckenstein, J.H. (2023), Integrated numerical modeling to quantify transport and fate of microplastics in the hyporheic zone, Water Research, 243, https://doi.org/10.1016/j.watres.2023.120349

Boos, J.-P., Gilfedder, B. S., & Frei, S. (2021), Tracking microplastics across the streambed interface: Using laserinduced-fluorescence to quantitatively analyze microplastic transport in an experimental flume. Water Resources Research, 57, e2021WR031064.
https://doi.org/10.1029/2021WR031064

Boos, J.-P., Dichgans, F., Fleckenstein, J.H., Gilfedder, B. S., Frei, S. (2024) Assessing the Behavior of Microplastics in Fluvial Systems: Infiltration and Retention Dynamics in Streambed Sediments. Water Resources Research, accepted

How to cite: Fleckenstein, J., Dichgans, F., Boos, J.-P., Gilfedder, B., and Frei, S.: Microplastic transport in rivers and their hyporheic zone – combining modeling and experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20181, https://doi.org/10.5194/egusphere-egu24-20181, 2024.

EGU24-20316 | ECS | Orals | HS1.3.5

Experimental Study on the Erodability of Microplastics in Muddy Environments 

Isabel Jalon-Rojas, Adeline Lemaire-Coqueugniot, Guillaume Gomit, Alicia Romero-Ramírez, and Sébastien Jarny

This study aims to elucidate the erodability behavior of microplastics in muddy environments like lakes, rivers, estuaries, and deltas, quantifying their critical shear stress on muddy sediment beds. Microplastics of diverse compositions, densities, shapes, and sizes were tested in a hydraulic flume with smooth and synthetic cohesive sediment beds. As flow intensity gradually increased, leading to particle mobilization, friction velocities and critical shear stresses were calculated. Initial results on smooth beds reveal that particle shape was a dominant factor in mobilization (sphere > pellet > fiber > sheet), followed by density: for equivalent shapes, denser particles required higher friction velocities for mobilization. Results from tests with different particle sizes and orientations relative to the flow highlight the influence of the exposed surface area: larger surface areas facilitate easier particle mobilization. Comparative experiments on smooth and muddy surfaces revealed higher shear stresses on cohesive sediment beds, attributed to particles sinking. Particle Image Velocimetry (P.I.V.) analysis showcased roughness-induced turbulence, marked by acceleration peaks and depressions, as the primary mechanism facilitating particle detachment from sediment.

How to cite: Jalon-Rojas, I., Lemaire-Coqueugniot, A., Gomit, G., Romero-Ramírez, A., and Jarny, S.: Experimental Study on the Erodability of Microplastics in Muddy Environments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20316, https://doi.org/10.5194/egusphere-egu24-20316, 2024.

EGU24-20585 | ECS | Orals | HS1.3.5

The impact of plastic pollution in sandy riverbeds 

Catherine Russell, Roberto Fernandez, Daniel Parsons, and Florian Pohl

Plastic is ubiquitous in the landscape and rivers are increasingly important vectors for its transport. Some riverbeds exhibit bedforms including ripples and dunes, which are well understood, but understanding of plastic in bedforms is in its infancy. In this study, flume tank experiments show that when plastic particles are introduced to sandy riverbeds, bedforms change character and behaviour. We detail i) mechanisms of plastic incorporation and transport in riverbed dunes, ii) the topographic changes that occur on the riverbed, and iii) quantify plastic-induced changes in sand transport downstream. We find that plastic directly affects bed topography and locally increases the proportion of sand suspended in the water column, even at very low concentrations in the sand. In the wider environment, such changes have the potential to impact river ecosystems and wider landscapes. Different plastic types and shapes have different impacts, therefore the classification of plastic ought to be consistent and comparable to sediment. Considering plastic as a sediment, we present a classification scheme, to enable better comparison of plastic to sediment such that we can better understand their interaction with sediment as a sedimentary particle, and therefore why plastics accumulate where they do. This is importantly not just another classification scheme, but a philosophically grounded solution to a long-standing challenge that is set to be of increasing significance in increasingly contaminated contemporary settings. We set the framework to a suite of questions that will aid understanding of plastic routing and accumulation in the rivers and the wider landscape.

How to cite: Russell, C., Fernandez, R., Parsons, D., and Pohl, F.: The impact of plastic pollution in sandy riverbeds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20585, https://doi.org/10.5194/egusphere-egu24-20585, 2024.

HS2.1 – Catchment hydrology in diverse climates and environments

EGU24-55 | PICO | HS2.1.1

Identification and mapping the surface water bodies that are sensitive to groundwater drought in the Godavari basin, India  

Thallam Prashanth, Sayantan Ganguly, Manoj Gummadi, and Dharmaraj Teppala

In recent times, several countries all around the world are experiencing groundwater droughts that are drying up surface water bodies (SWBs), such as rivers, marshes, lakes, etc. For implementing proper water management strategies, it is important to identify the SWBs that are continuously dependent upon the local groundwater reserve to feed them. SWBs that have some reserve throughout the year are fed by the local groundwater during the dry seasons. The rivers, lakes, and wetlands that exhibit these characteristics are referred to as perennial SWBs. Losing SWBs refers to the rivers, lakes, and wetlands for which the groundwater table is lower than the surface water elevation, and thus do not possess perennial characteristics. The water spread areas of SWBs in the Godavari basin are mapped by utilizing Normalized Difference Water Index (NDWI) or Automatic Water Extraction Index (AWEI). The NDWI or AWEI were obtained by using multi-temporal Landsat or Sentinel Satellite datasets in the Google Earth Engine (GEE) platform. Due to the limited spatial resolution of the satellite data, this analysis only considers water bodies with a surface area greater than 3,600 m2. The standardized water spread area index (SWSAI) is used to calculate the magnitude of the surface water drought of different water bodies with respect to space and time. The SWSAI is determined by using the water spread area from NDWI or AWEI by assuming that the water spread area increases due to increase in water surface elevation.  The standardized groundwater table index (SGWTI) is used here to compute the magnitude of groundwater table drought by using the depth of the water table in different observation wells obtained from various central and state government agencies in India. The primary goal of this study is to identify and map the drought sensitive zones responsible for river aridity by plotting correlation matrix for SGWTI of different observation wells. The second objective of this study is to map the spatio-temporal variation of SWSAI of different surface water bodies like ponds, lakes, and wetlands, etc. in the Godavari River Basin, India. The third aim is to determine the correlation between the SGWTI and SWSAI as well as identify the surface water bodies that are influenced by groundwater drought. By this procedure, it would be feasible to determine whether or not there is a connection between the travel time for the groundwater drought propagating from minor surface water bodies (wetlands, lakes, ponds, etc.) to major ones (rivers). It can thus be proved that the surface water dryness in wetlands, lakes progresses towards the rivers due to presence of groundwater drought in the river basin. A correlation (ranging from 0.81 to 0.9) between the depth of connectivity of surface water-groundwater with the SGWTI is computed in this study to demonstrate that the upper Godavari River is highly affected by the groundwater drought, whereas, the middle Godavari river is moderately influenced and the lower Godavari river is less influenced by it.

How to cite: Prashanth, T., Ganguly, S., Gummadi, M., and Teppala, D.: Identification and mapping the surface water bodies that are sensitive to groundwater drought in the Godavari basin, India , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-55, https://doi.org/10.5194/egusphere-egu24-55, 2024.

This study investigates the spatio-temporal dynamics of water quality in a 70 km2 mixed land use, lowland catchment in NE Germany over a four-year period (2018-2022). During this period with a consistent negative rainfall anomaly compared to the long-term average, the intermittent stream network exhibited three distinct hydrological phases each year, with important implications for water quality. Autumn and early winter featured a connecting phase, where spatially variable stream flows responded to rising water tables following increased rainfall and reduced evapotranspiration. The winter and early spring saw a fully connected phase, marked by increased stream flows throughput the catchment. Late spring and early summer experienced a disconnecting phase as flow gradually reduced and stopped in various parts of the catchment before ceasing altogether. A peat wetland in the centre of the catchment exhibited both the earliest and latest stream flows.

Water quality was characteristic of a eutrophic lowland catchment and displayed spatial variations linked to catchment soils and land use. During the connecting phase, stream water quality mirrored that of groundwater and saw mobilization of dissolved organic carbon from wetland areas. In the fully connected phase, stream water became enriched with contributions from soil water and a higher nitrate load from agricultural areas. The disconnecting phase was characterized by lower flows and higher temperatures, contributing to increasingly anoxic conditions which saw nitrate reduction, mobilization of redox elements (Fe and Mn) and release of P. Intermittency caused a transition in stream water quality from hydrological process control in the connecting phase to joint control of hydrological and biogeochemical processes in the fully connected phase and then to biogeochemical process control in the disconnecting phase.

Inter-annual water quality variation was associated with hydroclimate and catchment wetness dynamics, involving flushing and accumulation. Considering intermittency as an influencing variable changed the inter-annual characteristics of flow-concentration relationships compared with the previous perennial river stage, especially for nitrate. These findings have significant implications for the ecology and management strategies in similar catchments, highlighting the need to consider the seasonal hydrological phases for effective water quality management and ecological preservation.

How to cite: Wang, F., Tetzlaff, D., Freymueller, J., and Soulsby, C.: Hydrological connectivity dynamics in a mixed land use lowland catchment drive intra- and inter-annual variation in water quality in an intermittent stream network under drought conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-153, https://doi.org/10.5194/egusphere-egu24-153, 2024.

EGU24-9748 | ECS | PICO | HS2.1.1

The shape of the active length vs streamflow relation in temporary streams 

Nicola Durighetto and Gianluca Botter

River networks are not static entities, as they dynamically respond to the time-variant climatic conditions in the surrounding landscape. Over time, rivers change in both the streamflow Q, as the hydrograph continuously peaks and recedes, and active length L, as the temporary (i.e. non perennial) reaches wet up and dry down. As such, a correlation between L and Q has long been recognized in literature, starting with the first empirical studies dating back to 1968. More recently, a few conceptual frameworks have attempted to explain the physical processes that relate L with Q, showing how the shape of the L(Q) relation is determined by the spatial distribution of the subsurface transport capacity along the network (i.e. the maximum specific flow by unit contributing area delivered downstream in the hyporheic region). Knowing the functional form of the L(Q) relation can be useful in a number of ways, including the following: a) it creates a link between the temporal dynamics of L and Q, allowing one to exploit widely available streamflow datasets to study temporary streams; b) it gives information on invisible subsurface properties of the hyporheic zone; and c) it may provide more reliable predictions of the configuration of the active portion of the network during hydrological conditions that have not been observed yet.

In this contribution, we studied the shape of the L(Q) relation in 45 different catchments around the world, spanning a wide range of climates, geology, morphology, and catchment area. We found that L(Q) relations can be split in 3 main categories: a) generally increasing relations, b) relations showing a plateau for the higher values of Q due to the presence of a maximum potential network that can't be exceeded, and c) relations with a sigmoid shape, when the network length is constant for the driest hydrological conditions e.g. because it is fed by a local perennial source. We speculate that, in most cases, the presence of a plateau or sigmoid shape might not be visible in the data due to the limited number of observations for the relevant high and low flow conditions. For each catchment we also tested different functional forms for the L(Q) relation and selected 3 analytical forms that are best suited to fit the available data (exponential, gamma, power-law). The power law generally performed reasonably well, even though it overestimated L for the largest values of Q in those cases in which a maximum potential wet network is observed. In most cases, the exponential distribution described the plateau quite well but has a reduced performance for the lower flowrates. The gamma distribution, instead, shows the best performance in describing L(Q) relations in all categories. The proposed contribution aims at identifying new general patterns common to all temporary streams, creating new modelling tools that enable large scale studies and giving new tools for the effective monitoring of dynamic river networks.

How to cite: Durighetto, N. and Botter, G.: The shape of the active length vs streamflow relation in temporary streams, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9748, https://doi.org/10.5194/egusphere-egu24-9748, 2024.

Funded by the French Ministry of Ecology, the French Biodiversity Agency (OFB) and project partners, Explore2 aims to update knowledge about the impact of climate change on hydrology in France, and to support stakeholders in adapting their water management strategies. A multi-scenario and multi-model approach is uniformly applied across the country to encompass a wide range of possible futures for the entire 21st century and to assess uncertainties at each step of the climate and hydrology modelling.

This study aims to extend the results of Explore2 towards the prediction of flow intermittence in headwaters streams, which is initially impeded by the coarse resolution of Explore2 simulations. A statistical approach is necessary to link Explore2 hydrological projections on main rivers to the daily probability of flow intermittence in headstreams (PFI). PFI observations on historical period are derived from data of the French Observatoire National des Etiages (ONDE), which carries monthly visual assessments since 2012, from May to September, at more than 3300 upstream river sites prone to drying  [1]. PFI is then considered as the proportion of ONDE sites observed under drying conditions on partitions of France (76 second-level hydroecoregions (HER2) with median size of 4690 km² paving France).

To predict PFI, logistic regressions are adapted from previous studies [2, 3] and are first calibrated in each HER2 using time series of daily discharge provided by the French hydrometric monitoring network, HYDRO [4]. A diagnosis analysis between 2012 and 2022 consistently demonstrates good performance, with a median Kling-Gupta Efficiency (KGE) around 0.83 across all HER2. Logistic regressions are then re-calibrated considering daily discharge time series simulated by five hydrological models (HMs) of Explore2 driven by SAFRAN meteorological reanalysis [5]. Performance varies according to the HM (KGE medians ranging from 0.60 to 0.82).

Finally, the logistic regressions are applied to simulate daily PFI values at each HER2 for the entire 21st century  with future discharge simulated by the five HMs driven by 17 climate projections under RCP8.5 scenario. Results suggest an increased probability of intermittence in most of the hydrological ensemble runs and under most scenarios. This presentation will focus on the spatial variability of PFI response to climate change projected at different time leads.

 

References

[1] Nowak and Durozoi. Guide de dimensionnement et de mise en œuvre du suivi national des étiages estivaux. ONEMA, 2012.

[2] Beaufort et al. Extrapolating regional probability of drying of headwater streams using discrete observations and gauging networks. Hydrology and Earth System Sciences, 2018. doi:10.5194/hess-22-3033-2018.

[3] Sauquet et al. Predicting flow intermittence in france under climate change. Hydrological Sciences Journal, 2021. doi:10.1080/02626667.2021.1963444Y.

[4] Leleu et al. La refonte du système d’information national pour la gestion et la mise à disposition des données hydrométriques. Houille Blanche, 2014. doi:10.1051/lhb/2014004.

[5] Durand et al. A meteorological estimation of relevant parameters for snow models. Annals of Glaciology, 1993. doi:10.3189/s0260305500011277.

How to cite: Jaouen, T., Benoit, L., and Sauquet, E.: Predicting the evolution of intermittencies under climate change in France: exploitation of flow projections driven by CMIP5 climate models for Explore2 project, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9841, https://doi.org/10.5194/egusphere-egu24-9841, 2024.

EGU24-9917 | ECS | PICO | HS2.1.1

Spatial variability in C-N-P concentrations during the fragmentation of an intermittent stream in a temperate agricultural catchment 

Andrés Casanova, Rémi Dupas, Anne Jaffrezic, and Ophélie Fovet

Intermittent rivers and ephemeral streams (IRES) are watercourses that stop flowing at some point during the year. IRES are found in all climates and biomes and their occurrence is predicted to increase with climate change and increasing demand for freshwater. Knowledge of biogeochemical cycles in IRES is mainly based on research in the Mediterranean region. The region of Brittany in western France, characterised by a temperate oceanic climate and intensive agriculture, offers research opportunities to understand C-N-P dynamics in temperate IRES with high nutrient loadings.

In this work, we analyse the spatial variability of C-N-P concentrations in the intermittent stream network of the Kervidy-Naizin catchment (7 km²) during the different phases of intermittency. We hypothesise that the spatial variability of C-N-P concentrations increases during the stream fragmentation, as the formation of isolated pools leads to different physico-chemical conditions due to variable solar radiation, temperature, and nutrient availability. To investigate this, we conducted repeated synoptic sampling campaigns at a high spatial resolution (every 100 to 200 m) along the stream network during the spring-summer of 2023. We sampled forty sites and analysed, among others, DOC, DIN and TP and physico-chemical parameters (conductivity, redox potential, temperature and pH) during four field campaigns spanning from stream recession to the rewetting phase after the summer dry period.

The results showed an increasing spatial variability of concentrations with stream fragmentation, with spatial coefficients of variation increasing from 27% to 49% for DOC, from 15% to 64% for DIN and from 44% to 74% for TP. During the stream fragmentation, mean DOC concentrations increased from 2.43 to 4.76 mg.L-1, mean DIN concentrations decreased from 15.1 to 8.47 mg.L-1 and mean TP concentrations increased from 0.023 to 0.071 mg.L-1. Spatial patterns of concentrations observed during the flowing phase tended to be disrupted by the stream fragmentation, with isolated pools exhibiting extremely high or low concentration values. We interpret these changes in spatial patterns as a consequence of redox processes and nutrient assimilation.

How to cite: Casanova, A., Dupas, R., Jaffrezic, A., and Fovet, O.: Spatial variability in C-N-P concentrations during the fragmentation of an intermittent stream in a temperate agricultural catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9917, https://doi.org/10.5194/egusphere-egu24-9917, 2024.

EGU24-11267 | ECS | PICO | HS2.1.1

Increasing intermittence of the UK’s chalk streams into the future  

Eugene Magee, Catherine Sefton, Simon Parry, Stuart Allen, and Judy England

The chalk streams of the UK are globally rare, strongly intermittent in their upper reaches, and highly valued for their biodiversity and historical provision of water resources. Recent projections of river flows and groundwater levels under climate change in the UK, coupled to existing statistical models of hydrological state, enable the projection of spatiotemporal intermittence patterns into the near- and far-future.  

Catchments were selected for the study based on the availability of data and the performance of statistical models in the historical period.  Cumulative logit models, previously trained on historical data, were used in conjunction with state-of-the-art ensemble projections of future river flows and groundwater levels to simulate future hydrological state at multiple sites along chalk streams in the south-east of England.  Heatmaps visualise spatiotemporal variations in state, and intermittence metrics quantify the variability.   

The results show projected increases in drying into the future, both temporally, with greater duration of drying, and spatially, with intermittence extending downstream.  Some sites are likely to alter substantially, for example, on the river Chess with notable decreases in modelled flow permanence projected, from 75% in the baseline period (2005-2020) to 25% in the far future (2065-2080). 

This research provides quantifiable spatiotemporal dynamics of intermittence, informing water resource decisions, drought management and engagement activities on these high-profile streams.  The methods developed are adaptable for transfer to other catchments for which spatiotemporal mapping of intermittence patterns and future projections of driving variables exist. 

How to cite: Magee, E., Sefton, C., Parry, S., Allen, S., and England, J.: Increasing intermittence of the UK’s chalk streams into the future , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11267, https://doi.org/10.5194/egusphere-egu24-11267, 2024.

EGU24-12388 | PICO | HS2.1.1

Exploring tracer dynamics at different spatial scales in a pre-Alpine catchment with a temporary stream network 

Chiara Marchina, Amponsah William, Gelmini Ylenia, Borga Marco, and Zuecco Giulia

Hydrological studies on temporary streams are crucial for understanding their activation and response during wet and dry conditions. Additionally, the use of geochemical tracers (e.g., electrical conductivity, water stable isotopes, major ions) can help assess the impact of climate change on these ephemeral water bodies. This study aims to i) investigate the relation between discharge and tracer concentration at different spatial scales and at the seasonal and event scales; ii) analyze the effect of antecedent conditions on tracer temporal variability at different spatial scales; iii) compare the contribution of rainwater to stream runoff at three scales during selected rainfall-runoff events. The work relies on an integrated database of isotopic and geochemical compositions of water samples coupled with hydrometeorological data from the Regional Environmental Agency (ARPAV) in the 116 km2 Posina catchment in the Italian pre-Alps. The lithology consists mainly of carbonate rocks, and the typical fracturing of dolomites and limestones facilitates water infiltration, thus favoring the presence of temporary streams during dry periods. Conversely, the limited presence of volcanic rocks in some sub-catchments tends to favor perennial streams characterized by a rapid response to rainfall events. In this work, water samples were collected from the Posina river and its main tributaries between September 2015 and March 2019. Temperature and electrical conductivity were measured in the field by portable probes, whereas major ions and water stable isotopes were analyzed by ion chromatography and laser spectroscopy, respectively. Preliminary results show that relationships between discharge and tracer concentration reveal significant associations: δ18O increases with discharge, whereas electrical conductivity (EC) shows a decreasing trend with discharge, better represented by logarithmic and polynomial functions for different selected sections of the main streams and tributaries. Similar trends are observed for sulphates and sodium.  Discharge data at Ressi (a tributary flowing on volcanic rocks) and Posina at catchment outlet have also been compared with selected tracer data from water samples from these two sections. Positive correlations are found between average tracer concentration (δ2H, δ18O, and nitrates) and peak antecedent discharge, while negative correlations exist for δ2H, EC, chloride, sulphates, bicarbonate ions, sodium, magnesium, and calcium. Antecedent precipitation positively correlates with δ2H and nitrates but negatively with sulphates and sodium. EC shows positive (negative) correlations with δ2H and nitrates (sulphates and sodium), respectively, with varying patterns along different sections and tributaries. The 5-day antecedent rainfall exhibits the highest correlations with tracer compositions, particularly for EC, δ2H, and nitrates. The obtained results suggest the importance of an interdisciplinary approach in the analysis of the hydrological and geochemical connectivity of temporary stream networks.

How to cite: Marchina, C., William, A., Ylenia, G., Marco, B., and Giulia, Z.: Exploring tracer dynamics at different spatial scales in a pre-Alpine catchment with a temporary stream network, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12388, https://doi.org/10.5194/egusphere-egu24-12388, 2024.

EGU24-12911 | PICO | HS2.1.1 | Highlight

Flow intermittence patterns in European river networks under climate change: Assessing temporal and spatial changes 

Annika Künne, Louise Mimeau, Alexandre Devers, Sven Kralisch, Flora Branger, and Jean-Philippe Vidal

Climate change is driving a global shift in river hydrology. Future climate projections estimate that global warming will result in more frequent and intense hydrological droughts in certain regions of the world, including Europe. However, there are currently very few studies investigating the impact of climate change in non-perennial rivers, which are home to a rich aquatic biodiversity and may be particularly vulnerable to an increase in droughts. To comprehend the impact of climate change on drying river networks and its consequences on biodiversity, functional integrity and ecosystem services, it is paramount to model and project flow intermittence under climate change.

In this study, we assess flow intermittence patterns and transitions in six distinct European River Networks from the DRYvER project case studies (Datry et al. 2021), situated in diverse biogeographic regions including Spain, France, Croatia, Hungary, Czech Republic, and Finland. Encompassing watershed areas ranging from 150 km² to 350 km², we employed a hybrid modeling technique to predict spatio-temporal patterns of flow intermittence (Mimeau et al. 2023). Climate projection data were used to force the hybrid models, enabling an evaluation of future changes. Additionally, flow intermittence indicators reflecting impacts on ecological processes were jointly developed in the DRYvER project and computed to assess changes and trends in recent years from 1960 to 2021 and for projected periods up to 2100.

Results indicate that projected drying patterns expand temporally and spatially. Temporally, the increase is related to a higher frequency of ceasing streamflow, but also to prolonged individual drying events. Shifts in the seasonality of flow cessation were also observed, with flow intermittence occurring in atypical seasons, such as winter, and typical drying maxima in summer transitioning to an earlier onset in spring with later ends or second maxima in autumn. Spatially, the increase is related to both, the overall river length affected by flow intermittence and the increase of connected reaches affected by flow cessation, which in turn increases the patchiness of the river network. All streamflow intermittence indicators simulated for the six case studies in the past and future projections can be explored on the interactive web application DRYvER-Hydro (https://dryver-hydro.sk8.inrae.fr/). Besides, the calculated indicators can be utilized by other DRYvER partners for further ecological analysis and modeling. For instance Vilmi et al. (2023) used these indicators, among other data, to assess algal, fungal, bacterial, macroinvertebrate, and fish metacommunities.

This research provides valuable insights into the dynamic interactions between climate change and river hydrology, emphasizing the urgent need for adaptive strategies to mitigate the consequences on water resources, biodiversity, and ecosystem services in European river systems.

References:

Datry et al (2021) Securing Biodiversity, Functional Integrity, and Ecosystem Services in Drying River Networks (DRYvER). Res Ideas Outcomes 7:. https://doi.org/10.3897/rio.7.e77750

Mimeau et al (2023) Flow intermittence prediction using a hybrid hydrological modelling approach : influence of observed intermittence data on the training of a random forest model. 1–30. https://doi.org/10.5194/egusphere-2023-1322

Vilmi et al (2023) D2 . 6 : A report on meta-community spatio-temporal models and meta-community patterns across the six focal DRNs in Europe. https://www.dryver.eu/results/reports-and-documents

How to cite: Künne, A., Mimeau, L., Devers, A., Kralisch, S., Branger, F., and Vidal, J.-P.: Flow intermittence patterns in European river networks under climate change: Assessing temporal and spatial changes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12911, https://doi.org/10.5194/egusphere-egu24-12911, 2024.

EGU24-15164 | ECS | PICO | HS2.1.1

Development of low-cost soil moisture sensor to capture the response of headwater streams in lower Himalayan region 

Deependra Choudhary, Sumit Sen, and Rahul Kulkarni

A comprehensive exploration of streamflow dynamics at the watershed scale in non-perennial rivers is an arduous task. In the lower Himalayan region, the presence of numerous intermittent and ephemeral streams contributes to high volume of water for small duration and transports significant amount of sediment to downstream. Fluvial alterations reshape stream geomorphology, triggering flash floods. To map those head water streams, a comprehensive study within the lower Himalayan watershed of area 56.61 km2 has been done by developing the low-cost capacitive soil moisture sensors. This real time monitoring sensor is a microcontroller-based system and an indirect method for indicating the soil moisture content. These sensors have been strategically deployed across three distinct sub-watersheds within the headwater watershed to capture the continuous soil moisture response during the monsoon period in 2023. For analyzing this study, on-field data was collected from automated weather stations (AWS) to obtain rainfall data, which was complemented by the utilization of stage-discharge curves for a more thorough understanding of discharge fluctuation. During 2023 monsoon period 9 rainfall events were recorded and identified as small, medium, and high to get the rainfall- runoff relationship with antecedent moisture condition (AMC). From the analysis different signatures in capacitance value are found to be affected by several factors which include slope, % area, stream order and land cover. These thresholds will aid in accurately mapping streams, and by quantifying discharge capacity, sediment transportation analyses can be facilitated in future. This study will enhance management strategies for sediment transport and ecological health within the high-gradient headwater watersheds. 

How to cite: Choudhary, D., Sen, S., and Kulkarni, R.: Development of low-cost soil moisture sensor to capture the response of headwater streams in lower Himalayan region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15164, https://doi.org/10.5194/egusphere-egu24-15164, 2024.

EGU24-15302 | ECS | PICO | HS2.1.1

Combining citizen science data and the hierarchical structuring of temporary streams to reconstruct the patterns of channel wetting and drying 

Mirjam Scheller, Nicola Durighetto, Ilja van Meerveld, Jan Seibert, and Gianluca Botter

Temporary streams (i.e., non-perennial streams) cover more than half of the global stream network. They are highly dynamic systems and important habitats. Still, they have so far not been thoroughly monitored because gauging stations are expensive, not well suited for measuring zero flows, and provide only data for a single location in the stream network. An alternative way to monitor temporary streams is by visual assessment. However, on-the-ground surveys of stream networks tend to be highly time-consuming. Hence, visual observations by citizen scientists provide a great opportunity to collect high spatial- and temporal resolution data, even though there are challenges regarding the accuracy and irregularity of the observations.

To assess the potential of citizen science data to obtain temporal resolved information on the state of temporary streams, we used the observations submitted by citizen scientists using the CrowdWater app for 63 locations on a 5 km2 forested hill in Zurich, Switzerland. The number of observations per location during the last three years varied from 1 to 257 (median: 40). There was at least one stream state observation for 402 days, with a maximum of 42 observations per day and a median of 10 observations per day. In addition, trained staff monitored 59 streams (30 overlap with the citizen science data set) at an almost bi-weekly resolution during six months (24 days of observations at all 59 points).

The hierarchical structure of channel network dynamics postulates the existence of a fixed, unique order according to which stream segments are activated during network expansion (from the most to the least persistent). To understand the hierarchical structure of stream wetting and drying at the study site, we applied the graph-based method developed by Durighetto et al. (2023) on the available data. This data-driven method would allow us to fill the gaps of the irregular citizen science data (leading to 25,728 reconstructed observations compared to the 4,354 original observations). The hierarchical structures for the two datasets differed, even if only locations that were part of both data sets and the same period were used to determine the hierarchical structure. In the citizen science dataset, the order of activation of the observed stream locations is less clearly identifiable (i.e., more uncertain). This is likely due to the non-systematic and sporadic nature of the data, i.e., only a few stream observations on the same date, as well as errors in the data. Nonetheless, this information can be used to give guidance to the citizen scientists on which streams to observe more frequently because they provide the most crucial information about the wetting and drying patterns of the network.

 

Reference: Durighetto, N., Noto, S., Tauro, F., Grimaldi, S., & Botter, G. (2023). Integrating spatially-and temporally-heterogeneous data on river network dynamics using graph theory. Iscience, 26(8).

How to cite: Scheller, M., Durighetto, N., van Meerveld, I., Seibert, J., and Botter, G.: Combining citizen science data and the hierarchical structuring of temporary streams to reconstruct the patterns of channel wetting and drying, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15302, https://doi.org/10.5194/egusphere-egu24-15302, 2024.

EGU24-16251 | ECS | PICO | HS2.1.1

Using a hybrid hydrological modelling approach to simulate drying patterns in 3 non-perennial European river networks 

Louise Mimeau, Annika Künne, Flora Branger, Sven Kralisch, Alexandre Devers, and Jean-Philippe Vidal

Intermittent and ephemeral streams account for more than half of the world’s river channels, yet their hydrological functioning remains understudied. Modelling non-perennial river systems can help understanding the spatio-temporal patterns of drying and rewetting, but is challenging due to limited monitoring in intermittent river networks.

This study is part of the EU-funded project DRYvER, which aims to understand the repercussions of drying river networks for biodiversity, functional integrity, and ecosystem services (Datry et al. 2021). Here we propose a novel hydrological modelling approach using the J2000 distributed hydrological model (Krause et al. 2006), coupled with a Random Forest classification model, to predict daily and spatially distributed flow conditions (flowing or dry). The hybrid flow intermittence model is trained using observed flow condition data from diverse sources, such as water level measurements, photo traps, remote sensing, and citizen science applications (Mimeau et al, 2023). We evaluate the model's performance in three European River Networks in Finland, France, and Spain.

Results show that the hybrid flow intermittence model accurately predicts the drying events, with a probability of prediction of a drying event above 0.9 for the French and Finnish study cases. The spatio-temporal patterns of flow intermittence are contrasted among the 3 study cases: while the model simulates a few drying episodes during the summer season in the Finnish case study, mainly in the small upstream tributaries, it also simulates more complex drying patterns in the French and Spanish case studies, with drying episodes occurring throughout the year and drying events in the main river sections.

Additionally, we provide insights on the role of the observed data used to train the model on the simulated flow intermittence patterns. Results indicate that the quantity of observed data, as well as their temporal distribution, their spatial location in the river network, and the representativeness of the observed flow condition can have a significant impact on the simulation performance of flow intermittence. This study shows that combining different sources of observed flow condition data can help to reduce the uncertainty in predicting flow intermittence.

 

Datry et al. (2021) Securing Biodiversity, Functional Integrity, and Ecosystem Services in Drying River Networks (DRYvER). Research Ideas and Outcomes. https://doi.org/10.3897/rio.7.e77750.

Krause et al. (2006) Multiscale investigations in a mesoscale catchment: hydrological modelling in the Gera catchment. Advances in Geosciences. https://doi.org/10.5194/adgeo-9-53-2006.

Mimeau et al. (2023) Flow intermittence prediction using a hybrid hydrological modelling approach: influence of observed intermittence data on the training of a random forest model, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-1322.

How to cite: Mimeau, L., Künne, A., Branger, F., Kralisch, S., Devers, A., and Vidal, J.-P.: Using a hybrid hydrological modelling approach to simulate drying patterns in 3 non-perennial European river networks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16251, https://doi.org/10.5194/egusphere-egu24-16251, 2024.

EGU24-16283 | ECS | PICO | HS2.1.1

How drought can affect river network dynamics in a central Germany lowland river catchment 

Yao Li, Seifeddine Jomaa, Gunnar Lischeid, and Michael Rode

River network is usually not a static item. More than half of global river exhibit an intermittent pattern, ceasing to flow during drought and rewetting again as the environment getting wetter seasonally. Recently, climate change has led to intensified droughts in central and southern Europe, causing even perennial streams to transition to intermittent flow patterns. Understanding and estimating to what extent drought can affect river network expansion and contraction is important and remains challenging.

This study aims to link river network dynamics and subsurface flow and to identify the potential influence of prolonged drought periods on the groundwater-river connection, and concomitant river network dynamics changes. To this end, we have coupled a fully-distributed hydrological model (mHM) with a groundwater model (Modflow) to investigate how prolonged droughts affect river network dynamics at the meso-catchment scale. The model was implemented in the Bode catchment, spanning 3200 km² in central Germany, from 2000 to 2022, in which the period 2018-2022 is considered as drought. We calibrated the model using discharge and groundwater table depth data from 2004 to 2008. Subsequently, we validated it using observations of discharge, groundwater table depth, and river dryness and wetness from 2009 to 2022.

The results demonstrate that the model could reproduce the dryness and wetness of river networks. For the groundwater-river exchange, the length of streams with net water loss increased by 6% in the period 2018-2022 compared to 2004-2017. For the river network dynamics, temporally, total river network length shows an apparent decline. The mean and minimum river network length during recent drought years (2018-2022) decreased by 10.4% and 10.9% compared to 2004-2017, respectively. While the maximum river network of each year was reduced only by 4.37%.  Spatially, the decline of river network length mainly occurs in first and second order streams (60.2% and 25.8%). Further analysis of stream persistence shows that approximately 3% of stream reaches shift from perennial to intermittent pattern and around 8% of stream reaches transfer from intermittent pattern to permanently dry due to the drought from 2018 to 2022. This is likely not only to harm aquatic biota but to have a major impact on stream biochemistry as well.

How to cite: Li, Y., Jomaa, S., Lischeid, G., and Rode, M.: How drought can affect river network dynamics in a central Germany lowland river catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16283, https://doi.org/10.5194/egusphere-egu24-16283, 2024.

EGU24-17373 | ECS | PICO | HS2.1.1

Estimating the duration of flow status along non perennial rivers by satellite data 

Carmela Cavallo, Maria Nicolina Papa, Giovanni Negro, Massimiliano Gargiulo, Giuseppe Ruello, and Paolo Vezza

At present there is a great lack of hydrological information on non-perennial rivers. In many cases, there is no knowledge of which river reaches are subject to non-flow periods, and the duration of non-flow and dry periods remains unknown. Few hydrometric stations are present along non-perennial rivers, and these stations provide point information, limiting the ability to describe the flow conditions across a river reach. For example, they do not allow to distinguish a continuous line of flow from an isolated pools condition. In contrast, approaches based on field surveys or citizen science can provide information on flow condition over entire river reaches but their temporal resolution is generally poor. Within this framework, satellite remote sensing provides significant opportunities due to the possibility of monitoring large areas with high temporal resolution. However, the use of satellite images for monitoring non-perennial river regimes has so far been limited by the availability of images with adequate spatial resolution and their accessibility in terms of cost. Multispectral satellite data freely distributed by the European Space Agency's Copernicus Sentinel-2 mission, with a spatial resolution of 10 m and an acquisition frequency of approximately five days, represent an appropriate trade-off point for monitoring non-perennial rivers with active channels not covered by vegetation and larger than about 40 m.

In this study, we investigated the capability of Sentinel-2 data to differentiate among three flowing states of non-perennial rivers: "flowing" (F), "ponding" (P), and "dry" (D). The analysis was performed for 5 reaches of the streams Sciarapotamo, Mingardo and Lambro (Campania region, Italy). By analyzing the spectral signatures of land cover within river corridor, we identified the bands in which land cover classes are most differentiated. Utilizing these specific bands, we created a false-color image in which the pixels covered by water stand out from the background. The comparison between false color images and field acquired ground truth showed very good agreement. For all the archive data (since 2015) we identified one of the three possible flowing status: F, P and D. The acquired dataset was utilized to train a Random Forest model capable of predicting the daily occurrence of specific flowing statuses (F, P, D), using spatially interpolated rainfall and air temperature data as predictors. The model demonstrated strong performance in terms of accuracy (ranging from 82% to 97%) and true skill statistic (ranging from 0.65 to 0.95). In each of the five years of the observation period, all the reaches underwent no-flow condition for at least a few days and in some cases up to four months. Three of the five reaches were completely dry each year while the other two never dried completely. With its ability to monitor the presence of water in a cost-effective manner, this method has the potential to significantly improve the knowledge on non-perennial rivers regimes.

How to cite: Cavallo, C., Papa, M. N., Negro, G., Gargiulo, M., Ruello, G., and Vezza, P.: Estimating the duration of flow status along non perennial rivers by satellite data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17373, https://doi.org/10.5194/egusphere-egu24-17373, 2024.

EGU24-17603 | PICO | HS2.1.1

Process-based 3D groundwater flow model to simulate current and future stream intermittence in headwaters 

Ronan Abhervé, Clément Roques, Jean-Raynald de Dreuzy, Thibault Datry, Philip Brunner, Laurent Longuevergne, and Luc Aquilina

While the role of climate conditions in controlling streamflow intermittence is well recognised, the assessment and modelling of the role of groundwater remains a challenge. In this study, we use process-based 3D groundwater flow models to simulate stream intermittency in groundwater-fed headwaters. Streamflow measurements and stream network maps are considered together to constrain the effective hydraulic properties of the aquifers. The modelling framework has been applied and validated in pilot catchments with unconfined crystalline aquifers (France) with contrasting geomorphological settings. We present the calibration framework, the analysis of uncertainties and discuss the underlying mechanisms governing the different dynamics of streamflow intermittency. The models are then used to predict streamflow intermittence under future climate scenarios. Intuitively, with decreasing recharge rates, systems with lower storage capacities lead to higher water table fluctuations, increasing the proportion of intermittent streams and reducing future perennial flows. However, the pilot sites reveal nuanced feedback mechanisms among future climate variations, groundwater recharge dynamics, and stream intermittence, where the geomorphic characteristics of the landscapes are key to regulating these feedbacks.

How to cite: Abhervé, R., Roques, C., de Dreuzy, J.-R., Datry, T., Brunner, P., Longuevergne, L., and Aquilina, L.: Process-based 3D groundwater flow model to simulate current and future stream intermittence in headwaters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17603, https://doi.org/10.5194/egusphere-egu24-17603, 2024.

EGU24-2269 | ECS | Orals | HS2.1.4

Role of groundwater during hydrological extremes in the glaciated and snow-fed high Alpine catchment under climate change 

Xinyang Fan, Florentin Hofmeister, Bettina Schaefli, and Gabriele Chiogna

Groundwater plays a pivotal role in the water cycle but its interplay with hydrological processes has often been neglected or overly simplified in hydrological models of high-elevation catchments. This may increase uncertainties in future projections and impede a holistic understanding of the hydrological changes. High Alpine catchments, in fact, display complex surface and subsurface processes and lack of observations. Here, we investigate the role of alpine groundwater in the hydrologic response by partitioning the observed streamflow variations to glacier recessions, snowmelt, rainfall, and for the first time - groundwater fluxes at the Martell valley in Italy since the 2000s. To examine the dynamic interactions of these components in detail, we adopt a modeling framework that combines the physics-based model WaSiM (with an integrated groundwater module) with meteorological inputs obtained from the weather model WRF. Extensive field observations (meteorology, hydrology, geomorphology, piezometric levels, stable water isotopes) are collected to constrain the hydrological model parameters and for model evaluation. This study quantifies the contribution of groundwater in moderating the intensity and timing of hydrological extremes (high and low flows) in the selected high-elevation catchment and emphasizes the significance of groundwater in sustaining water availability in this sensitive environment subject to climate change.

How to cite: Fan, X., Hofmeister, F., Schaefli, B., and Chiogna, G.: Role of groundwater during hydrological extremes in the glaciated and snow-fed high Alpine catchment under climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2269, https://doi.org/10.5194/egusphere-egu24-2269, 2024.

EGU24-3373 | ECS | Orals | HS2.1.4

Spatio-temporal evolution of glacial lakes in the Upper Ganga basin, Central Himalayas 

Atul Kumar, Suraj Mal, and Udo Schickhoff

The rise in annual mean temperature due to anthropogenic climate change is causing faster melting and thinning of glaciers leading to the formation of new glacial lakes and the expansion of existing ones in the Himalayan region. This exponential growth of glacial lakes increases the availability of freshwater resources and escalates the risk of future Glacial Lake Outburst Floods (GLOFs).
In the present study, Glacial lake inventories for the Upper Ganga basin were generated at the sub-basin level for 1990, 2000, 2010 and 2020 using Landsat (TM and OLI) images and semi-automated methods to understand the evolution of glacial lakes, altitudinal, orientational and typology changes. We were able to map 2,554 (area: 170.15 sq. km) glacial lakes in 1990, 2,783 (area: 191.03 sq. km) in 2000, 2,834 (area: 201.44 sq. km) in 2010, and 3,118 (area: 210.87 sq. km) in 2020. Between 1990 and 2020, the total number of glacial lakes increased by 564 (22.08%) and the total area increased by 40.72 sq. km (23.93%). In the year 2020, glacial lakes were found in 31 sub-basins of the Upper Ganga basin, out of 31 sub-basins, Arun sub-basin had the maximum number of glacial lakes (n: 734 & area: 61.66 sq. km).
The mean elevation of glacial lakes increased from 5,044.81 m asl (1990) to 5,052.30 m asl (2020), showing an increase of 7.49 m asl. In 2020, the majority of the glacial lakes were distributed in the elevation zone of 5,000-5,500 m asl (n:1,404 & area: 113.79 sq. km). In the upper Ganga basin, majority of the glacial lakes were south-facing (491) in 2020.
End moraine-dammed (M(e)) lakes dominate among differnt types of glacial lakes. In 1990, there were 2,081 (M(e)) lakes, which increased to 2,413 in 2020, indicating towards increasing risk of future Glacial Lake Outburst Floods (GLOFs) in the Upper Ganga basin. 
Therefore, the present study provides vital insights into the glacial lake dynamics of the Upper Ganga basin at the sub-basin level and will help in identifying potentially dangerous glacial lakes and developing robust policies to mitigate the impact of future GLOF events.

How to cite: Kumar, A., Mal, S., and Schickhoff, U.: Spatio-temporal evolution of glacial lakes in the Upper Ganga basin, Central Himalayas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3373, https://doi.org/10.5194/egusphere-egu24-3373, 2024.

Runoff from the Tibetan Plateau (TP), known as the Asian water tower, is crucial to regional hydrological processes and the availability of water for large population living downstream. Climate change, especially marked atmospheric warming and altered precipitation patterns, have significantly affected the cryospheric hydrological process in the TP, particularly runoff. However, it is still unclear to what extent precipitation and temperature contribute to runoff change on the TP and the regional variability is not well understood. In this study, a large-scale, high-resolution, and well-calibrated distributed hydrological model was employed to simulate the long-term runoff of the TP over the past six decades (1961-2019). Then, spatiotemporal characteristics of runoff were analyzed. Furthermore, the impacts of precipitation and temperature on runoff variation were quantitatively estimated. The results found that the annual runoff decreased from southeast to northwest, and has been increasing over the past six decades. Notably, precipitation is a more important contributor than temperature across the plateau, contributing 72.08 % and 27.92 % to the runoff change, respectively. Besides, the influence of precipitation and temperature on runoff varies among basins, with the Daduhe Basin and the Inner Basin being the most and least influenced by precipitation, respectively. This research analyses historical runoff changes and provides insights into the contributions of climate change to runoff on the TP, which helps understand the hydrological response to climate change in mountain regions.

How to cite: Wang, Y. and Ye, A.: The quantitative attribution of climate change to runoff increase over the Tibetan Plateau, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3551, https://doi.org/10.5194/egusphere-egu24-3551, 2024.

EGU24-3824 | Posters on site | HS2.1.4

Characterizing the environmental and geochemical landscape of rock glacier outflows in the Intermountain West, USA 

Jeffrey Munroe, Matthew Morriss, Greg Carling, Debra Finn, Lusha Tronstad, and Scott Hotaling

The global cryosphere is rapidly changing in response to climate warming.  Rock glaciers may be more resilient to climate change than their surface ice and snow counterparts.  However, unlike surface ice features, rock glaciers are comprised of complex mixtures of ice and locally sourced rock, which may be tightly connected to local hydrologic conditions.  This close hydrogeologic connection appears to underlie substantial variability in the environmental conditions of streams associated with rock glaciers, even within the same geographic region.  Here, we analyze 13 years of field data (2011-2023) from 10 rock glaciers and 13 related ice features from four mountain ranges in Wyoming and Utah, USA, to characterize the environmental and geochemical landscape of their outflows.  Specifically, we compare water temperature, geochemistry, conductivity, and isotopic signatures (δ18O and δD) across mountain ranges and ice features.  We find an average surface water temperature of 0.97 ± 1.1 °C across all 10 rock glacier sites from all 13 years; -0.80 ± 0.82 °C at five glacier fed sites, and 1.21 ± 1.88 °C at six snowmelt fed sites.  Preliminary data from two summers of observations also reveal a consistent positive trend in specific conductivity of two rock glacier-fed streams, typical of water transitioning from snowmelt-dominated to ice-melt dominated sources.  Our results highlight the considerable variability in these ecosystems, even within mountain ranges, and underscore the need for wider sampling to better contextualize and monitor them in the future.  This context is critical when considering whether rock glaciers will promote resiliency of coldwater habitat under climate change, and the degree to which their contribution to alpine hydrologic systems may affect biodiversity and drinking water quality as contributions from snow and glacier ice decrease.

How to cite: Munroe, J., Morriss, M., Carling, G., Finn, D., Tronstad, L., and Hotaling, S.: Characterizing the environmental and geochemical landscape of rock glacier outflows in the Intermountain West, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3824, https://doi.org/10.5194/egusphere-egu24-3824, 2024.

EGU24-3961 | ECS | Posters on site | HS2.1.4

Open questions regarding the influence of topography on the terrestrial water cycle 

Sebastian Gnann, Jane Baldwin, Mark Cuthbert, Tom Gleeson, Wolfgang Schwanghart, and Thorsten Wagener

Topography affects the distribution and movement of water on Earth, but exciting puzzles remain and new discoveries regarding topographic controls continue to surprise us. In this contribution, we discuss some open questions regarding the influence of topography on the terrestrial water cycle based on a combination of literature review and data synthesis. How will changes in water and energy supply along elevation gradients translate into changes in actual evaporation, and how will this be modulated by plant physiological responses and topographically driven moisture redistribution? What role does groundwater play in sourcing the world's water towers, and how will this role change with melting of snowpacks and glaciers? What is the relative importance of topography (vs. climate and geology) in driving groundwater flow dynamics across scales, and how does topography influence inter-catchment groundwater flow or mountain block recharge? A key feature emerging from these questions is the presence of numerous interacting gradients and contrasts that explain many of the patterns we observe. Studying these interactions, and thus answering at least some of the questions posed above, has the potential to improve our understanding of hydrological systems and how they may evolve in the wake of global change.

How to cite: Gnann, S., Baldwin, J., Cuthbert, M., Gleeson, T., Schwanghart, W., and Wagener, T.: Open questions regarding the influence of topography on the terrestrial water cycle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3961, https://doi.org/10.5194/egusphere-egu24-3961, 2024.

EGU24-4092 | ECS | Posters on site | HS2.1.4

Cryosphere-groundwater connectivity in the mountain water cycle - where does meltwater go? 

Marit Van Tiel, Caroline Aubry-Wake, and Lauren Somers and the Mountain cryosphere-groundwater interactions working group

Both the mountain cryosphere -- comprising glaciers, snow, and permafrost -- and groundwater play crucial roles in shaping the hydrological cycle. However, their connectivity is not well understood. Understanding the importance of sub-surface meltwater flowpaths and the role of groundwater in mountain regions is critical to untangle 1) the fate of meltwater in the hydrological cycle and 2) the sensitivity of groundwater to a changing meltwater supply due to climate change.

Here, we synthesize studies which investigated the dynamics of meltwater flow through mountain aquifers. In general, snow-groundwater connectivity is better described than glacier-groundwater connectivity. However, estimations of meltwater recharge fluxes vary considerably across studies, which is not only a function of inherent catchment characteristics but also of the different methods used for the assessments. Estimates of the source contributions of mountain groundwater range between 2-60% for glacier melt and between 40-80% for snowmelt. These large numbers suggest that cryosphere-groundwater connectivity and the consequent delay in meltwater flow needs to be part of our conceptual understanding of the mountain water cycle. Still, there is a clear lack of understanding at which spatio-temporal scales this connection operates.

As glaciers retreat and snowpack diminishes, the relative importance of groundwater as catchment storage is expected to increase. This increase may however be partly compromised by declining recharge from the mountain cryosphere and changed recharge dynamics, with yet unknown effects on catchment-scale hydrological processes. We suggest a roadmap for future work to better quantify mountain cryosphere-groundwater connectivity and to predict climate change impacts on mountain water supplies.

How to cite: Van Tiel, M., Aubry-Wake, C., and Somers, L. and the Mountain cryosphere-groundwater interactions working group: Cryosphere-groundwater connectivity in the mountain water cycle - where does meltwater go?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4092, https://doi.org/10.5194/egusphere-egu24-4092, 2024.

In alpine catchments, evapotranspiration (ET) is regularly considered a minor component of the hydrological system and is therefore only rudimentarily regarded in modelling studies and climate change projections. The focus is usually on snow and glacier related processes, projecting a rapid retreat of glaciers in central Europe within the next few years and decreasing snow volumes at lower elevations due to climate warming. This leads to a reduction in the dominance of snow and glacier related processes. Changes in vegetation characteristics due to climate- and/or land use change will presumably lead to a relative increase in the importance of other processes such as ET, interception and soil moisture, which will affect spatial and temporal variations in discharge generation.

To identify spatial and temporal patterns of changing process importance, a case study of the Fundusbach catchment in Tyrol, Austria is conducted using the fully distributed and physically based model WaSiM-ETH. As the process representation within all hydrological models is affected by parameter equifinality, substantially different parameter combinations and therefore process representations can lead to similar values of performance criteria when looking at discharge only. To address this issue, elevation dependent, spatial and temporal parameter sensitivity analysis is coupled with a multi-objective calibration. This approach aims to improve the spatial and elevation dependent process representation within the model domain. Instead of calibrating on different output variables, additional field and remote sensing data are used to constrain the parameter space of individual submodels and thus the process behaviour. In a final step, the constrained model is calibrated against discharge. Based on this reference model, scenario analyses are carried out to investigate individual process responses to changes in climate and land use.

The results show, that integrating additional field data and constraining the calibration parameter space considerably improves the process representation within the model. Furthermore, first results show, that changes of the land cover do not influence the overall discharge regime, but ET and soil moisture. Increasing amounts of shrub cover limit infiltration and evaporation, while interception and soil moisture increase. Most process responses intensify with increasing elevation and reflect the spatial patterns of land cover.

How to cite: Herzog, A., Vormoor, K., and Bronstert, A.: Shifting hydrological process importance in alpine catchments: Combined effects of climate and land cover change on alpine evapotranspiration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4133, https://doi.org/10.5194/egusphere-egu24-4133, 2024.

EGU24-4160 | Orals | HS2.1.4

Water Availability Assessment in the Upper Colorado River Basin 

Matthew Miller, Natalie Day, Jesse Dickinson, John Engott, Casey Jones, Jacob Knight, Patrick Longley, Samuel Lopez, Melissa Masbruch, Morgan McDonnell, Olivia Miller, Noah Schmadel, Fred Tillman, and Daniel Wise

The lack of comprehensive water supply prediction capacity in most areas of the U.S. poses challenges in evaluating water availability. In order to improve water availability prediction and assessment, in 2019, the U.S. Geological Survey initiated planning efforts to intensively study five medium-sized basins throughout the U.S. over the next decade, including the Upper Colorado River Basin (UCOL). Research in the UCOL aims to provide insight into how past, present, and future snow conditions – including amount, timing, melt, and transitions from snow- to rain-dominated systems – impact water supply (quantity and quality) and the ability to meet demand. A specific emphasis is placed on how these processes affect water budget components and dissolved solids concentration and loading in the UCOL. A fully integrated groundwater-surface water hydrologic model (GSFLOW), and temporally dynamic dissolved solids models (SPARROW) that explicitly represent the groundwater contribution to dissolved solids loading to streams are being applied to meet the study objective. Comprehensive information on water diversion and groundwater pumping has been compiled and is being explicitly represented in the models to better represent human demand.  Temporal and spatial patterns in predicted water quantity and quality conditions are being evaluated in the context of past and projected future changes, summarized over 30-year time periods, in snow metrics.  Historical trends in multiple snow metrics, water budget components, groundwater levels, and dissolved solids provide context for evaluations of current conditions and motivation for further investigation and modeling. The tools and concepts developed in the UCOL will contribute to ongoing work in the other regional study basins as well as a forthcoming national water availability assessment. 

How to cite: Miller, M., Day, N., Dickinson, J., Engott, J., Jones, C., Knight, J., Longley, P., Lopez, S., Masbruch, M., McDonnell, M., Miller, O., Schmadel, N., Tillman, F., and Wise, D.: Water Availability Assessment in the Upper Colorado River Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4160, https://doi.org/10.5194/egusphere-egu24-4160, 2024.

EGU24-5085 | ECS | Posters virtual | HS2.1.4

Reservoir lakes in the Upper Harz Mountains (Germany): GIS Implementation and hydrochemical development 

Tanja Schäfer, Elke Bozau, and Alexander Hutwalker

Dam reservoirs were used for the continuous water supply to the ore mines in the Upper Harz Mountains. The first reservoirs were built in the 16th century. The dam heights reach up to 15 m and the stored water volumes are between 10,000 and 600,000 m3. There are about 70 of such lakes around Clausthal-Zellerfeld now. Hydrogeochemical data of the lakes have been investigated for about ten years (Bozau et al., 2015). A data management system combining GIS and hydrochemical data is prepared to facilitate data collection and interpretation.

The specific electrical conductivity (SEC) of the lake water ranges between approx. 30 and 280 µS/cm and can be used for the classification of these lakes. SEC lower than 50 µS/cm are typical for lakes mainly filled by rain water. SEC higher than 200 µS/cm are found in lakes near urban and anthropogenic influences. Due to the long dry periods of the last years an increase of the SEC is seen in the majority of lakes especially between spring 2015 and 2023. Because of extraordinary high precipitation in autumn 2023 this trend stagnates or even decreases in some lakes, but is still observable in the comparison between autumn 2015 and autumn 2023.

Especially those lakes with catchment areas strongly changed by forest decline are expected to show higher values of the SEC. In order to investigate this, spatial comparison with forest damage maps is planned. Furthermore, the concentrations of main ions will be investigated in addition to SEC values. Nitrate and potassium concentrations of the lake water should be the most sensitive indicators for forest decline and anthropogenic influences. A first evaluation of organic trace components (Bozau et al., 2022) did not confirm the classification based on the SEC.

 

Bozau, E., Licha, T., Stärk, H.-J., Strauch, G., Voss, I., Wiegand, B. (2015): Hydrogeochemische Studien im Harzer Einzugsgebiet der Innerste. Clausthaler Geowissenschaften, 10, 35-46.

Bozau, E., Licha, T., Warner, W. (2022): Natürliche und anthropogene hydrochemische Parameter der Oberharzer Bergbauteiche. FH-DGGV-Tagung, Jena, März 2022.

How to cite: Schäfer, T., Bozau, E., and Hutwalker, A.: Reservoir lakes in the Upper Harz Mountains (Germany): GIS Implementation and hydrochemical development, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5085, https://doi.org/10.5194/egusphere-egu24-5085, 2024.

EGU24-5178 | ECS | Posters on site | HS2.1.4

Water Resources Assessment of the Mountainous Upper Syr Darya Catchment 

Lucas Alcamo, Timo Schaffhauser, Jingshui Huang, and Markus Disse

Water is a strategic and highly contested resource in Central Asia. This is exasperated by a highly uneven distribution of this resource within the region as most of the water originates from the high-mountainous regions. In this study we evaluate the current water resources of the highly mountainous headwaters of the Syr Darya River. Trends in hydrometeorological data are investigated and the dominant hydrological processes are studied using hydrologic modeling. The Syr Darya is one of the two tributaries of the Aral Sea, which has been of high interest due to its drastic decrease. The headwaters investigated in this study include the Naryn and Karadarya Rivers, which originate in the mountainous regions of Kyrgyzstan and flow into the Ferghana Valley where they form the Syr Darya River. The discharge regime is dominated by nivo-glacial processes and therefore highly susceptible to climate change.

Streamflow and climatological data spanning from 1889 until 2018 is statistically analyzed and evaluated with regard to trends and change points. For example, at the gauge in Naryn City, an increase in streamflow can be observed, while precipitation peaks tend to shift to earlier months. The observed temperature increase is above the global average.

For a more comprehensive understanding of the water resources of the region the fully revised version of the Soil Water Assessment Tool (SWAT+) is used to represent the hydrological cycle of the catchments. The model is calibrated using daily streamflow gauges at several locations. In addition, evapotranspiration is calibrated using remotely sensed data from the Global Land Evaporation Amsterdam Model (GLEAM). The model is driven by three different sets of reference data from three ensembles of General & Regional Circulation Models (GCM and RCM, respectively). In detail, we used one RCM, (REMO) and the two sets of GCMs from ISIMIP2 (Inter-Sectoral Impact Model Intercomparison Project) and ISIMIP3. The ISIMIP data is based on the 5th and 6th phase of the Coupled Model Intercomparison Project (CMIP5 and CMIP6), respectively. The different driving climatological data sets are investigated with respect to multiple variables essential for an understanding of the water resources, such as streamflow, evapotranspiration, snow and soil moisture. Besides, observed trends and signals are investigated with respect to their dominant physical controls.

How to cite: Alcamo, L., Schaffhauser, T., Huang, J., and Disse, M.: Water Resources Assessment of the Mountainous Upper Syr Darya Catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5178, https://doi.org/10.5194/egusphere-egu24-5178, 2024.

EGU24-6458 | ECS | Posters on site | HS2.1.4

A distributed rainfall-runoff model for the investigation of climate change effects on river floods in the European Alps 

Luca Lombardo, Juraj Parajka, Peter Valent, and Alberto Viglione

The worsening of global climate change has increased both the frequency and intensity of extreme weather events, significantly impacting the dynamics of flooding. This convergence of factors results in intensified and prolonged precipitation, leading to river overflow and catastrophic floods. Elevated temperatures and rapid snowpack melting further contribute to the increase of flood risk. These impacts are particularly pronounced in mountainous regions, where the combination of steep terrain and increased precipitation amplifies the risk of flash and snowmelt generated floods.

The CLIM2FLEX project aligns with this intricate and evolving context, aiming to assess, under potential climate scenarios, the variations in the frequency and intensity of river floods generated by various mechanisms. Within the project framework, a crucial aspect involves constructing a modeling chain, complete with a hydrological module. This component is dedicated to translating climate inputs into continuous discharge time series, enhancing the project's capacity for in-depth analysis and dynamic modeling.

To do so, the main idea is to use a "new version" of the "TUWmodel" conceptual hydrological model to account for the inter-basin transfer of water and flood waves propagation (from upstream catchments to downstream catchments) through the implementation of a new routing routine based on the introduction of a Nash-Cascade module. Different calibration strategies are used at gauged sites to estimate the best model parameters. A machine learning based regionalization approach (HydroPASS) is then applied to infer model parameters at ungauged sites for hydrological streamflow predictions. 

The focus of this study encompasses the entire Great Alpine Region (GAR), posing significant modeling challenges. The region is predominantly characterized by mountainous terrain, consisting mainly of small catchments. Here, the effects of snow accumulation-melting cycles, as well as the presence of glaciers and other small-scale features, play a particularly crucial role.

The presentation at EGU will delve into preliminary findings concerning the applicability and reliability of the proposed hydrological modeling chain structure, along with the anticipated future steps in the research.

How to cite: Lombardo, L., Parajka, J., Valent, P., and Viglione, A.: A distributed rainfall-runoff model for the investigation of climate change effects on river floods in the European Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6458, https://doi.org/10.5194/egusphere-egu24-6458, 2024.

EGU24-6606 | ECS | Orals | HS2.1.4

Exploring the connectivity between glacier melt, groundwater and climate change in the Cordillera Blanca, Peru 

Gavin McNamara, Caroline Aubry-Wake, Lauren Somers, Jeffrey McKenzie, John W. Pomeroy, and Robert Hellström

Glacier melt is known to provide an important source of water to streamflow in glacierized tropical regions, especially during the dry season. Groundwater also contributes a significant amount to streamflow. However, the linkage between the two is often unclear: How much groundwater originates from glacier melt? More broadly, how will groundwater and surface water contributions to streamflow change as glaciers retreat and climate changes? We developed a glacio-hydrological model in the Cold Region Hydrological Modelling platform to explore the complex interactions among the cryosphere, surface water, and groundwater in Peru's Cordillera Blanca, specifically in the Quilcayhuanca valley. The model uses meteorological observations from the valley and is parameterized using numerous data sources and process-based studies in the valley. Our findings reveal that during the dry season, 24 % of streamflow is routed through the groundwater reservoir, increasing to 40 % during the lowest flows. In a simulation without glaciers, streamflow discharge decreases by 34 % during the wet season and by 54 % during the dry season, with the groundwater contribution to streamflow decreasing by 55 % and 52 % for the wet and dry seasons, respectively. This simplified approach suggests that approximately half of the annual groundwater contribution to the stream originates from glacier wastage. We conducted sensitivity scenarios to evaluate the basin's resilience to the range of possible changes in precipitation, temperature and glacier cover expected by 2100. In a nearly deglaciated basin, the sensitivity to the range of tested temperature (+0 to 5 °C) produced a streamflow ranging from -60 to -49 % of current conditions in the dry season, and the range of tested precipitation (-20 % to +20 %) produced a streamflow ranging between -78 to -35 % of current conditions, indicating a larger sensitivity to potential changes in precipitation. Expected ratio changes were smaller during the wet season but followed a similar pattern. In the most likely scenarios by 2100, under RCP 8.5, wet season streamflow is predicted to decrease by 17 to 27 %, and dry season streamflow by 28 to 52 %. Despite a substantial decline in snow and ice contributions under climate change and deglaciation, the groundwater zone's contribution to streamflow shows relatively minor changes, demonstrating the low sensitivity of the groundwater system to climate shifts and glacier variations.

How to cite: McNamara, G., Aubry-Wake, C., Somers, L., McKenzie, J., Pomeroy, J. W., and Hellström, R.: Exploring the connectivity between glacier melt, groundwater and climate change in the Cordillera Blanca, Peru, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6606, https://doi.org/10.5194/egusphere-egu24-6606, 2024.

EGU24-7718 | Orals | HS2.1.4

The peak water myth 

Walter Immerzeel and Francesca Pellicciotti

The peak water concept has emerged to represent the trajectory of future water resources from glacierised basins, and has been widely adopted by the glaciology community. This is based on the notion that runoff from glaciers will increase up to a point in the near future and then decrease, because the melt rates of glaciers per unit area increase due to higher temperatures, while glaciers shrink. There is a point in the future that the glacier area becomes so small that the increase in melt rate per unit area cannot compensate for the area loss, and the absolute amount of glacier melt water starts to decrease. This peak water concept has been featured by several prominent papers and by the IPCC. However, we hypothesize that this peak water concept is an oversimplification of reality and can mask the real trajectory of changes in water resources from mountain catchments. It is only a valid concept for a single glacier, and the effect largely disappears when a mountainous catchment consists of multiple glaciers with different size, thickness, and mass balance sensitivity as result of extensive debris cover, for example. Moreover, and more importantly, it ignores climate change impacts on the non-glacierised part of the mountainous catchment, such as the buffering by snow and groundwater storages and the role of vegetation, and shifts in the partitioning between “green” (evapotranspiration) and “blue” (river runoff) water in particular. In this talk, we show a few examples of such oversimplifications, and argue for a broader and holistic perspective on the impacts of climate change on mountain water resources.

How to cite: Immerzeel, W. and Pellicciotti, F.: The peak water myth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7718, https://doi.org/10.5194/egusphere-egu24-7718, 2024.

EGU24-9575 | Orals | HS2.1.4

Future glacier mass loss in the Tien Shan strongly impacts summer water availability  

Lander Van Tricht, Harry Zekollari, Matthias Huss, Inne Vanderkelen, Marit van Tiel, Loris Compagno, Philippe Huybrechts, and Daniel Farinotti

Glaciers in the Tien Shan act as natural reservoirs, storing freshwater in the form of snow and ice and releasing it during dry periods. This water source serves various purposes and is particularly crucial during dry periods, where it serves agriculture, hydropower, industry, and human consumption. Here, we use GloGEMflow to simulate the future evolution of all glaciers in the Tien Shan under CMIP6 SSP climate scenarios. In all climate scenarios, our results reveal an exceptionally pronounced retreat of the glaciers, surpassing the projected glacier loss for most regions of the world. By 2040, we project a loss of 30% of the glacier mass from 2020, which increases to 60% by 2100 under low emission scenarios (SSP1-1.9, SSP1-2.6) up to 90% under moderate to high emission scenarios (SSP3-7.0 and SSP5-8.5). This drastic retreat is driven by the unique climate of the Tien Shan, with most precipitation occurring during spring and early summer. Rising temperatures not only accelerate glacier melt but also reduce snow accumulation. Regardless of the scenario, we project that peak water from the glacier runoff will occur before 2050. By 2100, total annual glacier runoff decreases by 35% compared to the 2015-2020 mean level. The annual glacier runoff peak shifts from summer, when water demand is highest, to spring, presenting challenges for both agricultural and industrial sectors. We also examine and combine the simulated glacial runoff with information on water availability and demand from the ISIMIP framework. This helps to grasp and evaluate how important glacial meltwater is in the Tien Shan region. Our research provides essential insights for creating adaptive policies to handle water resources effectively at both local and regional level.

How to cite: Van Tricht, L., Zekollari, H., Huss, M., Vanderkelen, I., van Tiel, M., Compagno, L., Huybrechts, P., and Farinotti, D.: Future glacier mass loss in the Tien Shan strongly impacts summer water availability , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9575, https://doi.org/10.5194/egusphere-egu24-9575, 2024.

EGU24-10041 | ECS | Orals | HS2.1.4

Control processes of diurnal streamflow cycles along the longitudinal profile of an alpine river 

Klaus Vormoor, Till Francke, Anna Herzog, and Axel Bronstert

Snowmelt or ice melt typically control diurnal streamflow cycles during rain-free periods in high-altitude alpine catchments. Evapotranspiration-controlled streamflow cycles are less prominent, but can occur simultaneously (Mutzner et al., 2015). In general, the importance of evapotranspiration for the water balance of alpine catchments is likely to increase due to changing atmospheric boundary conditions and (related) changes in land cover. In this study, we focus on controls of diurnal streamflow cycles in the Fundusbach catchment (13 km²) in the Ötztal Alps (Austria). In addition to the official gauge at the catchment outlet, we have installed three further gauges along the longitudinal river profile. Here, we are recording the variability in water level/discharge at high temporal resolution (15 min) since June 2022. We have also adapted the deterministic spatially distributed hydrological model WaSiM with hourly and high spatial resolution (25 x 25 m²) for the Fundusbach catchment. Based on this model and the observation data, we are able to

  • determine the diurnal streamflow dynamics and their change along the longitudinal profile,
  • analyze the seasonal dynamics of diurnal streamflow patterns, and thus,
  • draw conclusions about the spatially and temporally changing control variables of the diurnal streamflow cycles (data- and model-attributed) for rain-free periods outside winter.

Results show that (i) the diurnal streamflow variability decreases along the longitudinal profile, (ii) the amplitude of meltwater driven runoff cycles decreases exponentially over the year, whereby (iii) evapotranspiration-driven cycles always seem to attenuate meltwater-driven cycles. At later points in the snow-free season, the signal of the evapotranspiration-induced streamflow cycles can occasionally be inferred directly from the measurement data. For these days, catchment evapotranspiration amounts can be determined from runoff data as the integral between the daily maximum (during nighttime) and minimum (during daytime). The results also indicate an altitude-dependency of the control processes along the longitudinal profile, which needs to be further investigated.

Reference:

Mutzner, R., Weijs, S.V., Tarolli, P., Calaf, M.C., Oldroyd, H.J., Parlange, M.B. (2015): Controls on the diurnal streamflow cycles in two subbasins of an alpine headwater catchment. Water Resour. Res., 51, 3403-3418. doi.org/10.1002/2014WR016581.

How to cite: Vormoor, K., Francke, T., Herzog, A., and Bronstert, A.: Control processes of diurnal streamflow cycles along the longitudinal profile of an alpine river, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10041, https://doi.org/10.5194/egusphere-egu24-10041, 2024.

EGU24-10334 | ECS | Orals | HS2.1.4

What is the monthly share of mountain water in lowland water abstractions? 

Sarah Hanus, Peter Burek, Mikhail Smilovic, Jan Seibert, and Daniel Viviroli

Mountainous areas play a crucial role in global water resources. Orographic precipitation provides mountains with disproportionately high precipitation, which can be stored seasonally or over many years as snow and ice. Therefore, mountains are often referred to as ‘water towers’, emphasising their vital contribution to water provision for human use. Nevertheless, on a global scale, knowledge about their relevance for lowlands is limited, especially beyond long-term annual averages (Viviroli et al., 2020). Therefore, this study aimed to first assess differences in the water supply of mountains and lowlands in large river basins globally. Second, the share of mountain runoff in lowland water abstractions was evaluated with a focus on monthly averages and intra- and interannual variability to identify hotspots of mountain importance.

Our study is based on global simulations of the large-scale hydrological model CWatM (Burek et al., 2020) at a resolution of 5arcmin (~10km) from 1990 to 2019. The model simulates water availability, water demand and water use. A glacier representation was added to depict mountain water resources more realistically (Hanus et al., submitted). We compared water availability and demand in mountain and lowland areas within each river basin to identify the distinct patterns regarding water quantity, seasonality and interannual variability in mountains. Additionally, we derived the share of mountain runoff in lowland surface water abstractions to explore the relevance of mountains for human water use.

The analysis of around 600 river basins globally confirmed that precipitation and runoff are disproportionally higher in mountain areas in most river basins, whereas water demand is comparatively low. Additionally, we found mostly a larger intra-annual variability and lower interannual variability in mountain runoff compared to lowland runoff.

The estimated share of mountain runoff in lowland surface water abstractions is largest in High Mountain Asia, western North America, parts of South America and Southern Europe. In 250 basins, the maximum monthly relative mountain runoff share in lowland surface water abstractions exceeds 10%, and 25% of the world population lives in the lowlands of these basins. In comparison, only 7% of the world's population lives in lowlands of basins where the long-term mean annual share of mountain runoff in lowland surface water abstractions exceeds 10%. Thus, the relevance of mountains for lowland water supply becomes more apparent when distinguishing between different months compared to long-term annual averages.

Burek, P., Satoh, Y., Kahil, T., Tang, T., Greve, P., Smilovic, M., Guillaumot, L., Zhao, F., and Wada, Y.: Development of the Community Water Model (CWatM v1.04) – a high-resolution hydrological model for global and regional assessment of integrated water resources management, Geosci. Model Dev., 13, 3267–3298, https://doi.org/10.5194/gmd-13-3267-2020, 2020.

Viviroli, D., Kummu, M., Meybeck, M., Kallio, M., & Wada, Y.: Increasing dependence of lowland populations on mountain water resources. Nature Sustainability3(11), 917-928, https://doi.org/10.1038/s41893-020-0559-9, 2020.

How to cite: Hanus, S., Burek, P., Smilovic, M., Seibert, J., and Viviroli, D.: What is the monthly share of mountain water in lowland water abstractions?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10334, https://doi.org/10.5194/egusphere-egu24-10334, 2024.

EGU24-11313 | Posters on site | HS2.1.4

Spatially distributed streamflow buffering by glaciers during recent droughts in Switzerland 

Pascal Buri, Michael McCarthy, Simone Fatichi, Philipp Brun, Dirk Karger, Liangzhi Chen, Massimiliano Zappa, Evan S. Miles, Thomas E. Shaw, and Francesca Pellicciotti

During dry and hot years in the Swiss Alps, melt water from glaciers can moderate streamflow deficits caused by reduced precipitation and enhanced evapotranspiration rates. However, little is known about how glacier melt water contribution to streamflow varies sub-seasonally and in space, especially further downstream from glacierized catchments, where additional streamflow contributions are modulated primarily by rainfall and the biosphere (vegetation, soils).

We study distributed catchment hydrology in Switzerland using a land surface model that constrains energy and mass fluxes using advanced physical representations of both cryospheric and biospheric processes at a 250 m spatial resolution. We simulate catchment runoff in Switzerland during the past 6 years, including two recent severe drought years (2018 and 2022), characterized by particularly warm summers and reduced precipitation. The model is forced with hourly observed meteorological data based on the weather station network SwissMetNet and the precipitation product RhiresD, and uses state-of-the-art land cover, soil characteristics, glacier area and debris thickness as initial conditions.

The spatially explicit simulations allow, when temporally aggregated, to trace upstream contributions of individual water balance components for any downstream point in the catchment. We use the model to quantify the amount and timing of glacier melt and how it affects downstream runoff composition, especially during drought conditions, along the river network. We do this across regions from the Swiss Alps’ headwaters to the lowlands in a spatially continuous way.

When comparing runoff composition during moderate summer months to periods of drought conditions in the Swiss Alps, our simulations show both an increase in intensity and downstream propagation of ice melt contribution to total runoff. During extreme drought periods, ice melt makes up >70% of streamflow (~doubling the contributions during more moderate periods) in some of the Alps’ headwater regions (>1500 m a.s.l.), and still exceeds 10% of streamflow contribution downstream of the pre-alpine region.

Quantifying the timing and amount of glacier melt contributions to downstream water resources under recent drought conditions improves our understanding of potential cryosphere-biosphere interactions and their impacts under future extreme scenarios, when cryospheric runoff contributions may be reduced or completely lost.

How to cite: Buri, P., McCarthy, M., Fatichi, S., Brun, P., Karger, D., Chen, L., Zappa, M., Miles, E. S., Shaw, T. E., and Pellicciotti, F.: Spatially distributed streamflow buffering by glaciers during recent droughts in Switzerland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11313, https://doi.org/10.5194/egusphere-egu24-11313, 2024.

EGU24-11621 | ECS | Orals | HS2.1.4

Exploring Neural Network Performance in Hydrological Modeling in a Mountainous Region of Morocco: A Case Study on LSTM and GRU Architectures for Runoff Prediction 

Karima Nifa, Abdelghani Boudhar, Haytam Elyoussfi, Youssra Eljabiri, Mostafa Bousbaa, Bouchra Bargam, and Abdelghani Chehbouni

This study thoroughly compared two types of neural networks, namely Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) recurrent neural networks (RNNs), within the context of hydrological modeling for predicting runoff in the Oum Er Rabia sub-basins. By assessing their performance on both daily and monthly scales, we aimed to understand the dynamics of runoff, which is crucial in water resources management. The combined analysis of predictions at both time scales provides a comprehensive perspective, using daily outputs for short-term decisions and monthly predictions for longer-term planning.

Using a hydroclimatic time series dataset from 2000 to 2019, incorporating key factors such as snow cover area, temperature, and rainfall that influence hydrological processes and significantly impact flow patterns, the research evaluates the predictive accuracy of the models at both scales. The results reveal nuanced differences in predictive accuracy, with average Kling-Gupta Efficiency (KGE) values for LSTM and GRU at daily and monthly scales, respectively, being 0.64, 0.52, and 0.46, 0.54. These findings provide insights into the strengths and limitations of each architecture in the mountainous region of Morocco.

The study enhances our understanding of the applicability of LSTM and GRU architectures in hydrological modeling, aiding practitioners in selecting models tailored to specific needs. By establishing a robust framework for short-term decision-making and long-term planning in water resource management, this research contributes to advancing predictive modeling and promoting sustainable water use while mitigating flood risks. The knowledge acquired paves the way for improved decision support in the critical area of water resource management.

How to cite: Nifa, K., Boudhar, A., Elyoussfi, H., Eljabiri, Y., Bousbaa, M., Bargam, B., and Chehbouni, A.: Exploring Neural Network Performance in Hydrological Modeling in a Mountainous Region of Morocco: A Case Study on LSTM and GRU Architectures for Runoff Prediction, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11621, https://doi.org/10.5194/egusphere-egu24-11621, 2024.

EGU24-13616 | Orals | HS2.1.4

Hydrological implications of the Chile Megadrought in high mountain basins and lessons for climate adaptation. 

James McPhee, Diego Hernandez, Maria Courard, Alonso Mejías, Zelalem Tesemma, Alain Pietroniro, and John Pomeroy

La Niña years are historically associated with precipitation deficits in central Chile. However, since the onset of the so-called Chile Megadrought in 2010, the teleconnection between the El Niño-Southern Oscillation phases and the hydroclimate in central Chile has either weakened or disappeared. This study investigates the hydrological response of high mountain watersheds to La Niña (LN) and megadrought conditions (MD) in the Andes of central Chile (30°S – 35°S) through physically-based simulation of processes at the watershed scale. It is shown that during LN years, winters and summers are colder, but spring seasons are warmer, while in MD years the summers are warmer. In addition, the hydrologic response to LN and MD is distinct and amplified during MD in terms of flow deficit.  Simulation results for five snow-dominated basins within the central Andes suggest lower efficiency in the transformation of precipitation to snowmelt flow (-3.7% and 1.6% with respect to the long-term average, for MD and LN, respectively), accompanied by higher evaporation (8.7% and 6.1%) and lower flow (-9.3% and -3.4%) relative to annual precipitation. Also, snow accumulation deficits at the end of winter propagate (-36.2% and -17.7%) with respect to the deficit of solid precipitation (-29.7% and -17.5%) and total precipitation (-26% and -19.3%), and during the MD the duration of snow is shorter compared to LN (-16.3 and -10.6 days). Thus, the key role played by snow processes and their variability in the hydrological response to droughts in central Chile is highlighted. The findings presented here are expected to inform ongoing discussion on adaptation strategies to climate change, as the observed climate during the megadrought (2010-?) is strikingly similar, on average, to GCM projections for this region toward the end of the 21st century.

How to cite: McPhee, J., Hernandez, D., Courard, M., Mejías, A., Tesemma, Z., Pietroniro, A., and Pomeroy, J.: Hydrological implications of the Chile Megadrought in high mountain basins and lessons for climate adaptation., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13616, https://doi.org/10.5194/egusphere-egu24-13616, 2024.

EGU24-13828 | ECS | Posters on site | HS2.1.4

Geological controls on groundwater chemistry in the Himalayan Indus River basin aquifers, India 

Poulomee Coomar, Suhail Lone Ahmed, Gh Jeelani, Saibal Gupta, and Abhijit Mukherjee

The upper Indus River basin aquifers spanning over the Himalayan, Karakoram, Hindu Kush ranges is a vast water scares region, which have escaped the notice of the groundwater scientists until recently. The work presented here aims to decipher the processes of groundwater-rock interactions in the shallow Trans-Himalayan Indus River basin aquifers of India. Located on the Indus-Tsangpo suture zone, the area provides a unique opportunity to study water-rock interaction processes in one of the coldest and highest inhabited regions of the world.

Alkaline to circumneutral groundwater are collected from wells mostly located in the meta basics and associated volcanoclastic of the Dras Volcanics (DV) and the granitoids and their extrusive equivalents of the Ladakh Plutonic Complex (LPC). Waters mostly belong to Ca-HCO3 and Ca-Mg-HCO3 facies. Ca-Na-HCO3 occurs as minor facies. Among bivalent cations Ca and Mg shows high degree of correlation, with a low Ca/Mg ratio. Ca-Mg-HCO3 relations suggest bivalents come from Ca-Mg pyroxenes and calcite of the meta-basalts, and calcic plagioclase. Ca-Mg pyroxenes are sourced from the DV, while Ca-feldspars only from the LPC, given the ones in DV are albitised. Decreasing trends of calcite saturation with Ca/Mg ratio hints secondary calcite precipitation. Among monovalent ions, Na + K versus SO42- + Cl- relations suggests, waters owe their Na content to silicates or cation exchange reactions when the ratio >1, and to inputs from saline springs or compounds when the ratio falls below unity. Nearly 60% of samples have Na in excess of Cl- (Na*), but only a minority of them correlates well with dissolved silica. However, thermodynamic calculations suggest waters are mostly in equilibrium with kaolinite, along with some Ca -, Na – smectites and in disequilibrium with all sorts of feldspars suggesting both Na- and K-feldspar weathering from both meta-basics and felsic lithologies. The absence of Na*-Si correlativity indicates simultaneous Na addition through ion-exchange processes or dissolution of non-halite hydrothermal precipitates; borax, trona, burkeite, being the most common. Lack of co-relation between Cl- and SO42- suggest dissimilarity in their provenance.  High Ca/ SO42- ratio precludes inputs from gypsum or anhydrite, so SO42- can only stem from sulphide oxidation or dissolution of sulphates like thenardite or jarosite, which are known to occur in vicinity of local hot springs.

 

How to cite: Coomar, P., Ahmed, S. L., Jeelani, G., Gupta, S., and Mukherjee, A.: Geological controls on groundwater chemistry in the Himalayan Indus River basin aquifers, India, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13828, https://doi.org/10.5194/egusphere-egu24-13828, 2024.

EGU24-14340 | ECS | Posters on site | HS2.1.4

Hydrological response to droughts in the Karnali basin of Nepal 

Pranisha Pokhrel, Sonu Khanal, Jasper Griffioen, Thom A. Bogaard, and Walter Immerzeel

The Karnali basin (40,000 sq km) in western Nepal is a pristine river basin with large potential for the development of hydropower and irrigation. The Karnali river sustains the biodiversity in the national parks downstream and supports the livelihoods of thousands of people. Any changes in the flow regime of the Karnali may therefore have far reaching consequences. This study focuses on analyzing the hydrological response of the Karnali to (multi-year) droughts. The objective is to understand how long the storages in the hydrological system, e.g. glaciers, snow, ground and soil water can buffer prolonged droughts. The hydrological model SPHY, calibrated with long-term river flow observations, is used for this purpose. We created synthetic drought time series by sampling from a 30-year historical forcing dataset based on ERA5. We then used these time series to force the SPHY model and we analyzed the change in streamflow composition as a function of drought duration. This study provides important insights in the buffering capacity of the river basin in a changing climate.

How to cite: Pokhrel, P., Khanal, S., Griffioen, J., Bogaard, T. A., and Immerzeel, W.: Hydrological response to droughts in the Karnali basin of Nepal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14340, https://doi.org/10.5194/egusphere-egu24-14340, 2024.

EGU24-14594 | ECS | Orals | HS2.1.4

HBV Performance under complex and poorly gauged context 

Mohamed El Garnaoui, Abdelghani Boudhar, Ismail Karaoui, and Abdelghani Chehbouni

In North African countries where water scarcity and limited data prevail, employing predictive hydrological modeling is crucial to gain accurate insights into current and future water reserves. Hence, these models parameters exhibit instability in this context due to the climate variability observed through basins. Therefore, our efforts focus on using a combination of measured data, remote sensing information, and reanalysis data for calibration and validation, to check the improvement in the result accuracy. Through this study, we simultaneously investigate the spatiotemporal stability of the HBV model in several sub-catchments of Oum Er-Rbia Basin, by improving the performance of a bucket-type conceptual model. We created a Nested Cross-Validation (NCV) framework to assess spatiotemporal stability. The framework uses optimal parameters from a donor catchment of the Hydrologiska Byråns Vattenbalansavdelning (HBV) model as inputs for target catchment parameter ranges. In particular, we evaluated HBV's capacity for prediction over time and space, as well as its impact on model parametrization throughout the regionalization process in the setting of sparse data catchments. As results, the HBV model is spatially transferable from one basin to another, with NSE ranging from  0.5 to 0.8 and KGE values between 0.1 to 0.9, meaning a moderate to high performance. The HBV optimum parameter sets exhibit unpredictable behavior over space. On the contrary, their inter-annual behavior is nearly identical. It also detected a decrease in the model's predictive skills over time, which can be explained by the research area's tendency to dry out year after year. Furthermore, employing KGE for calibration rather than NSE improves model predictive performance significantly. The model  calibration process with the KGE outperformed those with the NSE metric, especially when simulating high flows. Furthermore, the findings demonstrate a significant relationship between high model performance and high values of several optimal parameter sets throughout the calibration and validation periods.

Keywords: HBV model, poorly gauged basin, arid and semi-arid region, KGE, NSE.

How to cite: El Garnaoui, M., Boudhar, A., Karaoui, I., and Chehbouni, A.: HBV Performance under complex and poorly gauged context, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14594, https://doi.org/10.5194/egusphere-egu24-14594, 2024.

EGU24-14840 | ECS | Posters on site | HS2.1.4

Increased Precipitation Yet Decreased Runoff: Unveiling Hydrological Shifts in the Yellow River Source Region Through Permafrost, Snow, and Vegetation Dynamics 

Jiayong Shi, Juraj Parajka, Jianyun Zhang, Guoqing Wang, and Zhenxin Bao

This study presents a comprehensive analysis of the hydrological changes in the Yellow River source region, a key component of the Qinghai-Tibet Plateau's Three-River Source Region. During the period 1960-2020, we observed a significant increase in precipitation but paradoxically, a slight decrease in runoff. The region, characterized by its critical positioning at the boundary of permanent and seasonal permafrost, has undergone substantial environmental changes due to global warming. By integrating historical data and multi-source remote sensing, our research dissects the complex interactions between the altered permafrost, snow cover, and vegetation dynamics. We specifically examine how these changes influence the regional hydrological cycle, particularly focusing on the mechanisms leading to reduced runoff despite increased precipitation. Our findings provide novel insights into the impacts of climate change on high-altitude hydrological systems. They hold significant implications for water resource management and ecological conservation in the face of ongoing climatic shifts. This study contributes to the broader understanding of hydrological responses to environmental changes in sensitive mountainous regions.

How to cite: Shi, J., Parajka, J., Zhang, J., Wang, G., and Bao, Z.: Increased Precipitation Yet Decreased Runoff: Unveiling Hydrological Shifts in the Yellow River Source Region Through Permafrost, Snow, and Vegetation Dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14840, https://doi.org/10.5194/egusphere-egu24-14840, 2024.

EGU24-15204 | ECS | Posters virtual | HS2.1.4

Uncertainties Analysis of the Hydrological Modelling in Himalayan Region: A Case Study of Alaknanda River Basin 

Sagar Gupta, Nikunj K. Mangukiya, Ashutosh Sharma, Sumit Sen, Ankit Agrawal, Domenico De Santis, Christian Massari, and Silvia Barbetta

Understanding natural processes, particularly the water cycle, is inherently challenging due to their unpredictable and complex nature. This complexity is especially pronounced when employing hydrological models, where simplifications introduce various uncertainties. Failing to acknowledge and address these uncertainties can introduce biases into the model outcomes, potentially influencing subsequent decision-making processes. This issue is particularly pertinent in the Indian Himalayan Regions, where significant contributions come from melting of snow and glaciers.  The uncertainties in both model inputs and structures are exacerbated in this region, which is further compounded by the scarcity of reliable data. Consequently, there is a critical need to systematically quantify the diverse sources of uncertainty to ensure accurate and reliable hydrological predictions. This study focuses on the snow-dominant Alaknanda basin within the Indian Himalayan Region (IHR), encompassing three gauging stations. The SWAT+ hydrological model and Modular Assessment of Rainfall-Runoff Models Toolbox (MARRMoT) framework (Trotter et al., 2022) are employed to assess parameter and model structure uncertainties, respectively. The SWAT+ model, calibrated with the Latin Hypercube Sampling (LHS) algorithm, achieved Nash-Sutcliffe Efficiency (NSE) values of 0.56, 0.79, and 0.61. Parameter uncertainty is further examined using diverse parameter sets generated through the LHS algorithm. Furthermore, with the application of 47 lumped conceptual models within MARRMoT framework, assessment of model structure uncertainty underscores the varying importance of processes, particularly snow storage, soil moisture, and routing storage in the study region. The findings reveal that the inclusion of additional storage components in the model leads to a decline in performance, accompanied by an increase in complexity and uncertainties. Notably, the study concludes that, for the investigated region, the contribution of parameter uncertainty surpasses that of model structure uncertainty. These insights emphasize the need for a nuanced understanding of both parameter and structural uncertainties to enhance the reliability of hydrological predictions in data-scarce and complex regions like the IHR.

References:

Trotter, L., Knoben, W. J. M., Fowler, K. J. A., Saft, M., & Peel, M. C. (2022). Modular Assessment of Rainfall–Runoff Models Toolbox (MARRMoT) v2. 1: an object-oriented implementation of 47 established hydrological models for improved speed and readability. Geoscientific Model Development, 15(16), 6359–6369.

 

How to cite: Gupta, S., Mangukiya, N. K., Sharma, A., Sen, S., Agrawal, A., Santis, D. D., Massari, C., and Barbetta, S.: Uncertainties Analysis of the Hydrological Modelling in Himalayan Region: A Case Study of Alaknanda River Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15204, https://doi.org/10.5194/egusphere-egu24-15204, 2024.

EGU24-16220 | ECS | Posters on site | HS2.1.4

Changes in predictive skills through coupling a hydrological modelling framework with a glacier model  

Justine Berg, Pascal Horton, Martina Kauzlaric, Alexandra von der Esch, and Bettina Schaefli

The Himalayan Mountain range has a substantial glacier cover, supplying melt water to local communities in the drier season for irrigation and human consumption. Effects of climate change on glacier retreat and therefore melt water availability are expected to be severe. An accurate representation of glacier processes is thus of great importance to predict water availability under future climate projections. Hydrological models focus mostly on processes occurring in non-glacierised areas with often overly simplified glacier parametrization. This can lead to uncertainties in streamflow predictions, especially in highly glacierized catchments. Coupling a glacier model to a hydrological model can resolve some of these uncertainties by a more accurate description of glacier-related processes including ice melt, and providing the extent of glacier retreat, which is essential to quantify changes under a transient climate. In this study, we test the hypothesis that coupling the glacier model GloGEM with the hydrological modelling framework Raven can lead to an increase in predictive skills through a better glacier parametrization. The chosen hydrological modelling framework Raven allows for testing multiple hydrological model structures, accounting for uncertainties along the full modelling chain. The relevance of coupling a glacier model with a hydrological model is analysed in a test basin with in-situ measurements of glacier mass balance and streamflow. Modelling results from coupled and non-coupled model runs are evaluated with the available streamflow data.

How to cite: Berg, J., Horton, P., Kauzlaric, M., von der Esch, A., and Schaefli, B.: Changes in predictive skills through coupling a hydrological modelling framework with a glacier model , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16220, https://doi.org/10.5194/egusphere-egu24-16220, 2024.

EGU24-17796 | ECS | Posters on site | HS2.1.4

A model-based methodology for the delineation of complex alpine spring catchments 

Magdalena Seelig, Simon Seelig, Matevž Vremec, Thomas Wagner, and Gerfried Winkler

Spring catchments in Austria are frequently located in alpine regions that are strongly exposed to the effects of global warming. To predict their impact on spring flow, the delineation of hydrological catchments establishes the link between atmospheric input, catchment characteristics, and aquifer properties. This study proposes a delineation methodology that combines a lumped-parameter model with the analysis of stable isotope data. The model includes a semi-distributed snow module (CemaNeige) and a rainfall-runoff model (GR4J), which were applied iteratively to a set of potential catchments of varying extent and location to simulate spring flow. Constraining the models by spring flow data and remote sensing of snow cover distribution allowed us to differentiate plausible catchments from implausible ones. The mean catchment elevation was estimated based on stable hydrogen and oxygen data collected monthly at the springs. The proposed methodology was tested at two karst springs draining geologically complex catchments in different mountain ranges of the Northern Calcareous Alps, where the hydrological catchments deviate strongly from the orographic ones. The catchments lie mainly in mountainous plateau regions that are characterized by high altitudes and long-lasting snow cover. The model results and isotope analysis are in line with additional, independent information based on tracer experiments, structural geology, and speleology. The proposed methodology provides a quantitative, model-based approach to delineate plausible spring catchments in high alpine and complex hydrogeological settings. It thus forms the knowledge base for sustainable management of alpine freshwater resources under a changing climate.

How to cite: Seelig, M., Seelig, S., Vremec, M., Wagner, T., and Winkler, G.: A model-based methodology for the delineation of complex alpine spring catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17796, https://doi.org/10.5194/egusphere-egu24-17796, 2024.

EGU24-17858 | ECS | Orals | HS2.1.4

Temporal dynamics of water quality and microbial community composition in alpine springs 

Filip Paul Boanca, Magdalena Seelig, Clemens Karwautz, Winkler Gerfried, and Christian Griebler

Springs are vital water sources, and their vulnerability to environmental changes, particularly climate change, is of growing concern. The collaborative research project ECOSPRING, funded by the Austrian Academy of Sciences, focuses on the assessment of microbial communities and water quality patterns in selected springs all over Austria. Here, we will focus on understanding the response and vulnerability to hydrological events and climate change.

The first aim of the project is to characterize the springs based on their temporal dynamics in terms of physical-chemical characteristics. A detailed analysis of the dynamics in discharge, temperature, pH, EC, stable isotopes, essential nutrients, and major ions will provide valuable insights into the geological imprint and prevailing hydrological conditions, as well as on catchment areas.

Microbes are an integral component of aquatic ecosystems and can serve as sensitive indicators for environmental conditions. We will compare the microbial community composition in relation to the hydrogeological and physicochemical conditions.

Our research activities target two spatial scales, from a local perspective, with 14 springs in the province of Styria studied monthly, to a regional approach by sampling around 100 springs distributed all over Austria twice, in winter/spring and summer/autumn marking the expected hydrological extremes.

In the initial stages of our research, we gathered data from 15 selected springs of Styria. These springs exhibit a wide and dynamic spectrum in their physical-chemical properties. Together with records of discharge, springs could be categorized into stable, intermediate, and highly dynamic systems. Our preliminary results indicate a connection between these fluctuating physical-chemical conditions and the composition of the spring water microbiome. The underlying mechanisms driving these observed patterns are yet not fully understood and await further investigations.

In summary, this research project seeks to enhance our understanding of the vulnerability of spring waters to anthropogenic pressures such as climate change. The findings will provide a knowledge base for future water resources management and contribute to the sustainable use of these vital resources.

How to cite: Boanca, F. P., Seelig, M., Karwautz, C., Gerfried, W., and Griebler, C.: Temporal dynamics of water quality and microbial community composition in alpine springs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17858, https://doi.org/10.5194/egusphere-egu24-17858, 2024.

EGU24-18462 | Orals | HS2.1.4

Impacts of melting glaciers and snowpacks in High Mountain Asia on downstream water and food security  

Hester Biemans, Arthur Lutz, Wouter Smolenaars, Khalid Jamil, Fulco Ludwig, Sanita Dhaubanjar, and Walter Immerzeel

The high mountains of Asia store large volumes of water in their glaciers and snowpacks. Twelve large river basins, fed with meltwater from these mountains, are home to almost 2 billion people. In their floodplains, a significant fraction of the global food is produced (34% and 23% of the global rice and wheat production respectively). This makes the snow and ice in the High Mountains of Asia a very important water reserve on which both water- and food security for a huge population depend.However, the water supply from the mountains faces many threats. Glaciers and snowpacks are melting at unprecedented rates, and large parts of these reserves are likely to disappear by the end of the 21st century. At the same time, the dependence of downstream populations on mountain water resources is increasing, mainly due to increasing water needs, continuing groundwater depletion and changes in (monsoon) precipitation.Agriculture in the predominantly irrigated floodplains in Asia is very intensive, with often 2 or even 3 crops grown per year. In some of these agricultural areas, irrigation water supply is largely depending on the seasonal availability of meltwater. Any changes in meltwater supply could therefore have large impacts on the crop production, but science has only just started understanding the impacts of melting glaciers and snowpacks on food and water security of downstream populations.In this presentation we will look back on our recent work in which we quantified the current en future dependence of downstream crop production on water from the mountains in the Indus and Ganges basins. We also describe remaining challenges, and look ahead to the upcoming (ERC) 3POLE2SEA project,  that aims to quantify these upstream-downstream linkages in all twelve river basins river basins originating from the High Mountains of Asia. We expect that the 12 river basins have very different upstream-downstream dependencies, resulting in different current and future risks for water and food security, and therefore need different responses for effective adaptation. We explain how our research can contribute to making agriculture in one of the largest food producing areas in the world more resilient to changes in the mountains.

How to cite: Biemans, H., Lutz, A., Smolenaars, W., Jamil, K., Ludwig, F., Dhaubanjar, S., and Immerzeel, W.: Impacts of melting glaciers and snowpacks in High Mountain Asia on downstream water and food security , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18462, https://doi.org/10.5194/egusphere-egu24-18462, 2024.

EGU24-18725 | ECS | Posters virtual | HS2.1.4

Towards developing a streamflow forecasting system for data-poor mountainous watershed: an approach using parameter transfer 

Kavya Mammali, Sanjeev Kumar Jha, and Nicholas Kouwen

Studying the hydrological responses of the Indian Himalayan Region (IHR) is crucial given the rise in the frequency of floods and other natural disasters. The hydrological processes in this area are more complicated due to the extreme weather pattern and varied topography. Streamflow forecasting is made more difficult by the extremely low number of stream gauge stations and the absence of accurate stream flow data. The problem of lack of observational data in ungauged watersheds can be resolved by transferring model parameters from similar gauged basins (Regionalisation). According to the traditional regionalization procedures using rainfall-runoff models, donor and recipient catchments must be similar in a variety of ways, including slope, size, drainage pattern, area, etc. It is extremely difficult to locate a catchment with all those similarities. In this study, we use a fully distributed hydrological model WATFLOOD for developing a streamflow forecast of the Alakananda River basin where the stream flow observation is very limited for the calibration of the hydrological model. WATFLOOD is working based on Grouped Response Unit (GRU). The requirement that has to be satisfied for regionalization using the WATFLOOD model is that land cover classes of the ungauged watershed should be represented in the gauged watershed irrespective of their spatial distribution. Also, there should be as many as possible gauged sub-watersheds that represent each land cover class. We identified a similar watershed that has similar land cover classes and sufficient stream flow gauges to represent each of the land cover classes. The three-step calibration process of the WATFLOOD model for both river basins is carried out to transfer the parameters. The results of ongoing work will be presented at the conference.

How to cite: Mammali, K., Jha, S. K., and Kouwen, N.: Towards developing a streamflow forecasting system for data-poor mountainous watershed: an approach using parameter transfer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18725, https://doi.org/10.5194/egusphere-egu24-18725, 2024.

EGU24-18832 | Posters on site | HS2.1.4

Changing discharge patterns of springs characterized by nival flow regimes in the Austrian Alps 

Matevž Vremec, Magdalena Seelig, Simon Seelig, Raoul Collenteur, Thomas Wagner, Jutta Eybl, and Gerfried Winkler

Alpine spring runoff patterns recorded at gauging stations offer a unique observational window into the hydrological state of Alpine water systems. These systems play a crucial role in supplying water to downstream areas and are particularly sensitive to changes in temperature and precipitation. Using a dataset of spring discharge monitored at 29 stations by the Austrian Hydrographic Service, spanning 24 years, we conducted a trend analysis on both the quantity and timing of mean and extreme flows. The springs, which were clustered into groups based on the Pardé coefficient and autocorrelation analysis, are distributed over the whole area of the Austrian Alps with mean catchment elevation reaching up to 2500 m above sea level. The trend analysis was performed using the Mann-Kendall test and the Theil-Sen slope on seasonally and annually computed statistics describing the quantity and timing of the occurrence of mean and extreme flows. The results indicate that at springs with a nival flow regime (i.e., flow dominated by snow melt), winter discharge increased. However, during the summer period, differences emerged between two characteristic spring groups: (i) springs at higher-elevation catchments, mainly distributed in the west of the Austrian Alps, with a positive trend in summer, and (ii) springs in the eastern part of the Northern Alps, that displayed a decrease in summer discharge. Notably, differences in the trends for timing of maximum and minimum flows were also evident between these two groups. Furthermore, we compared the hydrological trends to precipitation trends in the spring areas to assess relationships between meteorological and hydrological patterns. These findings provide valuable insights into how the spring runoff patterns have evolved in the Austrian Alps over the past 24 years.

How to cite: Vremec, M., Seelig, M., Seelig, S., Collenteur, R., Wagner, T., Eybl, J., and Winkler, G.: Changing discharge patterns of springs characterized by nival flow regimes in the Austrian Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18832, https://doi.org/10.5194/egusphere-egu24-18832, 2024.

EGU24-19825 | ECS | Orals | HS2.1.4

Assessing Climate Change Impacts on Glacierized Catchments in Central Asia Using an Open Source Toolkit 

Phillip Schuster, Alexander Georgi, Azamat Osmonov, and Tobias Sauter

The impacts of climate change and the retreat of mountain glaciers will significantly affect the headwaters of high mountain river systems. Accurate predictions of future water availability are essential to mitigate local impacts. Despite the availability of various glacio-hydrological modeling tools and high-quality input datasets, their effective application in less developed countries facing severe climate change impacts remains limited. Accessible and cost-effective tools are particularly scarce, hindering engagement with water management stakeholders, especially at the local level.

We present MATILDA, an open-source toolkit for glacierized catchments that allows users to acquire and process public data, apply well-established glacio-hydrological modeling routines, and estimate climate change impacts on the catchment of their choice. The workflow integrates Google Earth Engine, several state-of-the-art online data sources, and calibration algorithms. Published as a Jupyter book, it can be executed in an online Python environment, allowing users to generate scenario-based hydrological projections and analyze trends in runoff contributions, requiring only runoff observations.

The workflow is outlined and discussed in terms of practical application, sensitivity and uncertainty, limitations, and possible improvements. With a view to two regional studies in the Tian Shan Mountains, we evaluate MATILDA’s practical potential to support water management decisions in high mountain areas. The first study assesses the impacts of glacier change on lake levels and local agriculture in the endorheic Issyk-Kul basin in Kyrgyzstan. The second study focuses on the Chirchik River Basin in Uzbekistan and it's crucial role for hydropower production and fresh water supply for the Tashkent metropolitan area.

How to cite: Schuster, P., Georgi, A., Osmonov, A., and Sauter, T.: Assessing Climate Change Impacts on Glacierized Catchments in Central Asia Using an Open Source Toolkit, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19825, https://doi.org/10.5194/egusphere-egu24-19825, 2024.

EGU24-20504 | Posters on site | HS2.1.4

Detecting Climate Change Impacts on Socio-Hydrological Systems in the Rocky Mountains, USA 

David Williams, Corrine Knapp, Bryan Shuman, Bart Geerts, Melissa Bukovsky, Brent Ewers, Shannon Albeke, Sarah Collins, Jeff Hamerlinck, Martha Inouye, Jewell Lund, Fabian Nippgen, and Ginger Paige

Observation networks established in complex mountain landscapes promise to address critical gaps in understanding of socio-hydrological systems and their process interactions operating at local to regional scales. Knowledge of vulnerabilities and risks founded on observed biophysical and socioeconomic conditions and responses is required to represent realistic scenarios in model simulations of climate change impacts on managed water resources. Socio-hydrological observatories often lack design coordination that consequently constrains the ability to link processes and detect feedbacks across scales and domain boundaries. The goal of the 5-year (2022-2027) project WyACT (Wyoming Anticipating Climate Transitions) is to build adaptive capacity in headwater mountain communities in the Greater Yellowstone Area of of the Rocky Mountains founded on observations, simulation modeling, and driven stakeholder needs and participation. A key feature of WyACT is the development, from the ground up, of a regional observatory network that explicitly coordinates observations of socioeconomic, hydrological, and ecological responses to climate-driven stressors. WY-SEaSON (Wyoming Socio-Environmental Systems Observatory Network) will quantify and monitor the range of responses of snowpack and soil moisture, streamflow, aquatic ecosystems, vegetation stress and fire risk, economic risk perception, and preferred adaptation pathways to a changing climate in a key headwaters region that feeds three major river drainages in western North America. This presentation highlights the structure of WY-SEaSON including the operating principles, goals, mission, and design with examples of emerging and integrated observations.

How to cite: Williams, D., Knapp, C., Shuman, B., Geerts, B., Bukovsky, M., Ewers, B., Albeke, S., Collins, S., Hamerlinck, J., Inouye, M., Lund, J., Nippgen, F., and Paige, G.: Detecting Climate Change Impacts on Socio-Hydrological Systems in the Rocky Mountains, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20504, https://doi.org/10.5194/egusphere-egu24-20504, 2024.

EGU24-118 | Posters on site | HS2.1.5

Precipitation, temperature, and vegetation indices analysis for Saudi Arabia region: Feasibility of Google Earth Engine 

Zaher Mundher Yaseen, Bijay Halder, Mohamed A. Yassin, and Sani I. Abba

Climatic disaster is continuously triggering environmental degradation and thermal diversification over the earth's surface. Global warming and anthropogenic activities are the triggering factors for thermal variation and ecological diversification. Saudi Arabia has also recorded precipitation, temperature, and vegetation dynamics over the past decades. Therefore, monitoring past precipitation, temperature, and vegetation condition information can help to prepare future disaster management plans and awareness strategies. The Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks - Climate Data Record (PERSIANN-CDR) from the Center for Hydrometeorology and Remote Sensing (CHRS) data portal and Moderate Resolution Imaging Spectroradiometer (MODIS) are applied for precipitation, Land Surface Temperature (LST), Enhance Vegetation Index (EVI), and Normalized Difference Vegetation Index (NDVI) from 2003 to 2021 respectively. Yearly mean LST, EVI, NDVI, and precipitation values are calculated through the Google Earth Engine (GEE) cloud computing platform. MODIS-based LST datasets recorded the highest temperatures is 43.02 °C (2003), 45.56 °C (2009), 47.83 °C (2015), and 49.24 °C (2021) respectively. In between nineteen years, the average mean LST increased by 6.22 °C and the most affected areas are Riyadh, Jeddah, Abha, Dammam, and Al Bahah. The mean Precipitation is recorded around 776 mm, 842 mm, 1239 mm, and 1555 mm for the four study periods, while the high precipitation area is Jazan, Asir, Baha, and Makkah provinces. In between nineteen years, 779 mm of precipitation is increasing in Saudi Arabia.  Similarly, the NDVI vegetation indices observed 0.885 (2003), 0.871 (2009), 0.891 (2015), and 0.943 (2021), while EVI observed 0.775 (2003), 0.776 (2009), 0.744 (2015), and 0.847 (2021). The R2 values of the LST and EVI correlation is 0.0239 (2003), 0.0336 (2009), 0.0136 (2015) and 0.0175 (2021) similarly correlation between LST and NDVI is 0.0352 (2003), 0.0265 (2009), 0.0183 (2015) and 0.0161 (2021) respectively. The vegetation indices indicate that the green space is gradually increasing in Saudi Arabia and the highly vegetated lands are Meegowa, An Nibaj, Tabuk, Wadi Al Dawasir, Al Hofuf, and part of Qaryat Al Ulya. This analysis indicates that the temperature is increasing but precipitation and green spaces are increasing because of the groundwater recharge through dam construction, precision agriculture, and planned build-up is helps to prepare Saudi Arabia as a green country. Therefore, more attention to preparing the strategic agricultural plants as well as other vegetation and artificial groundwater recharge can improve the country as a green nation. This analysis might help to prepare future planning, awareness, and disaster management teams to prepare for future disasters and strategic steps for sustainable development.

How to cite: Yaseen, Z. M., Halder, B., Yassin, M. A., and Abba, S. I.: Precipitation, temperature, and vegetation indices analysis for Saudi Arabia region: Feasibility of Google Earth Engine, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-118, https://doi.org/10.5194/egusphere-egu24-118, 2024.

Water is scarce in the northern Chihuahuan Desert, with ~350 mm/yr precipitation, potential evapotranspiration at 1800mm/yr, and rising mean annual temperatures by >2°C since 1960. The main water resources are the Ogallala, Pecos Valley, Dockum, and Edwards-Trinity Plateau aquifers, with depletion rates of ~1 m/yr. Despite the arid climate, the Monahans and Kermit dune fields host perched water tables 1-10 m below the surface, in up to 40 m of aeolian sand spanning the past ca. 2.6 ma, and isolated from the underlying Pecos Valley Aquifer by a Pliocene/Pleistocene fluvial gravel-rich clay. A 3D model based on borehole lithology shows a topographic inversion with a southwest-trending paleo-slope infilled with aeolian sand. The aeolian stratigraphy and basin modeling indicate progressive infilling by aeolian sand with periods of pluvial lake formation and soil development, with groundwater providing dune field stability for vertical accretion and limiting aeolian erosion. Cores of sediments retrieved from the Monahans and Kermit dune fields were sampled for OSL ages and yielded ages up to 500 ka 20 m below the surface of the dunes, with identified deposition periods between 545-470 ka, 300-260 ka, 70-45 ka and post 16 ka. A set of three monitoring wells equipped with data loggers revealed aquifer recharge of 35-40 cm in the Spring and Fall consistent with regional precipitation variability, and a daily recharge cycle of 3-8 mm potentially linked to plant uptake or gravitational forces. Deuterium and 18O isotopic ratios for the dune field aquifers indicate an evaporative enriched water source compared to the Pecos Valley Aquifer, Pecos River, and Chihuahuan Desert precipitation, consistent with local precipitation. Apparent 14C ages <1360 yr for aquifer waters from the upper 1 m indicate recent meteoric recharge. Older 14C ages of > 1.3 to 2.2 ka for waters ~30 m deep and at the western edge of the aquifer indicate mixing with Holocene recharge waters in a southwest flowing aquifer. In contrast, the Pecos Valley Aquifer yields 14C ages of ca. 0.9 to 40 ka with the youngest ages near the dune fields, which suggests recharge from these perched aquifers.

How to cite: Fournier, A. and Forman, S.: Origin, gradient, and recharge processes of perched aquifers of the Monahans and Kermit dune fields, northern Chihuahuan Desert, Texas, USA , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-765, https://doi.org/10.5194/egusphere-egu24-765, 2024.

EGU24-1165 | ECS | Orals | HS2.1.5

Agrohydrological modelling approach for assessing the impact of climate change on water resources and land management in the Messinian region, Greece. 

ismail bouizrou, Giulio Castelli, Gonzalo Cabrera, Lorenzo Villani, and Elena Bresci

The Mediterranean region is highly susceptible to the consequences of warming, leading to an increasing of extreme events such as droughts, severe heat waves, and precipitation events. The Messinia watershed (MW) is predominantly characterized by olive cultivation, encompassing approximately 70% of the landscape. These olive orchards constitute a vital component of the Mediterranean ecosystem, playing a crucial role in regional agriculture. The MW is a perfect illustration of a Mediterranean watershed significantly impacted by climate change, as well as soil degradation and a lack of effective land management practices.

In this context, agro-hydrological modelling emerges as a potent tool to address soil degradation and enhance water resource retention within the olive orchards at the watershed scale. To achieve this objective, the SWAT+ agrohydrological model was chosen for a comprehensive assessment of the potential impacts of climate change on water resources and ecosystems in the Messinia region. The adopted modelling approach involved both hard and soft calibration techniques, simulating four sub-watersheds of Messinia by incorporating remote sensing data, including evaporation and soil moisture, for multi-criteria model calibration.

The calibrated model was subsequently employed to assess the potential impacts of climate change on water resources and ecosystems in the Messinia region, utilizing various RCM climate scenarios. Our findings are valuable for addressing soil degradation, as well as for guiding land and water management practices in the Messinian watershed.

 

 

This research was carried out within the SALAM-MED project, funded by the Partnership for Research and Innovation in the Mediterranean Area Programme (PRIMA).

The content of this abstract reflects the views only of the author, and the Commission cannot be held responsible for any use that may be made of the information contained therein.

 

How to cite: bouizrou, I., Castelli, G., Cabrera, G., Villani, L., and Bresci, E.: Agrohydrological modelling approach for assessing the impact of climate change on water resources and land management in the Messinian region, Greece., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1165, https://doi.org/10.5194/egusphere-egu24-1165, 2024.

Desertification on the Mongolian Plateau is deepening, and sand and dust have great negative impacts on many countries in East Asia. Based on meteorological and socio-economic data in the context of climate change, this study analyzed the driving mechanisms and impacts of desertification and water body area response on the Mongolian Plateau using, among others, the GTWR model. The following conclusions were drawn: the area of the Mongolian Plateau showed a decreasing trend from 1990 to 2019, and the number of lakes larger than 1 km2 decreased by 173 or 537.3 km2 in Inner Mongolia, and by 737 or 2875.1 km2 in Mongolia, and all of them were dominated by lakes of 1-10 km2; and the analysis of the correlation between the area of the water bodies showed that the The reasons driving the change of water body area in Inner Mongolia Autonomous Region and Mongolia are similar and different, soil moisture and precipitation have obvious promotion effects, economic development and livestock numbers have different degrees of negative impacts on different countries; The GTWR model is used to represent the impacts of different influencing factors on the water body area in time and space, and the evaporation and GDP are shifted from slight inhibition to promotion, and the population and temperature are both inhibited. Soil moisture and livestock numbers are contributing; Surface water resource monitoring is important to deepen the desertification of the Mongolian Plateau and to provide better water resource recommendations and protection measures for the Mongolian Plateau.

How to cite: Yan, Y. and Cheng, Y.: Study of water body area changes in the desertification process of the Mongolian Plateau and analysis of driving factors, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1185, https://doi.org/10.5194/egusphere-egu24-1185, 2024.

EGU24-2567 | ECS | Orals | HS2.1.5 | Highlight

GIRHAF (Gridded hIgh-resolution Rainfall for the Horn of AFrica): a new rainfall product for detailed applications in a region beset by climate hazards 

Manuel F. Rios Gaona, Katerina Michaelides, and Michael Bliss Singer

Rainfall is one of the most important inputs for applications such as hydrological modelling, water resource allocation, flood/drought analysis, and climatic risk assessments. Currently, there exist numerous (global) products offering rainfall estimates at various spatio-temporal resolutions. Nevertheless, there are still places on Earth where the coverage and/or quality of such products is limited due to sparse ground-control data, thus constraining the robustness of input rainfall for hydrological and climate applications. Located in Eastern Africa, the Horn of Africa (HOA) is a place where climate impacts like droughts and floods frequently inflict a huge toll on the lives and livelihoods of millions residing in subsistence rural communities. For places like this, high resolution rainfall data are fundamental to understanding the availability of water resources, flood hazard, and soil moisture dynamics relevant to crop yields and pasture availability.

Here we introduce GIRHAF (Gridded hIgh-resolution Rainfall for the Horn of AFrica), which is a 20-year rainfall product, with a spatio-temporal resolution of 0.05°×0.05°, every 30 minutes. GIRHAF is based on downscaling CHIMES (Climate Hazards center IMErg with Stations) a pentad operational rainfall product which corrects microwave signals in IMERG (Integrated Multi-satellitE Retrievals for GPM -Global Precipitation Measurement mission-) by in situ rain gauging networks. The goal of this product is to offer the HOA region high-resolution rainfall fields that can support more detailed mechanistic analyses of historical rainfall and can also provide the base dataset required to develop stochastic rainfall models capable of simulating forecasted or projected climate scenarios. It is our aspiration that GIRHAF will enable improved responses to climatic hazards as well as better water resources management in the HOA region, and perhaps to allow people of this region to better prepare to future climate scenarios.

How to cite: Rios Gaona, M. F., Michaelides, K., and Singer, M. B.: GIRHAF (Gridded hIgh-resolution Rainfall for the Horn of AFrica): a new rainfall product for detailed applications in a region beset by climate hazards, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2567, https://doi.org/10.5194/egusphere-egu24-2567, 2024.

EGU24-4462 | ECS | Posters on site | HS2.1.5

Modeling the impact of climate and land use changes on future water resources dynamics in central Sicily, Italy 

Shewandagn Lemma Tekle and Brunella Bonaccorso

Drought events, worsened by climate change, produce detrimental impacts on freshwater availability especially in arid and semi-arid regions. The situation becomes more critical when these hydrologic extremes combine with land use change mainly caused by anthropogenic factors, such as urbanization, intensive farming, and industrial activities. The present study is designed to investigate the combined impacts of climate and land use changes on the future freshwater  stored in the artificial reservoirs of three adjacent river basins located in the central Sicily (Italy), i.e: Verdura (2 active reservoirs with capacities 9.2 Mmc and 4.19 Mmc), Imera Meridionale (one active reservoir with capacity 15 Mmc), and Platani (one active reservoir with capacity 20.7Mmc), using the Soil and Water Assessment Tool (SWAT) model. The reservoirs are used for irrigation, drinking water supply, and electric power generation. Future climate variables such as rainfall, minimum and maximum temperatures were derived from an ensemble Regional Climate Models for two main representative concentration pathway (RCP) scenarios, such as an intermediate emission scenario (RCP4.5) and a severe emission scenario (RCP8.5). A coupled multi-layer perceptron neural networks and cellular automata (MLP-CA) model was implemented to simulate future land use of the region considering the CORINE land cover in 2000, 2006, 2012, and 2018 as a reference dataset. The future land use is then projected until the mid-century (2048) in a six-year interval using the validated MLP-CA model. The soil data from the European soil data center (EUSDAC) was used as input for the SWAT model. The result indicated that the basins could experience a decrease in inflows to the reservoirs. The separate evaluation of climate change and land use changes indicated that the effect of climate change on streamflow variation is more pronounced than the effect of land use change only. In this study, we introduced new hydrological insights into the region by analyzing the attributions of climate change, land use change, and coupled climate and land use changes on the future freshwater availability which were overlooked in the previous studies. The implementation of the proposed approach can contribute to design environmentally sustainable and climate resilient river basin management strategies.

 

Keywords: MLP-CA, Land use change, Climate change, SWAT, Hydrological modeling, Water availability

How to cite: Tekle, S. L. and Bonaccorso, B.: Modeling the impact of climate and land use changes on future water resources dynamics in central Sicily, Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4462, https://doi.org/10.5194/egusphere-egu24-4462, 2024.

EGU24-5604 | Orals | HS2.1.5

An integrated hydrological modeling approach to assess the natural groundwater recharge trends in a Mediterranean coastal aquifer 

Anis Chekirbane, Khaoula Khemiri, Constantinos Panagiotou, and Catalin Stefan

Integrating physical models with socio-economic considerations is essential to sufficiently analyze complex hydrological systems and design effective strategies for groundwater management. This integrated approach offers an effective means of detecting links between aquifer properties and groundwater processes. This study aims to assess the impact of human activities and climate changes on groundwater resources. In particular, the final goal is to quantify the spatial distribution of natural groundwater recharge, which is needed to assess the impact of anthropogenic factors on sustainable groundwater management in the Chiba watershed, NE of Tunisia as an example of a stressed hydrosystem.

The proposed methodology is based on the estimation of natural groundwater recharge through hydrological modeling with the use of the SWAT model while considering land use/land cover changes occurring within the study area, coupled with the DPSIR (Drivers-Pressures-States-Impacts-Responses) socio-economic approach for time period 1985-2021. The surveys were constructed and processed based on the probability of occurrence for the degree of satisfaction with arguments related to the DPSIR parameter within the category of the 5-point Likert scale (ranging from level 1 - very low to level 5 - very high), including mean, standard deviation, and the consensus (CnS).
Chiba watershed was selected as a case study since its climate is representative of the Tunisian semi-arid context, and due to the high vulnerability of the existing groundwater systems with respect to human activities.

The hydrological simulations suggest a gradual decrease of 33% in the aquifer's natural recharge over the entire time period. The long-term average value of the annual recharge rate per sub-basin does not exceed 3 mm/year, keeping groundwater recharge levels in the basin relatively low. This observation is mainly attributed to climate change with CnS of 0.6 and over-exploitation of the water sources for irrigation purposes (CnS = 0.62), leading to aquifer depletion and degradation of groundwater-dependent ecosystems (CnS = 0.73). These results suggest that different management practices, such as more conservative water use (CnS = 0.6), long-term monitoring and Managed Aquifer Recharge (MAR) with wastewater (CnS = 0.76), can help rural residents to diversify their economies while preserving these water resources. However, although attempts of MAR have been undertaken, they remain insufficient to counter the pressure on the coastal aquifer, underlining the importance of preserving the fragile semi-arid landscape.

The proposed approach is applicable to other regions having similar climatic and socio-economic conditions. It also demonstrates that pure modeling solutions need to be coupled to the socio-economic approaches to be able to constitute a solid asset for sustainable water resources management of stressed hydro-systems.

 

Acknowledgments

This work is funded by National Funding Agencies from Germany,  Cyprus, Portugal, Spain, and Tunisia under the Partnership for Research and Innovation in the Mediterranean Area (PRIMA) and supported under Horizon 2020 by the European Union’s Framework for Research and Innovation.

How to cite: Chekirbane, A., Khemiri, K., Panagiotou, C., and Stefan, C.: An integrated hydrological modeling approach to assess the natural groundwater recharge trends in a Mediterranean coastal aquifer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5604, https://doi.org/10.5194/egusphere-egu24-5604, 2024.

EGU24-6984 | ECS | Posters on site | HS2.1.5

Westerly aridity in the western Tarim Basin driven by global cooling since the mid-Pleistocene transition 

Hongye Liu, Rui Zhang, Gaowen Dai, and Yansheng Gu

To explore the relationship between the global change, westerlies, and central Asian aridity, we report ~1.1 Ma local sedimentary environment changes according to high-resolution gamma ray (GR) from downhole logging, Grain size, magnetic susceptibility (MS), rubidium/strontium (Rb/Sr) ratios and total organic carbon (TOC) of an 800-m core (KT11) from the Kashgar region in the western Tarim Basin, arid zone of China. Four dominant sedimentation types, including lacustrine facies, delta facies, fluvial facies, and aeolian dunes, were identified through lithology and grain size frequency curves. The 1.1 Ma sedimentary successions experienced delta deposits with fluvial and aeolian deposits and lacustrines (1.1-0.6 Ma), alternating fluvial and aeolian facies with the occurrence of deltas and lacustrines (0.6-0.15 Ma), and aeolian facies interbedded with deltas and fluvial facies (0.15 Ma-present). Spectral analyses of the GR, MS, and Rb/Sr data reveal cycles with ~70 m, ~30 m and ~14 m wavelengths. These cycles represent ~100-kyr short-eccentricity, ~40-kyr obliquity and ~20-kyr precession frequencies, respectively and mainly are driven by orbitally forced climate change.

Stepwise drying sedimentary conditions and enhanced desertification indicated by increasing Rb/Sr ratios and proportion of aeolian sands, and decreasing TOC since the past 1.1 Ma, implied intensified westerlies, likely resulted from ice volume expansion and ongoing global cooling according to geological record comparison and simulations during the Last Glacial Maximum compared to preindustrial conditions, which may have controlled the expansion of the permanent deserts in inland Asia. These persistent drying trends and intensified westerly circulation in arid regions during glacial periods after the mid-Pleistocene Transition indicated by larger amplitudes of aeolian sand proportion than prior to 0.6 Ma are similar to those in the interior monsoonal Asia, where the larger-amplitude of median grain size indicated enhanced East Asian Winter monsoon intensity and drier glacials.

How to cite: Liu, H., Zhang, R., Dai, G., and Gu, Y.: Westerly aridity in the western Tarim Basin driven by global cooling since the mid-Pleistocene transition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6984, https://doi.org/10.5194/egusphere-egu24-6984, 2024.

EGU24-7068 | ECS | Orals | HS2.1.5

Exploring Drought Patterns in the Headwaters of the Tarim River Basin through an Integrated Surface-Groundwater Drought Index 

Xiaohan Yu, Xiankui Zeng, Dongwei Gui, Dong Wang, and Jichun Wu

The Tarim River Basin, China's largest inland river, has been grappling with persistent drought challenges. Over 90% of its water resources originate from the headwaters, heavily relying on groundwater. Existing drought indices often compartmentalize considerations of surface water and groundwater variables. Consequently, there is a necessity for a comprehensive drought index that accounts for the interplay between surface water and groundwater. This study employs the Copula function to formulate the Standardized Precipitation Evapotranspiration Groundwater Index (SPEGI), incorporating surface water (precipitation minus evaporation) and groundwater (changes in total water storage observed by GRACE satellite minus changes in output from the VIC model). SPEGI is computed using a moving average approach across various time scales (1, 3, 6, 12 months) and is juxtaposed with traditional indices such as Standardized Precipitation Evapotranspiration Index (SPEI), Standardized Soil Moisture Index (SSMI), and Standardized Groundwater Index (SGI). The findings underscore that SPEGI, grounded in the integrated consideration of surface and groundwater variables, provides a more comprehensive depiction of drought conditions in the study area. In contrast to traditional indices, SPEGI not only accounts for short-term precipitation and evaporation changes but also effectively reveals the characteristics of groundwater fluctuations. Additionally, by comparing SPEGI with NDVI data, the study delves into the desertification process in the region. The research discerns that SPEGI's assessment of drought resilience is more sensitive, manifesting an increasing trend in the desertification process with the enlargement of SPEGI's sliding window. Overall, this research contributes novel methodologies and empirical evidence for fostering sustainable water resource utilization and informing climate change adaptation decisions within the basin.

How to cite: Yu, X., Zeng, X., Gui, D., Wang, D., and Wu, J.: Exploring Drought Patterns in the Headwaters of the Tarim River Basin through an Integrated Surface-Groundwater Drought Index, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7068, https://doi.org/10.5194/egusphere-egu24-7068, 2024.

EGU24-7611 | ECS | Orals | HS2.1.5

Locating unsustainable water supplies for supporting ecological restoration in China's drylands 

Fengyu Fu, Shuai Wang, and Xutong Wu

China, with vast dryland areas, has undertaken extensive ecological restoration (ER) projects since the late 1970s. While ER is a crucial means against desertification and land degradation, it must be implemented in a water-sustainable manner to avoid exacerbating the carbon–water trade-off, especially in water-limited drylands. However, there is still limited research on accurately identifying water unsustainable ER regions in China's drylands. Here, we developed a water supply–demand indicator, namely, the water self-sufficiency (WSS), defined as the ratio of water availability to precipitation. With the use of remote sensing and multisource synthesis datasets combined with trend analysis and time series detection, we conducted a spatially explicit assessment of the water sustainability risk of ER in China's drylands over the period from 1987 to 2015. The results showed that 17.15% (6.36 Mha) of ER areas face a negative shift in the WSS (indicating a risk of unsustainability), mainly in Inner Mongolia, Shanxi, and Xinjiang provinces, driven by evapotranspiration. Moreover, 29.34% (10.9 Mha) of the total ER areas, whose area is roughly double that of water unsustainable ER areas, exhibit a potential water shortage with a significant WSS decline (-0.014 yr-1), concentrated in Inner Mongolia, Shaanxi, and Gansu provinces. The reliability of our findings was demonstrated through previous studies at the local scale and an analysis of soil moisture changes. Our findings offer precise identification of water unsustainable ER regions at the grid scale, providing more specific spatial guidance for ER implementation and adaptation in China's drylands.

How to cite: Fu, F., Wang, S., and Wu, X.: Locating unsustainable water supplies for supporting ecological restoration in China's drylands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7611, https://doi.org/10.5194/egusphere-egu24-7611, 2024.

EGU24-8825 | ECS | Orals | HS2.1.5

Assessing stream water scarcity and groundwater roles under global change in a Mediterranean watershed: the Onyar River basin (NE Catalonia, Spain) 

Paula Gabriela Cordoba Ariza, Ramon J. Batalla, Sergi Sabater, and Josep Mas-Pla

Mediterranean basins face significant water scarcity which requires examining long-term data to evaluate their trends in water availability and quality and assess management options. In this presentation, we explore the historical streamflow changes, the influencing climatic —streamflow, precipitation, temperature, and evapotranspiration (PET and AET)— and land-use factors, and the evolution of surface water quality in the Onyar River (Inner Catalan basins, NE Spain; 295 km2) during the last decades (1960-2020).

Results highlight a consistent decline in streamflow, most pronounced over the last two decades, accompanied by an increase in PET, and a probable decrease in groundwater recharge. These changes co-occurred with higher concentrations of river water ammonium and nitrate. We attribute these patterns to changes in land use such as afforestation and intensive fertilization, as well as increased groundwater withdrawal, particularly during irrigation seasons. Additional factors include growing urban water demand and the discharges of treated wastewater back into the river system. Evaluation of the relationship between groundwater and surface water using end-member mixing analysis of hydrochemical data points out an interesting scale-dependence behaviour: groundwater baseflow from alluvial formations was relevant in the smallest subbasins, whereas regional groundwater flow involving deeper aquifers could significantly contribute to stream discharge in the lowest zones of the basin. Since water balance alteration in the future climate scenarios will reduce the contribution of the headwater flow as well as groundwater storage and baseflow generation, reclaimed wastewater shows up as a relevant source to maintain stream runoff, yet its quality is low and might not be properly diluted by rainfall originated runoff.

These observations provide a comprehensive overview of the declining water quantity and quality in the Onyar River network, attributing these trends to an interplay of climatic and anthropogenic factors. They urge for integrated water resources management strategies to mitigate the implications of these environmental changes, such as protecting baseflow generating areas as well as controlling reclaimed wastewater quality.

Funding: G. Córdoba-Ariza acknowledges funding from Secretariat of Universities and Research from Generalitat de Catalunya and European Social Fund for her FI fellowship (2022 FI_B1 00105). 

How to cite: Cordoba Ariza, P. G., Batalla, R. J., Sabater, S., and Mas-Pla, J.: Assessing stream water scarcity and groundwater roles under global change in a Mediterranean watershed: the Onyar River basin (NE Catalonia, Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8825, https://doi.org/10.5194/egusphere-egu24-8825, 2024.

Intermittent rivers and ephemeral streams represent half of the global river network and span all climates. The intermittent rivers and ephemeral streams is a short-hand term for all flowing water that ceases to flow or that dries up completely at some point in time and/or space They are more frequent in arid and semi-arid areas but are also present in temperate, tropical humid, boreal, and alpine areas, where they are mainly located in headwaters. Their abundance is increasing due to climate change and water withdrawals for human activities.

The objective of this study is to represent the spatio-temporal dynamics of flow intermittence at the reach level in river of the seven sub-catchments of the Maures massif (between 1.5 km² and 70 km²).

First, two hydrological continuous models of varying complexities are performed: GR6J (lumped and conceptual), and SMASH (spatially distributed and conceptual) in terms of temporal calibration/validation, by dissociating dry and wet years, to asses the models’ability to simulate observed drying event over time. The metrics are based on daily flow records observed in the 7 catchments since 1968 to 2023.

In the second part, a regionalization method is tested on the spatially distributed model (SMASH). The HDA-PR approach (Hybrid Data Assimilation and Parameter Regionalization) incorporating learnable regionalization mappings, based on multivariate regressions is used. This approach consist to search for a transfer function that quantitatively relates physical descriptors to conceptual model parameters from multi-gauge discharge in order to produce a regional model.

Flow condition observed from multiple data sources (daily flow time series from gauging stations, phototrap installed along the river network taking daily pictures from 2021-04-01 to 2023-31-12, daily conductivity measurements series from 2021-01-01) are used to validate the ability of the regional model to simulate flow intermittence (prediction of dry events) at river section level.

The distributed modelling approach, with a high-resolution conceptual hydrological modeling at 0.250 km² and coupled with Hybrid Data Assimilation and Parameter Regionalization descriptors shows results highlight the effectiveness of HDA-PR surpassing the performance of a uniform regionalization method with lumped model parameters. However, the results on smallest catchments area are lowest.

The study shows the interest of using daily photos which are a good indication of the hydrogical state of the streams to obtain intermittence data and increasing the spatial coverage of observations in order to validate regional model.

How to cite: Folton, N., De Fournas, T., Colléoni, F., and Tolsa, M.: Modelling the intermittence of watercourses in the small French Mediterranean catchments of the Maures massif (Réal Collobrier ) with the SMASH platform (Spatially distributed Modelling and ASsimilation for Hydrology) , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9681, https://doi.org/10.5194/egusphere-egu24-9681, 2024.

EGU24-9899 | Orals | HS2.1.5

60,000 years of hydrologic connectivity on the Australian dryland margins: the case of the Willandra Lakes World Heritage Area 

Kathryn Fitzsimmons, Markus Fischer, Colin Murray-Wallace, Edward Rhodes, Tobias Lauer, Maike Nowatzki, Kanchan Mishra, and Nicola Stern

Australia is big, flat, old and arid: it is the driest inhabited continent on Earth. The catastrophic flooding of recent years has demonstrated not only the potential for extreme conditions at both ends of the hydroclimatic scale, but also how little we understand of the interplay between climatic, hydrological, and surface-process mechanisms affecting this part of the world. We know still less about long-term hydrological dynamics, particularly for the dry inland where water resources are scarce and land surfaces are susceptible to erosion, requiring careful management.

Records of past hydrological variability can help inform us about changing hydroclimate states and their impact on the land surface. The Willandra lakes system, located on the desert margins of southeastern Australia, is one of the few dryland areas which preserves long-term sedimentary records of hydrologic change. The headwaters of these lakes lie in the temperate highlands hundreds of kilometres to the east; as a result, lake filling and drying reflects the interaction between rainfall in the watershed and hydrologic connectivity across the catchment and between the lakes. Environmental change in the Willandra is recorded in the sediments of the lake shoreline dunes, preserved as semi-continuous deposition of different lake facies over 60,000 years.

Here we investigate long-term hydrologic connectivity across the Willandra lakes and their catchment. Our approach uses a novel integration of lake-level reconstruction based on lunette sedimentology, stratigraphy and luminescence geochronology, with hydrologic and palaeoclimatic modelling of key event time slices over the last 60 ky. We characterize the land-surface response to various hydroclimate states, so improving our understanding of dryland atmosphere-hydrosphere interactions.

How to cite: Fitzsimmons, K., Fischer, M., Murray-Wallace, C., Rhodes, E., Lauer, T., Nowatzki, M., Mishra, K., and Stern, N.: 60,000 years of hydrologic connectivity on the Australian dryland margins: the case of the Willandra Lakes World Heritage Area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9899, https://doi.org/10.5194/egusphere-egu24-9899, 2024.

EGU24-10078 | ECS | Orals | HS2.1.5 | Highlight

Wheat irrigation in Marrakech conditions: A Simulation Study using SALTMED 

El Houcine El Moussaoui, Aicha Moumni, Said Khabba, and Abderrahman Lahrouni

In Morocco, agriculture accounts for 80-90% of water resources. Available data show that the performance of current irrigation systems remains low to medium, with water losses at plots ranging from 30 to 40%, divided between percolation and evaporation. Gravity irrigation is almost total in the study area, resulting in significant percolation losses. In principle, this percolation contributes mainly to the recharge of the aquifer.

The purpose of this study was to evaluate, by simulation, the impact of irrigation techniques on wheat yield and growth using the generic agro-environmental model SALTMED under the climatic and soil conditions of zone R3, which is an irrigation area located in the region of Sidi Rahal about 40 km east of the city of Marrakech in the plain of Haouz. We started the study by calibrating the model based on two parameters: photosynthetic efficiency and harvest index. After calibration, we compared different irrigation techniques implemented in the model (surface irrigation, sprinkler irrigation, and drip irrigation). Simulation results showed that the drip irrigation technique is the most economical, exhibiting the lowest losses attributed to percolation and soil evaporation. Notably, percolation, a significant contributor to groundwater recharge, measured approximately 255.5 mm/season. In addition, the irrigation practice in the study area appears to be overestimated during the observed season and could be reduced by half, according to SALTMED. When the irrigation dose is halved, the simulated yield (grain and total biomass) decreases by only 1.33%.

How to cite: El Moussaoui, E. H., Moumni, A., Khabba, S., and Lahrouni, A.: Wheat irrigation in Marrakech conditions: A Simulation Study using SALTMED, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10078, https://doi.org/10.5194/egusphere-egu24-10078, 2024.

EGU24-10387 | ECS | Orals | HS2.1.5

Nitrogen modeling and performance of Multi-Soil-Layering (MSL)bioreactor treating domestic wastewater in rural community 

Sofyan Sbahi, Naaila Ouazzani, Abdessamed Hejjaj, Abderrahman Lahrouni, and Laila Mandi

The multi-soil-layering (MSL) bioreactor has been considered in the latest research as an
innovative bioreactor for reducing the level of pollutants in wastewater. The efficiency of the
MSL bioreactor towards nitrogen pollution is due to the mineralization of organic nitrogen in
aerobic layers to ammonia, and reactivity of ammonia nitrogen with soil and gravel by its
adsorption into soil layers followed by nitrification and denitrification processes when the
alternating phases of oxygenated/anoxic conditions occurs in the filter. In this study, we have
examined the performance of the MSL bioreactor at different hydraulic loading rates (HLRs)
and predicted the removal rate of nitrogen. To improve the prediction accuracy of the models,
the feature selection technique was performed before conducting the Neural Network model.
The results showed a significant removal (p <0.05) efficiency for five-day biochemical
oxygen demand (BOD 5,  86%), ammonium (NH 4 + , 83%), nitrates (NO 3 − , 81%), total kjeldahl
nitrogen (TKN, 84%), total nitrogen (TN, 84%), orthophosphates (PO 4 3− , 91%), and total
coliforms (TC, 1.62 Log units). However, no significant change was observed in the nitrite
(NO 2 − ) concentration as it is an intermediate nitrogen form. The MSL treatment efficiency
demonstrated a good capacity even when HLR increased from 250 to 4000 L/m 2 /day,
respectively (e.g., between 64% and 86% for BOD 5 ). The HLR was selected as the most
significant (p < 0.05) input variable that contribute to predict the removal rates of nitrogen.
The developed models predict accurately the output variables (R 2  > 0.93) and could help to
investigate the MSL behavior.

How to cite: Sbahi, S., Ouazzani, N., Hejjaj, A., Lahrouni, A., and Mandi, L.: Nitrogen modeling and performance of Multi-Soil-Layering (MSL)bioreactor treating domestic wastewater in rural community, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10387, https://doi.org/10.5194/egusphere-egu24-10387, 2024.

EGU24-11799 | ECS | Orals | HS2.1.5 | Highlight

Exploring the mechanisms controlling dryland hydroclimate in past 'warmer worlds' 

Monika Markowska, Hubert B. Vonhof, Huw S. Groucutt, Michael D. Petraglia, Denis Scholz, Michael Weber, Axel Gerdes, Richard Albert, Julian Schroeder, Yves S. Krüger, Anna Nele Meckler, Jens Fiebig, Matthew Stewart, Nicole Boivin, Samuel L. Nicholson, Paul S. Breeze, Nicholas Drake, Julia C. Tindall, Alan M. Haywood, and Gerald Haug

Drylands cover almost half of Earth’s land surfaces, supporting ~30% of the world’s population. The International Panel on Climate Change predicts increasing aridification and expansion of drylands over the course of this century. As we approach new climate states without societal precedent, Earth’s geological past may offer the best tool to understand hydroclimate change under previously, allowing us to elucidate responses to external forcing. Paleo-records from previously warm and high-CO2 periods in Earth’s past, such as the mid-Pliocene (~3 Ma), point towards higher humidity in many dryland regions. 

Here, we examine desert speleothems from the hyper-arid desert in central Arabia, part of the largest near-continuous chain of drylands in the world, stretching from north-western Africa to the northern China, to elucidate substantial and recurrent humid phases over the past 8 million years. Independent quantitative paleo-thermometers suggest that mean annual air temperatures in central Arabia were approximately between 1 to 5 °C warmer than today. The analyses of the isotopic composition (δ18O and δ2H) of speleothem fluid inclusion waters, representing ‘fossil rainwater’, reveal an aridification trend in Arabia from the Late Miocene to Late Pleistocene during Earth’s transition from a largely ‘ice-free’ northern hemisphere to an ‘ice-age’ world. Together, our data provide evidence for recurrent discrete wetter intervals during past warmer periods, such as the Pliocene. Data-model comparisons allow us to assess the agreement between our paleoclimate data and climate model output using the HadCM3 isotope-enabled model simulations during past ‘warmer worlds’ – namely the mid-Piacenzian warm period (3.264 to 3.025 Ma). To assess the hydroclimate response to external forcing, we examine model output from a series of sensitivity experiments with different orbital configurations allowing us to postulate the mechanisms responsible for the occurrence of humid episodes in the Arabian desert, with potential implications for other dryland regions at similar latitudes. Together, our approach unveils the long-term controls on Arabian hydroclimate and may provide crucial insights into the future variability.

How to cite: Markowska, M., Vonhof, H. B., Groucutt, H. S., Petraglia, M. D., Scholz, D., Weber, M., Gerdes, A., Albert, R., Schroeder, J., Krüger, Y. S., Meckler, A. N., Fiebig, J., Stewart, M., Boivin, N., Nicholson, S. L., Breeze, P. S., Drake, N., Tindall, J. C., Haywood, A. M., and Haug, G.: Exploring the mechanisms controlling dryland hydroclimate in past 'warmer worlds', EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11799, https://doi.org/10.5194/egusphere-egu24-11799, 2024.

EGU24-12194 | ECS | Orals | HS2.1.5

High resolution surface soil moisture microwave products: intercomparison and evaluation over Spain 

Nadia Ouaadi, Lionel Jarlan, Michel Le Page, Mehrez Zribi, Giovani Paolini, Bouchra Ait Hssaine, Maria Jose Escorihuela, Pascal Fanise, Olivier Merlin, Nicolas Baghdadi, and Aaron Boone

Surface soil moisture (SSM) products at high spatial resolution are increasingly available, either from the disaggregation of coarse-resolution products such as SMAP and SMOS, or from high-resolution radar data such as Sentinel-1. In contrast to coarse resolution products, there is a lack of intercomparison studies of high spatial resolution products, which are more relevant for applications requiring the plot scale. In this context, the objective of this work is the evaluation and intercomparison of three high spatial resolution SSM products on a large database of in situ SSM measurements collected on two different sites in the Urgell region (Catalonia, Spain) in 2021. The satellite SSM products are: i) SSMTheia product at the plot scale derived from a synergy of Sentinel-1 and Sentinel-2 using a machine learning algorithm; ii) SSMρ product at 14 m resolution derived from the Sentinel-1 backscattering coefficient and interferometric coherence using a brute-force algorithm; and iii) SSMSMAP20m product at 20 m resolution obtained from the disaggregation of SMAP using Sentinel-3 and Sentinel-2 data. Evaluation of the three products over the entire database showed that SSMTheia and SSMρ yielded a better estimate than SSMSMAP20m, and SSMρ is slightly better than SSMTheia. In particular, the correlation coefficient is higher than 0.4 for 72%, 40% and 27% of the fields using SSMρ, SSMTheia and SSMSMAP20m, respectively. The lower performance of SSMTheia compared to SSMρ is due to the saturation of SSMTheia at 0.3 m3/m3. The time series analysis shows that SSMSMAP20m is able to detect rainfall events occurring at large scale while irrigation at the plot scale are not caught. This is explained by the use of Sentinel-2 reflectances, which are not linked to surface water status, for the disaggregation of Sentinel-3 land surface temperature. The approach can therefore be improved by using high spatial and temporal resolution thermal data in the perspective of new missions such as TRISHNA and LSTM. Finally, the results show that although reasonable estimates are obtained for annual crops using SSMTheia and SSMρ, poor performance is observed for trees, suggesting the need for better representation of canopy components for tree crops in SSM inversion approaches.

How to cite: Ouaadi, N., Jarlan, L., Le Page, M., Zribi, M., Paolini, G., Ait Hssaine, B., Escorihuela, M. J., Fanise, P., Merlin, O., Baghdadi, N., and Boone, A.: High resolution surface soil moisture microwave products: intercomparison and evaluation over Spain, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12194, https://doi.org/10.5194/egusphere-egu24-12194, 2024.

    The Yellow River (YR) is 5464 km long and the cradle of Chinese civilization. It is also well known for being the most sediment-laden river and having the largest vertical drop over its course. Although the YR accounts for only 3% of China’s water resources, it irrigates 13% of its cropland. Exceptional historical documents have recorded frequent occurrence of YR flooding events that resulted in huge losses of lives and property.
    The earliest observational record of YR runoff, beginning in 1919 at the Shanxian gauge station, is too short to study centennial-scale variability. Since the start of the Anthropocene in the 1960s, frequent human activities have resulted in large deviation between observed streamflow. The reconstruction of annual historical natural runoff of the YR is necessary to quantify the amount of anthropogenic YR water consumption in recent decades. Tree rings, with the merits of accurate dating and annual resolution, have been widely used in runoff reconstruction worldwide. In this study, 31 moisture-sensitive tree-ring width chronologies, including 860 trees and 1707 cores, collected within the upper-middle YR basins were used to reconstruct natural runoff for the middle YR course over the period 1492–2013 CE.
    The reconstruction provides a record of natural YR runoff variability prior to large-scale human interference. Most of the extreme high/low runoff events in the reconstruction can be verified with historical documents. The lowest YR flow since 1492 CE occurred during 1926–1932 CE and the YR runoff in 1781 is the highest. These two extreme values could be regarded as a benchmark for future judicious planning of water allocation. Since the late 1980s, observed YR runoff has fallen out of its natural range of variability, and there was even no water flow for several months each year in the lower YR course during 1995 to 1998. Especially concerning was that the inherent 11-year and 24-year cycles of YR became disordered following the severe drought event in late 1920s, and eventually disappeared after the 1960s.
    Year-to-year variability in YR water consumption by human activities (WCHA) was quantified, which showed good association between crop yields and acreage in Ningxia and Inner Mongolia irrigation regions. Meanwhile, WCHA was strongly negatively correlated with sediment load at Toudaoguai and Shanxian stations, which led to a 58% reduction of sediment load in Toudaoguai (upper reach) and 29% in Shanxian (middle reach). 
    If human activities continue to intensify, future YR runoff will be further reduced, and this will negatively impact agriculture, human lives, and socioeconomic development in the middle and lower basins of the YR. To reduce the risk of recurring cutoff of streamflow in the YR lower basin, water should be allocated judiciously. Our reconstructed YR natural runoff series are important for future YR water resource management. In addition, our results also provide an important model of how to distinguish and quantify anthropogenic influence from natural variability in global change studies.

How to cite: Liu, Y.: Changes and attribution of natural runoff in the Yellow River over the past 500 years, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13979, https://doi.org/10.5194/egusphere-egu24-13979, 2024.

EGU24-14057 | ECS | Posters on site | HS2.1.5

Turbulent fluxes at kilometer scale determined by optical-microwave scintillometry in a heterogeneous oasis cropland of the Heihe River Basin 

Feinan Xu, Weizhen Wang, Chunlin Huang, Jiaojiao Feng, and Jiemin Wang

Observations of kilometer-scale turbulent fluxes of sensible (H) and latent heat (LE) are required for the validation of flux estimate algorithms from satellite remote-sensing data and the development of parameterization schemes in the hydro-meteorological models. Since 2019, two sets of Optical and Microwave scintillometer (OMS) systems have been operated in the Heihe River Basin of northwestern China, one on an alpine grassland of upper reaches, another on an oasis cropland of middle reaches, to measure both the areal H and LE. Combined with the observations of eddy-covariance (EC) and meteorological tower systems in both sites, an improved procedure for OMS data processing is proposed. The newly proposed procedure especially improves the preprocessing of raw scintillation data, properly uses the current probably better Lüdi et al. (2005) method in deriving meteorological structure parameters, and chooses the coefficients of similarity functions by Kooijmans and Hartogensis (2016) in calculating fluxes. Evaluated with the results of rather homogeneous grassland, the area-averaged H and LE over the heterogeneous oasis are then determined. Estimates of H and LE agree reasonably well with those obtained from EC in most cases. However, the most interesting is that LE over the oasis during the early crop growing stages is clearly larger than that of EC; while both agree well during the longer crop grown periods. Footprint analysis shows that, compared with EC, the OMS has clearly larger source area that contains a slight area of orchard and shelterbelts distributed near the light path, leading to larger LE during the early stages of crop growth. The area-averaged evapotranspiration (ET) over the oasis is then analyzed more acceptably, which varies from 3 to 5 mm day-1 depending on meteorological conditions during the 39 days of the crop growing period. These results are used to validate the Penman-Menteith-Leuning Version 2 (PML-V2) scheme.

How to cite: Xu, F., Wang, W., Huang, C., Feng, J., and Wang, J.: Turbulent fluxes at kilometer scale determined by optical-microwave scintillometry in a heterogeneous oasis cropland of the Heihe River Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14057, https://doi.org/10.5194/egusphere-egu24-14057, 2024.

    Recurrent droughts in history, especially climatic aridity since the mid-20th century have aroused great social anxiety about the water resources in the Chinese Loess Plateau (CLP). Given lacking of extended instrumental-like records, new precipitation reconstructions in the CLP are badly needed for objectively evaluating the current precipitation situation, understanding the spatial-temporal differences, and serving for predicting the future. Here we present a tree-ring-based 248-year regional precipitation reconstruction (P8–7) in the Heichashan Mountain, which can significantly represent the past dry-wet variations in the eastern CLP (ECLP). P8–7 explains 48.72% of the instrumental record, reveals a wetting trend since the early 2000s and attains the second wettest period over the past 248 years in 2014–2020 AD. The 1920s/2010s is recorded as the driest/wettest decade. 1910–1932 AD ranks as the driest period over the past centuries. The 19th century is comparatively wet while the 20th century is dry. Precipitation in the ECLP and western CLP (WCLP) has changed synchronously over most time of the past two centuries. However, regional difference exists in the 1890s–1920s when a gradually drying occurred in the ECLP, while not evident in the WCLP, although the 1920s megadrought occurred in the CLP. Moreover, the 20th-century drying in the ECLP begins in the 1950s, later than the WCLP. It reveals that P8–7 variability is primarily influenced by the Asian Summer Monsoon and related large-scale circulations. The seismic phase shift of the contemporaneous Northern Hemispheric temperature may also be responsible for the 1920s megadrought.

How to cite: Cai, Q. and Liu, Y.: Hydroclimatic characteristics on the Chinese Loess Plateau over the past 250 years inferred from tree rings, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14189, https://doi.org/10.5194/egusphere-egu24-14189, 2024.

EGU24-16291 | ECS | Orals | HS2.1.5

A New Perspective on Agricultural Drought Periods: A Mediterranean Semi-Arid Context 

Kaoutar Oukaddour, Michel Le Page, and Younes Fakir

Extreme weather events have an increasing repercussions on ecosystems in recent years. By comprehending how vegetation responds to climatic extremes, their effects may be mitigated. In a semi-arid Mediterranean region, this study examines the temporal connections of the main triggers of agricultural drought, low precipitation, vegetation growth, thermal stress, and soil water deficit. Drought periods and their characteristics were determined using a revised run theory approach. The Pearson correlations across various spatial scales revealed a moderate to low degree of concordance among the drought indices. This discrepancy can be attributed to the geographical heterogeneity and climatic variations observed among the agrosystems within the basin.

The cross-correlation analysis demonstrated the cascading impacts resulting from reduced precipitation. During drought events, the significant connection between precipitation deficits and vegetation persists for at least one month across most index pairs. This suggests that agricultural drought occurrences can be temporally linked through the selected drought indices. The study unveiled short-, mid-, and long-term effects of precipitation deficiencies on soil moisture, vegetation, and temperature. As anticipated, variables like soil moisture and surface temperature, being more instantaneous, exhibited no lag in response to precipitation. Notably, vegetation anomalies at the monthly time step displayed a two-month lag, indicating a preceding impact of vegetation on precipitation.

Employing the run theory to identify drought events and stages with different thresholds revealed substantial variability in drought characteristics namely the duration, the magnitude magnitude, and the intensity. This variability was notably influenced by the selection of both normality and drought thresholds.

How to cite: Oukaddour, K., Le Page, M., and Fakir, Y.: A New Perspective on Agricultural Drought Periods: A Mediterranean Semi-Arid Context, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16291, https://doi.org/10.5194/egusphere-egu24-16291, 2024.

EGU24-17049 | ECS | Orals | HS2.1.5

Potential of the Photochemical Reflectance Index in Understanding Photoinhibition and Improving Irrigation Water Efficiency in the Mediterranean Zone 

Zoubair Rafi, Saïd Khabba, Valérie Le Dantec, Patrick Mordelet, Salah Er-Raki, Abdelghani Chehbouni, and Olivier Merlin

Morocco's semi-arid region faces challenges due to limited water resources, necessitating efficient irrigation practices for sustainable agriculture. Precision agriculture, coupled with advanced technologies like the Photochemical Reflectance Index (PRI), holds great potential for optimizing irrigation water usage and enhancing crop productivity in this environment. This abstract provides a comprehensive overview of integrating precision agriculture techniques, PRI, and Net Radiation (Rn) to improve irrigation water efficiency and maximize crop productivity in Morocco's semi-arid zone. The study presents and analyzes an experimental investigation of the PRI signal in a winter wheat field throughout an agricultural season to comprehend its dependence on agro-environmental parameters such as global radiation (Rg) and Rn. Rn directly impacts the energy absorbed by plants, a crucial factor for photosynthesis. Elevated Rn levels generally increase energy availability for photosynthetic processes, resulting in higher chlorophyll fluorescence and PRI values. However, excessive Rn can lead to photoinhibition, damaging the photosynthetic apparatus and reducing photosynthetic efficiency. Understanding the interplay between net radiation, PRI, and photoinhibition is crucial for optimizing agricultural practices. Monitoring and managing net radiation levels allow farmers to ensure that the energy available for photosynthesis remains within the optimal range, minimizing the risk of photoinhibition while maximizing crop productivity. Additionally, the daily water stress index based on PRI (PRIj), developed independently of structural effects related to leaf area index (LAI), showed a coefficient of determination (R2) of 0.74 between PRIj and Rn. This reflects the extent of excessive light stress experienced by the wheat field throughout the experiment. In conclusion, the integration of precision agriculture techniques, specifically PRI, offers a promising approach to enhance irrigation water efficiency in Morocco's semi-arid zone. By employing this innovative tool, farmers can optimize water usage, reduce environmental impacts, and ensure the long-term sustainability of agriculture.

How to cite: Rafi, Z., Khabba, S., Le Dantec, V., Mordelet, P., Er-Raki, S., Chehbouni, A., and Merlin, O.: Potential of the Photochemical Reflectance Index in Understanding Photoinhibition and Improving Irrigation Water Efficiency in the Mediterranean Zone, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17049, https://doi.org/10.5194/egusphere-egu24-17049, 2024.

EGU24-17321 | ECS | Orals | HS2.1.5

Quantifying Olive Tree Evapotranspiration in Semi-Arid Regions through Remote Sensing-Based SEBAL Model: Validation with Optical-Microwave Scintillometer 

Hamza Barguache, Jamal Ezzahar, Mohamed Hakim Kharrou, Said Khabba, Jamal Elfarkh, Abderrahim Laalyej, Salah Er-Raki, and Abdelghani Chehbouni

Accurately assessing sensible (H) and latent (LE) heat fluxes, along with evapotranspiration, is crucial for comprehending the energy balance at the biosphere-atmosphere interface and enhancing agricultural water management. Although the eddy covariance (EC) method is commonly employed for these measurements, it has limitations in providing spatial representativeness beyond a few hundred meters. Addressing this challenge, optical-microwave scintillometers (OMS) have emerged as a valuable tool, directly measuring kilometer-scale H and LE fluxes. These measurements serve to validate satellite remote sensing products and model simulations, such as the Surface Energy Balance Algorithm for Land (SEBAL). In this study, OMS measurements were utilized to assess the fluxes simulated by the SEBAL model at the Agdal olive orchard near Marrakech city. The results revealed that SEBAL's estimated sensible heat fluxes were 3% higher than those measured by OMS, while latent heat fluxes were approximately 15% lower. Based on these findings, we infer that OMS can effectively validate satellite-driven surface energy balance models, thereby supporting agricultural water management.

How to cite: Barguache, H., Ezzahar, J., Kharrou, M. H., Khabba, S., Elfarkh, J., Laalyej, A., Er-Raki, S., and Chehbouni, A.: Quantifying Olive Tree Evapotranspiration in Semi-Arid Regions through Remote Sensing-Based SEBAL Model: Validation with Optical-Microwave Scintillometer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17321, https://doi.org/10.5194/egusphere-egu24-17321, 2024.

EGU24-17560 | ECS | Posters virtual | HS2.1.5

Estimation of Irrigation Water Demand in the Southern Mediterranean Region through Explicit Integration of Irrigation Processes in a Land Surface Model: A Case Study of the Tensift Catchment (Morocco). 

Ahmed Moucha, Lionel Jarlan, Pére Quintana-Segui, Anais Barella-Ortiz, Michel Le Page, Simon Munier, Adnane Chakir, Aaron Boone, Fathallah Sghrer, Jean-christophe Calvet, and Lahoucine Hanich

The utilization of water by various socio-economic sectors has made this resource highly sought after, especially in arid to semi-arid zones where water is already scarce and limited. In this context, effective management of this resource proves to be crucial. Our study aims to: evaluate the performance of the new irrigation module in ISBA, quantify the water balance, and assess the impact of climate change and anthropogenic factors on this resource by the horizon of 2041-2060, utilizing high-resolution futuristic forcings from the study (Moucha et al., 2021). To assess the ISBA model with its new irrigation module, we initially compared observed and predicted fluxes with and without activation of the irrigation module. Subsequently, we compared irrigation water inputs at the ORMVAH-defined irrigated perimeters within the Tensift basin. The results of this evaluation showed that the predictions of latent heat flux (LE) considering all available stations in the basin shifted from -60 W/m² for the model without irrigation to -15 W/m². This indicates that the integration of the new irrigation system into ISBA significantly improves the predictions of latent heat flux (LE) over the period 2004-2014 compared to the regular model. Considering the irrigated perimeters, the study results demonstrated that the model with the integration of the irrigation module was capable of replicating the overall magnitude and seasonality of water quantities provided by ORMVAH despite a positive bias. Exploration of the water balance at the Tensift basin level revealed the ISBA model's ability, equipped with its irrigation module, to describe complex relationships among precipitation, irrigation, evapotranspiration, and drainage. Finally, the assessment of the impact of climate change and vegetation cover for the period 2041-2060, utilizing high-resolution SAFRAN forcings projected to the same horizon (Moucha et al., 2021), revealed an increase in irrigation water needs. These results are of paramount importance in the context of sustainable water resource management in arid and semi-arid regions.

How to cite: Moucha, A., Jarlan, L., Quintana-Segui, P., Barella-Ortiz, A., Le Page, M., Munier, S., Chakir, A., Boone, A., Sghrer, F., Calvet, J., and Hanich, L.: Estimation of Irrigation Water Demand in the Southern Mediterranean Region through Explicit Integration of Irrigation Processes in a Land Surface Model: A Case Study of the Tensift Catchment (Morocco)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17560, https://doi.org/10.5194/egusphere-egu24-17560, 2024.

EGU24-17649 | ECS | Orals | HS2.1.5

Comprehensive Analysis of Hydrological Dynamics and Uncertainties in the Moroccan High Atlas: A Focus on Seasonal Precipitation, Runoff, and Flood Events 

Myriam Benkirane, Abdelhakim Amazirh, El Houssaine Bouras, Adnane Chakir, and Said Khabba

The Mediterranean regions, particularly the Moroccan High Atlas, is exposed to natural risks associated with the hydrological cycle, notably intense precipitation events that trigger sudden floods. This research delves into the subtleties of hydrological dynamics in the High Atlas watersheds, specifically in the Zat watershed, to comprehend the seasonality of precipitation and runoff and elucidate the origins of floods.

The results reveal a strong correlation between observed and simulated hydrographs, affirming the model's capability to capture complex hydrological processes. Evaluation metrics, particularly the Nash coefficient, demonstrate a robust model performance during the calibration phase, ranging from 61.9% to 90%. This attests to the model's ability to reproduce the dynamic nature of hydrological systems in the Moroccan High Atlas.

It is noteworthy that the study identifies the snowmelt process as a significant factor of uncertainty in runoff flooding parameters. The complexities associated with snowmelt, especially in the context of spring precipitation, emerge as a crucial factor influencing uncertainties in the simulated results. This finding underscores the importance of accurately representing snowmelt dynamics in hydrological simulations for regions prone to natural risks.

Moreover, the integration of Probability Distribution Functions and Monte Carlo simulations, coupled with rigorous evaluation metrics, enhances our understanding of calibration parameter uncertainties and validates the model's performance. The identified influence of snowmelt on runoff flooding parameters provides crucial insights for future model improvements and the development of effective mitigation strategies in regions vulnerable to natural risks. This research contributes to advancing hydrological modeling practices in complex terrain.

 

Keywords: Seasonality, Rainfall-Runoff, Floods, Calibration, Monte Carlo simulation, Parameter Uncertainty, Hydrological Modeling, Snowmelt Dynamics, Natural Risks.

How to cite: Benkirane, M., Amazirh, A., Bouras, E. H., Chakir, A., and Khabba, S.: Comprehensive Analysis of Hydrological Dynamics and Uncertainties in the Moroccan High Atlas: A Focus on Seasonal Precipitation, Runoff, and Flood Events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17649, https://doi.org/10.5194/egusphere-egu24-17649, 2024.

The Mediterranean area is recognized as a hotspot for climate change challenges, with noticeable patterns of rising temperatures and dryness. Olive agroecosystems are particularly affected by the increasing aridity and global climatic changes. Despite being a symbol of the Mediterranean and traditionally grown using rainfed agricultural practices, olive growers have to adapt to cope with higher temperatures, drought, and more frequent severe weather incidents, necessitating their attention and adaptation (Fraga et al., 2020). Moreover, crop production in Morocco heavily relies on irrigation because rainfed cropping has limited productivity (Taheripour et al., 2020). The olive sector is of great importance in Morocco, and there is an urgent need to implement sustainable water management practices. This includes water-saving strategies such as regulated and sustained deficit irrigation (RDI and SDI) to sustain olive production and strengthen the sector's resilience to climate change and water scarcity. These strategies primarily differ in terms of their irrigation timing and the quantity of water applied (Ibba et al., 2023). This study aims to evaluate the effect of two deficit irrigation strategies on productive parameters of the Menara olive cultivar, to serve as a tool for operational irrigation water management and appraise the adaptive responses of this cultivar under conditions of induced drought stress. In pursuit of this aim, an experiment was carried out in an olive orchard over two consecutive years (2021 and 2022), comparing four treatments of regulated deficit irrigation (RDI): T1 (SP 100- NP 70% ETc), T2 (SP 100- NP 60% ETc), T3 (SP 80- NP 70% ETc), T4 (SP 80- NP 60% ETc) and two treatments of sustained deficit irrigation (SDI): T5 (70% ETc) and T6 (60% ETc), with fully irrigated trees T0 (100% ETc). The findings showed that controlled water stress, as applied through regulated deficit irrigation (RDI), did not exert a severe impact on the flowering traits and yield of the Menara olive cultivar. Notably, the RDI strategy, particularly under T4 treatment, allowed for the reduction of supplied water by 20% in sensitive periods (SP) flowering and from the beginning of oil synthesis to harvest and by 40% in the normal period (NP)during pit hardening, respectively, without compromising fruit yield. However, the SDI strategy, characterized by restricted water availability, which reduced total water application under T5 and T6 treatments by 30% and 40% throughout the entire season, led to a decline in the fruit yield by about 50% and resulted in the most significant drop in water productivity, ranging from 19% to 33% compared to the control T0. Furthermore, the findings underscored the adaptability of responses to water stress and elucidated the consequential impact of each irrigation strategy on the performance of Menara olive trees across successive years, particularly the importance of regulated deficit irrigation as a water management strategy and the need to consider its implication on flowering traits and crop yield over successive growing seasons to establish the enduring adaptability of this locally cultivated olive cultivar.

How to cite: Ibba, K., Er-Raki, S., Bouizgaren, A., and Hadria, R.: Sustainable Water Management for Menara Olive Cultivar: Unveiling the Potential of Regulated and Sustained Deficit Irrigation Strategies in Morocco, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17808, https://doi.org/10.5194/egusphere-egu24-17808, 2024.

EGU24-17983 | ECS | Orals | HS2.1.5

Comparison of C-band radar and infrared thermal data for monitoring corn field in semi-arid area. 

Abdelhafid Elallaoui, Pierre-Louis Frison, Saïd Khabba, and Lionel Jarlan

In semi-arid Mediterranean regions, the scarcity and limitations of water resources pose major challenges. These invaluable resources are threatened by various factors such as climate change, population growth, urban expansion, and agricultural intensification. Specifically, agriculture, which consumes approximately 85% of the water in the semi-arid zone of the South Mediterranean region, directly contributes to the depletion of groundwater. To promote rational irrigation management, it becomes imperative to monitor the water status of crops. Remote sensing is a valuable technique allowing for monitoring crop fields in different parts of the electromagnetic spectrum giving complementary information about crop parameters. The main objective of this study is to assess the potential of radar and Infrared Thermal data for monitoring the water status of crops in semi-arid regions. In this context, a radar system was installed in Morocco, in the Chichaoua region, consisting of 6 C-band antennas mounted on a 20-meter tower. These antennas are directed towards a maize field. This system allowed for radar data acquisition in three different polarizations (VV, VH, HH) with a 15-minute time-step over the time period extending from September to December 2021. Additionally, the system is complemented by continuous acquisitions from a Thermal Infrared Radiometer (IRT) at 30-minute intervals. These data are further supplemented by in-situ measurements characterizing crop parameters (state of the cover, soil moisture, evapotranspiration and meteorological variables). The study initially focused on analyzing the diurnal cycle of radar temporal coherence. The results indicated that coherence was highly sensitive to wind-induced movements of scatterers, with minimal coherence when wind speed was highest in the late afternoon. Moreover, coherence was also responsive to vegetation activity, particularly its water content, as the morning coherence drop coincided with the onset of plant activity. Subsequently, the study examined the potential of the relative difference between surface vegetation temperature and air temperature to monitor the water status of crops. The results showed that during a period of imposed water stress, the amplitude of this difference increased. These results open perspectives for monitoring the water status of crops using radar and thermal observations with a high revisit frequency.

How to cite: Elallaoui, A., Frison, P.-L., Khabba, S., and Jarlan, L.: Comparison of C-band radar and infrared thermal data for monitoring corn field in semi-arid area., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17983, https://doi.org/10.5194/egusphere-egu24-17983, 2024.

EGU24-18201 | ECS | Orals | HS2.1.5

Analyzing Tree Degradation in the Haouz Plain through Remote Sensing: Assessing the Impact of Drought and Spatial Extent 

Youness Ablila, Abdelhakim Amazirh, Saïd Khabba, El Houssaine Bouras, Mohamed hakim Kharrou, Salah Er-Raki, and Abdelghani Chehbouni

Trees characterized by persistent foliage, like olive trees, serve as indispensable assets in arid and semi-arid regions, exemplified by the Haouz plain in central Morocco. The decline in water resources for irrigation, attributed to climate change and excessive underground water extraction, has led to significant degradation of tree orchards in recent years. Employing remote sensing data, we conducted a spatial analysis of tree degradation from 2013 to 2022 using the supervised classification method. Subsequently, a drying speed index (DS) was computed based on the Normalized Difference Vegetation Index (NDVI) derived from Landsat-8 data, specifically focusing on the identified trees. This DS was then correlated with the Standardized Precipitation Index (SPIn) to elucidate the connection between tree degradation and drought, as indicated by precipitation deficit. The findings reveal a discernible declining trend in trees, with an average decrease in NDVI by 0.02 between 2019 and 2022 compared to the reference period (2013-2019). This decline has impacted an extensive area of 37,550 hectares. Furthermore, the outcomes derived from the analysis of SPI profiles depict a prolonged period of dryness, particularly extreme drought in the past four years, characterized by SPI values consistently below -2. Notably, a high correlation coefficient (R) of -0.87 and -0.88 was observed between DS and SPI9 and SPI12 respectively, emphasizing the strong linkage between drying speed and the duration and intensity of drought. These findings emphasize the reliability of NDVI as an effective tool for precise classification of tree land cover. Additionally, they underscore the significant influence of drought on the degradation of trees in the Haouz plain.

How to cite: Ablila, Y., Amazirh, A., Khabba, S., Bouras, E. H., Kharrou, M. H., Er-Raki, S., and Chehbouni, A.: Analyzing Tree Degradation in the Haouz Plain through Remote Sensing: Assessing the Impact of Drought and Spatial Extent, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18201, https://doi.org/10.5194/egusphere-egu24-18201, 2024.

EGU24-18295 | ECS | Posters on site | HS2.1.5

The relevance of Rossby wave breaking for precipitation in the world’s arid regions 

Andries Jan De Vries, Moshe Armon, Klaus Klingmüller, Raphael Portmann, Matthias Röthlisberger, and Daniela I.V. Domeisen

Precipitation-related extremes in drylands expose more than a third of the world population living in these regions to drought and flooding. While weather systems generating precipitation in humid low- and high-latitude regions are widely studied, our understanding of the atmospheric processes governing precipitation formation in arid regions remains fragmented at best. Regional studies have suggested a key role of the extratropical forcing for precipitation in arid regions. Here we quantify the contribution of Rossby wave breaking for precipitation formation in arid regions worldwide. We combine potential vorticity streamers and cutoffs identified from ERA5 as indicators of Rossby wave breaking and use four different precipitation products based on satellite-based estimates, station data, and reanalysis. Rossby wave breaking is significantly associated with up to 80% of annual precipitation and up to 90% of daily precipitation extremes in arid regions equatorward and downstream of the midlatitude storm tracks. The relevance of wave breaking for precipitation increases with increasing land aridity. Contributions of wave breaking to precipitation dominate in the poleward and westward portions of subtropical arid regions during the cool season. In these regions, climate projections for the future suggest a strong precipitation decline, while projections of precipitation extremes are highly uncertain due to the influence of the atmospheric circulation. Thus, our findings emphasize the importance of Rossby wave breaking as an atmospheric driver of precipitation in arid regions with large implications for understanding projections and constraining uncertainties of future precipitation changes in arid regions that are disproportionally at risk of freshwater shortages and flood hazards.

How to cite: De Vries, A. J., Armon, M., Klingmüller, K., Portmann, R., Röthlisberger, M., and Domeisen, D. I. V.: The relevance of Rossby wave breaking for precipitation in the world’s arid regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18295, https://doi.org/10.5194/egusphere-egu24-18295, 2024.

EGU24-19012 | Orals | HS2.1.5

Decoupling the Influence of Climate Change and Natural Variability on the Middle Eastern Shamal Wind  

Hamza Kunhu Bangalth, Jerry Raj, Udaya Bhaskar Gunturu, and Georgiy Stenchikov

The Middle Eastern Shamal, a prominent north-northwesterly wind, plays a crucial role in the Arabian Peninsula's climate and environment. Originating from the interaction between a semipermanent anticyclone over northern Saudi Arabia and a cyclone over southern Iran, it influences regional climate. The Shamal is essential in transporting dust and pollutants from the Tigris-Euphrates to the Persian Gulf, affecting air quality, health, and travel. Its potential as a renewable energy source also highlights its importance for the region's future energy strategies.

However, understanding the time series of the Shamal wind is a complex task, owing to the intertwined influences of natural climate variability and human-induced climate change. While climate change is a critical factor, natural variability driven by internal climate modes like the Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and North Atlantic Oscillation (NAO) also significantly influences these winds. These oscillations, operating over multidecadal scales, alongside the overarching trend of climate change, form a complex web affecting the regional climate. 

This study addresses the challenge of decoupling the impacts of climate change and natural climate variability on the Shamal wind. Our analysis employs Empirical Mode Decomposition (EMD), a relatively new approach that allows us to decouple the influence of various internal climate modes from that of anthropogenic climate change. This method surpasses traditional techniques by avoiding assumptions of linearity and stationarity. The study utilizes ERA5 reanalysis data to analyze summer and winter Shamal winds.

Preliminary findings indicate that internal climate modes like the AMO are equally significant as climate change in influencing Shamal wind in the past. This insight is crucial for more accurate projections and predictions of future Shamal wind behavior, benefiting the Middle East's environmental management, health, and renewable energy sectors.

How to cite: Bangalth, H. K., Raj, J., Gunturu, U. B., and Stenchikov, G.: Decoupling the Influence of Climate Change and Natural Variability on the Middle Eastern Shamal Wind , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19012, https://doi.org/10.5194/egusphere-egu24-19012, 2024.

EGU24-19172 | Orals | HS2.1.5

Assessing the possibilities of Sentinel products for qualifying and quantifying soil water status of agricultural systems in southern France  

Claude Doussan, Urcel Kalenga Tshingomba, Nicolas Baghdadi, Fabrice Flamain, Arnaud Chapelet, Guillaume Pouget, and Dominique Courault

Water management poses a pervasive challenge in southern France, exacerbated by increasing summer droughts linked to global warming. Water use during spring and summer increases and gets more variable in term of quantity used for crops. Agricultural water use is highly influenced by the diversity in irrigation practices and technics (sprinkler irrigation, drip irrigation, flooding, etc.) ; and can lead to tensions among water users. It is thus essential to estimate field water use at basin scale, as well as crop water status, in order to further optimize water delivered for irrigation. Advances in remote sensing, particularly with Sentinel 1 (S1) and 2 (S2) data, facilitated the development of soil moisture products (SMP) with improved spatial and temporal resolution to characterize soil water in agricultural plots. These SMP products are accessible through the Theia French public platform and suitable for main crops, with NDVI below 0.75 or surfaces with moderate roughness. These specifications can be met for a variety of crop conditions in the south of France. Yet, the validity of the SMP products under various agricultural plot conditions, considering slope, orientation, roughness, and soil moisture, remains to be assessed over extended time periods. From another point of view, such SMP products do not presently apply to orchards plots, which are however, an essential but overlooked component of water use in irrigation and deserve further examination with S1 and S2 data. The objective of our study is twofold: (i) to test SMP products for field crops in different settings and among years, (ii) to preliminary test if S1 data, combined to S2 data, may be linked to soil moisture in orchard plots. Results reveal for (i) that differences can appear between SMP products and soil moisture in various monitored plots, primarily due to variability within farming systems. Beyond a specific slope and vegetation threshold, the correlation does not improve significantly. For (ii), in orchards plots, using a time smoothing of data, S1 VV-retrodiffusion data and NDVI from S2 seem to correlate with soil moisture measurements, with an RMSE < 0.05 cm3/cm3 and enable detection of irrigation events. This study shows that S1 and S2 data are valuable in estimating soil moisture of agricultural plots, giving however some limits in their use, and gives some hope in their further use for orchards water management.

How to cite: Doussan, C., Kalenga Tshingomba, U., Baghdadi, N., Flamain, F., Chapelet, A., Pouget, G., and Courault, D.: Assessing the possibilities of Sentinel products for qualifying and quantifying soil water status of agricultural systems in southern France , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19172, https://doi.org/10.5194/egusphere-egu24-19172, 2024.

EGU24-19511 | Posters on site | HS2.1.5

OurMED PRIMA-funded Project: Sustainable Water Storage and Distribution in the Mediterranean 

Seifeddine Jomaa, Amir Rouhani, Maria Schade, J. Jaime Gómez-Hernández, Antonio Moya Diez, Maroua Oueslati, Anis Guelmami, George P. Karatzas, Emmanouil A Varouchakis, Maria Giovanna Tanda, Pier Paolo Roggero, Salvatore Manfreda, Nashat Hamidan, Yousra Madani, Patrícia Lourenço, Slaheddine Khlifi, Irem Daloglu Cetinkaya, Michael Rode, and Nadim K Copty

The Mediterranean Region is a unique mosaic of different cultures and climates that shape its peoples, natural environment, and species diversity. However, rapid population growth, urbanisation and increased anthropogenic pressures are threatening water quantity, quality, and related ecosystem services. Known as a climate change hotspot, the Mediterranean region is increasingly experiencing intensifying droughts, diminished river flows, and drier soils making water management even more challenging. This situation calls for an urgent need for water management to shift from a mono-sectoral water management approach based on trade-offs, to more balanced multisectoral management that considers the requirement of all stakeholders. This means that sustainable water management requires ensuring that water is stored and shared fairly across all sectors at the basin scale.

The research project OurMED (https://www.ourmed.eu/) is part of the Partnership for Research and Innovation in the Mediterranean Area (PRIMA) Programme supported by the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No 2222. The project was launched in June 2023 and will continue for three years with a grant of 4.4 million euros to develop a holistic water storage and distribution approach tightly integrated into ecosystem services at the river basin scale.

OurMED builds on the multidisciplinary skills of 15 consortium Partners and comprises universities, NGOs, research centres and SMEs from ten countries with complementary expertise in hydrology, hydrogeology, agronomy, climate change, social sciences, remote sensing, digital twins, ecology, and environmental sciences, among others, making it a truly interdisciplinary project. OurMED includes eight distinct demo sites, representing diverse water-related ecosystem properties of the Mediterranean landscape. These include the catchment areas of Bode (Germany), Agia (Crete, Greece), Konya (Turkey), Mujib (Jordan), Medjerda (Tunisia), Sebou (Morocco), Arborea (Sardinia, Italy), and Júcar (Spain). The Mediterranean basin, as a whole, is considered as an additional regional demo site to ensure replicability and reproducibility of proposed solutions at larger scales. 

OurMED vision combines not only technologically-advanced monitoring, smart modelling and optimization capabilities, but also provides data fusion and integrated digital twin technologies to make optimized solutions readily available for decision making. OurMED concept and its implementation to the different demo sites will be presented and discussed.

How to cite: Jomaa, S., Rouhani, A., Schade, M., Gómez-Hernández, J. J., Moya Diez, A., Oueslati, M., Guelmami, A., Karatzas, G. P., Varouchakis, E. A., Tanda, M. G., Roggero, P. P., Manfreda, S., Hamidan, N., Madani, Y., Lourenço, P., Khlifi, S., Daloglu Cetinkaya, I., Rode, M., and Copty, N. K.: OurMED PRIMA-funded Project: Sustainable Water Storage and Distribution in the Mediterranean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19511, https://doi.org/10.5194/egusphere-egu24-19511, 2024.

EGU24-20067 | ECS | Orals | HS2.1.5

Impact Of Ocean Layer Thickness on The Simulation Of African Easterly Waves in High-Resolution Coupled General Circulation Model Simulations 

Jerry Raj, Elsa Mohino Harris, Maria Belen Rodriguez de Fonseca, and Teresa Losada Doval

African easterly waves (AEWs) play a crucial role in the high-frequency variability of West African Monsoon (WAM) precipitation. AEWs are linked to more than 40% of the total Mesoscale Convective Systems (MCSs) in the region and these MCSs contribute approximately 80% of the total annual rainfall over the Sahel. Moreover, around 60% of all Atlantic hurricanes, including 80% of major hurricanes, have their genesis associated with AEWs. The simulation of AEWs poses challenges for General Circulation Models (GCMs), for instance, coarse-resolution models in CMIP5 cannot simulate distinct northern and southern AEW tracks. Additionally, accurately simulating rainfall over West Africa proves to be a challenge for these models due to the involvement of multiscale processes and the influence of complex topography and coastlines. 

The present study investigates the impact of ocean layer thickness on the simulation of African easterly waves (AEWs) using a high-resolution coupled General Circulation Model (GCM). The study employs high-resolution global simulations conducted using the climate model ICON as part of the next Generation Earth System Modeling Systems (nextGEMS) project. Two experiments, each spanning 30 years with a horizontal resolution of 10 km, are conducted. These experiments vary in terms of the thickness of the layers in the upper 20m of the ocean. In one experiment, the upper 20m ocean layers have a thickness of 2m, whereas in the other, it is 10m. The representation of two types of AEWs with periods of 3-5 days and 6-9 days are analyzed in the simulations. There is a notable disparity in the representation of African easterly waves (AEWs) between these two experiments. The simulation with thicker ocean layers exhibits less intense wave activity over the Sahel and equatorial Atlantic for 3-5 day AEWs which is evident in the eddy kinetic energy field. This corresponds to diminished convection and negative precipitation anomalies for 3-5 day AEWs compared to the 2m upper ocean layer thickness simulation. In the case of 6-9 day AEWs, the simulation with thicker ocean layers exhibits intensification of wave activity over northern West Africa.

How to cite: Raj, J., Mohino Harris, E., Rodriguez de Fonseca, M. B., and Losada Doval, T.: Impact Of Ocean Layer Thickness on The Simulation Of African Easterly Waves in High-Resolution Coupled General Circulation Model Simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20067, https://doi.org/10.5194/egusphere-egu24-20067, 2024.

EGU24-20356 | ECS | Posters on site | HS2.1.5

Seasonal Water Turbidity Dynamics in Arid Central Asia: A Case Study of Lake Balkhash, Kazakhstan, Under Changing Environmental Conditions 

Kanchan Mishra, Kathryn E. Fitzsimmons, and Bharat Choudhary

Lake Balkhash, one of the largest inland lakes in Central Asia, plays a pivotal role in providing water and ecosystem services to approximately 3 million people. However, like many water bodies in dryland regions worldwide, Lake Balkhash's hydrology has been significantly affected by climate change and land cover and land-use shifts driven by population growth and water-intensive economic activities. To manage these vital water resources effectively, monitoring the health of water bodies is essential for effective water resource management, security, and environmental conservation. Turbidity, a water quality indicator, measures the water clarity and represents a broader environmental change, allowing us to assess the water body's health and the extent of anthropogenic impact on the entire catchment. It is a measure of water clarity and serves as a crucial indicator of water health, as it represents the primary mechanism for transporting pollutants, algae, and suspended particles.

The present study investigates the temporal and spatial variability of turbidity in Lake Balkhash. We utilize the normalized difference turbidity index (NDTI) with Landsat satellite data spanning from 1991 to 2022 to map turbidity. We consider various climatic and anthropogenic factors, including precipitation, temperature, wind speed and direction, and water levels in and around the lake.

Our findings reveal an overall declining turbidity trend over interannual and seasonal timescales. The results provide a significant negative correlation between turbidity, temperature, and water levels at both temporal scales. However, no straightforward relationship emerges between turbidity and precipitation or wind variables. Specifically, during spring and summer, turbidity exhibits a strong association with temperature and water levels, while in the fall season, water levels are more closely correlated with turbidity. These results underscore the substantial impact of rising temperatures and fluctuations in water levels on the turbidity dynamics of Lake Balkhash. These findings highlight that the warming climate and alterations in lake hydrology pose significant risks to water quality, indicating that monitoring water health alone may not suffice to mitigate the impacts of climate change and human activities.  

How to cite: Mishra, K., Fitzsimmons, K. E., and Choudhary, B.: Seasonal Water Turbidity Dynamics in Arid Central Asia: A Case Study of Lake Balkhash, Kazakhstan, Under Changing Environmental Conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20356, https://doi.org/10.5194/egusphere-egu24-20356, 2024.

EGU24-20398 | Posters on site | HS2.1.5

Analysis of operational droughts in an alpine Mediterranean basin using a conjunctive use model of surface and groundwater resources 

Juan-de-Dios Gómez-Gómez, Antonio Collados-Lara, David Pulido-Velázquez, Leticia Baena-Ruiz, Jose-David Hidalgo-Hidalgo, Víctor Cruz-Gallegos, Patricia Jimeno-Sáez, Javier Senent-Aparicio, Fernando Delgado-Ramos, and Francisco Rueda-Valdivia

Extreme events, and particularly, droughts are a main concern in Mediterranean basins that will be increased in the future due to climate change (CC), according to the forecasting for the region made by researchers. A novel integrated approach is proposed to analyze operational droughts and their propagation in future CC scenarios at a basin scale. This approach has been applied to the Alto Genil basin (Granada, Spain), an alpine Mediterranean basin with the singularity of having an important snow component in its precipitation regime. The Standardized Precipitation Index (SPI) methodology has been applied to the variable Demand Satisfaction Index (DSI) at a monthly scale to evaluate operational droughts. A conjunctive use model of surface and groundwater resources developed with the code Aquatool has been used to obtain historical and future DSI monthly series. It is an integrated management model that includes all water demands, water resources (surface, groundwater, and their interaction), regulation and distribution infrastructures in the Alto Genil system. The Vega de Granada aquifer is a key element of the water supply system such for agricultural needs as for guarantee the urban supply to the city of Granada. Groundwater flow in this important aquifer has been simulated with a distributed approach defined by an eigenvalue model to integrate it in the management model, and in order to obtain a more detailed analysis of its future evolution. The proposed methodology consists of the sequential application of the following steps: (1) generation of future scenarios for the period 2071-2100 to obtain series of precipitation (P) and temperature (T); (2) application of a chain of models: a rainfall-runoff model (Témez) coupled with a snowmelt model to obtain runoff (Q) series in subbasins of Alto Genil basin, a crop water requirement model (Cropwat) to get agricultural demand series, and an integrated management model (Aquatool) to get historical and future series of DSI; and (3) analysis of operational droughts comparing historical and future series of the Standardized Demand Satisfaction Index (SDSI), which is the application of the SPI methodology to the variable DSI. A cluster analysis of variables P and Q has been made in order to define homogeneous hydroclimatic areas by aggregation of subbasins. It will allow us to perform an analyses of the heterogeneity in  the propagation of droughts.

Aknowledments: This research has been partially supported by the projects: STAGES-IPCC (TED2021-130744B-C21), SIGLO-PRO (PID2021-128021OB-I00), from the Spanish Ministry of Science, Innovation and Universities, RISRYEARTH (Recovery funds), and “Programa Investigo” (NextGenerationEU).

How to cite: Gómez-Gómez, J.-D., Collados-Lara, A., Pulido-Velázquez, D., Baena-Ruiz, L., Hidalgo-Hidalgo, J.-D., Cruz-Gallegos, V., Jimeno-Sáez, P., Senent-Aparicio, J., Delgado-Ramos, F., and Rueda-Valdivia, F.: Analysis of operational droughts in an alpine Mediterranean basin using a conjunctive use model of surface and groundwater resources, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20398, https://doi.org/10.5194/egusphere-egu24-20398, 2024.

EGU24-20616 | Orals | HS2.1.5

Integrating Multi-Sensor and Multi-Platform Technologies for Enhanced Assessment of Spectral Indices and Phenological Dynamics in a Seasonal Tropical Dry Forest 

Magna Moura, Rodolfo Nobrega, Anne Verhoef, Josicleda Galvíncio, Rodrigo Miranda, Bruna Alberton, Desiree Marques, Cloves Santos, Bruno Nascimento, Maria Maraiza Pereira, and Patricia Morellato

The Seasonal Tropical Dry Forest (STDF) known as Caatinga occupies approx. 10% of the Brazilian territory. Its vegetation exhibits rapid phenological responses to rainfall resulting in corresponding increases in gross primary productivity and biomass production. Determining the timing of the start and end of the growing season is very important to ecosystem studies and to precisely quantify the carbon balance. Satellite-derived vegetation indices have been widely used to capture the vegetation dynamics in response to fluctuating environmental conditions. However, the spatial and temporal resolution of these indices cannot capture fine vegetation features and phenology metrics in a highly biodiverse and heterogeneous environment such as the Caatinga. On the other hand, phenocameras have been successfully used for this particular purpose for tropical and dry ecosystems. Complementarily, proximal spectral response sensors (SRS) have been used to allow computation of vegetation indices as phenology proxies. Due to their ability to capture high spatial resolution imagery, Unmanned Aerial Systems (UAS) or drones, can deliver an excellent spatial and a very good temporal resolution for diverse detailed vegetation studies. In this context, the objective of this study was to verify whether multi-sensor and multi-platform technologies provide an enhanced assessment of spectral indices and phenological dynamics of the Caatinga. The field campaign occurred in a pristine area of caatinga vegetation, located at the Legal Reserve of Caatinga, Embrapa Semi-Arid, Petrolina, Brazil. Indices for detecting phenology dynamics were obtained using multi-spectral cameras installed on unmanned aerial vehicles (UAV), field spectral response sensors (SRS), phenocameras (digital RGB cameras) and MODIS satellite data (visible and near infrared) from 2020 to 2023. Environmental driving data were measured via instrumentation installed on a flux tower. Standard statistical measures, including correlation coefficients were employed to verify the relationship observed on Normalized Difference Vegetation Index (NDVI), Photochemical Reflectance Index (PRI), and Green Chromatic Coordinate (Gcc) determined by different sensors and platforms. We observed a substantial and fast increase in Gcc, NDVI and PRI immediately after rainfall events. The sensitivity of NDVI and PRI to changes in vegetation can vary depending on factors such as vegetation greenness, overall plant health, and stress responses according to the environmental conditions of the study area. Particularly during the dry season, indices derived from higher spatial resolution sensors consistently showed lower NDVI values compared to those obtained from proximal spectral response sensors (SRS) and drones. Our observations indicate that the representation of vegetation captured by satellites and drones aligns well with the data obtained from phenocamera and proximal SRS platforms. The combination of high temporal resolution provided by SRS and phenocameras resulted in improved and more reliable indices that will be indispensable for evaluating the response of Caatinga vegetation to current and future conditions.

Funding: This study was supported by the São Paulo Research Foundation-FAPESP (grants ##2015/50488-5, #2019/11835-2; #2021/10639-5; #2022/07735-5), the Coordination for the Improvement of Higher Education Personnel - CAPES (Finance Code 001), the National Council for Scientific and Technological Development - CNPq (306563/2022-3).

How to cite: Moura, M., Nobrega, R., Verhoef, A., Galvíncio, J., Miranda, R., Alberton, B., Marques, D., Santos, C., Nascimento, B., Pereira, M. M., and Morellato, P.: Integrating Multi-Sensor and Multi-Platform Technologies for Enhanced Assessment of Spectral Indices and Phenological Dynamics in a Seasonal Tropical Dry Forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20616, https://doi.org/10.5194/egusphere-egu24-20616, 2024.

EGU24-20999 | ECS | Orals | HS2.1.5

Soil and rock water dynamics in a semiarid karst savanna undergoing woody plant encroachment

Pedro Leite, Bradford Wilcox, Daniella Rempe, and Logan Schmidt

EGU24-804 | ECS | Orals | HS2.1.9

The role of proglacial rock glaciers in redistributing glacial meltwater 

Bastien Charonnat, Michel Baraer, Janie Masse-Dufresne, Eole Valence, Jeffrey McKenzie, Chloé Monty, Kaiyuan Wang, and Elise Devoie

The deglaciation of high mountain ranges is leading to the expansion of proglacial areas, which encompasses diverse permafrost and ground ice landforms. These features exert an increased influence on the hydrology and hydrogeology of alpine catchments as glaciers retreat. Despite the heightened attention received by rock glaciers for the last decades, their role within the broader hydrological and hydrogeological valley system remains understudied. Previous studies have highlighted rock glaciers’ ability to act as hydrological storage and to buffer water release from alpine catchments. However, there is a lack of studies about their ability to modify the groundwater flow paths in a proglacial valley system and to redistribute glacial meltwater. This study addresses this knowledge gap by investigating how the rock glacier redistributes glacial meltwater in a study catchment.

Shar Shäw Tágà (Grizzly Creek) is a subarctic glaciated catchment located in the St. Elias Mountains, Yukon (Canada) that experiences significant glacial retreat. A non-relict rock glacier at the outlet of a glacial sub-catchment obstructs the valley thalweg, with only a few springs exhibiting minimal discharge from its front. These minor springs contrast remarkably with the substantial discharge observed at higher elevations above the rock glacier.

Water level, water temperature and electrical conductivity variables were monitored in identified springs throughout the summer 2022. Results were compared to meteorological data with wavelet coherence analysis to determine the springs’ origins and drivers. Additionally, multiple sampling campaigns were conducted in the summers of 2022 and 2023 to analyze major ions concentrations and water stable isotopes signatures in the catchment’s streams.

The results reveal that the rock glacier serves as a critical obstacle and deflector to subsurface meltwater, either forcing upstream meltwater to penetrate deeper into the subsurface, or redirecting lateral subsurface flow to resurge at its front, forcing part of the alluvial floodplain shallow aquifer to reach the surface.

While rock glaciers are often considered potential water reservoirs, this study illuminates their dual role as critical deflectors for shallow subsurface flow in proglacial valley systems. They can impede glacial meltwater flow, originating alternative pathways toward deep aquifers or lowlands’ surface waters. Such findings nuance the ability of rock glaciers to store and release glacial meltwater, as they can deflect shallow subsurface flow. Additionally, it shows that rock glaciers can force infiltration and resurgence of water at specific locations, affecting the broader mountain hydrogeological system. Furthermore, it enforces their critical role in the future of water resources supplied by high mountain ranges in a deglaciation context.

How to cite: Charonnat, B., Baraer, M., Masse-Dufresne, J., Valence, E., McKenzie, J., Monty, C., Wang, K., and Devoie, E.: The role of proglacial rock glaciers in redistributing glacial meltwater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-804, https://doi.org/10.5194/egusphere-egu24-804, 2024.

Spaceborne gravimetry is the only satellite method that can observe terrestrial water storage at a continental scale. The time variable gravity field, observed by GRACE and GRACE-FO, is a measure of mass transport primarily in the global water cycle. In this contribution we analyse the runoff-storage relationship in the GRACE time frame for the pan-Arctic drainage basins. Over these boreal catchments, the conventional hysteresis-type formulation requires algorithmic adaptations in order to accommodate snowload and base-flow during winter periods. We show that the parameters involved in the pan-Arctic runoff-storage relationships are transferable, albeit with a few exceptions, between the various catchments. This remarkable fact allows us access to determining runoff from ungauged drainage areas across the pan-Arctic. As a result we can quantify the total freshwater flux from pan-Arctic basins into the Arctic Ocean.

How to cite: Sneeuw, N., Yi, S., Saemian, P., and Tourian, M. J.: Estimating runoff from pan-Arctic basins through an improved runoff-storage relationship using satellite gravimetry in the GRACE period 2002-2019, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2098, https://doi.org/10.5194/egusphere-egu24-2098, 2024.

EGU24-2191 | ECS | Orals | HS2.1.9

Process-based modeling of the streamflow generation in a highly glaciated Alpine headwater catchment since the last little Ice Age (i.e., 1850). 

Florentin Hofmeister, Xinyang Fan, Madlene Pfeiffer, Inga Labuhn, Ben Marzeion, Bettina Schaefli, and Gabriele Chiogna

The streamflow generation related to snow and glacier melt is particularly sensitive to temperature fluctuations and, hence, highly affected by global warming. However, the non-linear and complex interaction between streamflow contributions originating from snow melt versus glacier melt and being transferred to stream via the subsurface complicates the investigation of climate-induced changes in high-elevation catchments. We used the physically-based hydrological model WaSiM to simulate the climate-induced changes in the streamflow generation in the Kaunertal (Austria), a highly glaciated Alpine headwater catchment. The simulations extend from the last little Ice Age (i.e., 1850) to 2015. Large-scale climate processes of a general circulation model (GCM) were dynamically downscaled with the Weather Research & Forecasting Model (WRF) to the central Alpine region at a 2 km spatial resolution from 1850 to 2015. The WaSiM model parameters were transferred from a WaSiM configuration driven by station data and partly optimized by a manual calibration on observed streamflow. For model evaluation, a multi-objective approach was chosen considering streamflow, SWE, snow cover duration, and glacier mass balances. The hydrological model results showed a good representation of the individual components and seasonal streamflow generation. However, difficulties exist in the spatial representation of the heterogeneous and small-scale differences in the snowpack. In addition, there are limitations in the simulation of glacier evolution using WaSiM over long periods (> 30 years) in highly glaciated catchments, as WaSiM does not contain an ice flow routine that can simulate the glacier dynamics during advance or retreat. Despite the cascade of uncertainties in this complex model chain (i.e., GCM, WRF, WaSiM), the results of the long-term simulation show interesting dynamics and enable an analysis of streamflow generation for periods where no observational data is available. For instance, glacier melt indicates a high dependence on the development of summer temperatures (i.e., JJA). The rising temperatures led to an earlier onset of snow and glacier melt, which shifted the streamflow regime and increased the daily streamflow magnitude, especially from 1995 onwards. The next step will be the comparison of the hydrological model results with those from other headwater catchments in the eastern Central Alps with a different degree of glaciation. The novelty lies in comparing 165 years of simulated streamflow and the contributions from snow and glacier melt. This comparison will validate the transferability and generalizability of the complex model chain and the simulation results.

How to cite: Hofmeister, F., Fan, X., Pfeiffer, M., Labuhn, I., Marzeion, B., Schaefli, B., and Chiogna, G.: Process-based modeling of the streamflow generation in a highly glaciated Alpine headwater catchment since the last little Ice Age (i.e., 1850)., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2191, https://doi.org/10.5194/egusphere-egu24-2191, 2024.

EGU24-2310 | ECS | Posters on site | HS2.1.9

Spring floods and their major influential factors in the source region of the Yangtze River during 2001–2020 

Ying Yi, Shiyin Liu, Yu Zhu, Kunpeng Wu, and Fuming Xie

    Many reservoirs have been constructed in the Yangtze River basin, however, spring floods in its source region pose increasingly severe challenges to reservoirs operation and water resources management due to increased climatic variability under global warming. Understanding spring flood variability and their major influential factors under changing climates is crucial to improving water management, agricultural irrigation, reservoir operation, and flood prevention. In this study, we have examined the spring flood characteristics and their influential factors in the source region of the Yangtze River based on station data and multisource remote sensing products during 2001–2020. Late Mays have seen most of the highest spring flood discharge, while some springs have experienced multiple peaks. Extreme spring floods were identified in the years 2012, 2013, 2019, and 2020, with the highest peak discharge (1365.83 m3/s) and longest flood duration (47 days) in 2019. Spring snowmelt played a key role in 2019 spring flood and others were also driven by snowmelt in the UJSB. We defined Snow Water Volume (SWV) as an indicator of the precondition for high spring flood. In 2019, large winter SWV along with spring snowfall melted into meltwater under the rising temperature, resulting in extreme spring flood event in late April. Whereas, in 2012 and 2020, snowmelt and rainfall combined to contribute to the extreme spring flood events in late Mays. In 2013, although snowmelt made a contribution to the first spring flood peak, the flood event at the end of May was primarily contributed by rainfall. Based on spatiotemporal variations in spring SWV and the isotherm of critical temperature for snow melting, the key regions dominating spring floods were identified as the regions with large amount of SWV. Weather pattern analysis showed that the enhanced Westerly jets in winters brought about large snowfall and extended snow cover in the region which can be released as floods triggered by rapid increase in air temperature in the coming spring.

How to cite: Yi, Y., Liu, S., Zhu, Y., Wu, K., and Xie, F.: Spring floods and their major influential factors in the source region of the Yangtze River during 2001–2020, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2310, https://doi.org/10.5194/egusphere-egu24-2310, 2024.

EGU24-5329 | ECS | Orals | HS2.1.9

Contribution of glacier melt to runoff under climate change using a conceptual hydrological model in selected high alpine regions in Austria 

Caroline Ehrendorfer, Franziska Koch, Sophie Lücking, Thomas Pulka, Hubert Holzmann, Philipp Maier, Fabian Lehner, Herbert Formayer, and Mathew Herrnegger

The timing and quantity of snow and ice melt in high-alpine regions is of great importance, especially for time-sensitive processes such as hydropower production. In most conceptual hydrological models, the simulations of these components are frequently only based on simple temperature index methods, and the question arises whether these are sufficient to derive useful information on changing runoff seasonality and quantities for hydropower producers.

This study examines the quantitative and seasonal changes in glacier melt contribution to total runoff under climate change in several Austrian high-alpine catchments with hydropower production (Stubaital, Stubachtal, Kölnbrein/Maltatal, Schlegeis/Zillertal). As the estimation of precipitation model inputs for areas with complex terrain is characterised by a high degree of uncertainty, an undercatch-correction adapted for high-alpine areas was applied, integrating information from local weather stations, topography and iterative feedback from the modelled water balance. The conceptual, semi-distributed rainfall-runoff model COSERO was set up for the case study regions.  To cover long-term changes, the model was run for Stubai- and Stubachtal for the reference period (1990-2020) and future scenarios (2021-2100) with daily timesteps. In addition to the daily timesteps, COSERO was also coupled with the physically-based snowpack model Alpine3D for simulations in the Kölnbrein and Schlegeis catchments for recent decades to implement the simulation of relevant components of the water balance including snow and ice processes at an hourly timestep based on more complex energy-balance modelling. Besides air temperature and precipitation, the coupling requires additional hourly meteorological input such as radiation, relative humidity and wind information.

The combination of COSERO with Alpine3D improves results at the hourly timestep, but the conceptual model delivers satisfying results on its own as well. Moreover, the results are in line with literature and show the expected decrease of ice volume and ice melt in coming years. By 2050, the ice melt contribution to total runoff is significantly reduced in all case study areas and seasonality shifts due to less ice melt and earlier snowmelt in the form of more winter and spring runoff and less flow in summer are prevalent. In addition, we show that the modelling of the water balance components in the past can be greatly improved by using the undercatch-corrected precipitation data.

 

Acknowledgements: We thank the VERBUND Energy4Business GmbH, the Austrian Climate Research Programme (ACRP), the Austrian Research Promotion Agency (FFG), and the ÖBB for funding, fruitful discussions and providing us with data.

How to cite: Ehrendorfer, C., Koch, F., Lücking, S., Pulka, T., Holzmann, H., Maier, P., Lehner, F., Formayer, H., and Herrnegger, M.: Contribution of glacier melt to runoff under climate change using a conceptual hydrological model in selected high alpine regions in Austria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5329, https://doi.org/10.5194/egusphere-egu24-5329, 2024.

EGU24-5531 | ECS | Posters on site | HS2.1.9

Enhancing Snow Ablation Modeling in the Generation of Gridded Snow Water Equivalent Data 

Michelle Yu, Christopher Paciorek, Alan Rhoades, Mark Risser, and Fernando Perez

Snow Water Equivalent (SWE) is a critical parameter for understanding water availability in regions with seasonal snow cover. Ensuring an accurate representation of SWE across regular spatial and temporal intervals is essential and plays a pivotal role in hydrological and climatological studies. This work critically examines the ablation modeling strategy employed by the University of Arizona daily 4km SWE dataset (UA SWE), a widely adopted SWE gridded product in the United States, highlighting limitations inherent in methodologies that rely solely on temperature data.

Recognizing the utility of a more nuanced perspective to capture the complexities of snowmelt dynamics, we propose a novel method that incorporates a diverse set of meteorological and terrain characteristics as input variables in the predictive modeling of snow ablation. Our approach is further extended to directly model SWE, eliminating the need for intermediate ablation estimation and providing a more intuitive solution for empirical SWE prediction.

Our versatile methodology can be easily applied to produce high-resolution gridded SWE data. By addressing deficiencies in a leading empirical approach, our technique aims to enhance the accuracy of SWE representation at both the point and grid levels.

How to cite: Yu, M., Paciorek, C., Rhoades, A., Risser, M., and Perez, F.: Enhancing Snow Ablation Modeling in the Generation of Gridded Snow Water Equivalent Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5531, https://doi.org/10.5194/egusphere-egu24-5531, 2024.

EGU24-7278 | ECS | Orals | HS2.1.9

Cold-laboratory experiments to observe meltwater and ice layer interactions in snowpacks 

Connor Shiggins, Douglas Mair, James Lea, and Isabel Nias

The fate of percolating surface meltwater encountering ‘impermeable’ ice layers is uncertain in the accumulation zone of the Greenland Ice Sheet (GrIS). Often, ice layers are considered to retard meltwater and cause lateral runoff. However, modelled and field-based observations in the percolation zone of the GrIS have suggested ice layers are not necessarily impermeable and meltwater can breakthrough, percolating to deeper depths of snow/firn and consequently inferring a greater refreezing capacity within the accumulation zone. The physical and thermal conditions which control the permeability of ice layers remain unclear and effective parameterisation of these processes is lacking for snow/firn modelling of melt, refreezing and runoff. Here we present repeat cold-laboratory experiments which seek to understand how meltwater interacts with thin ice layers (5 to 20 mm) for two differing thermal regime contexts whereby the surrounding snow/firn thermal regime is either (i) below or (ii) at the melting point.

We find that under extreme melt regimes, ice layers continually retard wetted fronts of percolating meltwater when the thermal regime of the snowpack is below the melting point. This barrier results in the snowpack at depth remaining at least ~1oC cooler than snow above the ice layer which is saturated with meltwater. We also find that the ice layer forces ~35% of the percolating meltwater to runoff, cooling the overlying snow and increasing the refreezing capacity of the snow closer to the snowpack surface. The remaining ~65% of meltwater ponds and later refreezes on the ice layer, thickening the impenetrable surface.

When the thermal regime of the surrounding snow/firn is at the melting point, we find that meltwater is able to pond without refreezing, resulting in the ice layer failing and allowing deeper percolation into the snowpack. These findings suggest that the thermal regime of a snowpack is crucial for the structural integrity of an ice layer and thus the permeability of a snowpack.

Consequently, these findings have implications for parameterising meltwater runoff and ice layer integrity in snow and firn models which incorporate ‘impermeable’ barriers in their domains. Future work will continue to explore similar experiments with thicker ice layers (~60 mm) to determine whether ice layer breakthrough is primarily a function of snow/firn thermal regime and/or ice layer thickness. 

How to cite: Shiggins, C., Mair, D., Lea, J., and Nias, I.: Cold-laboratory experiments to observe meltwater and ice layer interactions in snowpacks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7278, https://doi.org/10.5194/egusphere-egu24-7278, 2024.

EGU24-9702 | ECS | Posters on site | HS2.1.9

Inferring Debris Properties on Debris-Covered Glaciers: Implications for Glacier Modelling 

Vicente Melo Velasco, Evan Miles, Michael McCarthy, Thomas E. Shaw, Catirona Fyffe, and Francesca Pellicciotti

Debris, ranging from thin surface dust to medial moraines and thick, continuous layers in ablation zones, partially covers glaciers all around the world. By modifying energy transfer from the atmosphere to the ice, the supraglacial debris layer fundamentally controls sub-debris melt rates. Debris physical properties such as surface roughness (z0) and thermal conductivity (k) have only been derived from local measurements at a few sites, and modelling studies of debris-covered glaciers have often relied on literature values. The correct representation of these properties in energy-balance models is crucial for understanding the climate-glacier dynamics and how debris-covered glaciers will behave in the future. There are several established methods to derive these properties from field measurements, yet relatively few studies undertake to measure properties for their sites, or to evaluate the resulting property values.

We undertook an observational campaign to investigate supraglacial debris properties at Pirámide Glacier, in the central Chilean Andes. First, we used established approaches, as well as some variations on those approaches, to derive z0 from wind-temperature tower data and k from thermistor strings in the debris at three glacier locations. Second, we determined locally-optimal k and z0 values to reproduce observed ice melt: we optimised k by simulating energy conduction through the debris with the surface temperature as an input, then optimised z0 by running a complete energy-balance model using the observed surface meteorology. We then conducted point-scale energy-balance modelling using the z0 and k values obtained i) with the derivations from field measurements; ii) through optimisation, or; iii) from the typical values found in literature. This allowed us to evaluate how the different methods perform by comparing the modelled and measured ice melt. 

Our results show that deriving local debris properties from measurements is challenging and that measured values can differ significantly from common literature values. The values derived from measured data can vary significantly depending on the method employed. It is important to note that these values can also differ significantly from the values required by an energy-balance model to accurately represent sub-debris ice melt. Furthermore, energy-balance models typically assume a representation of heat transfer within the supraglacial debris layer based solely on conduction and require a bulk thermal conductivity value. This highlights the necessity of efforts to reevaluate measurements in the field and reconsider our definition of debris properties in melt modelling.

How to cite: Melo Velasco, V., Miles, E., McCarthy, M., Shaw, T. E., Fyffe, C., and Pellicciotti, F.: Inferring Debris Properties on Debris-Covered Glaciers: Implications for Glacier Modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9702, https://doi.org/10.5194/egusphere-egu24-9702, 2024.

EGU24-12337 | ECS | Orals | HS2.1.9

Current and future glacier melt contribution to groundwater dynamics in a high-altitude, Himalaya basin 

Caroline Aubry-Wake and Walter Immerzeel

While mountain groundwater in glacierized regions has gained increasing attention, comprehensive insights of glacier melt contributions to groundwater and their resurfacing patterns remain limited. Our study employs a cryosphere-surface hydrology model in combination with numerical groundwater simulations to estimate the water table variations across the high-altitude Langshisha basin in the Langtang Himalaya (4094-6049 m). We evaluate surface water-groundwater interactions amidst current and projected climatic conditions. Utilizing in-situ weather forcings and evaluated with field measurements, our findings indicate that glacier melt contributes up to 70% of groundwater recharge in the Langshisha basin during the 2012-2020 period. This substantial contribution is attributed to the basin's considerable glacier cover (40%) and its high elevation, where cold temperatures in areas above 5300 m limit melt and are underlain by permafrost, restricting recharge. Groundwater simulations based on these recharge rates reveal a high sensitivity to hydraulic conductivity parameters but are constrained by field measurements of creek exfiltration indicating a water table near the surface along the main streams. The combination of groundwater simulations and field measurements suggests that groundwater exfiltration along the proglacial stream is a predominant surface-water-groundwater exchange mechanism within the basin. Considering the important role of glacier melt in groundwater recharge, our study applies future climate scenarios to gauge the impact of warming trends and glacier retreat on surface water-groundwater dynamics within the basin.

How to cite: Aubry-Wake, C. and Immerzeel, W.: Current and future glacier melt contribution to groundwater dynamics in a high-altitude, Himalaya basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12337, https://doi.org/10.5194/egusphere-egu24-12337, 2024.

EGU24-13919 | Orals | HS2.1.9 | Highlight

Accounting for interannual variability in dust accelerated snowmelt in process-based hydrologic prediction, Rocky Mountains, USA 

S. McKenzie Skiles, Patrick Naple, Otto Lang, and Joachim Meyer

Seasonal mountain snowmelt is an important contributor to surface water resources and groundwater recharge in the midlatitudes, making forecasting of snowmelt timing and duration critical for accurate hydrologic prediction. Net solar radiation, controlled primarily by snow albedo, is the main driver of snowmelt in most snow covered environments. Lowering of snow albedo from episodic dust deposition has been shown to be an important control on snowmelt patterns in the Rocky Mountains of the Western United States. Here, we compare and contrast trends in dust impacted albedo over the previous two decades with a focus on two regions: 1) the Colorado Rockies, headwaters of the Colorado River, which recieves dust from the southern Colorado Plateau and 2) the Wasatch Mountains (UT), headwaters of the Great Salt Lake, which recieves dust from the Great Basin. Results show that while snow darkening occurs every year, the magnitude of impact is spatially and temporally variable, and there are no emerging relationships that indicate when 'high-impact' dust years will occur. To account for spatial and interannual variability in dust impacted net solar radiation in hydrologic prediction we developed a spatially distributed process-based snowmelt model that incorporates near-real time snow albedo from remote sensing and incoming solar radiation from numerical weather prediction. The model improves simulated timing of snowmelt initiation and duration in all years, even those with lower dust impacts, demonstrating the importance of accurate snow albedo in snowmelt modeling. 

How to cite: Skiles, S. M., Naple, P., Lang, O., and Meyer, J.: Accounting for interannual variability in dust accelerated snowmelt in process-based hydrologic prediction, Rocky Mountains, USA, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13919, https://doi.org/10.5194/egusphere-egu24-13919, 2024.

EGU24-14158 | Posters on site | HS2.1.9

Enhancing NESDIS Global Automated Snow and Ice Cover Mapping System 

Peter Romanov

A new version of the Global Multisensor Automated Snow and Ice Mapping System (GMASI) has been implemented into operations at NESDIS is summer 2023. The new system is an upgrade of the previous version of the GMASI which was operated since 2006. The system provides information on the snow and ice distribution for NOAA numerical weather prediction and climate models as well as for a number of other atmosphere and land remote sensing products. The retrieval algorithm uses satellite observations in the visible/infrared and in the microwave spectral bands and delivers daily spatially continuous (gap-free) maps of the snow and ice cover.  

Compared to previous version, the new system incorporates data from a larger set of microwave sensors and features an enhanced retrieval algorithm. The spatial resolution of the output maps has been improved from es improved from 4km to 2km.  In the presentation we provide details of the data processing algorithm and of the output product focusing on the improvements and upgrades. We demonstrate that the output of the new GMASI system closely matches the accuracy of snow maps produced within NOAA Interactive Multisensor Snow and Ice Mapping System (IMS) and agrees well to in situ station snow depth report. Improvements to the retrieval algorithm mostly affected reproduction of small-scale features in the snow and ice cover distribution, particularly in alpine areas.  In the same time, large-scale climatologically-important cryosphere features as the continental and hemisphere snow and ice extent estimated with the new snow and ice maps remain consistent with the previous version of the product. 

How to cite: Romanov, P.: Enhancing NESDIS Global Automated Snow and Ice Cover Mapping System, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14158, https://doi.org/10.5194/egusphere-egu24-14158, 2024.

EGU24-15373 | ECS | Posters on site | HS2.1.9 | Highlight

The importance of small glaciers for accurate projection of future runoff in High Mountain Asia 

Alexandra von der Esch, Matthias Huss, Marit Van Tiel, Justine Berg, Tarang Patadiya, Pascal Horton, Saurabh Vijay, and Daniel Farinotti

High Mountain Asia is characterized by a substantial glacier coverage with glaciers of varying sizes. These glaciers are crucial in the area's hydrological cycle since they feed large rivers such as the Indus, Ganges, and Brahmaputra rivers. However, ongoing climate change is having a significant negative impact on glacier mass and projections show strong further declines of glacier mass in the future. This is raising concerns about future water security. How big the impact of the evolution of small glaciers (< 2 km2) is towards changing water availability remains to be investigated.

Most studies focus on the regional evolution of glaciers as a whole, which means that small-scale glaciers are often overlooked due to larger glaciers dominating the signal in area and volume changes, despite the fact that small glaciers make up about 30% of the glacierized area in High Mountain Asia. To address this issue, we applied the Global Glacier Evolution Model (GloGEM) to simulate all ca. 100’000 glaciers of High Mountain Asia (Regions 13-15 of the Randolph Glacier Inventory v6.0) under various climate scenarios in the period of 1980-2100. We compared the spatio-temporal variability of the timing of peak water, as well as glacier volume change, between small and large glaciers for a set of approximately 30 catchments in the headwater of Indus, Ganges and Brahmaputra rivers.

We find that there is a larger difference between future scenarios for the timing of peak water for smaller glacier, with it ranging from 2030-2060 and then runoff declining rapidly. Meanwhile, peak water for larger glaciers is likely to occur between 2070-2080 according to an intermediate emission scenario, with glacier runoff decreasing gradually thereafter. As for the ice volume change, smaller glaciers are expected to reach volumes close to zero near the year 2080, while larger glaciers are expected to reach this point only after 2100. The quicker response of small glaciers compared to large glaciers emphasize the need for a particular focus on small glaciers to better understand their responses to climate change and make accurate projections about local and regional scale near future water availability.

How to cite: von der Esch, A., Huss, M., Van Tiel, M., Berg, J., Patadiya, T., Horton, P., Vijay, S., and Farinotti, D.: The importance of small glaciers for accurate projection of future runoff in High Mountain Asia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15373, https://doi.org/10.5194/egusphere-egu24-15373, 2024.

EGU24-15646 | Posters on site | HS2.1.9

Combined use of evolutionary algorithms and hydrological models to simulate snow cover and flow in alpine basins 

Jose David Hidalgo Hidalgo, Antonio Juan Collados Lara, David Pulido Velazquez, Eulogio Pardo Iguzquiza, Juan de Dios Gomez Gomez, and Francisco Jose Rueda Valdivia

Snow cover area, which can be obtained from satellite, is a valuable information to simulate streamflow in snow-dominated mountain basins where snowmelt is a major runoff factor. However, usually satellite do not provide long completed snow cover area spatiotemporal series, which are required to calibrate and validate hydrological models. It is due to difference limitations, as presence of clouds, sensor failure, low revisit time or spatial resolution, or recent launch.

Cellular automata models, which use precipitation and temperature as driving variables and some transition rules between cells through calibrated parameters, are capable of capturing the dynamics of snow cover area. Therefore, they can be used to complete and extend the information provided by satellite.

In this work, we simulate long series of daily streamflow in the Canales basin (Sierra Nevada, south Spain) by combining a cellular automata model and the Snowmelt Runoff Model. The Snowmelt Runoff Model is a degree-day model that requires data of temperature, precipitation, and snow cover area and has been widely used in simulation of streamflow in snow-dominated mountainous basins around the world.

The water resources in the Canales basin are regulated by a reservoir, which contributes to supply the Granada city water demand. The main resources stored in reservoir come from Sierra Nevada Mountains during the melting season. Therefore, the dynamics of snow is essential to simulate streamflow in the Canales basin.

It has been also used to simulate future local climate scenarios generated for specific level of warming in peninsular Spain.

Aknowledments: This research has been partially supported by the projects: STAGES-IPCC (TED2021-130744B-C21), SIGLO-PRO project (PID2021-128021OB-I00), SIERRA-CC project (PID2022-137623OA-I00) from the Spanish Ministry of Science, Innovation and Universities, and SER-PM (2908/22) from the National Park Research Program.

How to cite: Hidalgo Hidalgo, J. D., Collados Lara, A. J., Pulido Velazquez, D., Pardo Iguzquiza, E., Gomez Gomez, J. D. D., and Rueda Valdivia, F. J.: Combined use of evolutionary algorithms and hydrological models to simulate snow cover and flow in alpine basins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15646, https://doi.org/10.5194/egusphere-egu24-15646, 2024.

EGU24-16055 | Posters on site | HS2.1.9

A Central Asian pro-glacial discharge database for improving hydrological models 

Eric Pohl, Mukhammed uulu Esenaman, Ardamehr Halimov, Dominik Amschwand, Tomas Saks, and Jingheng Huang

Central Asia’s mountain rivers are to a large degree fed by snow and ice melt and are a crucial contributor of fresh water downstream for millions of people. The attribution of how these meltwater sources will change their contribution to stream flow in a warmer future are, however, very uncertain. A major reason for this is an extremely sparse hydrometeorological monitoring network. This affects the calibration and validation of large-scale cryo-hydrological models that could be used for the task, or the validation and bias correction of reanalysis and remote sensing data needed to run such models. In combination with uncertainties about the glacier mass balances in the region, hydrological models are facing a pronounced equifinality problem. In order to improve this, and to understand better the glacier response to the current meteorological forcing in different climate zones of Central Asia, we instrumented 8 pro-glacial streams in Kyrgyzstan and Tajikistan with automated runoff gauges running at hourly resolution to also capture diurnal variability. These measurements complement the already (re-)established glaciological monitoring network at most of these sites and allow tackling the equifinality problem by constraining many variables. Here, we present first results from this database that shall serve to improve hydrological model calibration and parameterization, and understand relationships between meteorological forcing, annual glacier mass balance and meltwater generation. We also discuss instrumenting strategies and problems, and uncertainties related to gauge calibration.

How to cite: Pohl, E., uulu Esenaman, M., Halimov, A., Amschwand, D., Saks, T., and Huang, J.: A Central Asian pro-glacial discharge database for improving hydrological models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16055, https://doi.org/10.5194/egusphere-egu24-16055, 2024.

EGU24-18059 | ECS | Posters on site | HS2.1.9

On the Importance of groundwater constraining in hydrological modeling of the Pamir region 

Jingheng Huang, Eric Pohl, and Juan Carlos Richard-Cerda

Central Asia is a climate change hot spot, facing an unprecedented juxtaposition of regional climate- and water-related issues. Meltwater from the Pamir Mountains plays a crucial role in Central Asia's hydrological cycle, and its response to climate change has been widely investigated using glacial-hydrological models. However, the hydrological simulation in Pamirs is highly uncertain, primarily driven by data scarcity and the complex interplay between climatic factors and glacier dynamics. Ongoing efforts concentrate on including more calibration data and constraining the uncertainty about the exact internal process representation of hydrological models. However, the quality of the groundwater simulation is often neglected. Groundwater reservoirs, buffering meltwaters and providing river flow when little to no surface runoff occurs, are extremely important in the Pamir region. Although physically based groundwater models provide a more detailed picture of the possible evolution of the system, empirical groundwater models are often used in hydrological modeling due to their minimal input data requirements and low computational cost compared to physically based models. However, the traditional empirical groundwater model with single linear storage is not suitable for the Pamir region. The region is characterized by a variety of sedimentary deposits in different landscape morphologies, resulting in varying delays in water recharge, release, and storage capacities. We improved the baseflow representation by coupling two linear groundwater reservoirs (one fast and one slow) into a widely-used hydrological model in the region. A representative catchment in the central Pamir, the Gunt River basin, is used as a case study to demonstrate the importance of groundwater in constraining the hydrological calibration process. Groundwater is the only contribution to winter river discharge in the Gunt basin and can thus be used as an indicator of groundwater parameter constraint. Here we show that the hydrological model can achieve good performance (in terms of daily discharge, seasonal snow cover fraction, and annual glacier mass balance) even when calibrated with only total daily discharge and winter baseflow. Especially the baseflow calibration helps constraining snowmelt onset in spring and improving adjustments of precipitation and temperature, which are the most uncertain sources in hydrological modeling in the region. Despite improvements, degree day factors still show a large variability. The resulting model equifinality problem still leads to predictive uncertainty, indicating that more glacier observations are needed for a sound process understanding. Based on the simulated results, the hydrological cycle in Gunt was analyzed and compared with previous studies.

How to cite: Huang, J., Pohl, E., and Richard-Cerda, J. C.: On the Importance of groundwater constraining in hydrological modeling of the Pamir region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18059, https://doi.org/10.5194/egusphere-egu24-18059, 2024.

EGU24-18338 | ECS | Posters on site | HS2.1.9

Assessing the use of GPR and drone snow data for model development and runoff predictions in Northern Sweden 

Ilaria Clemenzi, David Gustafsson, Viktor Fagerström, Daniel Wennerberg, Björn Norell, Jie Zhang, Rickard Pettersson, and Veijo Pohjola

In cold regions, snow is a crucial component of the cryosphere, experiencing changes such as decreasing snowpack and snow cover. These changes impact the seasonal amount of snow and cause a shift in the timing of spring floods, particularly in mountainous areas. The complex and diverse snow processes and interactions in mountainous environments challenge making accurate predictions on snow and runoff. Moreover, snow is not uniformly distributed in space and time, which emphasizes the importance of monitoring mountain snowpack to enhance the understanding of hydrological processes and improve forecasting in the face of changing conditions. In the past few years, ground penetrating radar and drone acquisitions have emerged as a state-of-the-art methodology for obtaining snow data at high spatial resolution with a significant area coverage compared to traditional point observations. This study used data from ground penetrating radar and drone acquisitions to develop and evaluate a new snowfall distribution function based on wind speed, direction and topography to model wind redistribution in the semi-distributed hydrological model HYPE. We assessed the effect of the new snowfall distribution function compared to the one based on wind direction and topography on the snow distribution close to the accumulation peak in the Överuman catchment, Northern Sweden. We further assessed the impact of the two snowfall distribution functions on the catchment runoff predictions. Results show that the snowfall distribution function based on wind speed and direction better simulated the snow spatial distribution in the catchment than the snowfall function based on wind direction. Ground penetrating radar and drone acquisitions provided complementary model development and evaluation information.

How to cite: Clemenzi, I., Gustafsson, D., Fagerström, V., Wennerberg, D., Norell, B., Zhang, J., Pettersson, R., and Pohjola, V.: Assessing the use of GPR and drone snow data for model development and runoff predictions in Northern Sweden, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18338, https://doi.org/10.5194/egusphere-egu24-18338, 2024.

EGU24-18443 | ECS | Orals | HS2.1.9

Snow accumulation dynamics and its contribution to the hydrology of a glacierized catchment in the Northern Pamirs 

Achille Jouberton, Stefan Fugger, Thomas Shaw, Evan Miles, Marin Kneib, Abdulhamid Kayumov, Ardamehr Halimov, Hofiz Navruzshoev, Husraf Kabutov, Firdavs Vosidov, and Francesca Pellicciotti

Mountain glaciers are shrinking at accelerating rates due to enhanced ablation and reduced accumulation. In High Mountain Asia (HMA), recent glacier and snow changes have been highly heterogeneous, due to differences in accumulation regimes and sensitivity of glacier mass balances to temperature increases. The Pamir-Karakoram region is well known for hosting some of the only glaciers featuring neutral or even positive mass balance since the 2000, yet the causes for this anomaly are not fully understood, neither how long it will persist in the future nor its hydrological implications. In the semi-arid basins of Central Asia, snow- and glacier melt sustains most of the annual streamflow, with glacier melt being especially important towards the end of the dry summers. However, very few direct observations exist at high elevation, hindering the quantification of glacier mass inputs which is essential to estimate the long-term sensitivity of glaciers to warming. 

In this study, we combine in-situ hydro-meteorological observations with remote sensing observations to constrain a land-surface model and understand snow accumulation dynamics at a glacierized catchment in the Pamir mountains of Tajikistan. In-situ snow height and mass changes have been collected since 2021 from automatic weather stations, time-lapse cameras and pressure loggers in seasonally frozen lakes, providing a uniquely rich dataset for this region. We use MODIS, Landsat-8 and Sentinel-2 satellite images to derive snow cover dynamics at high spatial and temporal resolutions, and very high-resolution (2m) optical stereo imagery (Pleiades) to derive spatially resolved snow depths. These in-situ and remote-sensing observations are then used to inform a land-surface model that we force with statistically downscaled and bias-corrected reanalysis data (ERA5-Land) at 100m spatial and hourly temporal resolution, from 2015 to 2023.

We use our model to dissect the glacier mass balance seasonal dynamics, to quantify how much mass is gained through snowfall and avalanches, and how much mass is lost through melting and sublimation. We find that glaciers in our catchment receive a large part (58 %) of their annual mass input (1081 mm w.e.) from March to July, suggesting that spring and early summer precipitation events are key to control accumulation and therefore dictate glacier mass balances. Importantly, 11% of the annual snowfall is returned to the atmosphere via sublimation. At the catchment scale, snowmelt contributes to 67% of the annual runoff (625 mm), followed by glacier melt (24%) and rain (9%). When most of the seasonal snowpack has melted out (usually in August), glacier melt becomes the dominant contribution (with 55% in September). In most of the study period years, the glacier mass balance is close to neutral, but it turned negative in the last three years, where warmer conditions have led to more rapid seasonal snowpack melt-out and higher glacier ELAs, deteriorating the health of these previously spared glaciers and casting doubts on their ability to provide fresh water during the dry summers in the longer term.

How to cite: Jouberton, A., Fugger, S., Shaw, T., Miles, E., Kneib, M., Kayumov, A., Halimov, A., Navruzshoev, H., Kabutov, H., Vosidov, F., and Pellicciotti, F.: Snow accumulation dynamics and its contribution to the hydrology of a glacierized catchment in the Northern Pamirs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18443, https://doi.org/10.5194/egusphere-egu24-18443, 2024.

EGU24-19899 | Posters on site | HS2.1.9

Flood modelling of a partly glacierized catchment in the Himalayas in a context of climate change 

Domenico De Santis, Christian Massari, Silvia Barbetta, Farhad Bahmanpouri, Viviana Maggioni, Sagar Gupta, Ashutosh Sharma, Ankit Agarwal, and Sumit Sen

The Himalayan region is severely exposed to the flood risk due to the heavy rainfall during the summer monsoon. The dynamics of the hydrological response during extreme events is relatively less understood, because of several complex and interactive processes. In this scenario, the use of rainfall-runoff models capable of adequately taking these processes into account could be crucial for reliable flood forecasting. However, in areas with such complex topography, accurately characterizing meteorological forcing and streamflow dynamics remains a challenging task due to the lack of ground measurements. Furthermore, in highly glacierized Himalayan basins, the significant contribution to streamflow by snow and ice melting has been shown to be progressively increasing due to its sensitivity to climate change, in parallel with the loss in glacier mass.

In this study, a conceptual and parsimonious hydrological model was implemented in semi-distributed mode and calibrated against streamflow and glacier loss volume data simultaneously. The MISDc-2L model was modified to simulate not only the snow accumulation and melt, but also the glacier melting in the ice-covered fraction of sub-basin area, assumed to occur once the seasonal snowpack is locally depleted. The Alaknanda River (one of the two headstreams of the Ganges) was chosen as a case study because it experiences several disastrous flood events in recent years. The basin upstream the Rudraprayag gauge was considered (≈8600 km2), for the period 2000-2020. The Randolph Glacier Inventory v7.0 was employed to locate glacierized areas, while glacier storage change data were extracted from available literature studies. Elevation data from NASADEM and hourly variables from ERA5-Land reanalysis dataset were used. A joint objective function was considered for calibration, including the Kling-Gupta efficiency, a high-flows hydrological signature and the error in glacier stored water loss. The model, constrained with glacier storage change data, was found to be able to provide good hydrological performances, both in calibration and validation, also with specific reference to annual flood peaks.

Despite the simplicity and the flood-oriented approach, the proposed modelling procedure simulated the dominant hydrological processes in a physically plausible way, in a basin with high-altitude glacierized areas in a context of climate change. The goal of adequately characterizing the contribution of glacier melt to total streamflow was pursued by aiming for consistency with additional data sources.

 

This work was funded by:

-          the Next Generation EU - Italian NRRP, Mission 4, Component 2, Investment 1.5, call for the creation and strengthening of 'Innovation Ecosystems', building 'Territorial R&D Leaders' (Directorial Decree n. 2021/3277) - project Tech4You - Technologies for climate change adaptation and quality of life improvement, n. ECS0000009. This work reflects only the authors’ views and opinions, neither the Ministry for University and Research nor the European Commission can be considered responsible for them.

-          the FLOSET Project 'Probabilistic floods and sediment transport forecasting in the Himalayas during the extreme events’, funded in the context of the 'ITALY-INDIA JOINT SCIENCE AND TECHNOLOGY COOPERATION CALL FOR JOINT PROJECT PROPOSALS FOR THE YEARS 2021 2023'.

How to cite: De Santis, D., Massari, C., Barbetta, S., Bahmanpouri, F., Maggioni, V., Gupta, S., Sharma, A., Agarwal, A., and Sen, S.: Flood modelling of a partly glacierized catchment in the Himalayas in a context of climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19899, https://doi.org/10.5194/egusphere-egu24-19899, 2024.

EGU24-19969 | Orals | HS2.1.9

Correction of raingages' snow undercatch at meteorological stations using data from snow surveys: an Armenian case study 

Vazken Andréassian, Amalya Misakyan, and Artur Gevorgyan

The hydrological analysis of high elevation catchments is particularly difficult for two reasons:

. first, precipitation measurements are scarce at higher elevations,

. second, even when there are precipitation measurements, the collected amounts are strongly biased due to the well-known effect of wind on snowflakes.

Several formulations have been proposed to correct this wind-dependent underestimation of solid precipitation amounts. They all depend on at least one parameter, which must be calibrated for the specific location. At a few locations in the world, a double-fenced shielded raingage can be used to provide a reference precipitation amount, and the parameter of the correction can be determined experimentally. But at most locations, we have no real way to parameterize the adjustment relationship.

We use here a newly released dataset comprising 30 years of data for 11 stations located at high elevation in Armenia, where the precipitation gage network is strongly impacted by snow undercatch. Using ground snow surveys jointly with a degree-day based snow accumulation and melt model, we show that we can propose an adapted parameterization of the correction formula.

How to cite: Andréassian, V., Misakyan, A., and Gevorgyan, A.: Correction of raingages' snow undercatch at meteorological stations using data from snow surveys: an Armenian case study, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19969, https://doi.org/10.5194/egusphere-egu24-19969, 2024.

EGU24-335 | ECS | PICO | HS2.1.10

Isotope Hydrology progress in sub-Saharan Africa. What information for water management?  

Bertil Nlend, Fréderic Huneau, and Suzanne Ngo Boum-Nkot

The utility of isotope techniques in hydrological investigations stems from their ability to label water sources and cycling processes including surface/groundwater interaction, water residence times, flow pathways, evaporation fluxes, and solute processes, to name a few. In Africa, they have been applied since four decades following the severe drought of the 1970s, and can now be summarized in important case studies. This review focusing on Cameroon (often called the little Africa) aims to put together all the stable and radioactive isotopic data (>500 samples from rainfall, surface and groundwater) published in the country to: (i) identify the drivers responsible for precipitation isotopes spatial variation and climatological implications, (ii) elucidate the groundwater recharge mechanisms over the countries and relationships with rivers, and (iii) highlight the existence of paleo-groundwater in the country. It is found that rainfall stable isotopes variation is linked to the migration of the Intertropical Convergence Zone (ITCZ). The groundwater recharge can be diffuse and focused. This latter mechanism is mainly observed in the semi-arid region. It is in this relatively dry region that most of the paleo-groundwater resources are identified thanks to 14C dating. This information will be useful to develop water management strategies regarding all the challenges (e.g., climatic and demographic) faced by the country. Finally, this paper discusses the gaps groundwater isotope hydrology can still fill for contributing to a sustainable development of the country. Reflections provided here can be extend in each country of the sub-Saharan Africa region.

How to cite: Nlend, B., Huneau, F., and Ngo Boum-Nkot, S.: Isotope Hydrology progress in sub-Saharan Africa. What information for water management? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-335, https://doi.org/10.5194/egusphere-egu24-335, 2024.

Arid and semi-arid areas are characterized by low annual rainfall that is unevenly distributed in time and space. These low and variable rainfall conditions are exacerbated by the effects of climate change, resulting in increasing agricultural losses for rain-fed crops. To overcome this, several water conservation techniques have been developed to safeguard agricultural yields. For example, supplemental irrigation using catchment basins is a climate change adaptation solution that has been promoted for many years in drought-prone areas. Unfortunately, this technique has had limited success in the Sahel due to the large amount of water lost through infiltration into the basins. These losses are closely related to the type of lining chosen to seal the runoff collection basins. Using a factorial analysis model, this paper highlights farmers' preferences for four of the most popular liners in Burkina Faso. Based on Waso-2 method, the survey was conducted in 2022 among 41 pond-owning farmers in the Central, Central Plateau and Central South regions. The results clearly show that the choice of liner has little to do with its availability and cost: producers focus all their attention on the liner's ability to improve the watertightness of their ponds and on the complexity of its maintenance. Concrete is therefore the first choice of producers as it is the most watertight, weatherproof, and durable, but also the most expensive. It is followed by plastic sheeting, a highly waterproof material available on the market, but not very durable. Clay comes third, despite its availability and low cost. Well-known in traditional architecture for ensuring the comfort of buildings, clay has proved ineffective for waterproofing submerged structures where the ground is unstable or cracked. Bitumen came last, as it is little known for pond protection and is not available in rural Burkina Faso.

Keywords: Rainwater harvesting basin, sealing solutions, supplemental irrigation, Waso-2.

How to cite: Kaboré, T. V. R.: Analysis of farmers' perception about sealing techniques for runoff harvesting ponds: the case of Burkina Faso., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-668, https://doi.org/10.5194/egusphere-egu24-668, 2024.

EGU24-2318 | ECS | PICO | HS2.1.10

Hydrological Model Performance Assessment across several Moroccan Catchments: Investigating the Effect of Model Attributes, Catchment Features, and Precipitation Inputs 

Oumar Jaffar, Abdessamad Hadri, El Mahdi El Khalki, Khaoula Ait Naceur, Mohamed El Mehdi Saidi, Yves Tramblay, and Abdelghani Chehbouni

Hydrology research can benefit significantly from large-sample hydrology studies by offering the possibility for better hydrological models’ assessment and by providing a suitable ground for identifying catchment characteristics that influence model performance. In our study, we conducted a performance assessment of eight monthly lumped rainfall-runoff models (GR2M, XM, WM, VUB, abcd, DWBM, GR5M, and Wapaba) in 30 Moroccan catchments, forced by rainfall data from 34 rain gauges. During the study period 1983-2019, we investigated the relationship between model performance (quantified with KGE) and both model complexity and structural attributes. Furthermore, we conducted correlation analysis to explore possible connections between this performance and catchment features (more than 180 features were considered), and we additionally examined how the models respond to three precipitation input data, namely ERA5, CHIRPS, and PERSIANN-CDR. Our findings revealed that no hydrological model was the best (or the worst) across the entire set of catchments. The model performance was found to be more influenced by model structure than by its degree of complexity, and more by hydro-climatic characteristics, particularly those related to calibration and calibration relative to validation, than by non-hydro-climatic factors. Among the investigated features, the Pearson correlation between observed rainfall and runoff was the strongest characteristic influencing model performance. Furthermore, this study (i) emphasized the essential role of rainfall and runoff data richness, in terms of wet and dry years, in enhancing model performance even if the calibration data is only relatively richer than the validation data and (ii) showed that dry periods are more beneficial to model performance than wet ones. Finally, our study revealed a consistent pattern in the models’ responses to the different rainfall forcings; with ERA5 consistently yielding the best model performance and PERSIANN-CDR consistently resulting in underperformance. This consistent behavior of the models was best explained by the linearity between the employed rainfall products and the catchments' observed runoff.

How to cite: Jaffar, O., Hadri, A., El Khalki, E. M., Ait Naceur, K., Saidi, M. E. M., Tramblay, Y., and Chehbouni, A.: Hydrological Model Performance Assessment across several Moroccan Catchments: Investigating the Effect of Model Attributes, Catchment Features, and Precipitation Inputs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2318, https://doi.org/10.5194/egusphere-egu24-2318, 2024.

EGU24-2694 | PICO | HS2.1.10

The Interplay between Land Use Changes and Hydrological Processes in the Upper Offin Basin of Ghana 

Seifu Tilahun, Afia Sarpong Anane Gyebi, Junias Adusei-Gyamfi, Andoh Kwaku Amponsah, Gerald Atampugre, and Olufunke Cofie

The transformation of the food system is intricately linked to the effective management of land and water resources, particularly in regions where diverse land uses compete for limited space. The upper Offin sub-basin serves as a prime example of this complexity, where agricultural, mining, and agroforestry practices fight for arable land, influencing the local food system and changes in hydrological processes. This study aims to comprehend the flow paths, the status of water resources, and land use changes in the agroforestry-dominated landscape of the upper Offin basin in Ghana. To assess historical land use patterns, Landsat images were utilized, alongside trend analyses of past hydro-climatic variables and a Thornthwaite-based water balance incorporating inputs from remote sensing and secondary data spanning from 1981 to 2022. Furthermore, the study instrumented an upland Mankran watershed in the upper Offin, where citizen scientists measured basic hydrological variables in three landscape positions—such as daily rainfall, streamflow rates, and groundwater levels—and water quality parameters (nitrate, phosphate, and mercury) from June to October 2023. The analysis revealed that annual and monthly rainfall exhibited minimal changes over the study period (1981–2022). Forest areas experienced a general decrease, while croplands and built-up areas increased between 2008 and 2021, impacting water balance components. Actual evapotranspiration (AET) based on the water balance model and WaPOR data demonstrated a decreasing trend, while streamflow at the basin outlet increased from 1986 to 2012. The runoff coefficient and the hydrological simulation based Thornthwaite-based water balance demonstrated that subsurface flow dominated the runoff processes, constituting approximately 20% of the average annual rainfall. This is also supported by the nitrate concentrations only peaked in rivers in June, while agricultural wells exhibited consistently high concentrations throughout the rainy period, suggesting leaching through subsurface flow. Phosphate concentrations increased in streams as the rainy period progressed, mirroring well concentrations, and mercury concentrations were low in surface water but four times higher in groundwater, indicating further the subsurface flow dominance. This study provides crucial insights for informed decision-making regarding the hydrological processes amid changing landscapes for sustainable agriculture and biodiversity preservation in the region. The emphasis on subsurface flow dominance underscores its significance in potential transport mechanisms for water quality within the landscape. Landscape management interventions must consider the role of subsurface flow to safeguard environmental resources, enhance water quality, and protect human health.

How to cite: Tilahun, S., Anane Gyebi, A. S., Adusei-Gyamfi, J., Amponsah, A. K., Atampugre, G., and Cofie, O.: The Interplay between Land Use Changes and Hydrological Processes in the Upper Offin Basin of Ghana, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2694, https://doi.org/10.5194/egusphere-egu24-2694, 2024.

EGU24-3573 | ECS | PICO | HS2.1.10

Exploring Trends, Patterns, and Drivers of African Surface Water Dynamics 

Patrick Sogno, Igor Klein, Soner Uereyen, Felix Bachofer, and Claudia Kuenzer

Water, a fundamental resource for both ecosystems and human populations, faces escalating challenges in Africa due to water stress and changes in climate, demography, and socioeconomics. Because these changes are happening at a rapid pace, it is essential to understand the dynamics of water bodies and the factors that impact them to ensure sustainable usage strategies. Our research aims to analyze the long-term trends of surface water availability in Africa, identify the causal impacts on major water bodies, and explore the similarities between different lakes.

We use daily time series based on Earth observation, including the MODIS-based Global WaterPack for a daily uninterrupted time series of the continent's surface water area. Furthermore, we incorporate daily time series of hydrologically relevant variables such as precipitation, total evapotranspiration, groundwater, soil moisture, and Gross Primary Productivity (GPP) to analyze their impact on surface water dynamics of major African lakes. For this, we employ the Peter and Clark Momentary Conditional Independence causal identification algorithm. Our findings reveal subbasin-wide surface water and GPP to be the dominant drivers of surface water dynamics in most cases. We further find that dynamically similar lakes often share common drivers, allowing the generation of regional lake clusters. Understanding the drivers of African lakes may significantly help in the formulation of sustainable development strategies.

In conclusion, our continent-wide analysis provides valuable insights, particularly beneficial for stakeholders engaged in international development and ecosystem protection and restoration. As we deal with the challenges of water resource management in Africa, our research aims to contribute substantively to the formulation of strategies that foster sustainability and resilience in the face of evolving environmental and socio-economic conditions.

How to cite: Sogno, P., Klein, I., Uereyen, S., Bachofer, F., and Kuenzer, C.: Exploring Trends, Patterns, and Drivers of African Surface Water Dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3573, https://doi.org/10.5194/egusphere-egu24-3573, 2024.

The recent 5-season drought in the Horn of Africa, which contributed to food security issues that nearly resulted in a declaration of famine by the UN, has renewed interest in the “East African Paradox” (cf. Rowell et al., 2015): despite observed drying trends in the March-April-May “long” rains, global coupled climate models—whose output is increasingly used to drive hydrological models and inform projections of the socioeconomic risks of climate change in East Africa—project increases in seasonal rainfall totals over both the historical period and throughout future projections in the region. This ‘Paradox’ could arise from low-frequency internal variability causing drying even if long-term trends are wetting or from structural biases in climate models (e.g. simulation of the equatorial Pacific Ocean) that cause spurious trends in model simulations. Large Ensembles, including for SST-forced runs, make differentiating between internal variability and biases in model mean behavior more feasible, and another decade of observational data since the emergence of the ‘Paradox’ helps improve our understanding of historic internal variability.

We use a large multi-model ensemble of opportunity of coupled and SST-forced runs from the latest model generation (CMIP6), spanning the observational record, to revisit the magnitude and causes of the ‘Paradox’. We find that drying trends in the long rains are timescale-dependent and weaker than they were during the peak ‘Paradox’ period. This is mostly well modeled by the SST-forced ensemble, though coupled models continue to have erroneously strong wetting trends. The ‘Paradox’ therefore is reduced to what are the causes of low frequency SST trends and why coupled models cannot reproduce them.  We will discuss if these changes are the result of natural variability temporally masking the forced trend and what the sign of that trend might be.  These results have implications for projections of future climate impacts with a potentially quantifiable range of internal variability providing more actionable information than the deep uncertainty on forced trends introduced by structural model errors.

How to cite: Schwarzwald, K. and Seager, R.: Revisiting the ‘East African Paradox’: CMIP6 models also fail to simulate observed drying trends in the Horn of Africa Long Rains, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4687, https://doi.org/10.5194/egusphere-egu24-4687, 2024.

EGU24-5288 | PICO | HS2.1.10

Spatial prediction of borehole yield in southern Mali using machine learning classifiers 

Victor Gómez-Escalonilla, Oumou Diancoumba, Dasso Yolande Traoré, Esperanza Montero, Miguel Martín-Loeches, and Pedro Martínez-Santos

Groundwater plays a vital role in drinking water supply, food security and ecosystem services. Approximately 2.5 billion people worldwide rely exclusively on groundwater to meet their daily needs, while hundreds of millions of farmers depend on groundwater resources to sustain their livelihoods. Groundwater potential mapping based on machine learning (ML-GPM) can be used to support groundwater exploration, planning and management practices. Most ML-GPM studies aim to predict a positive or negative outcome, that is, to identify areas of high or low groundwater potential. This work takes this conventional bivariate outcome approach one step further by predicting borehole yields and applying a multiclass approach. The method is illustrated through an application over a study area of 21,000 km2, including the administrative region of Bamako and the municipalities of Kati and Kangaba in the Koulikoro region of southern Mali. Logistic Regression, Gradient Boosting and Extra Trees classifiers were trained on an imbalanced multiclass database of 483 boreholes and 20 explanatory variables. The explanatory variables include information on lithology, geomorphology, soil, land use/land cover, topography, drainage and slope-related variables and rainfall, among others. All models returned prediction scores between 0.80 and 0.87. The most important variables include elevation, vegetation cover, basement depth and geology. The alluvial sediments of the Niger river banks, especially in the southern and northern sectors, are clearly associated with the most productive class. In contrast, the Mandingue plateau has the lowest groundwater potential. The piedmont areas present an intermediate groundwater perspective. These maps could be used to inform water supply policy at a regional scale.

How to cite: Gómez-Escalonilla, V., Diancoumba, O., Traoré, D. Y., Montero, E., Martín-Loeches, M., and Martínez-Santos, P.: Spatial prediction of borehole yield in southern Mali using machine learning classifiers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5288, https://doi.org/10.5194/egusphere-egu24-5288, 2024.

EGU24-6712 | PICO | HS2.1.10

Developments and Challenges in Operating a Hydrometeorological Research Observatory in the Western Sudanian Savanna - Ten Years of WASCAL Observatory Experience 

Jan Bliefernicht, Samuel Guug, Rainer Steinbrecher, Frank Neidl, Ines Spangenberg, Leonard K. Amekudzi, Emmanuel Quansah, Patrick Davies, Heye Bogena, Roland Baatz, Ursula Gessner, Thomas Jagdhuber, Francis Oussou, Seyni Salack, Belko Diallo, Kehinde O. Ogunjobi, Souleymane Sy, Windmanagda Sawadogo, Verena Huber Garcia, and Harald Kunstmann

West Africa is a data-poor region, and long-term hydrometeorological field experiments are very limited but are essential for a better understanding of climate change and land use change impacts in this vulnerable region. This study provides a detailed overview of WASCAL hydrometeorological observatory, which was established in 2013 in the Sudan savanna of Burkina Faso and Ghana. This region is characterized by strong land use changes due to a rapid increase of agricultural land. The observatory is therefore designed to study the effects of land use changes on land-atmosphere exchange processes and other terrestrial land surface processes and characteristics. It consists of a network of state-of-the-art hydro-meteorological measurement equipment (e.g., automatic weather stations, agrometeorological stations) complemented by innovative devices such as cosmic ray neutron sensors for improved soil moisture monitoring. A unique component of the observatory is a micrometeorological experiment using eddy covariance towers implemented at five contrasting land use sites to study the impacts of land use change on water, energy, and greenhouse gas fluxes. The datasets of the WASCAL observatory are needed as key information for the development and evaluation of land surface models, hydrological models, and improved regional climate models and other environmental modelling approaches and products. In this presentation, we provide a detailed overview of the current development of the WASCAL observatory. In addition, selected results from the inter-twined field, remote sensing, and RCM modeling studies are presented.

How to cite: Bliefernicht, J., Guug, S., Steinbrecher, R., Neidl, F., Spangenberg, I., Amekudzi, L. K., Quansah, E., Davies, P., Bogena, H., Baatz, R., Gessner, U., Jagdhuber, T., Oussou, F., Salack, S., Diallo, B., Ogunjobi, K. O., Sy, S., Sawadogo, W., Huber Garcia, V., and Kunstmann, H.: Developments and Challenges in Operating a Hydrometeorological Research Observatory in the Western Sudanian Savanna - Ten Years of WASCAL Observatory Experience, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6712, https://doi.org/10.5194/egusphere-egu24-6712, 2024.

EGU24-8158 | ECS | PICO | HS2.1.10 | Highlight

Investigating the human-water dynamics leading to increased drought and flood risk in Kitui, Kenya. 

Marlies H Barendrecht, Ruben Weesie, Alessia Matanó, Maurizio Mazzoleni, and Anne F. Van Loon

During the past decades, the county of Kitui in Kenya, has experienced severe droughts. Both rain seasons have failed for several years in a row. While the region is known for its aridity and the droughts it experiences, the region also experiences regular flooding. Both drought and flood events have had devastating impacts, leading to widespread water and food insecurity. In this study, we developed a system-dynamics model to investigate the interplay between drought and flood risk and how this is influenced by human-water interactions. We model the system’s hydrology, as well as drought and flood impacts and human actions and adaptation. We aim to estimate model parameters using hydrological and impact data and fit the model to the case study areas. The fitted model is used to investigate changes in drought and flood risk over the years and how these vary across three different case study areas. We investigate how both climatic drivers and human actions and responses to the changing environment influence drought and flood risk. This analysis provides insights into the main drivers of drought and flood risk and the model allows for an exploration of the policies and measures that could be implemented to reduce risk in the future.

How to cite: Barendrecht, M. H., Weesie, R., Matanó, A., Mazzoleni, M., and Van Loon, A. F.: Investigating the human-water dynamics leading to increased drought and flood risk in Kitui, Kenya., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8158, https://doi.org/10.5194/egusphere-egu24-8158, 2024.

EGU24-8886 | PICO | HS2.1.10

Enhancing Rainfall Estimates in East Africa by Merging TAHMO Precipitation Gauge Data with Remote Sensing Rainfall Products 

Vincent Hoogelander, Nick van de Giesen, Rolf Hut, Jianzhi Dong, Camille Le Coz, and George Sserwada

Sub-Saharan Africa heavily relies on remotely-sensed rainfall measurements due to a lack of in-situ rainfall data. While a high number of satellite-based rainfall products do exist, they are typically developed and tested in regions with a high density of ground data. The Trans-African Hydro-Meteorological Observatory (TAHMO) aims to tackle the ground data gap by installing and operating a dense network of weather stations in Sub-Saharan Africa. As part of the TEMBO Africa project, TAHMO data were used to make a new regional rainfall product in East Africa based on the SM2Rain algorithm.  Subsequently, this regional product was merged with a reanalysis product (ERA5) and two MW/IR-based rainfall products (IMERG-L and CHIRPS) based on the Statistical Uncertainty analysis-based Precipitation mERging framework (SUPER). Within this framework, merging weights are based on error variances of the rainfall products determined from quadruple collocation on a pixel-to-pixel basis. The merged product and the individual products are evaluated using data of the individual TAHMO stations. Our findings indicate that the merged product outperforms the individual products in most selected evaluation metrics.  ERA5 has the highest contribution in the merged product, followed by SM2Rain. Both IMERG and CHIRPS have limited contribution in the merged product due to a high error variance. The ultimate goal of this study was to develop a workflow to enhance the accuracy of rainfall measurements in Sub-Saharan Africa by leveraging information from TAHMO data and different existing products, contributing to the improvement of remotely-sensed rainfall measurements in Sub-Saharan Africa.

We welcome suggestions on possible improvements and operational implementation, as well as ideas on how to use this merged product to understand the sources of error in satellite-based rainfall measurements in Sub-Saharan Africa.

 

TEMBO Africa: The work leading to these results has received funding from the European Horizon Europe Programme (2021-2027) under grant agreement n° 101086209. The opinions expressed in the document are of the authors only and no way reflect the European Commission’s opinions. The European Union is not liable for any use that may be made of the information

How to cite: Hoogelander, V., van de Giesen, N., Hut, R., Dong, J., Le Coz, C., and Sserwada, G.: Enhancing Rainfall Estimates in East Africa by Merging TAHMO Precipitation Gauge Data with Remote Sensing Rainfall Products, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8886, https://doi.org/10.5194/egusphere-egu24-8886, 2024.

EGU24-9889 | ECS | PICO | HS2.1.10

Data rescue of millions of daily precipitation and temperature records collected within the Congo Basin 

Derrick Muheki, Bas Vercruysse, Christophe Verbruggen, Dominique Kankonde Ntumba, Ed Hawkins, Félicien Meunier, Fils Makanzu Imwangana, Hans Verbeeck, Julie M. Birkholz, José Mbifo, Kim Jacobsen, Koen Hufkens, Krishna K. T. Chandrasekar, Olivier Dewitte, Olivier Kapalay Moulasa, Pascal Boeckx, Peter Thorne, Seppe Lampe, Théophile Besango Likwela, and Wim Thiery

Local and distant archives of observed weather data present unique opportunities for scientists to obtain long time series of the historical hydrology and climate for many regions of the world. Unfortunately, most of these observational records are still to-date available only on paper, and thus require digitization and transcribing to machine-readable formats to facilitate analysis of hydroclimatic trends. Here we discuss the data rescue efforts for hydroclimatic data recorded at 36 climate stations in the Democratic Republic of Congo from the early 1950’s to-date. We describe the procedures we follow to digitize over 10,000 paper records of daily precipitation and temperature within archives both in the Democratic Republic of Congo and Belgium, and subsequently the steps to transcribe this data set using different methods including machine learning. Furthermore, we undertake quality control and quality assessment of the transcribed data. The resultant time series, comprised of millions of observations from the archived data, will resolve the challenges of limited available hydroclimatic data within the Congo basin and expedite research on the hydroclimate in the basin.

How to cite: Muheki, D., Vercruysse, B., Verbruggen, C., Ntumba, D. K., Hawkins, E., Meunier, F., Imwangana, F. M., Verbeeck, H., Birkholz, J. M., Mbifo, J., Jacobsen, K., Hufkens, K., Chandrasekar, K. K. T., Dewitte, O., Moulasa, O. K., Boeckx, P., Thorne, P., Lampe, S., Likwela, T. B., and Thiery, W.: Data rescue of millions of daily precipitation and temperature records collected within the Congo Basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9889, https://doi.org/10.5194/egusphere-egu24-9889, 2024.

EGU24-13236 | ECS | PICO | HS2.1.10

Determinants of soil field-saturated hydraulic conductivity across sub-Saharan Africa: texture and beyond 

Aida Bargués Tobella, Leigh A. Winowiecki, Douglas Sheil, and Tor G. Vågen

Soil infiltration is a critical hydrological process governing water security and related ecosystem services. The infiltration capacity of soils is largely controlled by their hydraulic conductivity. Hence, understanding soil hydraulic conductivity is critical for effective soil and water management. Despite recent efforts in assembling measurements of soil hydraulic conductivity, global databases and derived pedotransfer functions lack coverage in the tropics. Africa, in particular, remains sparsely represented in these global databases, and representative observations of soil hydraulic properties are few and of mixed form and quality.

In this presentation, we introduce a new dataset of soil infiltration measurements and accompanying indicators of soil and land health collected systematically using the Land Degradation Surveillance Framework (LDSF) in 3573 plots from 83 100 km2 sites across 19 countries in sub-Saharan Africa and present the results from a recent study* where we used these data to (a) determine field-saturated hydraulic conductivity (Kfs) and (b) explore which variables best predict variation in Kfs.

Our results show that sand content, soil organic carbon (SOC), and woody cover had a positive relationship with Kfs, whereas grazing intensity and soil pH had a negative relationship. Our findings highlight that, despite soil texture being important, structure also plays a critical role. These results suggest significant opportunities to improve soil hydrological functioning through management and restoration practices that protect and enhance soil structure. Enhancing SOC content, limiting livestock stocking rates, promoting vegetation cover, particularly woody vegetation, and preventing and halting soil erosion can increase Kfs. This evidence can guide sustainable land management practices and restoration interventions across the region for improved soil health and water security.

Our dataset expands existing regional and global databases of soil hydraulic properties, improving coverage for Africa and providing field data for underrepresented land uses and soils. As such, we envision that this dataset can contribute to improved understanding and prediction of soil hydraulic properties and to improved Earth system and land surface models for applications in Africa.

 

* Bargués-Tobella, A., Winowiecki, L.A., Sheil, D., and Vågen, T.G. Determinants of soil field-saturated hydraulic conductivity across sub-Saharan Africa: texture and beyond. Water Resources Research. DOI 10.1029/2023WR035510. In-press.

How to cite: Bargués Tobella, A., Winowiecki, L. A., Sheil, D., and Vågen, T. G.: Determinants of soil field-saturated hydraulic conductivity across sub-Saharan Africa: texture and beyond, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13236, https://doi.org/10.5194/egusphere-egu24-13236, 2024.

EGU24-13773 | ECS | PICO | HS2.1.10

Multi-Objective Calibration of Nile River Basin Using Recovered Records 

Irenee Felix Munyejuru and James Stagge

The transboundary Nile River Basin (NRB) occupies a tenth of the African continent and supports the daily livelihood of approximately 300 million people in 11 riparian countries. The NRB is hydrologically complex: two major watersheds, the Blue and White Nile, contribute about 85% of the total annual discharge; more than 50 % of the White Nile’s water is lost over the Sudd wetland; and the Blue and White Nile watersheds produce dramatically different seasonal hydrologic responses due to differences in hydroclimate and lake/wetland storage. The Inter-Tropical Convergence Zone (ITCZ) drives anomalies in temperature and precipitation; however, this atmospheric driver likely produces distinct hydrologic responses that depend on the spatial center over the Blue or the White Nile headwaters. Quantifying this effect requires a well-calibrated hydrologic model of the entire watershed under near-natural conditions, including hydrologic routing through major lakes and the Sudd wetland. This study aims to calibrate such a hydrologic model and recreate the hydrologic response of the major watersheds in the NRB using recovered records that extend to 1901, thereby greatly increasing the period used for model calibration and approximating near-natural responses prior to construction of several modern reservoirs. We employed GR4J, a parsimonious rainfall-runoff hydrologic model, because of its flexibility and minimal data requirements to match the NRB’s limited data availability, particularly during the early 1900s. Climate drivers, including precipitation and daily minimum/maximum temperatures were based on the Global Soil Wetness Project Phase 3 (GSWP3). Discharge data for model calibration were acquired from the Global Runoff Data Centre (GRDC) and through digitization of long discharge records from Hurst (1958). The NRB was discretized into 36 hydrological response units (HRUs), and calibrated using stepwise, multi-objective approach at 16 gauge locations between 1901 and 1964. In addition to avoiding the effects of several modern reservoirs, this early calibration period also avoided the most severe effects of climate change, as supported by the lack of discernible trends using the Mann-Kendall test. Our results show a successful calibration of the GR4J hydrological model to reasonably reproduce discharge at multiple locations across the NRB, with Nash-Sutcliffe Efficiencies of 0.83 and 0.64 at the outlets of the Blue and the White Nile, respectively. Additionally, the calibrated model accurately captured an abrupt change of Lake Victoria levels during the 1960s, affirming its reliability in simulating regional climate disruptions and lake dynamics. The model can therefore be used to study the sensitivity of major watersheds in the NRB and serves as a benchmark for understanding anthropogenic-induced departures from the natural hydrological behavior of the Nile River.

Keywords: Nile River Basin, GR4J, Calibration, Hydrology

How to cite: Munyejuru, I. F. and Stagge, J.: Multi-Objective Calibration of Nile River Basin Using Recovered Records, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13773, https://doi.org/10.5194/egusphere-egu24-13773, 2024.

EGU24-19265 | ECS | PICO | HS2.1.10

Multi-scale and multi-model approaches to water management – application to drought and irrigation in Morocco 

Sven Berendsen, Justin Sheffield, Chiara Corbari, Nicola Paciolla, Diego Cezar Dos Santos Araujo, Ahmad Al Bitar, Kamal Labbassi, and Zoltan Szantoi

Water management is a problem of matching supply and demand whilst sustaining environmental conditions for a range of sectors and ecosystems, potentially under changing conditions of climate or demand. In dryland regions, this is particularly difficult given low available water supply and high climate variability, often with lack of data for operations, planning and design. Addressing these challenges at national scale requires whole-system approaches to incorporate the range of relevant sectors and their interactions, and multi-scale approaches to capture the large-scale drivers of water availability and the fine-scale variability of supply and demand within catchments, irrigation districts or urban areas.

In the context of the AFRI-SMART project “EO-Africa multi-scale smart agricultural water management” funded under the ESA EO Africa - National Incubators EXPRO+ programme, we have developed a multi-scale, multi-model approach to help address water management challenges in Morocco. On-going drought conditions in the country for the past 5 years have left reservoirs without water for irrigation, which must be prioritized for public water supply, impacting on food production, agricultural exports and farmer incomes. More accurate information on water resources distribution in space and time across scales and sectors is needed to address sustainable agriculture, to help guarantee food and water security, and increase resilience to hydro-meteorological extremes.

At national scale multiple sources of information from ground observations, satellite remote sensing, and climate and hydrological models are integrated to provide the best estimate of hydroclimate and drought indices to characterize the large-scale variability in water supply. This feeds into basin scale hydrological modeling, focused on the Oum Er-rbia basin using the HydroBlocks modelling framework, which combines a 1-D land surface model with a cluster-based landscape representation, allowing large-domain simulations at 10s metres resolution. HydroBlocks is coupled to the RAPID stream flow routing scheme to provide high resolution stream flow estimates. Predicted stream flow is routed to the main reservoirs in the basin which are simulated using a simple mass balance approach. Withdrawals from the reservoirs are supplied to one of the basin’s irrigation districts of Doukkala. Actual and optimized irrigation water needs for specific crops, at fine resolution (daily, 10 m) are predicted using the energy-crop-water balance model FEST-EWB-SAFY driven by Landsat LST and Sentinel2 vegetation indices.

The system is used to provide historic reconstructions of water availability and analyzed to identify times of supply risks. The system is also implemented in monitoring and seasonal forecast mode as a tool to understand upcoming risks to water supply and potential interventions to reduce risks, such as provision of early warning of risks, options for adjusted reservoir management, or altered/optimized irrigation scheduling. An open online decision support tool has been developed to provide intuitive near real-time visualization of information from the satellites/models and explore forecasts and future scenarios. We also discuss the collaboration with end user groups in helping to define the management problem and identification of critical decisions in water management across scales.

How to cite: Berendsen, S., Sheffield, J., Corbari, C., Paciolla, N., Dos Santos Araujo, D. C., Al Bitar, A., Labbassi, K., and Szantoi, Z.: Multi-scale and multi-model approaches to water management – application to drought and irrigation in Morocco, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19265, https://doi.org/10.5194/egusphere-egu24-19265, 2024.

EGU24-336 | ECS | Orals | HS2.1.11

Improving runoff generation knowledge through baseflow campaigns 

Camyla Innocente dos Santos, Julian Klaus, and Pedro Luiz Borges Chaffe

Predictions from Global Climate Models point to increasing water scarcity across the Global South. However we currently lack understanding of how these predicted changes propagate through the hydrological cycle to smaller-scale systems. This lack of understanding is due to limited knowledge of hydrological processes, which persists in tropical, subtropical, and arid environments of the Global South. Clear blueprints exist for experimental catchment setups that allow us to understand spatiotemporal catchment processes (e.g., the Long Term Ecological Research LTER, the Critical Zone Observatory network CZO, and the Terrestrial Environmental Observatories TERENO); yet, it is not feasible to maintain such dense experimental networks in the understudied Global South. Reconciling snapshot baseflow campaigns as sources of data can be an alternative to expanding hydrological observation, particularly in developing countries where long-term records are scarce and pressure on water resources is growing. Here, we present results from baseflow campaigns in small nested catchments across different landscape elements to improve a rainfall-runoff model (geomorphologic instantaneous unit hydrograph) and provide insights into spatial patterns of flow, catchment water storage, and estimates of streamflow sources. The Peri Lake Experimental Catchment (19 km²) is characterized by granite and diabase dike and covered by the Atlantic rainforest. We measured baseflow discharge and sampled isotopes (δ18O and δ2H) at 25 catchments (areas ranging from 0.02 to 5.33 km²). Through combining flow velocity and discharge, we incorporated spatial variations of velocity in the channels during runoff, using a constant relationship between velocity and celerity. The Nash values were above 0.80, and we eliminated the need for concentration time formulas, where uncertainty reaches 500%. Combining isotopes and discharge enhanced our knowledge of the role of geology, with the Spearman coefficient between the percentage of granite and specific discharge being -0.68 (p-value < 0.05). We conceptualize that the diabase dikes are shallower with greater permeability, functioning as a conductor and supplier of water during baseflow. Simulations with a 3D surface-subsurface hydrological model  verify the capacity of the observed baseflow patterns in this catchment with heterogeneous geology. The results suggest that measurements in nested catchment during baseflow conditions reflect the heterogeneity of the different sources that contribute to streamflow. Snapshot measurement and sampling  campaigns are a powerful tool to understand runoff generation patterns in subtropical and tropical catchments of the Global South where continuous monitoring is hard to implement.

How to cite: Innocente dos Santos, C., Klaus, J., and Chaffe, P. L. B.: Improving runoff generation knowledge through baseflow campaigns, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-336, https://doi.org/10.5194/egusphere-egu24-336, 2024.

EGU24-896 | ECS | Orals | HS2.1.11

Water level regimes, forest composition, and forest functioning in floodplain forests in southeastern Brazil 

Aline Meyer Oliveira, Fernanda Gianasi, Patrícia Vieira Pompeu, Rubens Manoel dos Santos, and Ilja van Meerveld

Floodplain forests are unique ecosystems at the interface between rivers and terrestrial environments. They provide important ecosystem services, such as biodiversity conservation and flood control. However, they are also one of the most threatened ecosystems. Vegetation composition in floodplain forests depends on the flood regime, but there is a lack of knowledge on the relation between the water level regime and forest composition and functioning for the seasonally dry tropics. As a result, it is unclear how these forests will be impacted by climate change.

In the WatForFun (“Water level regime and forest functioning in floodplain forests”) project, we brought together an interdisciplinary team of hydrologists and ecologists to better understand the relation between flood dynamics (e.g., flood frequency and duration) and tree species composition, phylogenetic diversity, functional diversity and taxonomic diversity. Fieldwork was conducted in six seasonally flooded forests in the state of Minas Gerais in southeastern Brazil. Three floodplains are located in the Rio Grande basin (Capivari, Jacaré, and Aiuruoca), and another three in the São Francisco basin (Jequitaí, Verde Grande, and Carinhanha). The floodplains encompass a gradient in climate, from humid subtropical to seasonal dry tropical. For each floodplain, we identified five geomorphological eco-units based on the vegetation composition: marginal levee, lower terrace, upper terrace, lower plain, and higher plain. We surveyed the vegetation at each site and installed groundwater wells and surface water level loggers to monitor the water level regime. We sampled xylem water, soil water, groundwater, surface water and precipitation to identify the sources for tree water uptake based on the stable isotopes of hydrogen and oxygen.

The eco-units differ from each other with regards to vegetation composition, phylogenetic and taxonomic diversity, and in terms of flood duration and flood frequency. The terraces remained flooded for longer periods of time than the other eco-units. The flood duration for the levees differed for the two basins. The xylem water was more depleted during the wet season than during the dry season, suggesting that trees change water uptake strategies depending on water availability. These findings help us to better understand the relation between floods and vegetation composition and to predict the impacts of climate change on vegetation composition and diversity.  

How to cite: Meyer Oliveira, A., Gianasi, F., Vieira Pompeu, P., Manoel dos Santos, R., and van Meerveld, I.: Water level regimes, forest composition, and forest functioning in floodplain forests in southeastern Brazil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-896, https://doi.org/10.5194/egusphere-egu24-896, 2024.

EGU24-1529 | ECS | Posters on site | HS2.1.11

Understanding water use strategies of Central European tree species in dependency on groundwater depth 

Clara Rohde, Alberto Iraheta, Matthias Beyer, Gökben Demir, and Maren Dubbert

In 2003, 2015, and 2018 extreme droughts caused severe depletion in soil water storage, decreased groundwater tables, and severe damage to forest ecosystems in Europe, such as increased mortality rate. In the future, such extreme droughts will be more likely to occur due to climate change. Therefore, it is crucial to understand and develop mitigation strategies and responses to reduced water availability of European trees for drought resilience.

Tree species significantly differ in their response to drought. Isohydric trees, for example, which are often deep-rooted, close their stomata when sensing a change in soil water potential while anisohydric trees - often shallow-rooted - continue to transpire even when soil moisture declines. As a result, anisohydric trees have an increased risk of hydraulic failure under drought stress because of their high stomatal conductance. Moreover, it is assumed that deep-rooted trees are more resilient to droughts than shallow-rooted trees because these trees possess an enhanced capacity to better withstand periods of drought. However, when naturally deep-rooted and isohydric trees lose their stable water source connection they might be strongly susceptible to drought. In this study, we examine the different below and above-ground mitigation strategies of common central European tree species in a temperate climate.

We chose a mixed forest stand composed of Fagus sylvatica L., Carpinus betulus L., Fraxinus excelsior L., and Quercus spp. trees on a hillslope in NW Germany where a natural gradient of groundwater distance (> 4 m top site, ~ 1.50 m valley) exists and variable rooting depths are found. Observations of soil and plant water status, as well as groundwater level at three hillslope positions (top, slope, valley), started in May 2023. Two point-dendrometers per tree species and hillslope position providing annual tree growth were used to determine tree water potential. Sap flow sensors (three per tree species and position) were installed to estimate plant water use and stem water content as well as for upscaling to tree and stand-level photosynthesis. All sensors will run another growing season for comparative analysis.

Although the year 2023 was not particularly dry and no severe soil water depletion was observed, the first growing season measurements indicate that e.g. C. betulus and F. excelsior are performing better - i.e. showing higher sap flux velocities and higher growth rates - in the valley than at the top position. Potential reasons could include the proximity of the groundwater table in the valley, trees being less limited in their transpiration efforts. However, other factors such as differing shading and less competition to C. betulus trees, which are more abundant uphill, need to be explored further.

How to cite: Rohde, C., Iraheta, A., Beyer, M., Demir, G., and Dubbert, M.: Understanding water use strategies of Central European tree species in dependency on groundwater depth, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1529, https://doi.org/10.5194/egusphere-egu24-1529, 2024.

EGU24-3398 | ECS | Posters on site | HS2.1.11

Soil and plant water ages in two Pinus radiata forests with markedly different annual precipitation amounts  

Lutz Klein, Bruce Dudley, Julian Klaus, and Dean Meason

Pinus radiata, which grows under a wide range of climate conditions, makes up the majority of the planted forests in New Zealand leading to concerns over the impact of this non-native species on water availability and quality. Transit times of water through the vadose zone reflect water fluxes and affect runoff chemistry. However, little is known on how vadose zone transit times differ for forests of the same species under different precipitation regimes. Our goal here is to evaluate how root water uptake (RWU), water transit times, and groundwater recharge in Pinus radiata plantations differ under variant precipitation. We investigated soil water fluxes and RWU in nine soil profiles in two Pinus radiata forests with greatly differing annual precipitation amounts (2934 mm vs. 725 mm) in New Zealand’s South Island. We estimated water age of vadose zone and xylem water using an isotope-enabled version of the one dimensional hydrological model Hydrus 1-D. We inversely derived the model parameters using a Monte-Carlo simulation with Latin hypercube sampling with times series of soil moisture and soil and xylem water stable isotopes. 
At the dry forest site, we found that transpiration and recharge accounted for over 80%, and around 10% of annual precipitation, respectively. At the wet forest site transpiration accounted for 24% and recharge 70% of annual precipitation. RWU at the dry forest site was nearly constantly soil moisture-limited while vapour pressure deficit was the limiting factor at the wet forest site. At the dry forest site, a large range of water ages contributed to RWU. During dry periods water age of RWU was high, but dropped sharply in surface soil layers and RWU following intense precipitation events. This was not observed at the wet forest site where soil water age and xylem water age were less variable. While at the wet forest site Pinus radiata almost exclusively relied on water from the current season for RWU, at the dry forest site significant amounts of RWU in the summer stemmed from winter precipitation.   Our results demonstrate not only greater impacts of these plantation forests on soil water balances in more arid climates, but also suggest greater susceptibility of dryland forests to variation in precipitation regimes.  

How to cite: Klein, L., Dudley, B., Klaus, J., and Meason, D.: Soil and plant water ages in two Pinus radiata forests with markedly different annual precipitation amounts , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3398, https://doi.org/10.5194/egusphere-egu24-3398, 2024.

EGU24-7687 | ECS | Orals | HS2.1.11

Soil moisture dynamics of forest soils – magnitude, persistence and implications of soil water repellency  

Pascal Benard, Julian Schoch, Andrea Mazza, Peter Lehmann, and Andrea Carminati

Soil water repellency has been observed across a range of ecosystems, including forests. Among other parameters such as organic matter content and quality, climate, and soil texture, the magnitude and persistence of water repellency is controlled by the initial soil moisture content. With the increasing risk of prolonged and recurrent drought events across Europe causing significant increases in tree mortality, the feedback between soil moisture and soil rewetting is of increasing importance, as delayed soil rewetting may prolong water stress beyond drought events and reduce the plant available water. In this study, we quantified the local contact angle (sessile drop method) and in-situ rewetting dynamics (electrical resistivity tomography), including their relationship with initial soil moisture (sorptivity), of forest soils with contrasting vegetation.

The results showed a fundamental difference in the persistence of water repellency and rewetting dynamics between an oak and a spruce stand. Despite prolonged precipitation (> 100 mm) following a dry summer, the sandy loam topsoil under spruce did not rewet after rain events, indicating persistent water repellency and fast water percolation to greater depth via preferential flow paths. In contrast, the sandy loam topsoil under oak rewetted after rainfall and was unaffected by water repellency, despite the similarly high initial contact angle of about 85° of dry soil at both sites.

Our results highlight the importance of moisture dependence and persistence of soil water repellency for plant-available soil water in forests. The striking persistence of low soil moisture in topsoil, in combination with shallow-rooted spruce may explain in parts the severe dieback of spruce across Europe. Furthermore, the hydrological response of repellency-affected forest sites is likely to be influenced by the feedback between initial soil moisture, soil wettability and its persistence, and soil rewetting dynamics.

How to cite: Benard, P., Schoch, J., Mazza, A., Lehmann, P., and Carminati, A.: Soil moisture dynamics of forest soils – magnitude, persistence and implications of soil water repellency , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7687, https://doi.org/10.5194/egusphere-egu24-7687, 2024.

Bimodal runoff behavior, characterized by two distinct peaks in flow response, often leads to significant stormflow and associated flooding. Understanding and characterizing this phenomenon is crucial for effective flood forecasting. However, this runoff behavior has been understudied and poorly understood in semi-humid regions. This study delves into the mechanisms behind delayed stormflow generation in a mountainous forested watershed within the semi-humid regions of North China. We assess the influence of soil water content and groundwater levels on the threshold behavior of delayed stormflow. Results indicate that the threshold behavior of the bimodal hydrograph is jointly controlled by soil water storage and groundwater levels, with soil water storage serving as the initiating factor for delayed stormflow. The groundwater replenishment and subsequent rise in groundwater level, crucial for the delayed stormflow, occur specifically when the soil water storage reaches 200 mm amid rainfall. At this point, shallow groundwater flow is promptly mobilized, swiftly moving into the channel and leading to the initiation of delayed stormflow. Notably, upon reaching a specific threshold groundwater level, each hillslope responds almost simultaneously, establishing a more extensive hydrological connectivity between the hillslopes and the stream channel. A substantial volume of shallow groundwater is released within a day, resulting in a hybrid bimodal hydrograph. These findings can enhance our understanding of the groundwater stormflow generation mechanism in semi-humid forest watersheds and contribute to the refinement of related runoff generation theories. 

How to cite: Cui, Z. and Tian, F.: Bimodal Hydrographs in Semi-humid Forested Watershed: Controlling Factors and Generation Mechanism , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7747, https://doi.org/10.5194/egusphere-egu24-7747, 2024.

EGU24-8425 | Orals | HS2.1.11

Rainfall partitioning by vegetation in China 

Yafeng Zhang, Chuan Yuan, Ning Chen, and Delphis Levia

Rainfall partitioning into stemflow, throughfall, and interception loss by vegetation alters hydrological and biogeochemical fluxes between vegetation and soil, and further affects water and nutrient balances at local, catchment, and regional scales. Here, we compiled a comprehensive dataset of rainfall partitioning by vegetation (forests, shrublands, croplands, and grasslands) in China. Based on this dataset, we delineate the general characteristics of rainfall partitioning in China from field observations. We summarize the best-fit functions reported for rainfall partitioning fluxes as a function of rainfall amount, as well as the rainfall thresholds for throughfall and stemflow initiation. We explore the patterns of the proportions of stemflow, throughfall, and interception loss to the gross rainfall across vegetation types in China. We determine whether and to what extent the chemical composition of rainwater is altered during rainfall partitioning processes. We use a machine learning method (boosted regression trees) to model the relative effects of cross-site biotic and abiotic predictors on each of the rainfall partitioning fluxes (%) and on the magnitude of chemical alteration in throughfall and stemflow. Our study avails a global readership to the findings of a large cache of Chinese studies that have been inaccessible hitherto, would aid in an accurate estimation of water and nutrients budget in vegetated ecosystems worldwide, and are helpful for making viable strategies to enhance forestry water resources management.

How to cite: Zhang, Y., Yuan, C., Chen, N., and Levia, D.: Rainfall partitioning by vegetation in China, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8425, https://doi.org/10.5194/egusphere-egu24-8425, 2024.

EGU24-10997 | ECS | Posters on site | HS2.1.11

Modelling surface water and energy transfer in karstic mediterranean forests 

Brune Raynaud--Schell, Jérôme Demarty, Jordi Etchanchu, Chloé Ollivier, Léna Collet, Jean Kempf, Jean-Marc Limousin, Olivier Marloie, Albert Olioso, Jean-Marc Ourcival, Guillaume Simioni, and Véronique Leonardi

Droughts are a major factor in the vulnerability of Mediterranean ecosystems, particularly forest ecosystems, which are mainly located in karstic environments. Under the effects of global change, these environments are exposed to increasingly frequent and intense droughts. Recent ecophysiological and isotopic studies have shown that tree roots are able to feed deep enough in the epikarst to support transpiration during periods of water stress. However, the quantification of stocks and temporal dynamics are not yet fully established. This calls for the development of models adapted to the complexity of the environment, with the aim of improving our knowledge of both aquifer recharge and the hydric functioning of forests. The work carried out in this study goes in this direction. It aims to suggest, implement and test a SVAT-type model of energy and water exchanges at the soil-vegetation-atmosphere interface, adapted to Mediterranean forest environments in karstic zones. The modelling objective is dual: i) to jointly simulate the processes of diffuse infiltration into the soil (i.e. the superficial part of the root zone) and rapid infiltration into the network of karstic fractures (i.e. the deep part of the root zone); ii) to simulate the transpiratory and water extraction processes throughout the root zone. To do this, an adaptation of the SiSPAT model was developed and then deployed for the first time on two sites in the ICOS network, namely the forest sites of Font-Blanche (Bouches-du-Rhône, P.I. URFM) and Puéchabon (Hérault, P.I. CEFE). The results highlight the importance to represent both diffuse and preferential flows in SVAT modelling for karstic areas. It particularly shows that preferential infiltration builds up deep water reserves throughout the year. It helps to reproduce better observed transpiration by the plant canopy during periods of water stress. It also significantly affects the different hydrological components of the surface, e.g. runoff and drainage to the aquifers.

How to cite: Raynaud--Schell, B., Demarty, J., Etchanchu, J., Ollivier, C., Collet, L., Kempf, J., Limousin, J.-M., Marloie, O., Olioso, A., Ourcival, J.-M., Simioni, G., and Leonardi, V.: Modelling surface water and energy transfer in karstic mediterranean forests, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10997, https://doi.org/10.5194/egusphere-egu24-10997, 2024.

EGU24-11093 | Orals | HS2.1.11

Are spatial patterns of soil moisture or percolation affected by throughfall heterogeneity? Empirical evidence from a beech-dominated forest. 

Anke Hildebrandt, Fischer-Bedtke Christine, Metzger Johanna Clara, Demir Gökben, and Wutzler Thomas

Heterogeneity in throughfall, caused by the redistribution of precipitation in the vegetation canopy, has repeatedly been hypothesized to influence the variation in soil water content and runoff behavior, especially in forests. However, observational studies directly relating the spatial variation in the soil water content or dynamics to net precipitation are rare. Here, we investigate how throughfall patterns affect the spatial heterogeneity in the soil water response in the main rooting zone. We assessed rainfall, throughfall, and soil water content (at two depths, 7.5 and 27.5 cm) in a 1 ha temperate mixed beech forest plot in Germany during the 2015 and 2016 growing seasons using independent, high-resolution, stratified, random designs. Because the throughfall and soil water content cannot be measured at the same location, we used kriging to derive the throughfall values at the locations where the soil water content was measured.

Spatial patterns of throughfall were related to canopy density. Although spatial autocorrelation decreased with increasing event size, temporally stable throughfall patterns emerged, resulting in the reoccurrence of higher- and lower throughfall locations across precipitation events. Linear mixed-effects model analysis showed that while soil water content patterns were poorly related to spatial patterns of throughfall, the increase in soil water content after rainfall was strongly related. More water was stored in the soil in areas where throughfall was elevated. At the same time, however, the local soil water response was modified by the soil wetness itself in a way that suggests processes of rapid drainage and runoff. Locations with a lower than average topsoil water content tended to store less of the input water, indicating locally enhanced preferential flow. In contrast, in the subsoil, locations with above average water content stored less water than their drier counterparts. In addition, macroporosity also modified how much water was retained in soil storage.

Overall, throughfall patterns influenced soil water content much less than soil water dynamics shortly after rainfall events. Furthermore, drainage reduced the soil moisture variation within hours to days, when returning from the wetted to the dry state. Therefore, we conclude that percolation rather than the soil water content is affected by small-scale spatial heterogeneity in canopy input patterns.

Reference

Fischer-Bedtke, C., Metzger, J. C., Demir, G., Wutzler, T., and Hildebrandt, A.: Throughfall spatial patterns translate into spatial patterns of soil moisture dynamics – empirical evidence, Hydrol. Earth Syst. Sci., 27, 2899–2918, https://doi.org/10.5194/hess-27-2899-2023, 2023.

How to cite: Hildebrandt, A., Christine, F.-B., Johanna Clara, M., Gökben, D., and Thomas, W.: Are spatial patterns of soil moisture or percolation affected by throughfall heterogeneity? Empirical evidence from a beech-dominated forest., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11093, https://doi.org/10.5194/egusphere-egu24-11093, 2024.

EGU24-11540 | Posters on site | HS2.1.11

Climate change drives hydrological decoupling of a central European beech forest 

Daniela Sauer, Simon Drollinger, Michael Dietze, Dominik Seidel, Daniel Schwindt, and Jago Birk

Climate change models suggest increasing rain variability for Europe in the next decades, with hypothesised cascading effects on ecosystems. We evaluate decadal-scale data of a measuring plot in a beech forest in central Germany to test these model-based suggestions and potential implications by empirical evidence.

Based on 15 min resolution metrics of precipitation and subsequent water pathways towards and within the soil, we show medium-term trends in rainfall characteristics and their modulation by biota.

Rain event durations and rain amounts per event tended to decrease over the observation period, while rain intensity increased, accommodating the effect of the two former parameters on annual precipitation. This change in precipitation patterns, together with canopy structure caused a systematic decrease in throughfall ratios and an exponentially enhanced throughfall variability.

Our results suggest that changing rainfall and throughfall patterns will progressively decouple hydrological links in one of Europe’s most extensive ecosystem types. Based on the observed trends, we discuss effects of changing vegetation-modulated rain-input on ecosystem functioning and soil-hydrological trajectories to be anticipated in the near to mid-term future.

How to cite: Sauer, D., Drollinger, S., Dietze, M., Seidel, D., Schwindt, D., and Birk, J.: Climate change drives hydrological decoupling of a central European beech forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11540, https://doi.org/10.5194/egusphere-egu24-11540, 2024.

EGU24-11844 | Orals | HS2.1.11

Time-lapse photography – a tool for unravelling the intricate complexity of eco-hydrologic processes 

Laurent Pfister, Bonanno Enrico, Fabiani Ginevra, Gourdol Laurent, Hissler Christophe, Huck Viola, Iffly Jean François, Keim Richard, Martínez-Carreras Núria, Mestdagh Xavier, Montemagno Alessandro, Penna Daniele, Schymanski Stan, and Zehe Erwin

For decades, field data collection has been largely in decline in favour of environmental modelling – the latter being considered less labour and cost-intensive. However, this trend goes against the grain with new observational field data having repeatedly been the source of breakthroughs in science (e.g., high-frequency measurements in stream water, in-situ monitoring of the isotopic composition of tree xylem water, imaging of infiltration pathways with electrical resistivity tomography, or time-lapse mapping of surface-saturation dynamics with thermal infrared imagery). Hypotheses generated from this type of novel, integrative, observations offer the potential to free hydrological concepts from the restrictions of typical datasets.

However, recent technological developments in field instrumentation have also revealed an increasingly complex landscape heterogeneity. General organizing principles have been proposed to explain river basin complexity. Deciphering this heterogeneity remains very challenging – essentially because eco-hydrologic processes occur over a wide range of spatial and temporal scales and vary by multiple orders of magnitude. The dilemma here is that we could continue instrumenting our catchments to the point of littering, and still miss out on processes or features that we were simply not looking for.

Here, we demonstrate the potential for time-lapse photography to unravel the complex organisation of eco-hydrologic processes at various temporal and spatial scales. This technique (also called undercranking) consists of taking regular frames with a camera and subsequently speeding up the action during playback. We installed a wildlife monitoring camera (RECONYX Hyperfire 2 Professional White Flash Camera) in the forested Weierbach experimental catchment (WEC) – an interdisciplinary Critical Zone observatory dedicated to the long-term study of hydrological, hydro-geochemical, and eco-hydrological processes. The rainfall-runoff response of the WEC is characterized by a strong seasonality, with pronounced summer low flows and winter high flows (resulting from a complex interplay of multiple eco-hydrological processes). The full time-lapse video of a hillslope-riparian zone-stream transect in the Weierbach catchment spans from December 2020 to July 2022 and is available online via https://youtu.be/74S7DfT7Uhs.

The high-speed playback of pictures recorded between December 2020 and July 2022, combined with in-situ eco-hydrological measurements reveals a comprehensive view of contrasted seasons with gradually changing processes. In winter, snowfall events trigger a slow but gradual snow-fed groundwater recharge (recorded by soil moisture probes and groundwater wells). Balmy weather in spring announces the onset of leaf-out and a recession in groundwater levels and hydrographs. In summer, vegetation is highly dynamic and growing, while groundwater levels and discharge evolve between high and low levels along successive dry and wet sequences. With cooler autumn temperatures and wet weather, leaf senescence starts, and the groundwater system switches back to a rain-fed recharge state.

The combination of a four-season-long time-lapse sequence of the pulse of the Weierbach with a high-frequency, multi-parameter dataset is offering an innovative opportunity for combining ‘soft’ and ‘hard’ data across multiple scales and eventually improving the dialogue between experimentalists and modelers. Such an alternative source of information may eventually become the starting point for a new cycle of hypothesis framing and testing.

Further information on this study is available at https://doi.org/10.1002/hyp.15026.

How to cite: Pfister, L., Enrico, B., Ginevra, F., Laurent, G., Christophe, H., Viola, H., Jean François, I., Richard, K., Núria, M.-C., Xavier, M., Alessandro, M., Daniele, P., Stan, S., and Erwin, Z.: Time-lapse photography – a tool for unravelling the intricate complexity of eco-hydrologic processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11844, https://doi.org/10.5194/egusphere-egu24-11844, 2024.

Plant canopies divert a portion of precipitation to the base of their stems through “stemflow”, a phenomenon that influences the canopy water balance, soil microbial ecology, and intrasystem nutrient cycling. However, a comprehensive integration of stemflow into theoretical and numerical models in natural science remains limited. This perspective examines three unresolved, fundamental questions hindering this integration, spanning the canopy to the soil. First, the precise source area within the canopy that generates stemflow is undefined. Thus, we asked, “whence stemflow?” Current common assumptions equate it to the entire tree canopy, a potentially misleading simplification that could affect our interpretation of stemflow variability. Second, we asked what are the various conditions contributing to stemflow generation—beyond rain, to dew and intercepted ice melt—and could the exclusion of these volumes consequently obscure an understanding of the broader implications of stemflow? Third, we explored ”whither stemflow?” This question extends beyond how much stemflow infiltrates where, into what uptakes it and from where. Addressing these questions is constrained by current observational and analytical methods. Nevertheless, by confronting these challenges, the stemflow research community stands to make significant strides in comprehending this unique hydrological component and situating it within the broader context of natural science.

How to cite: Van Stan, J. and Pinos, J.: Three Fundamental Challenges to the Advancement of Stemflow Research and Its Integration into Natural Science, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12393, https://doi.org/10.5194/egusphere-egu24-12393, 2024.

EGU24-12425 | ECS | Posters on site | HS2.1.11

Importance of vegetation structure for predicting evapotranspiration in a tropical mosaic landscape 

Raunak Kirti, Alejandra Valdés-Uribe, and Dirk Hölscher

Evapotranspiration (ET) is a critical process within the hydrological cycle, susceptible to shifts due to changes in land use. In tropical forest regions, widespread transformations often result in mosaic patterns of land-use types. Our goal was to explore the importance of vegetation structure, topography, meteorology and soil for the spatial variability of ET in a tropical mosaic landscape. We used a random forest machine learning technique for spatial data, employing forward feature selection and cross-validation to prevent overfitting. Our study region is situated in north-eastern Madagascar and is mainly composed of forest fragments, vanilla agroforests, rice fields and fallow land of shifting cultivation. We used a combination of open-source data products derived from various satellite experiments. Daily ET data were retrieved from the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS). Forest structure predictors from GEDI and PROBA-V, meteorological data from ERA5, topography from JAXA and soil data from ISRIC were obtained. The variables included in the L3 algorithm to calculate ECOSTRESS ET daily data were not included in the study to prevent bias in the models. The models achieved high accuracy for the spatial prediction of ET (R2) of 0.76 and 0.82 for different days. Besides other biophysical variables, leaf area index, tree cover and tree height were important variables in predicting ET. Our findings thereby underscore the crucial role of forest structure on ET even in complex structured tropical mosaic landscapes.

How to cite: Kirti, R., Valdés-Uribe, A., and Hölscher, D.: Importance of vegetation structure for predicting evapotranspiration in a tropical mosaic landscape, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12425, https://doi.org/10.5194/egusphere-egu24-12425, 2024.

EGU24-15823 | Orals | HS2.1.11

Diurnal Vegetation Moisture Dynamics and Water Stress: Insights from GNSS Reflectometry-Derived Vegetation Water Content 

Milad Asgarimehr, Jens Wickert, Adriano Camps, and Dara Entekhabi

The dynamics of Vegetation Water Content (VWC) throughout the day reflect how plants cope with water stress, trying to replenish lost water during daylight hours. Traditional radar sensors have shown sensitivity to diurnal vegetation moisture fluctuations but struggle due to their limited sampling rates, making it difficult to monitor daily patterns effectively. Innovations like Global Navigation Satellite Systems Reflectometry (GNSS-R) present a promising solution to overcome these limitations.

In this study, we leverage GNSS-R measurements from the NASA Cyclone (CYGNSS) mission, launched in late 2016, to study diurnal VWC cycles in Amazon's evergreen forests. CYGNSS offers high sampling rates and increased sensitivity to VWC, penetrating vegetation layers effectively with longer L-band wavelengths. The eight satellites of CYGNSS provide frequent measurements in tropical regions across different times of the day.

Our results uncover distinct differences between morning and evening VWCs over Amazon. We have observed a strong correlation (R = 0.75) between VWC and Vapor Pressure Deficit (VPD) throughout 2019, indicating VPD as a crucial factor influencing water stress. The diurnal VWC cycles in the Amazonian peatland demonstrate disruptions during arid periods and emphasize the significant role of VPD in governing vegetation diurnal moisture dynamics.

Our findings bridge the information gap on water stress in vegetation, showing the potential of VWC derived from advanced remote sensing technologies. It complements in-situ data on water potential gradients, offering valuable insights into vegetation water status in these critical ecosystems.

How to cite: Asgarimehr, M., Wickert, J., Camps, A., and Entekhabi, D.: Diurnal Vegetation Moisture Dynamics and Water Stress: Insights from GNSS Reflectometry-Derived Vegetation Water Content, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15823, https://doi.org/10.5194/egusphere-egu24-15823, 2024.

EGU24-16271 | ECS | Posters on site | HS2.1.11

Modeling the effects of forest stand characteristics on the water dynamics of mountain forests 

Franciele de Bastos and Hubert Hasenauer

Mountain forests are essential for reducing runoff, sediment transport, and risk of natural hazards. In this analysis we address the protection function of mountain forests by assessing the interactions among the forest structure and the water dynamics. We are specifically interested in the forest's ability to reduce the outflow during a 10-day rainfall period according to the leaf area index (LAI) of the forested areas. The study was conducted using 31 Norway spruce (Picea abies) forest stands covering a wide range of LAI located in the Rindbach watershed in Austria. The elevation ranges from 446 m to 1379 m, and the predominant soil type is the Orthic Rendzina. From 1960 to 2022, the mean average annual precipitation was 1498 mm, and the mean average annual temperature was 6.6 °C. We use the biogeochemical ecosystem model Biome-BGC with its parameter settings for European tree species to simulate the daily carbon, nitrogen, water, and energy flux dynamics and assess the relative proportion of the daily water balance parameters during the 10-day rain period grouped according to the leaf area index (LAI). Our results for the 10-day rain period with a total accumulation of 135.3 mm (about 9.7 % of the annual rainfall in the area) suggest: (i) Norway spruce forest areas with an LAI < than 1 m²/m², outflow was evident on the first day of rainfall while Norway spruce forests with an LAI ≥ 7 m2/m-2 exhibited the first outflow on the ninth day of rainfall. (ii) This resulted in a 4 to 5 times lower outflow compared to forest stands with an LAI < 1m²/m² (e.g. 51.3 versus 11.1 mm, within 10 days). This emphasizes the importance of forest vegetation coverage in reducing runoff, avoiding flooding, mudslides, and sediment transport, and improving the protection function of mountain forests.

How to cite: de Bastos, F. and Hasenauer, H.: Modeling the effects of forest stand characteristics on the water dynamics of mountain forests, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16271, https://doi.org/10.5194/egusphere-egu24-16271, 2024.

EGU24-18190 | ECS | Posters on site | HS2.1.11

Wintertime Tree Surface Temperature Dynamics in Boreal and Sub-Alpine Forests Revealed by Thermal Infrared Imaging 

Vincent Haagmans, Giulia Mazzotti, Clare Webster, and Tobias Jonas

Canopy surface temperature is a critical state variable of land surface models. During winter, it plays a key role in modulating energy fluxes between atmosphere, canopy air space, and sub-canopy snowpack. Understanding these surface temperature dynamics spatially and temporally is becoming increasingly important as recent hyper resolution models are now capable of resolving snow-forest interactions at the scale of individual trees and within concrete canopy structure.

Here, we present a novel dataset and analyze spatio-temporal wintertime canopy surface temperaturedynamics derived from ground-based thermal infrared (ThIR) images. Panoramic ThIR images were captured in forest gaps and dense stands at up to hourly intervals throughout diurnal cycles in boreal and sub-alpine forests. Postprocessing enabled documentation of absolute vertical and azimuthal tree surface temperature distributions within the forest under varying meteorological conditions. Our observations revealed the spatiotemporal dynamics of canopy temperatures offsets relative to ambient air temperatures. Positive offsets mainly followed direct insolation patterns within the 3-dimensional canopy structure in case of clear sky conditions. Insolated stems in forest gaps were observed to be up to 20 degrees above the surrounding canopy, while at the same time shaded stems could be up to 3 degrees colder than the canopy. Moreover, combining ThIR observations with RGB imagery further demonstrated evidence of insolation driven unloading of snow intercepted by the canopy, providing valuable data for further development of hyper resolution forest snow models.

How to cite: Haagmans, V., Mazzotti, G., Webster, C., and Jonas, T.: Wintertime Tree Surface Temperature Dynamics in Boreal and Sub-Alpine Forests Revealed by Thermal Infrared Imaging, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18190, https://doi.org/10.5194/egusphere-egu24-18190, 2024.

Potential climate change impacts on water resources have been extensively assessed in Norway due to substantial changes in climate in the recent decades. However, the combined and isolated effects of forest and forest management have been rarely considered in the climate impact studies in Norway although about 38% of the land area is covered by forest. This study aims to improve hydrological impact projections in forest dominant catchments by considering the effects of forest growth and management and to attribute hydrological changes to climate and forest changes. The eco-hydrological model SWIM (Soil and Water Integrated Model) was applied to simulate hydrological processes and extremes for two micro-scale, two meso-scale and two macro-scale catchments, accounting for the effects of spatial scale. The climate projections were generated by three EURO-CORDEX (Coordinated Downscaling Experiment for the European domain) regional climate models (RCMs) for two RCPs (Representative Concentration Pathways, RCP2.6 and RCP4.5) and were bias corrected using the quantile-mapping method. Forest development over time was simulated as a function of climate determining growth and SSP-dependent harvest levels determining wood outtake. The simulations were initialized with the forest status of the year 2020 and different forest types are distinguished according to structural characteristics represented by three key parameters: leaf area index, mean tree height and surface albedo. Preliminary simulation results show that there are minor changes (within ±5%) in hydrological processes under the combinations of the climate and forest scenarios for these catchments. Climate change is the major driver of hydrological change at the catchment scale whereas forest development mainly influences the spatial distribution of the hydrological fluxes. The results further indicate that forest growth under a warming climate helps to reduce the risk of the floods and drought slightly by reducing surface runoff in wet periods and increasing base flow in dry periods, respectively.

How to cite: Huang, S., Eisner, S., Wong, W. K., and Cattaneo, N.: The potential impacts of climate change and forest management on water resources for micro-, meso- and macro-scale catchments in cold regions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18681, https://doi.org/10.5194/egusphere-egu24-18681, 2024.

Sardinia island is a reference for ecohydrological studies on past and future climate change effects, representing typical conditions of the western Mediterranean Sea basin. Ecosystems are heterogenous, and trees optimize the use of water through the root systems, uptaking water from the deep layers.

Two micrometeorological towers have been installed in two different sites under different precipitation conditions. The first is installed in Orroli (annual precipitation of about 600 mm), a case study of the ALTOS European project, which is a patchy mixture of wild olive trees and C3 herbaceous that grow in a shallow under a rocky layer of basalt, partially fractured (soil depth 15 40 cm), with a tree cover percentage of 33% in the footprint. Instead, the second is in a mountainous forest site of Quercus ilex characterized by steeper slopes and rocky outcrops (mean annual precipitation of about 800 mm), and tree cover percentage of 68% in the footprint. In both sites land surface fluxes and CO2 fluxes are estimated using the eddy correlation technique, soil moisture was estimated with water content reflectometers, and periodically leaf area index (LAI) were estimated, while tree transpiration component is estimated using the sap flow sensors.

The following objectives are addressed:1) pointing out the dynamics of land surface fluxes, soil moisture and CO2 for two contrasting sites; 2) assess the impact of vegetation dynamics and type on the CO2 and water balance dynamics; 3) evaluate the soil effect on water and energy budgets.

The Orroli site is more controlled by rainfall seasonality, and vegetation species use the source of water stored in the deep rocky layer to sustain their physiological activity. In the Orroli site we found seasonal dynamics in the CO2 flux and in the evapotranspiration (ET) terms, which are higher when grass and woody vegetation species are present and lower when the grass component dies. Instead, we found a constant flux of ET in the Marganai highlighting the high efficiency of tree species in extract the deep sources of water. ET is higher in the Orroli site as long as the grass species are present in live form, and then LE is higher in the Marganai forest. The ET of Quercus ilex in the Marganai forest seems being not controlled by surface soil moisture, because the annual precipitation is enough for sustain the transpiration needs of that fraction of tree cover. The results confirm a threshold of 700 mm/year of rain, below which rain can restrict tree cover growth.

How to cite: Corona, R., Sirigu, S., Montaldo, N., and Katul, G. G.: On the Evapotranspiration estimates of two contrasting and Heterogenous Ecosystems in a Mediterranean region, Sardinia, under water limited conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19390, https://doi.org/10.5194/egusphere-egu24-19390, 2024.

EGU24-419 | ECS | Posters on site | HS2.1.12

Exploring the landscape heterogeneity and the hydrological diversity in three contrasted observatories of the French critical zone research infrastructure OZCAR 

Julien Ackerer, Sylvain Kuppel, Isabelle Braud, Sylvain Pasquet, Ophélie Fovet, Anne Probst, Marie Claire Pierret, Laurent Ruiz, Tiphaine Tallec, Nolwen Lesparre, Sylvain Weill, Christophe Flechard, Jean Luc Probst, Jean Marçais, Agnes Riviere, Florence Habets, Sandrine Anquetin, and Jerome Gaillardet

The French OZCAR critical zone network offers the opportunity to conduct multi-site studies and to explore the critical zone functioning under contrasted climate, geology, vegetation and land use. In this study, an integrated modeling of the water cycle is performed with the ecohydrological model EcH2O-iso in three long-term observatories: (1) the Naizin watershed characterized by an oceanic climate, a metamorphic bedrock and an intensive agriculture (north-west of France, AgrHyS observatory); (2) the Aurade watershed, a watershed with a warmer semi-continental oceanic climate, a sedimentary geological substratum and a crop cover with a wheat-sunflower rotation (south-west of France, Aurade observatory) and; (3) the Strengbach watershed characterized by a mountain climate, a granitic bedrock, and a beech-spruce forest cover (north-east of France, OHGE observatory).

Modeling robustness is evaluated by taking advantage of the large database for critical zone sciences including stream flow, water level in piezometers, and evapotranspiration fluxes measured from climatological stations and flux-towers located in the watersheds. Our comparative study brings these general outcomes: (1) the long term CZ evolution controlling the regolith thickness strongly impacts the total water storage in watersheds; (2) the Quaternary geomorphological evolution influences the current hydrological partitioning and the separation of hydrologically active and inactive water storage; (3) Both internal watershed characteristics and external forcings, such as current atmospheric forcing and recent land use need to be considered to infer stream persistence and to understand hydrological diversity; and (4) the observed hydrological diversity cannot be fully understood without considering a continuum of time scales in CZ evolution.

 

Overall, this work illustrates the strength of critical zone networks, allowing a new level of multi-site and comparative studies that are crossing several observatories and encompassing a wide diversity of geology and climate.

 

How to cite: Ackerer, J., Kuppel, S., Braud, I., Pasquet, S., Fovet, O., Probst, A., Pierret, M. C., Ruiz, L., Tallec, T., Lesparre, N., Weill, S., Flechard, C., Probst, J. L., Marçais, J., Riviere, A., Habets, F., Anquetin, S., and Gaillardet, J.: Exploring the landscape heterogeneity and the hydrological diversity in three contrasted observatories of the French critical zone research infrastructure OZCAR, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-419, https://doi.org/10.5194/egusphere-egu24-419, 2024.

EGU24-2143 | Posters on site | HS2.1.12

Time matters: photosynthetic vs. weathering-induced C drawdown and the role of dust inputs along a one-million-year soil weathering gradient on the Galápagos Islands 

Franz Zehetner, Martin H. Gerzabek, J. Gregory Shellnutt, Pei-Hao Chen, I Nyoman Candra, Kuo-Fang Huang, and Der-Chuen Lee

The Galápagos archipelago, a chain of islands formed by hotspot volcanism on the Nazca tectonic plate, exhibits a pronounced rock age gradient with distance from the volcanic hotspot from west to east. Here, we investigate chemical weathering along a soil chronosequence (1.5 to 1070 ka) under humid conditions. Our results show considerable loss of base cations already in the early to intermediate phases of weathering (e.g. 95% of Na and 78% of Mg lost from the topsoil after 26 ka) and almost complete loss from the entire profile in soils older than 800 ka. Depletion of Si was less pronounced, with topsoil losses of 24% and 63-68% after 26 ka and >800 ka, respectively. Total weathering flux and associated CO2 consumption rates estimated from profile-scale element losses in this study exceeded catchment-scale estimates reported for other volcanic islands or global averages during the early weathering phase, but were much lower in the intermediate and late phases. Nevertheless, total C drawdown was dominated by soil organic C sequestration (70-90% share) rather than inorganic, weathering-induced CO2 consumption during early pedogenesis (≤4.3 ka), and the relative importance switched in the intermediate and late phases (90-95% share of weathering-induced C drawdown at ≥166 ka). Dust deposition derived from a nearby ocean sediment core was <20% of total basalt mass loss at the young and intermediate-aged sites, but reached 40-60% at the older sites (>800 ka). Our results suggest that (1) young volcanic surfaces are very efficient (inorganic and organic) C sinks, (2) the development of thick soil covers at advanced pedogenic stages effectively shields the underlying rocks from further weathering, and (3) dust inputs become an increasingly important biogeochemical factor in such highly weathered environments.

How to cite: Zehetner, F., Gerzabek, M. H., Shellnutt, J. G., Chen, P.-H., Candra, I. N., Huang, K.-F., and Lee, D.-C.: Time matters: photosynthetic vs. weathering-induced C drawdown and the role of dust inputs along a one-million-year soil weathering gradient on the Galápagos Islands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2143, https://doi.org/10.5194/egusphere-egu24-2143, 2024.

EGU24-4999 | Posters on site | HS2.1.12 | Highlight

Lessons learned from 15 years of TERENO: the integrated TERrestrial ENvironmental Observatories in Germany 

Steffen Zacharias, Theresa Blume, Heye Bogena, Ralf Kiese, Erik Borg, Peter Dietrich, Susanne Liebner, Hans Peter Schmid, Martin Schrön, and Harry Vereecken

The need to develop and provide integrated observation systems to better understand and manage global and regional environmental change is one of the major challenges facing Earth system science today. In 2008, the German Helmholtz Association took up this challenge and launched the German research infrastructure TERrestrial ENvironmental Observatories (TERENO). The aim of TERENO is to establish and to maintain a network of observatories as a basis for an interdisciplinary and long-term research programme to investigate the effects of global environmental change on terrestrial ecosystems and their socio-economic consequences. State-of-the-art methods from the field of environmental monitoring, geophysics, and remote sensing are used to record and analyze states and fluxes in different environmental compartments from groundwater through the vadose zone, surface water, and biosphere, up to the lower atmosphere. To date, four observatories are part of the network, and over the past 15 years we have gained collective experience in running a long-term observing network, thereby overcoming unexpected operational and institutional challenges, exceeding expectations and facilitating new research. Today, the TERENO network is a key pillar for environmental modelling and prediction in Germany, an information hub for regional stakeholders, a nucleus for international collaboration, an important anchor for large-scale experiments, and a trigger for methodological innovation and technological progress. We will present the main lessons learned from this 15-year endeavour, and illustrate the need to continue long-term integrated environmental monitoring programmes in the future.

How to cite: Zacharias, S., Blume, T., Bogena, H., Kiese, R., Borg, E., Dietrich, P., Liebner, S., Schmid, H. P., Schrön, M., and Vereecken, H.: Lessons learned from 15 years of TERENO: the integrated TERrestrial ENvironmental Observatories in Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4999, https://doi.org/10.5194/egusphere-egu24-4999, 2024.

EGU24-7396 | Posters on site | HS2.1.12

Developing a coupled hydrological model for UK chalk catchments 

Mostaquimur Rahman, Ross Woods, Francesca Pianosi, Fai Fung, and Rafael Rosolem

Chalk forms one of the most important aquifers in the UK. Extending over large parts in the south-west, chalk aquifers account for more than half of the groundwater used for drinking in England and Wales. Groundwater held in these aquifers supports flows in chalk rivers. Hence, chalk aquifers play an important role in sustaining the riverine ecosystem. It is, therefore, important to assess and manage freshwater resources in these catchments. Here we develop and evaluate a distributed numerical model for simulating coupled subsurface and land surface hydrological processes including soil moisture variability, flow, and groundwater dynamics in chalk catchments. The parsimony and computational efficiency of this model make it possible to perform numerous simulations within a reasonable time. This allows for sensitivity analysis, calibration, and multiple scenario analysis that are useful in management decision making.

How to cite: Rahman, M., Woods, R., Pianosi, F., Fung, F., and Rosolem, R.: Developing a coupled hydrological model for UK chalk catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7396, https://doi.org/10.5194/egusphere-egu24-7396, 2024.

EGU24-9338 | ECS | Posters on site | HS2.1.12

The importance of in-situ soil moisture observations to evaluate the main drivers of event runoff characteristics in a small-scale catchment 

Adriane Hövel, Christine Stumpp, Heye Bogena, Andreas Lücke, and Michael Stockinger

A catchment’s runoff response to precipitation largely depends on the antecedent soil moisture in the catchment, but also on hydro-meteorological conditions in terms of, e.g., evapotranspiration. Studies investigating the effects of hydro-meteorological conditions on runoff event characteristics at the small catchment scale with daily temporal resolution mostly used surrogate measures for soil moisture, e.g., derived from hydrological models or using the antecedent precipitation index (API). Here, we applied a time-series based pattern search to 11 years of daily in-situ measured soil moisture in three depths (5, 20, 50 cm) at 33 locations in the Rollesbroich catchment (40 ha) in Germany to identify key variables influencing runoff event characteristics under similar wetness patterns. After identifying wetness patterns, we split the corresponding runoff responses into similar and dissimilar ones by means of goodness-of-fit criteria and analyzed their respective hydro-meteorological variables and event runoff coefficients (ERC), i.e., the proportion of rainfall that transforms into runoff during an event. Results showed that for similar soil moisture patterns, mean potential evapotranspiration, and antecedent soil moisture in all three depths had a smaller standard deviation for similar runoff responses than for dissimilar. This indicates a larger influence on the runoff response compared to rainfall-derived variables such as total event rainfall, maximum event rainfall intensity, or API. Furthermore, during runoff events under similar wetness conditions, the Spearman rank correlation coefficient (ρ) indicated a low average correlation between ERC and API (ρ=0.17). In terms of antecedent soil moisture conditions, the highest correlation between ERC and antecedent soil moisture was observed in the topsoil at 5 cm depth (ρ=0.43), while at 20 cm (ρ=0.16) and 50 cm (ρ=0.30) depths, the correlations were comparatively lower. Our study indicates that using the API as a substitute for antecedent wetness conditions may not be able to comprehensively reflect the relation between the runoff response and antecedent soil moisture conditions in the topsoil in the given catchment. Consequently, the results show that topsoil moisture measurements are more suitable than the surrogate API for assessing the impact of hydro-meteorological variables on daily runoff characteristics.

How to cite: Hövel, A., Stumpp, C., Bogena, H., Lücke, A., and Stockinger, M.: The importance of in-situ soil moisture observations to evaluate the main drivers of event runoff characteristics in a small-scale catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9338, https://doi.org/10.5194/egusphere-egu24-9338, 2024.

EGU24-9375 | ECS | Posters on site | HS2.1.12

Link between groundwater storage and landscape changes in mountainous areas: the Kahule Khola watershed (Nepal) 

Kapiolani Teagai, John Armitage, Léo Agélas, Christoff Andermann, and Niels Hovius

In many watersheds of various sizes, the role played by groundwater to sustain river flow is still misunderstood. This is the case in mountainous areas where geological features as fractures, altered or unaltered bedrocks and steep slopes notably play an important role for storing groundwater into the subsurface. The groundwater support to low flows was considered for a long time as a minor contribution, due to the steep slopes in those areas. But in Nepal, it is estimated that 2/3 of the volume of rivers comes from the exfiltration of groundwater through resurgences. Though several attempts were made with numerical modelling based on data monitoring and field surveys to quantify river-groundwater exchanged fluxes, some ambiguities remain. Especially regarding the impact of landscape change in a mountainous topography. The aim of this work is to characterize the subsurface infiltration, recharge, and storage mechanisms of a mountainous hydrogeological system in the Himalayas using field investigations and numerical modelling. In the Kahule Khola watershed (Nepal), a steep catchment of 33 km² whose altitudes range between 1000 and 3500 masl, various field experiments were made to identify groundwater pathways into the altered subsurface and to catch the river/groundwater interactions: seismic and electric surveys (ERT), infiltration tests, physical and isotopic measurements of springs/streams and the water tracking on the surface with loggers installed along gullies in the overall watershed. The region is submitted to intense rainfall as monsoon, intercalated by dry periods in which the river flow is still sustained. Moreover, by closing ancient fractures and opening new ones, earthquakes can deviate springs and change the surface water/groundwater pathways. This contributes to reshaping the landscape. However, the spatial and temporal contribution of groundwater to maintain a baseflow in the river is not quantified yet, in space and time. The ERT data from a time-lapse realized before and after monsoon show a deep alteration zone with a shallow humid layer of 10 m thick at least all year long under the slopes. Areas of low resistivity reveal infiltration zones and preferential flow paths. These areas are recharged in the wet season and drained in the dry season. At the surface, we estimate an average hydraulic conductivity at saturation of 3,5.10-5 m.s-1 in 150 cm depth which suggest an infiltration rate higher than the average rainfall rate (~3000 mm.year-1). In order to quantify the groundwater storage into the subsurface, a numerical groundwater model in 2D has been developed (Python) and is able to simulate and quantify the water storage dynamics of a spatial and temporal pre-defined domain. The data measured on the field will be used to define the initial conditions of future scenarios.

How to cite: Teagai, K., Armitage, J., Agélas, L., Andermann, C., and Hovius, N.: Link between groundwater storage and landscape changes in mountainous areas: the Kahule Khola watershed (Nepal), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9375, https://doi.org/10.5194/egusphere-egu24-9375, 2024.

EGU24-13095 | Posters on site | HS2.1.12

Hydrological, biogeochemical, and ecological linkages at the land-sea margin: Insights from a coastal critical zone network 

Holly Michael, Dannielle Pratt, Yu-Ping Chin, Sergio Fagherazzi, Keryn Gedan, Matthew Kirwan, Angelia Seyfferth, Lee Slater, Stephanie Stotts, and Katherine Tully

Ghost forests and abandoned farms are stark indicators of ecological change along world coastlines, caused by sea level rise (SLR). These changes adversely affect terrestrial ecosystems and economies, but expanding coastal marshes resulting from SLR also provide crucial ecosystem services such as carbon sequestration and mediate material fluxes to the ocean. A US-NSF Critical Zone Network project was designed to understand the hydrological, ecological, geomorphological, and biogeochemical processes that are altering the functioning of the marsh-upland transition in the coastal critical zone. We have instrumented six sites in the mid-Atlantic region of the US, along the coastlines of the Atlantic Ocean, Delaware Bay, and Chesapeake Bay where marshes are rapidly encroaching into forests and farmland. Field observations, laboratory experiments, and modeling are revealing the drivers and impacts of coastal change, as well as feedbacks among competing processes that accelerate or reduce rates and magnitude of change. We discuss examples of processes and feedbacks and highlight the importance of interdisciplinary exploration and synthesis in advancing process understanding at the land-sea transition.

How to cite: Michael, H., Pratt, D., Chin, Y.-P., Fagherazzi, S., Gedan, K., Kirwan, M., Seyfferth, A., Slater, L., Stotts, S., and Tully, K.: Hydrological, biogeochemical, and ecological linkages at the land-sea margin: Insights from a coastal critical zone network, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13095, https://doi.org/10.5194/egusphere-egu24-13095, 2024.

EGU24-13395 | Posters on site | HS2.1.12

Exploring Earth's Critical Zone Through the U.S. Critical Zone Collaborative Network 

Elizabeth W. Boyer, Bhavna Arora, Emma Aronson, Holly Barnard, Steven Holbrook, Jeffery S. Horsburgh, Lixin Jin, Praveen Kumar, Holly Michael, Jeff Munroe, Julia Perdrial, Claire Welty, and Jordan Read

The Critical Zone Collaborative Network (CZ Net) is a national research initiative in the United States supporting investigations of the Earth's critical zone (CZ) -- the vital near-surface environment extending from the top of the vegetation canopy to the weathered bedrock beneath. CZ Net fosters collaboration, data sharing, and interdisciplinary research to understand complex landscapes. The network comprises nine thematic clusters covering diverse geological, climatic, and land use settings. The thematic clusters explore many areas, including bedrock geology's effects on landscapes and ecosystems, ecosystem responses to climate and land-use disturbances, processes occurring between land and sea affected by sea-level rise, land-water interactions in agricultural regions, water and carbon cycles in arid regions, the impact of mineral dust transported in the atmosphere on ecosystems, water storage's influence on landscape and ecosystem processes, relationships between landscapes and microbial communities, and ecosystem processes in cities. A coordinating hub provides cross-cluster support. In the presentation, we introduce CZ Net and the focal research areas of each thematic cluster. We consider synthesis work addressing environmental challenges faced by the CZ, which is under increasing pressure to meet societal needs while safeguarding the environment for future generations. Further, we discuss opportunities for engagement with the network, reflecting CZ Net's dedication to advancing knowledge and addressing critical environmental issues through collaborative efforts. International coordination through developing a network of networks can foster collaborative research that transcends national boundaries, allowing scientists to combine expertise, data, and resources for a deeper understanding of CZ processes. Such collaboration is imperative for addressing pressing global environmental challenges.

How to cite: Boyer, E. W., Arora, B., Aronson, E., Barnard, H., Holbrook, S., Horsburgh, J. S., Jin, L., Kumar, P., Michael, H., Munroe, J., Perdrial, J., Welty, C., and Read, J.: Exploring Earth's Critical Zone Through the U.S. Critical Zone Collaborative Network, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13395, https://doi.org/10.5194/egusphere-egu24-13395, 2024.

EGU24-15452 | ECS | Posters on site | HS2.1.12

Exploring fluvial morphodynamics through scales  

Boris Gailleton, Philippe Steer, Philippe Davy, and Wolfgang Schwanghart

Surface processes control mass transfer efficiency on Earth, responding to tectonic and climatic forcings. These forcings impact landscape dynamics across a wide range of temporal scales, from individual events (e.g., storms) to geological time spans (e.g., Cenozoic climate cooling). Bridging these temporal scales poses a significant challenge for Landscape Evolution Models (LEMs). While LEMs are conventionally employed to study the effects of climate or tectonics on landscape dynamics over geological time, numerical methods simulating short-term processes such as landslides, floods, erosion, and sediment transport struggle to be projected beyond a few hundred years. 

In this contribution, we address this challenge by leveraging a recent model development—graphflood—that enables the computation of hydro-stationary water surfaces and discharge using a simplified shallow water approximation. This new model shows an order-of-magnitude improvement in speed over its predecessors, achieved through the efficiency of algorithms applied to directed acyclic graphs. Through testing induced subgraph dynamic traversals for initial calculations of a stationary state and employing GPU techniques to maintain the state to slower erosion and deposition processes, we demonstrate the potential for an additional order-of-magnitude reduction in computation time for fluvial dynamics. We also investigate how the computation of landslide runout using a shallow water approximation with a friction coefficient modified to account for velocity-weakening can be introduced within the same numerical framework. 

First, we explore various sets of fluvial erosion and deposition laws (e.g., stream power, Meyer Peter Muller) to determine the minimal representation needed for fluvial morphodynamics and projecting them across scales at the lowest computational cost. We then perturb the system with landslides processes and observe the controls on its resilience to external forcings. Lateral dynamics (e.g., lateral erosion, deposition, interaction with valley walls) and the model's ability to capture different river states (e.g., high flow vs low flow, flood) emerge as crucial elements in understanding the complexity of river responses to climato-tectonic perturbations. 

How to cite: Gailleton, B., Steer, P., Davy, P., and Schwanghart, W.: Exploring fluvial morphodynamics through scales , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15452, https://doi.org/10.5194/egusphere-egu24-15452, 2024.

EGU24-15453 | Posters on site | HS2.1.12

High Mountain Plateau Margin Critical Zone Observatory, Kaligandaki River Nepal 

Christoff Andermann, Kristen Cook, Basanta Raj Adhikari, Niels Hovius, and Rajaram Prajapati

Mountains are hotspots for earth surface processes, with very fast erosion rates, mass movements, catastrophic flooding and enhanced geochemical weathering rates. These landscapes respond quickly to external forcing by tectonics and/or climate. As a consequence, the hazard potential in mountains is very high, and mountains produce a wide range of large catastrophes which often have wide-reaching impacts on infrastructure and human lives. Furthermore, mountains can be considered as the water towers of the world, as they are very effective at harvesting water from the atmosphere, storing it, and redistributing it to the adjacent lowlands. The key role of mountain regions can be extended endlessly to other disciplines such as ecology, climatology, social sciences and so forth. Yet, despite their importance, high mountains remain inaccessible and notoriously understudied. High elevation terrains are only lightly covered by monitoring systems, with elevations >2500 m asl. widely underrepresented in global monitoring networks (Shahgedanova et al., 2021). The Himalayan mountains are particularly poorly covered by coordinated monitoring observatories.

In this contribution we present the set up and overview results of the ~last 10 years of integrated critical zone monitoring in the Kaligandaki Catchment in the central Himalayas in Nepal.

Motivated by fundamental research questions on coupled surface process and the high mountain water cycle in the Himalayan mountain range, we began observation in the Kaligandaki Catchment with two major stations for climatological and hydrological monitoring that have operated continuously over the past 10 years. At each location trained personal conducted manual river water sampling for river water geochemistry and suspended sediment monitoring as well as water discharge and bulk meteorological parameters. These observations were complemented by targeted short-term deployments and field sampling campaigns to cover the full spatial extent as well as the seasonal variability. Research question range from organic carbon export, climate and erosion feedback as well as water pathways in high mountains to large mass-movements and intramountain sediment storage and feedbacks with landscape evolution.

Our findings from the past 10 years of monitoring motivate the development of a more substantial observatory in the Kaligandaki catchment, which is particularly suited as a critical zone observatory in the Himalayas. The Kaligandaki is a trans-Himalayan river that connects the Tibetan Plateau through the Himalaya to the low elevation foreland. The river crosses distinct climatological, ecological, tectonic, and geomorphic zones, including the arid high elevation plateau, the rapidly uplifting high Himalaya and monsoon precipitation maxima, and the middle hills. The river corridor is highly prone to flood and landslide hazards, and is experience increasing development and human impact, particularly road construction and hydropower. In addition, the river basin is highly sensitive to changing precipitation patterns, which have brought anomalous rainfall and flooding in recent years, and to changing melting patterns, which affect water resources. Together with local partners and the international research community we are proposing this unique catchment as potential integrated mountain critical zone observatory in order to close the monitoring gap in the highest mountain range on Earth.

Literature:

Shahgedanova, M., et al. 2021, https://doi.org/10.1659/MRD-JOURNAL-D-20-00054.1

How to cite: Andermann, C., Cook, K., Adhikari, B. R., Hovius, N., and Prajapati, R.: High Mountain Plateau Margin Critical Zone Observatory, Kaligandaki River Nepal, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15453, https://doi.org/10.5194/egusphere-egu24-15453, 2024.

EGU24-15523 | Posters on site | HS2.1.12

The impact of groundwater dynamics on landsliding and hillslope morphology: insights from typhoon Morakot and landscape evolution modelling 

Philippe Steer, Lucas Pelascini, Laurent Longuevergne, and Min-Hui Lo

Landslides represent a pervasive natural hazard, exerting a significant influence on hillslope morphology in steep regions. Intense rainfall events are well-established as primary triggers for landslides, particularly those characterized by high rainfall intensity, intermediate to long durations, and substantial cumulative precipitation during and before the event. While the evolving roles of soil saturation and mechanical properties are well-identified in shallow landslide occurrences, the influence of groundwater dynamics on the triggering of deep-seated or bedrock landslides remains less understood. Despite this knowledge gap, deep-seated landslides play a dominant role in the volume budget of landslide catalogs and serve as the primary geomorphological process shaping hillslope evolution in steep regions. In this study, we explore the impact of groundwater dynamics on landslide triggering. Our investigation focuses initially on landslides triggered during Typhoon Morakot, examining their relationship with water table fluctuations derived from the HydroModPy 3D hydrogeological model, forced by water recharge data obtained from the Community Land Model CLM 4.0. Analyzing several contrasting catchments, we demonstrate a strong correlation between the locations and depth of deep-seated landslides and the instability predicted by a simple landslide model that integrates pore pressure and water table depth. Notably, these predictions are valid within specific ranges of hydrogeological (i.e., aquifer thickness, porosity, and conductivity) and mechanical (i.e., cohesion and friction angle) parameters, providing valuable insights into the hydrogeological and mechanical properties of the studied catchments. In an exploratory study, we then shift our focus to the longer-term geomorphological impact of rainfall-triggered landslides on hillslope evolution and morphology. Using a coupled 2D model of water table evolution and landsliding, we investigate topographic changes at the hillslope scale, under different scenarios. Our investigation considers the influence of seasonal recharge, intense rainfall events, and hillslope hydrological convergence or divergence perpendicular to the hillslope orientation on resulting hillslope morphology and dynamics. Overall, our results particularly highlight the role of groundwater dynamics on hillslope finite shape.

How to cite: Steer, P., Pelascini, L., Longuevergne, L., and Lo, M.-H.: The impact of groundwater dynamics on landsliding and hillslope morphology: insights from typhoon Morakot and landscape evolution modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15523, https://doi.org/10.5194/egusphere-egu24-15523, 2024.

EGU24-17282 | ECS | Posters on site | HS2.1.12

Assessing the impact of stress–dependent hydraulic properties on hillslope-scale groundwater flow and transport 

Ronny Figueroa, Clément Roques, Ronan Abherve, Landon Halloran, and Benoit Valley

The occurrence of springs and their connectivity within stream networks is typically associated with three key controlling factors: climate, topography and the distribution of hydraulic properties. In crystalline media, this distribution is often related to lithology and the presence of fractures. In addition, tectonic and topographic stresses can modify properties through compressive and extensional forces acting on the rock mass and fractures. However, these controls are rarely considered for hillslope scale applications. The aim of this research is to investigate the effects of stress on bedrock hydraulic properties and their implications for groundwater flow and transport at the hillslope scale. A numerical experiment has been designed that combines linear poroelasticity to simulate the distribution of permeability and porosity, together with groundwater flow and transport simulations. Different slope and stress conditions are examined, providing a comprehensive sensitivity analysis framework.

Our results show that vertical stress leads to a decrease in permeability and porosity at depth, following an exponential-like trend. Increasing the proportion of lateral stresses relative to the total vertical stresses reduces the mean permeability and porosity and increases the variance in the distribution along the hillslope. For high values of lateral stress, a low permeability domain develops downslope at the valley bottom due to the accumulation of compressive stresses, while the extensive regime at the crest provides higher permeabilities. As expected, groundwater flow simulations revealed that the partitioning of flow paths is strongly influenced by such heterogeneous stress-induced permeability and porosity fields. As stress increases, groundwater flow becomes more channelized in the near subsurface, strongly deviating from the classical Dupuit model. We also found that the distribution of normalized groundwater discharge rates shows higher values in the upper part of the seepage zone than in the lower part. By analyzing the results of particle tracking simulations, we found that mean residence times increase with higher external stress due to a decrease in mean permeability. In addition, the shape of the residence time distribution is strongly modified by the channeling of groundwater flow with increasing lateral stress, with the probability of shorter residence times increasing as stress increases. We discuss the implications of these fundamental results for our understanding of the role of stress in groundwater-dependent systems, with important insights into the recharge, storage and discharge mechanisms that may control the resilience of landscapes to the effects of climate change.

How to cite: Figueroa, R., Roques, C., Abherve, R., Halloran, L., and Valley, B.: Assessing the impact of stress–dependent hydraulic properties on hillslope-scale groundwater flow and transport, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17282, https://doi.org/10.5194/egusphere-egu24-17282, 2024.

EGU24-17490 | Posters on site | HS2.1.12 | Highlight

Hydroclimatic versus geochemical controls on silicate weathering rates 

Sylvain Kuppel, Yves Goddéris, Jean Riotte, and Laurent Ruiz

Water is the first order controlling factor of the weathering reactions. In the recent years, efforts have been made towards the building of model cascades able to simulate the water fluxes and the residence time of the water in the various compartments of the critical zone. Those hydrological constrains are then injected into numerical models simulating the water-rock interactions from the surface down to the impervious bedrock. In this contribution, we describe such a model cascade, where the water-rock interaction model WITCH is fed by the process-based ecohydrological model EcH2O-iso. This model cascade, WITCH2O, is designed for the modeling of water fluxes & stores, as well as the weathering reactions and transport of weathering products (including atmospheric CO2 consumption), from the vertical profile to the catchment scale, and from the submonthly to decadal time scales. We deployed WITCH2O along a gneiss-saprolite-ferralsol profile in a small tropical forested catchment in peninsular India. Long-term observations of water and geochemical fluxes are available, allowing for a 2-step model calibration and evaluation (hydrological and geochemical) across the different processes simulated. Using various temporal averages of simulated water fluxes and stores, preliminary results highlight that seasonal hydrological variability (driven by monsoon dynamics and deep root water uptake) is key for capturing groundwater nutrient concentrations, despite highly-buffered water table variations. We also explore how this non-linear dependence of weathering fluxes upon hydrological states is modulated by the propagation of uncertainties regarding i) modeled hydrology and ii) uncertainties in geohydrochemical properties (e.g. reactive surface and mineral abundance).

How to cite: Kuppel, S., Goddéris, Y., Riotte, J., and Ruiz, L.: Hydroclimatic versus geochemical controls on silicate weathering rates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17490, https://doi.org/10.5194/egusphere-egu24-17490, 2024.

EGU24-20178 | Posters on site | HS2.1.12

Coevolution in the critical zone: the key role of fast hydrologic processes 

Patricia Saco, Juan Quijano Baron, Jose Rodriguez, Mariano Moreno de las Heras, and Samira Azadi

Feedback effects between hydrology, vegetation and erosion processes are pervasive across landscapes. These tight interactions lead to the coevolution of landscape patterns that modulate landform shape and regulate many other critical zone processes. We study these feedbacks and interactions using simulations from landform evolution models that account for the effect (and feedbacks) of spatially and temporally varying hydrologic pathways and vegetation over landscapes displaying a variety of vegetation patterns. 

We first present results from a landscape evolution modelling framework, that accounts for a comprehensive representation of hydrology and vegetation, including the effect of various vegetation pools on erosion processes. The model includes interacting modules for hydrology, dynamic vegetation, biomass pools partition, and landform evolution. Our simulations indicate that each of the biomass pools provides a specific erosion protection mechanism at a different time of the year. As rainfall events and the resulting vegetation growth and protection are asynchronous, the maximum values of erosion are associated with runoff at the beginning of the rainy season when vegetation protection is not as its maximum. These results show how rapid hydrological processes affecting vegetation have long term implications for landform development. Results for a Eucalyptus savanna landscape study site in the Northern Territory (Australia) showed that models that do not account for the vegetation dynamics can result in prediction errors of up to 80%.  

We also present simulations of the coevolution of landforms and vegetation patterns in selected sites with patchy Acacia Aneura (Mulga) vegetation.  These sites display a sparse vegetation cover and strong patterns of surface water redistribution, with runoff sources located in the bare areas and sinks in the vegetation patches. This effect triggers high spatial variability of erosion/deposition rates that affects the evolving topography and induces feedbacks that shape the dynamic vegetation patterns. We run simulations using rainfall, vegetation and erosion data, and vegetation parameters previously calibrated for Mulga sites in the Northern territory. We further investigate the effect of alterations in hydrologic connectivity induced by climate change and/or anthropogenic activities, which affect water and sediment redistribution and can be linked to loss of resources leading to degradation. We find that an increase in hydrologic connectivity can trigger changes in vegetation patterns inducing feedbacks with landforms leading to degraded states. These transitions display non-linear behaviour and, in some cases, can lead to thresholds with an abrupt reduction in productivity. Critical implications for management and restoration are discussed.  

How to cite: Saco, P., Quijano Baron, J., Rodriguez, J., Moreno de las Heras, M., and Azadi, S.: Coevolution in the critical zone: the key role of fast hydrologic processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20178, https://doi.org/10.5194/egusphere-egu24-20178, 2024.

HS2.2 – From observations to concepts to models (in catchment hydrology)

EGU24-766 | ECS | Posters on site | HS2.2.1

Estimating open channel surface flow velocities under low luminosity conditions, using fluorescent quinine-based tracing techniques and UAS imagery 

Soheil Zehsaz, João L. M. P. de Lima, Jorge M. G. P. Isidoro, M. Isabel P. de Lima, and Ricardo Martins

This study discusses the application of innovative fluorescent quinine-based tracer techniques to estimate surface flow velocities under low luminosity conditions. Quinine is known for its luminescent properties when exposed to ultraviolet A (UVA) light. This research involves fieldwork measurements conducted in open channels with varying hydraulic characteristics. The application of quinine solutions in liquid and solid (ice cubes) states into the water flow allows the recording of the movement of the tracers. This movement is registered by tracking the leading edge of the liquid tracer plume or solid particles over specific time intervals. An Unmanned Aerial System (UAS) equipped with a camera was used to record the movement of the tracers in the channels. To benchmark the performance of the quinine-based tracers, flowmeter-based velocity maps and a thermal tracer technique were employed in the experiments. Results indicated that both liquid and solid quinine solution tracers successfully estimated open channel surface flow velocities under low luminosity conditions. The quinine solid tracer can be used as a dual (fluorescent-thermal) tracer and, despite its smaller volume used in the experiments compared to the liquid tracer, the solid form was easier to track. This was attributed to the conservation of a higher quinine concentration for longer periods of time in the solid tracers, resulting in a higher contrast easier to identify. On the other hand, the liquid tracer faded earlier due to diffusion in the turbulent flow. Nonetheless, the main advantage of using the liquid over the solid tracer was its easier availability for the experiments. This study highlights the applicability and reliability of quinine-based tracers in estimating surface flow velocities, in low luminosity conditions. The use of the UAS in the measurements’ set-up facilitated and enhanced data collection, contributing to the accuracy of the results. The observational approach allowed for capturing the inherent luminescent properties of quinine when exposed to UVA light using minimal tracer quantities.

How to cite: Zehsaz, S., L. M. P. de Lima, J., M. G. P. Isidoro, J., P. de Lima, M. I., and Martins, R.: Estimating open channel surface flow velocities under low luminosity conditions, using fluorescent quinine-based tracing techniques and UAS imagery, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-766, https://doi.org/10.5194/egusphere-egu24-766, 2024.

EGU24-1581 | Posters on site | HS2.2.1

How changing environmental conditions affect soil water isotopic composition in pre-Alpine grassland soils 

Natalie Orlowski, Tanja Vollmer, and Katrin Schneider

Alpine and pre-Alpine grasslands offer crucial ecosystem services like fodder production, biodiversity support, carbon sequestration, and water retention. However, changing environmental conditions like rising temperatures threaten these grassland soils, potentially disrupting their functionality. Understanding how climate change and farming practices impact soil functions and eco-hydrological processes is vital for developing effective strategies to sustainably manage these grasslands.

For this study, we conducted soil water isotope and soil water balance measurements from 2018-2019 in the grassland lysimeters of the TERENO Pre-Alpine observatory along an elevation gradient. Several lysimeters were translocated from the higher-elevation site Graswang (860 m a.s.l., control site) to the lower lying site at Fendt (600 m a.s.l., climate-change site). This gradient represents a 2°C temperature rise along with a 400 mm precipitation decrease at the climate-change site. Our study aimed to explore how elevated temperature and reduced precipitation affect soil hydrological and soil water isotopic composition seasonally, annually and with regard to soil depth.

We did not find significant differences in the isotopic composition at 0.1m soil depth among the different lysimeter groups. Differences in soil water isotopic composition between the lysimeter groups become more pronounced at deeper soil layers, which are typically less affected by daily temperature fluctuations.

Despite higher temperatures at the climate-change site, soil water isotopes closely followed the Local Meteoric Water Line, indicating minimal evaporation. However, the line-conditioned excess (lc-excess) significantly differed between the control and the climate-change site across depths. In contrast, no differences were found between the Fendt and Graswang climate-change site’s isotopic values at any depth. This suggests a stronger influence of actual evapotranspiration at the climate-change site visible in the lc-excess values. Overall, this research enhances our understanding of climate change's impact on water cycling through pre-Alpine grassland soils at varying altitudes. This insight could help to manage these grasslands sustainably in the face of climate change.

How to cite: Orlowski, N., Vollmer, T., and Schneider, K.: How changing environmental conditions affect soil water isotopic composition in pre-Alpine grassland soils, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1581, https://doi.org/10.5194/egusphere-egu24-1581, 2024.

EGU24-1751 | ECS | Posters virtual | HS2.2.1

Isotopic fingerprint of precipitation in NW Argentina 

Sonia Valdivielso, Jesica Murray, Ashkan Hassanzadeh, Daniel Emilio Martínez, and Enric Vázquez-Suñé

The isotopic composition of rainfall varies spatially and temporarily, depending on the climatic phenomena that originate the movement of air masses, their moisture content and the isotope fractionation processes that occur until precipitation falls isotopic composition of rainfall varies spatially and temporarily, depending on the climatic phenomena that originate the movement of air masses, their moisture content and the isotope fractionation processes that occur until precipitation falls.

One passive precipitation collector was installed in the lower part of Los Pozuelos basin, is located in the extreme northwest of Argentina, in the province of Jujuy. 19 accumulated precipitation samples were collected in the installed passive precipitation collector from 26 January, 2020 to 27 March, 2023. The objectives of this study are: (I) characterizing climatic variables; (II) Characterizing the isotopic composition of precipitation; (III) Establishing relationships between stable isotopes and the identified variables; and (IV) Identifying the trajectories of the air masses responsible for precipitation.

The time series of air temperature, relative humidity, precipitation, wind speed, solar radiation, OLR and SST exhibit a clear seasonal pattern, with the exception of the SST anomaly. The variables generally show a parametric distribution, except for daily rain. The δ18O and δ2H values of the 19 precipitation samples collected show interannual variation. The summer precipitation is depleted in heavy isotopes, has a high d-excess value and corresponds to the highest precipitation rates. This is due to the fact that the moisture masses have a greater continental extent in summer and convective precipitation dominates, both in the Amazon region and in the central and northern mountain ranges of the Andes. This is reflected in the high values of convective precipitation rate (CPR) and the lowest ORL values in the Los Pozuelos basin during the year. In winter, the heavy isotope enrichment in precipitation is due to the colder sea surface temperatures and lower evaporation associated with the Pacific Ocean compared to the Atlantic. Finally, the relationship of the isotopic composition of precipitation to the identified variables was determined. δ18O and δ2H show a high and direct correlation to each other, but inversely to precipitation amount and relative humidity. D-excess shows a moderate degree of correlation and the same tendency to increase as OLR.

The back trajectories of the HYSPLIT model air masses indicates that in summer, the dominant source of humidity was the Atlantic Ocean, which crossed both the Amazon basin and the Río de la Plata and Gran Chaco basins. A smaller percentage of the air masses is blown over by westerly winds from the Pacific Ocean. This is because the period of study is influenced by La Niña events, which cause an intensification of the westerly winds. In spring, all air masses come from the Pacific Ocean. In winter, the dominant source of humidity was the Pacific Ocean. The application of this methodology in the Los Pozuelos basin validated the appropriateness of our methods, contributing positively to the overall comprehension of water resource dynamics in the region.

How to cite: Valdivielso, S., Murray, J., Hassanzadeh, A., Martínez, D. E., and Vázquez-Suñé, E.: Isotopic fingerprint of precipitation in NW Argentina, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1751, https://doi.org/10.5194/egusphere-egu24-1751, 2024.

EGU24-2059 | Orals | HS2.2.1

Using Chlorine-36 to understand the sources of solutes in rivers: A new use for an old tracer 

Ian Cartwright, Zibo Zhou, William Howcroft, Keith Fifield, and Dioni Cendon

The radioisotope 36Cl, which has a half life of 301 ka, is traditionally used to estimate groundwater residence times of deep old groundwater in large basins. However, systematic variations in R36Cl values in young shallow catchment waters permit its use in determining the sources of solutes in rivers. Elevated R36Cl values in precipitation were recorded during the 1950s to 1970s due to the atmospheric nuclear tests. Some of this bomb-pulse 36Cl is likely to still be present in shallow catchment waters. Additionally, as R36Cl values of precipitation generally increase with distance from the ocean, groundwater older that ~7 ka that was recharged during periods of low sea levels in the Holocene is likely to have higher R36Cl values than modern rainfall. Most of the water from within catchments that sustains streamflow (e.g., the shallower parts of the groundwater system, interflow, bank storage waters, riparian groundwater) is less than a few thousand years old. There is negligible decay of 36Cl over those timescales, and thus R36C values will reflect the initial R36C values of those waters.

River water from the intermittent Avoca catchment in southeast Australia has R36Cl values of 32 to 67 that are generally higher than those of modern rainfall (R36Cl = 25 to 35) but similar to shallow (<50 m deep) near-river groundwater (R36Cl = 51-61). These data indicate that much of the solute load is derived from the input of older waters (mean residence times of up to a few thousand years) stored within the catchment rather than evapotranspiration of recent rainfall. River water from the headwaters of the nearby perennial Barwon catchment has higher R36Cl values (38-46) than local rainfall (14-20) and most of the shallow groundwater (21 to 31). These high R36Cl values reflect the input of bomb-pulse 36Cl from shallow catchment waters. Downstream, R36Cl values of the river water decrease to 20 to 31, reflecting the inputs of solutes from groundwater that again has mean residence times of up to a few thousand years.

36Cl has allowed the origins of solutes in these rivers to be better understood. In both cases, the volume of older groundwater contributing to these rivers is moderate to minor. However, due to much higher salinities, these minor groundwater inflows influence solute geochemistry. 36Cl was particularly useful in distinguishing between evapotranspiration of recent rainfall and input from waters stored within the catchment as a source of stream river. In turn, this helps understand catchment functioning and solute fluxes within the catchments. Additionally, the palaeoclimate signal of initial R36Cl values adds to the understanding of groundwater residence times and recharge processes in catchments. 

How to cite: Cartwright, I., Zhou, Z., Howcroft, W., Fifield, K., and Cendon, D.: Using Chlorine-36 to understand the sources of solutes in rivers: A new use for an old tracer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2059, https://doi.org/10.5194/egusphere-egu24-2059, 2024.

Sub-surface flow pathways and transit times of water to rivers are vital catchment characteristics that determine how climate change and land use affect surface water quality and runoff amounts. These catchment characteristics also determine the appropriateness of catchment scale management decisions to control water quality and runoff.

Conservative hydrologic tracers remain reliable, accurate tools to partition river flows among flow pathways, and calculate transit times. For example, hydrogen (H) and oxygen (O) stable isotopes provide the data for robust calculation of the young (less than a few months old) fraction of river flow. H and O isotopes also have the potential to be integrated into the next generation of 'isotope-enabled' hydrological models, which are designed to provide accurate flow-source partitioning and flow estimates outside the range of historical climate conditions.

Currently, the use of H and O stable isotopes as hydrologic tracers in large catchment scale hydrology across New Zealand is hindered by the requirement for extensive, non-routine sampling. To lower this hurdle, we have prepared national databases of precipitation and river water isotope data, and developed national-scale, time varying isotope models (isoscapes).      

Here, I describe our development of precipitation and river isoscapes for New Zealand, and initial calculations of young water fractions across New Zealand rivers.

Database development used a combination of regional government, research and citizen science collections. Our databases now include regular long-term (>18 months) sampling from around 100 rivers, and over 100 precipitation sites nationally.

Using these databases, we have developed isoscapes using a range of statistical modelling techniques.  Sinusoidal precipitation isoscape results suggest that strong seasonal cycles of precipitation stable isotope values in some areas of New Zealand (but not others) are conducive to calculation of young water fractions for rivers and may require consideration for interpreting sources of recharge to groundwater and river water. Our machine-learning precipitation isoscape captures much of the non-seasonal temporal variation that dominates in windward areas of New Zealand. These results have wider implications for the application of stable isotopes as hydrological tracers in regions with mixed marine- and continental-type climates.

Results indicate that precipitation isoscapes can now be combined with regular river sampling to provide robust comparisons of young water fractions at a regional level.

How to cite: Dudley, B., Hill, A., McKenzie, A., and Yang, J.: Lag times and flow pathways of New Zealand's river catchments: Developing robust national scale metrics using stable isotopes  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2661, https://doi.org/10.5194/egusphere-egu24-2661, 2024.

Seasonality plays a critical role in the rate, timing and magnitude of hydrological and chemical transport in permafrost underlain mountain catchments. During spring, large volumes of water are delivered as snowmelt, yet infiltration is limited by the presence of frozen ground and shallow flow pathways rapidly deliver water to streams. As thaw progresses, catchment storage capacity increases, runoff pathways lengthen, and previously frozen soil water becomes mobile. Changing storage capacity and activation of deeper flow paths can alter the degree of mixing in storage and alter transit time distributions of outgoing fluxes. Water age can reveal vital information about catchment storage and flow pathways however, limited work has been conducted on characterizing water age dynamics in permafrost underlain catchments due to logistical challenges associated with working in cold and remote catchments. Here we characterize the age dynamics of two headwater catchments underlain with continuous permafrost located in Tombstone Territorial Park in Yukon, Canada. Both streams are considered to be non-perennial as they consistently freeze to the bed over winter. Both watersheds are primarily overlain by peat soils and have virtually no intra- and sub-permafrost groundwater contributions to streamflow. Considering the lack of hydrological characterization in this environment, our objectives are to; (1) evaluate the rate, timing, and magnitude of all hydrological fluxes, (2) utilize Bayesian mixing analysis to partition runoff into rain and snow contributions, and (3) apply StorAge Selection (SAS) functions to characterize water age dynamics in both catchments. The SAS framework can characterize variability in transit times and characterize preferential movement of water through storage, as it can assess age dynamics of water at the catchment scale by age tagging all parcels of water stored within and moving out of a hydrological system. We utilized snow survey, discharge, meteorological and eddy covariance data to quantify the inputs and outputs of the basins. Additionally, we utilized frost surveys and continuous soil moisture/temperature data to estimate active layer thickness across the basin and potential mobilization of previously frozen water. We used Isosnow, a spatially distributed parsimonious model, to simulate isotopic evolution of snow and snowmelt. A total of 410 mm precipitation entered the basin, 45% of which was snow, which melted over 4 weeks. Evapotranspiration (ET) approximately equaled discharge and increased in magnitude as summer progressed. Mixing results suggest nearly all (> 90%) of runoff during freshet was snow water in both catchments, indicating very little mixing with old water during this period. In contrast, the majority of rain left the basin as ET. The water balance and SAS framework indicate significant contributions of melting ground ice to discharge post freshet, highlighting the importance of late season rains for a particular year on discharge in the following year. The SAS framework also indicates that ET is composed primarily of very young water, likely due to high storage capacity of peat and shallow root depth of tundra vegetation. High discharge led to a more uniform SAS function for discharge, indicating greater mixing of storage during high flows.

How to cite: Grewal, A., Harman, C., and Carey, S.: Water age dynamics in non-perennial permafrost underlain catchments: Insights from hydrometrics, end-member mixing, and StorAge Selection functions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4408, https://doi.org/10.5194/egusphere-egu24-4408, 2024.

Continuing negative rainfall anomalies, coupled with climate change projections of increased drought severity and frequency, result in an urgent need to increase resilience and integration in land and water management strategies in many regions of the World. However, complex interactions between landcover change, hydrological partitioning and water availability are difficult to quantify, especially at different spatio-temporal scales. We will present insights from integrated monitoring and tracer-aided modelling approaches from the long-term experimental catchment Demnitzer Mill Creek catchment, NE Germany. We combine stable water isotopes measured at different compartments of the critical zone and landscape with process-based tracer-aided models of different complexity to investigate and quantify ecohydrological fluxes and dynamics of water storage, pathways and ages. Such tracer-aided, ecohydrological modelling frameworks provide robust science-based evidence for policy makers allowing quantitative assessment of landuse effects on water availability and effective communication with stakeholders. Our findings also underscore the urgent requirement for enhancing resilience and promoting integrated strategies in managing land and water resources to better respond to drought.

How to cite: Tetzlaff, D., Smith, A., Luo, S., and Soulsby, C.: Integrated monitoring and isotope-aided modelling to assess ecohydrological fluxes and storage dynamics in a drought sensitive lowland catchment, Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4416, https://doi.org/10.5194/egusphere-egu24-4416, 2024.

Water limitation has become one of the most pressing threats to groundwater and forest resources also in the north. Despite increased precipitation in many high latitude regions, suggested by both empirical observations and climate models, large regions are on a trajectory of increasing water limitation that already caused substantial loss of forest biomass, threatening targets for biodiversity, carbon sequestration, and bioeconomy. Key to these northern challenges are how the intensification of the water cycle results in earlier snowmelt, enhanced evapotranspiration (ET) rates, lower groundwater levels during the vegetation period and declining summer runoff. In my talk, I will present 25 years of consistent water isotopic data from precipitation, groundwater and stream flow in order to disentangle critical processes that determine the availability of water for trees and streams during the growing season. I will draw my examples from the Krycklan Catchment Study (KCS) that has supported water isotope research for over tree decades. The research infrastructure is based on a 6790 ha catchment and includes a dozen gauged streams, 150 groundwater wells, 500 permanent forest inventory plots, a large radar system for tree water content measurements and a 150 meter tall tower for biosphere-atmosphere carbon and water exchange processes. The combination of long-term monitoring, shorter-term research projects, and large-scale experiments, including manipulations of the water cycle related to climate, forest management and peatland restoration. This work has contributed to our process understanding of water in the boreal landscape, while also supporting the development of better models and guidelines for research, policy, and management.

How to cite: Laudon, H.: Intensification of the water cycle in northern catchments: Long-term isotopic and hydrometric evidence and consequences   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4645, https://doi.org/10.5194/egusphere-egu24-4645, 2024.

EGU24-6220 | ECS | Orals | HS2.2.1

A multiscale analysis using young water fractions and transit time distributions in the Yellow River Source Area 

Jinzhu Fang, Michael Stockinger, Yibo Yang, Peng Yi, Christine Stumpp, Jijie Shen, Ling Xiong, and Jiayong Shi

Estimating water yield is a crucial aspect of evaluating water conservation strategies and ensuring sustainable development in watersheds. The widespread application of isotopes to quantify the temporal dynamics of precipitation transforming into runoff has helped to identify the influence of watershed runoff and mixing processes on nutrient transport and biogeochemistry. Nevertheless, in permafrost regions characterized by strong landscape heterogeneity, sparse and discontinuous data collection poses challenges in obtaining isotope data of permafrost thaw meltwater for studying its influence on catchment hydrology. The primary objective of this study is to assess the accuracy and reliability of the convolution integral model in simulating the transit time distribution in permafrost regions, considering the introduced parameters. Additionally, the study aims to evaluate the water retention capacity of the permafrost watershed and explore the key physical control factors influencing the impact of permafrost thaw on mean transit time (MTT). The northeastern part of the Qinghai-Tibet Plateau, situated in the source region of the Yellow River (SAYR), is at the boundary between discontinuous permafrost and seasonal frozen ground. Permafrost degradation is evident, leading to a complex runoff generation mechanism. Within five nested sub-catchments of the SAYR region (20,000~120,000 km2), we collected high-resolution water stable isotope data for both rainfall and runoff, and we quantified the contribution of permafrost thaw meltwater during the melting period. The influence of permafrost meltwater from the active layer on water transit times was accounted for in the convolution integral method by introducing an additional source contributing to runoff (Q0, x% contribution with isotope ratio δ0). The study finds that additional sources of soil melt water runoff contribution are crucial to solving the problem of non-convergence of the convolution integral model in permafrost areas, and the MTTs of the watersheds are mainly influenced by river channel topography, the water retention capacity of the watersheds depended on the topographical and morphological characteristics of the watershed, and is secondarily affected by land use type, soil type, and frozen soil thermal stability.

How to cite: Fang, J., Stockinger, M., Yang, Y., Yi, P., Stumpp, C., Shen, J., Xiong, L., and Shi, J.: A multiscale analysis using young water fractions and transit time distributions in the Yellow River Source Area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6220, https://doi.org/10.5194/egusphere-egu24-6220, 2024.

Understanding erosion and sediment transport is essential for the sustainable management of water and soil resources in the critical zone. Soil erosion is considered as the main threat to soils and poses food security problems. Given these significant challenges, it is important to understand and prioritize the processes that control erosion dynamics and sediment transfers within watersheds.

However, these dynamics exhibit strong spatio-temporal variability, as illustrated by the wide dispersion of relationships between suspended sediment concentrations and liquid discharge (Q) at catchment outlets. However, these dispersions are often interpreted based on the variability along the sediment axis (e.g., origin and availability of particles), while very few studies have focused on the variability along the discharge axis (water origin). In particular, the interactions between groundwater flow and sediment transport have been little studied.

The aim of this study is to assess the impact of groundwater flow on sediment transport dynamics in two headwater catchments (respectively 1.07 km² at Brusquet and 0.86 km² at Laval) of the Draix-Bléone observatory with different vegetation cover rate (respectively 80% at Brusquet and 30% at Laval). The work first involved developing an EMMA (End-Member Mixing Analysis) method for decomposing flood hydrographs and separating the respective contributions of groundwater flow and surface runoff for each flood using the high-frequency conductivity signal, highly correlated to sulfate concentrations, as a tracer discriminating these two water compartments.

This EMMA method was used to calculate groundwater contributions during 120 floods between 2015 and 2020 in the Laval catchment and 116 floods between 2013 and 2020 in the Brusquet catchment. Analysis of the results of these decompositions revealed seasonal variations in groundwater contributions in both catchments, with winter and spring floods showing higher groundwater contributions than summer and autumn floods. These decompositions made it possible to examine the dynamics of fine sediment transport during floods as a function of surface runoff rate and to identify the impact of groundwater on hydrosedimentary processes (effect of dilution or of remobilization of riverbed sediment). By comparing the results of the decompositions from the two catchments, it was possible to assess the impact of vegetation cover on the contribution of groundwater to flood and on each catchment sediment dynamics.

Overall, this study suggests that the use of high frequency conductivity signals as tracer of water origin offers a promising approach to performing high frequency decompositions of flood hydrographs. The results of the decompositions highlight the importance of groundwater flows for understanding hydrosedimentary processes in headwater catchments (~km²).

How to cite: Fischer, O., Legout, C., Le Bouteiller, C., and Nord, G.: Study of the contribution of groundwater to hydrosedimentary processes in two Mediterranean mountainous watersheds using the high frequency conductivity signal as a tracer of water origin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6278, https://doi.org/10.5194/egusphere-egu24-6278, 2024.

EGU24-6285 | Orals | HS2.2.1

Modelling the isotopic signatures of solutes derived from weathering reactions 

Jennifer Druhan and Paolo Benettin

High-resolution water chemistry records in rivers typically show that the routing of reactive solutes through the Critical Zone is a dynamic process that can change drastically across hydrologic responses. Quantitative transient models are needed to interpret these riverine solute measurements as emergent signatures of coupled geochemical and ecohydrological functioning. In this context, the stable isotope signatures of geogenic solutes offer a unique opportunity to disentangle processes such as the dissolution or primary minerals, precipitation of secondary phases and ecological nutrient cycling. Here, we describe the first merging of a parsimonious hydrological model featuring time-variant fluid age distributions with a geochemical model for isotopically fractionating weathering reactions. Using SiO2(aq) and the corresponding silicon isotope ratio δ30Si as an example, we show that the stable isotope signatures of riverine solutes produced by weathering reactions reflect a component of the fluid age distribution that is unique to the corresponding solute concentrations. This distinct sensitivity offers a novel diagnostic tool to interpret the SiO2(aq) and δ30Si dynamics recorded in six low-order streams spread across a diversity of climates, geologies, and ecosystems.

How to cite: Druhan, J. and Benettin, P.: Modelling the isotopic signatures of solutes derived from weathering reactions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6285, https://doi.org/10.5194/egusphere-egu24-6285, 2024.

EGU24-6550 | ECS | Orals | HS2.2.1

Stable silicon isotope signatures reflect the storage and flow paths of fluid draining through both mesoscale hillslopes and natural watersheds. 

Andrew Guertin, Charlie Cunningham, Julien Bouchez, Marine Gelin, Jon Chorover, Peter Troch, Hannes Bauser, Minseok Kim, Louis Derry, and Jennifer Druhan

The variety of transit times and pathways water takes from infiltration to discharge through a hillslope determines the dynamic storage of the system, the capacity for water-rock-life reactivity, and ultimately the chemical composition of streamflow. In the laboratory, fluid phase stable Si isotopes (δ30Si) enrich through time during secondary silicate mineral formation as Si is removed from solution1. However, despite streams being weighted towards young waters, discharge from individual catchments commonly maintains a stable, often strongly fractionated δ30Si signature, reflective of chemically evolved solute signatures2. Furthermore, each individual catchment exhibits its own characteristic δ30Si signature in the stream discharge, even for comparable extents of Si depletion from solution. Such intra-site variability was attributed to a combination of multiple fractionation pathways (plant uptake and mineral precipitation) and the unique structure of fluid storage and drainage through each catchment. Here, we use three replicate artificial hillslopes at the Landscape Evolution Observatory (LEO) in Tucson, Arizona as model catchments to test if δ30Si of discharge can be described by an isotope-enabled reactive transport model (RTM) constrained by both the characteristic transit time distribution (TTD) and fractionation pathways of LEO. At the LEO hillslopes, the role of vegetation and hence the compounding effects of ecosystem cycling can be omitted, limiting δ30Si fractionation solely to the effects of mineral precipitation. We collected samples, with constrained TTDs, and measured δ30Si from the discharge at the outlet of each hillslope during three randomized storm events of varying intensity. The δ30Si in aqueous discharge reflects a clear and consistent signature of fractionation that is confined to a narrow range of values, much like natural upland watersheds, despite highly variable irrigation scenarios, retaining a signature across the three hillslopes defined by the unique hydrologic flow paths of the replicated system.  We offer a quantitative and process-based framework describing these observations using an isotope-enabled RTM3. Close agreement between this coupled RTM and the discharge measurements from LEO supports our hypothesis that the δ30Si of headwater streams is reflective of both characteristic watershed TTDs and fractionation pathways. By applying this new understanding to reexamine upland watershed datasets we can gain insight into fluid flow paths and contributions of various fractionation pathways to water circulation through the shallow subsurface Critical Zone.

 

1Fernandez, N. M., Zhang, X., & Druhan, J. L. (2019). Silicon isotopic re-equilibration during amorphous silica precipitation and implications for isotopic signatures in geochemical proxies. Geochimica et Cosmochimica Acta, 262, 104-127. https://doi.org/https://doi.org/10.1016/j.gca.2019.07.029

2Fernandez, N. M., Bouchez, J., Derry, L. A., Chorover, J., Gaillardet, J., Giesbrecht, I., et al. (2022). Resiliency of silica export signatures when low order streams are subject to storm events. Journal of Geophysical Research: Biogeosciences, 127, e2021JG006660. https://doi.org/10.1029/2021JG006660

3Druhan, J. L., & Benettin, P. (2023). Isotope Ratio – Discharge Relationships of Solutes Derived From Weathering Reactions. American Journal of Science, 323. https://doi.org/10.2475/001c.84469

How to cite: Guertin, A., Cunningham, C., Bouchez, J., Gelin, M., Chorover, J., Troch, P., Bauser, H., Kim, M., Derry, L., and Druhan, J.: Stable silicon isotope signatures reflect the storage and flow paths of fluid draining through both mesoscale hillslopes and natural watersheds., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6550, https://doi.org/10.5194/egusphere-egu24-6550, 2024.

EGU24-6956 | ECS | Posters on site | HS2.2.1

Sulfur and oxygen isotope ratios constrain riverine sulfate sources and terrestrial pyrite oxidation 

Huiying Hu, Changqiu Zhao, Sen Xu, Rongfei Wei, Teklit Zerizghi, Qiyu Tan, and Qingjun Guo

Pyrite oxidation, coupled with carbonate weathering, can be a source of carbon dioxide (CO2) in the atmosphere over geological timescales. However, this source of CO2 is an important but not entirely understood component of the long-term carbon cycle. The exact identification of the riverine sulfate sources and terrestrial pyrite weathering flux is crucial for a quantitative understanding of this source, but it still faces great challenges. Sulfur and oxygen isotope ratios are widely used to constrain sulfate sources. Here, we reviewed the effect of pyrite oxidation on the carbon cycle and synthesized sulfur isotope and oxygen isotope data for global rivers. We also figured out the fluxes of riverine sulfate caused by pyrite oxidation in various rivers around the world using a Bayesian model that is based on the sulfur and oxygen isotope ratios in riverine sulfates and local end elements. The highest pyrite-derived sulfate fluxes were found in the Mississippi River (198.3 ± 37.8 Gmol SO42-year-1). Higher pyrite oxidation rates occurred in areas with higher runoff rates, and global climate change may have also affected pyrite oxidation rates. This may assist in re-evaluating the role of chemical weathering on the carbon cycle and improve the theory of the carbon cycle.

How to cite: Hu, H., Zhao, C., Xu, S., Wei, R., Zerizghi, T., Tan, Q., and Guo, Q.: Sulfur and oxygen isotope ratios constrain riverine sulfate sources and terrestrial pyrite oxidation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6956, https://doi.org/10.5194/egusphere-egu24-6956, 2024.

EGU24-7183 | ECS | Posters on site | HS2.2.1

Temperature Profiles due to Groundwater Flow in a Subsurface Porous Medium with a Heat Convective Boundary 

Chia-Hao Chang, Bo-Tsen Wang, and Jui-Pin Tsai

The temperature in subsurface porous media (i.e., subsurface temperature) has been popularly treated as a natural tracer of groundwater flow. Several previous studies usually neglected the thermal boundary effects to build simple geothermal models for simulating the subsurface temperature. Although a few studies considered the thermal boundary effects, their models considered the thermal boundaries under either specific-temperature or specific-heat-flux conditions. However, these models are expectedly inapplicable to the cases of subsurface porous media with convective thermal boundary conditions. This study hence proposes a heat-transport model for describing the subsurface temperature induced by a heat convective boundary. The model is composed of a heat conduction-advection equation subject to a convective boundary condition at the bottom of a porous medium. The study results show how the convective boundary effects influence he subsurface temperature and indicate the effects are dominated by some parameters, including the medium thicknesses, medium thermal conductivity, heat transport coefficient, and groundwater flux.

How to cite: Chang, C.-H., Wang, B.-T., and Tsai, J.-P.: Temperature Profiles due to Groundwater Flow in a Subsurface Porous Medium with a Heat Convective Boundary, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7183, https://doi.org/10.5194/egusphere-egu24-7183, 2024.

EGU24-8015 | ECS | Orals | HS2.2.1

Revealing the origin, age and seasonality of streamflow, soil waters and transpiration 

Marius G. Floriancic, Scott T. Allen, and James W. Kirchner

The forest water cycle is dominated by vegetation-mediated processes, such as interception, infiltration, and transpiration, that greatly impact the redistribution of waters between the atmosphere and subsurface. Based on a three-year time series of water stable isotopes in precipitation, soils of various depths, groundwater, streams and xylem from the “WaldLab Forest Experimental Site” in Zurich, Switzerland, we estimated seasonal signals and the fractions of more recent and older waters across the different compartments of the forest water cycle. These findings yield new understanding of water transport in forest ecosystems.

Seasonal variation in streamflow isotopic signatures was small, indicating that annual streamflow was dominated by old waters draining from subsurface storages. Mobile and bulk soil waters all showed a distinct seasonal signature, with the seasonal amplitude decreasing with depth and mobile soil waters varying less than bulk soil waters. Young water fractions and new water fractions in forest soils decreased with increasing depth, indicating different degrees of subsurface mixing with waters from previous events and seasons. The fractions of recent precipitation in soil waters were generally smaller in summer than in winter, revealing the effects of interception and evaporation. Xylem water signatures in beech and spruce trees largely matched the bulk soil water signatures. The relative lack of soil water recharge in summer led to both species predominantly transpiring winter precipitation. Canopy interception did not substantially alter the isotopic signal of precipitation, but where it is more significant it could bias interpretations of transit times and seasonal precipitation partitioning.

How to cite: Floriancic, M. G., Allen, S. T., and Kirchner, J. W.: Revealing the origin, age and seasonality of streamflow, soil waters and transpiration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8015, https://doi.org/10.5194/egusphere-egu24-8015, 2024.

EGU24-8684 | ECS | Posters on site | HS2.2.1

CFC stream water mean transit times reveal subsurface flow processes across scales at Krycklan 

Tamara Kolbe, Virginie Vergnaud-Ayraud, Barbara Yvard, and Kevin Bishop

Catchment transit time distributions span the range from minutes to hours (e.g. overland flow) to years, decades and longer. As time-variant catchment descriptors they are useful indicators for flow and transport processes. Stable water isotopes are established tracers to inform about young water components in stream water, but are less well-suited to defining ages for the older components of the transit time distribution. To infer slow flow water components, tracers that are able to date water over longer timescales are needed.

Here, we used atmospheric tracers (i.e. chlorofluorocarbons (CFCs)) that are able to cover the timescale of subsurface flow over decades to determine mean transit times of stream water. CFCs are well established tracers for dating groundwater, but their use is limited in surface waters as they might partially reequilibrate with ambient atmospheric concentrations of CFCs within a few hours. We measured CFCs at different subcatchment outlets of the Krycklan catchment basin under different flow conditions (49 samples in total). Krycklan is a boreal research catchment in northern Sweden at which stable water isotopes are extensively used to understand hydrological processes. The CFC results show that stream water mean transit times vary between 32 years and 59 years. These ages are similar to those observed for groundwater in the aquifer. This, and the patterns for individual CFCs suggest limited reequilibration with contemporary atmospheric CFC concentrations. Mean transit times across scales are independent of catchment size suggesting local groundwater contributions to streams. Furthermore, mean transit times negatively correlate with specific discharge supporting findings of increasing young water components during high flow conditions.

 

How to cite: Kolbe, T., Vergnaud-Ayraud, V., Yvard, B., and Bishop, K.: CFC stream water mean transit times reveal subsurface flow processes across scales at Krycklan, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8684, https://doi.org/10.5194/egusphere-egu24-8684, 2024.

EGU24-11340 | ECS | Orals | HS2.2.1

South African Mediterranean Catchments Comparison Using Environmental Tracers and Hydrochemistry 

Angela Welham, Jared Van Rooyen, Andrew Watson, Reynold Chow, and Alakendra Roychoudhury

Water quantity and quality in Mediterranean catchments are of concern due to evaporation rates often exceeding rainfall rates. Spatio-temporal hydrological shifts caused by climate change within these environments affect the catchment's hydrodynamics. The Western Cape region in South Africa boasts Mediterranean climate and is dependent on rainfall and surface water to recharge dams, which support various industrial, domestic, and agricultural sectors. The 2015 – 2018 Western Cape drought decreased the contribution of surface sources, leading to an increase in groundwater dependence across industries. This exerted pressure on both the hydrological system and ecosystem functionality leading to water security issues. To determine sustainable water management strategies, environmental tracers (stable and radioactive isotopes) and hydrochemical analyses were applied to two data-poor contrasting catchments hosting important estuarine wetlands in the Western Cape. Verlorenvlei Catchment, a semi-arid environment, is predominantly occupied by agricultural practices (potatoes, citrus, grapes, and rooibos). In contrast, the Eerste River Catchment is a wetter region but is subjected to high urban modifications such as wastewater treatment plants, informal/formal settlements, water diversion and canalization. To disentangle the two wetland watersheds' temporal and spatial hydrological characteristics four sample campaigns were completed in March, June, September, and November 2023. Water samples (i.e., event-based rainfall, surface water and groundwater) were analysed for isotopes (δ18O, δ2H, 3He, 4He,21Ne, 20Ne, 22Ne, 36Ar, 40Ar, 84Kr, and 136Xe) and major ions. Within the topographically and surface water delineated watershed, the Verlorenvlei estuary experiences high evaporation compared to other surface waters, hence is reliant on baseflow to support its hydrological functioning. During prolonged dry periods, groundwater from outside the watershed predominantly supports the wetland. However, under normal or above-average rainfall conditions, support shifts to local groundwater. Two sandstone and shale-dominated sub-catchments within the watershed exhibit overlapping groundwater isotope ratios and water types compared to the Verloren sub-catchment, suggesting a disproportionately high groundwater contribution from both sub-catchments into the wetland. Conversely, the Eerste River Catchment water quality is of a greater concern. The Macassar coastal wetland is less vulnerable to evaporation and depends on two perennial rivers for support. However, strong surface water-groundwater interconnectivity and an approximate 9-month lag in recharge suggest a high baseflow response. Therefore, the Macassar wetland can likely maintain a steady water level due to continuous streamflow support by groundwater discharge during dry periods, unlike in Verlorenvlei. Despite these Mediterranean catchments’ different settings, they share a high sensitivity to rainfall and evaporation changes. To mitigate the impact of projected droughts on these respective wetlands, the government’s water management department is encouraged to improve its water regulations and policies, taking into account both local and regional groundwater support. Additionally, water agencies should actively engage more with stakeholders to raise water awareness and improve water management (e.g., organizing monthly seminars to discuss water recycling, water-conserving irrigation systems, and other related strategies).

How to cite: Welham, A., Van Rooyen, J., Watson, A., Chow, R., and Roychoudhury, A.: South African Mediterranean Catchments Comparison Using Environmental Tracers and Hydrochemistry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11340, https://doi.org/10.5194/egusphere-egu24-11340, 2024.

EGU24-11479 | ECS | Orals | HS2.2.1

The EXPECT method: a multi-tracer approach for reliable high temporal resolution young water fraction estimates 

Alessio Gentile, Jana von Freyberg, Davide Gisolo, Davide Canone, and Stefano Ferraris

The portion of recently introduced water molecules in a stream, known as the young water fraction, is crucial in catchment intercomparison studies. The unweighted or flow-weighted average young water fraction in a catchment, over the period of isotope sampling, can be assessed through the ratio of flow-weighted or unweighted seasonal isotope cycles amplitudes in streamwater (A(*)S) and precipitation (AP), respectively. The symbol ‘*’ here indicates a flow-weighted variable. However, the young water fraction resulted to be a no-stationary quantity within individual catchments.

Indeed, past studies revealed that young water fractions increase with stream discharge (Q). Accordingly, the rate of increase in young water fraction with increasing Q has been defined as the discharge sensitivity of young water fraction (S*d). S*d has been quantified as the parameter of a non-linear equation that expresses how AS(Q) varies with Q. Such parameter is directly obtained by fitting a sine curve, with amplitude AS(Q), on streamwater isotope data. Accordingly, in catchments with sparse isotope data S*d could be highly uncertain.

In this study, we introduce a novel approach designed to enhance the temporal resolution of young water fraction estimates, consequently refining the determination of S*d. Our proposed method, referred to as EXPECT, is grounded in three fundamental assumptions.

  • We propose a mixing relationship that follows an exponential decay of EC with an increasing young water fraction.
  • We posit that the two-component hydrograph separation technique, utilizing measured Electrical Conductivity (EC) as a proxy of water age and the aforementioned exponential mixing relationship, can effectively delineate the proportion of young and old water in a stream by using appropriate end-members.
  • We assume that the EC value of the young water endmember (ECyw) is lower than that of the old water endmember (ECow).

The two endmembers, ECyw and ECow, have been adjusted through a calibration process by aligning the unweighted and flow-weighted average young water fractions obtained through hydrograph separation with the corresponding values derived from seasonal isotope cycles (AS/AP  and A*S/AP, respectively).

The method has been tested in three small catchments in the Alptal valley, Switzerland, returning promising results. Nevertheless, we emphasize the importance of considering the limitations of EC as a tracer and the peculiar characteristics of the catchments under investigation for the appropriate application of the EXPECT method.

Keywords: Stable water isotopes, Electrical Conductivity, Young water fraction, Discharge Sensitivity

Acknowledgements: This publication is part of the project NODES which has received funding from the MUR –M4C2 1.5 of PNRR with grant agreement no. ECS00000036.

References

Gentile, A., von Freyberg, J., Gisolo, D., Canone, D., and Ferraris, S.: Technical Note: two-component Electrical Conductivity-based hydrograph separaTion employing an EXPonential mixing model (EXPECT) provides reliable high temporal resolution young water fraction estimates in three small Swiss catchments, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-1797, 2023.

 

How to cite: Gentile, A., von Freyberg, J., Gisolo, D., Canone, D., and Ferraris, S.: The EXPECT method: a multi-tracer approach for reliable high temporal resolution young water fraction estimates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11479, https://doi.org/10.5194/egusphere-egu24-11479, 2024.

EGU24-11764 | ECS | Posters on site | HS2.2.1

Approaching mass (im)balance when using artificial DNA tracer using DNA extraction methods 

Sören Köhler, Jan Willem Foppen, Peter Chifflard, Florian Leese, and Yvonne Schadewell

Artificial tracers play an important role in hydrological studies that aim to identify subsurface flow paths. Tracers can be used to investigate water transit times but also, for example, to assess if a structure is leak-proof. Recently, artificial DNA (artDNA) has been proposed as a tracer alongside traditional tracers such as salt. However, like traditional tracers, artDNA suffers from input tracer mass loss. This is even more pronounced in the case of artDNA. Different approaches were proposed to improve the recovery of tracer mass and thus reach the required limit of detection and quantification required for the analysis. Using column tests, a controlled experiment was designed to examine the recovery success of DNA extraction and the detachment from soil via a buffer. In each case water was spiked with artDNA, flushed through the column and subsequently the remaining molecules recovered using a magnetic bead extraction method. The ongoing experiments will show the enhancement of artDNA tracer recovery by using methods for DNA extraction from molecular biology. Further, to recover potential substrate-bound artDNA and possibly identify one source of the observed mass imbalance, a phosphate-containing buffer of high pH was used to detach artDNA from the substrate inside the column. The results will be cross-factored by comparing the recovery of tracer mass in the plain eluate vs. the DNA extracted from the eluate and by determining the substrate-bound artDNA in both cases. Insights from this experiment and the methodological advancement will be fundamental for the use of artDNA-based tracing in hydrological research.

How to cite: Köhler, S., Foppen, J. W., Chifflard, P., Leese, F., and Schadewell, Y.: Approaching mass (im)balance when using artificial DNA tracer using DNA extraction methods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11764, https://doi.org/10.5194/egusphere-egu24-11764, 2024.

End-member mixing analysis (EMMA) has been frequently applied to advance our understanding of hydrologic pathways, water sources, and surface water and groundwater interactions in catchment hydrology. Very recently, EMMA has been applied to hydrogeological systems to better understand groundwater recharge and movement. In conjunction with diagnostic tools of mixing models (DTMM), EMMA relies on eigenvectors extracted from coincident time series of geochemical and isotopic values measured at the same location to characterize the mixing space (numbers of end-members and conservative tracers), identify end-members, and quantify their contributions to streamflow and the groundwater system. However, this traditional approach limits the use of EMMA in many studies with small sample sets (short intervals). We hypothesize that EMMA can be extended to studies with infrequent sampling schemes if samples are collected from multiple scales or locations within a catchment by adding an additional mixing model assumption that end-members are consistent over varying scales. In other words, the underlying assumption means that only contributions of end-members vary with scales. This work uses two examples to demonstrate the success of EMMA for analyzing short-duration time series of water samples collected from multiple locations, one from a glacierized catchment in Bhutan and the other from a hydrogeological study in volcanic setting of El Salvador. The success was evaluated by independent tracers (not used in EMMA and also no direct connection with those used in EMMA) and semi-independent tracers (e.g., specific conductance (SC) and pH, which are chemically related to geochemical tracers used in EMMA). In the glacierized catchment, a three-end-member mixing model was developed using geochemical tracers for streamflow with contributions from glacier melt and direct precipitation, shallow groundwater (below and in front of glaciers), and catchment groundwater (base flow generated outside the glacierized area). The projections using the EMMA results and the measured values were very well correlated for independent and semi-independent variables, including SC (R2 = 0.97, slope =0.98, p < 0.001), pH (R2 = 0.70, slope =1.1, p < 0.001), stream temperature (R2 = 0.77, slope =0.6, p < 0.001), and δ18O (R2 = 0.90, slope =1.16, p < 0.001; not used in EMMA in this case). In the case of El Salvador study, three end-members were also identified for a number of groundwater wells, with direct precipitation and two types of groundwater from different geologic settings. The El Salvador model was validated using SC (R2 = 1.00, slope =0.97, p < 0.001) and sulfur (R2 = 0.87, slope =0.81, p < 0.01) that were not used in EMMA. The successful application of this new approach will significantly extend the application of EMMA to catchments that are difficult to access, or frequent sampling is impractical.

How to cite: Liu, F. and Gierke, J.: A New Approach to Conduct End-Member Mixing Analysis in Catchment Hydrology and Hydrogeology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12055, https://doi.org/10.5194/egusphere-egu24-12055, 2024.

EGU24-12536 | Posters on site | HS2.2.1

Using Stable Water Isotopes to Estimate Source Water Contribution in a Tidal Marshland 

Sophia Bradach, Jing Yan, Sunendra Joshi, Mohammad Afsar, and Yan Jin

Sea level rise due to climate change is exacerbating issues of saltwater intrusion and contamination. Identifying sources of water in coastal marshland under the influences of tides is critical in assessing vulnerability and developing strategies to protect coastal ecosystems. Mixing models such as end-member mixing, allow the contributions of salt and freshwater to be quantified using conservative tracers such as water isotopes. Using stable water isotopes as tracers to assess the impact of saltwater intrusion in coastal environments has been limited compared to their application in catchment hydrology. This study aims to explore the feasibility of using water isotopes to quantify the salt and freshwater dynamics in a tidal salt marsh at the St. Jones Reserve (39.10 N, 75.44 W) in Delaware, USA.  During a full tidal cycle, porewater samples were collected from piezometers (at 30 and 100 cm depths below the surface) at four sampling sites along a saline gradient at St. Jones Reserve.  Samples were taken at specific time intervals to capture the full effect of the tide. The isotope composition of the collected porewater samples was measured using a Liquid Water Isotope Analyzer (LWIA). End member analysis will be used to estimate the relative contributions of salt and freshwater at each point along the salt gradient. By quantifying these contributions, we hope to gain insights into the potential impacts of saltwater intrusion on the tidal marsh ecosystem. The information will allow better understanding of the hydrological conditions of the marshland and aid interpretations of an array of soil physical and chemical properties and processes being studied at the site.

How to cite: Bradach, S., Yan, J., Joshi, S., Afsar, M., and Jin, Y.: Using Stable Water Isotopes to Estimate Source Water Contribution in a Tidal Marshland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12536, https://doi.org/10.5194/egusphere-egu24-12536, 2024.

EGU24-12870 | ECS | Orals | HS2.2.1

Development of a model agnostic isotope tracer simulator  

Tegan Holmes, Tricia Stadnyk, and Alain Pietroniro

Isotope tracers can benefit hydrologic modeling, by adding observational data relating to evaporation and water ages as a supplement to flow data. A few hydrologic models have had tracers embedded in their software, resulting in numerous studies and identified benefits from isotope tracer simulation. A key barrier to more wide-spread application of linked flow and isotope simulation in hydrologic modeling is the considerable effort required to add an isotope tracer simulation to an existing model, which requires an uncommon overlapping expertise in both hydrologic model development and isotope tracer science. To expand the utilization of isotope tracers, a model agnostic isotope tracer simulator (MAITsim) has been developed, which can currently simulate two common stable isotope tracers (deuterium and oxygen-18) in association with a wide range of hydrologic models. 

MAITsim runs as a post-processing model using outputs from a hydrologic model as inputs, such that only the model specific linkage needs to be set up in order to simulate both flow and isotope tracers. The tracer simulator is compatible with any flux-state model with unidirectional flow paths, as it uses no pre-determined spatial sub-divisions (any combination of soil layers, sub-catchments and hydrologic response units can be linked to MAITsim). The model includes both mixing and evaporative fractionation and is designed to be numerically stable in wet and desiccating conditions. 

The MAITsim model results are compared to an existing embedded isotope tracer model (isoWATFLOOD). The next phase in development is to test MAITsim functionality and performance in multiple existing hydrologic models. 

How to cite: Holmes, T., Stadnyk, T., and Pietroniro, A.: Development of a model agnostic isotope tracer simulator , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12870, https://doi.org/10.5194/egusphere-egu24-12870, 2024.

EGU24-13916 | ECS | Posters on site | HS2.2.1

A comparison of Lumped Convolution approach and Ensemble Hydrograph Separation in soil transit time distribution estimations: case study of San Francisco catchment 

Pablo Peña, David Windhorst, Patricio Crespo, Edison Timbe, Esteban Samaniego, and Lutz Breuer

Mean Transit Time (MTT) and Transit time distribution (TTD) functions are crucial for understanding the temporal dynamics of water flow through a catchment system, particularly in the context of rainfall-runoff processes that govern the solute storage and transport. Traditionally, these insights have been assessed using lumped TTD functions through models based on quasi-linearity and steady-state conditions. 
In contrast, the Ensemble Hydrograph Separation technique (EHS) presents a promising alternative for estimating TTD through multiple linear equations representing the relation between tracer fluctuations. This approach is advantageous, eliminating the need for continuous time series data of tracer measures and avoiding constraints related to the shape of transit distributions or system stationarity. However, EHS faces a sensitivity challenge in its regularization process, governed by a parameter denoted as "v," making the technique susceptible to either under-smoothing or over-smoothing the TTD function. Consequently, the judicious estimation of the regularization parameter within EHS becomes imperative.
This study aims to investigate how both the traditional lumped TTD approach and the innovative EHS method contribute to our understanding of catchment hydrology. The present investigation was conducted using stable water isotope data of stream and soil water collected in a typical Andean tropical mountain cloud forest catchment. The sampling was conducted at six sites along two altitudinal transects (at elevations of 3000 m, 2000 m, and 1000 m), encompassing two distinct land covers (forest and pasture). At each site, soil water samples were collected at three different depths (0.10, 0.25, and 0.40 m below ground). The main objective is to assess the feasibility of substituting one method with the alternative by comparing their performance using different evaluation criteria such as the Nash-Sutcliffe coefficient (NSE), mean absolute error (MAE), and coefficient of determination (R2).
Through Monte-Carlo simulations, we calibrated the “v” parameter and conducted a comprehensive comparison of both approaches. At 75% of the monitoring points, we observed NSE and R2 coefficients exceeding 0.65. These results align with previous studies, emphasizing the feasibility of assuming stationary conditions in humid tropical ecosystems. The study systematically examined the concordance between the Lumped TTD approach and Ensemble Hydrograph Separation (EHS) findings when utilizing similar TTDs. Furthermore, it provided a detailed analysis of the strengths and limitations of EHS implementation with actual real data. The insights gained from this research can be extrapolated to identify situations where each approach may be more suitable, offering valuable recommendations for their future application in various catchments.

How to cite: Peña, P., Windhorst, D., Crespo, P., Timbe, E., Samaniego, E., and Breuer, L.: A comparison of Lumped Convolution approach and Ensemble Hydrograph Separation in soil transit time distribution estimations: case study of San Francisco catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13916, https://doi.org/10.5194/egusphere-egu24-13916, 2024.

EGU24-16018 | Posters on site | HS2.2.1

Understanding snow meltwater fractional contributions to streamflow in a subarctic catchment 

Pertti Ala-aho, Kashif Noor, Jeffrey M. Welker, Kaisa-Riikka Mustonen, Björn Klöve, and Hannu Marttila

Snow plays an important role in the Northern water cycle providing temporary water storage, and resulting in high flows during spring snowmelt. Snow is experiencing rapid changes due to global warming, and process-based understanding of how snowmelt interacts with the environment is becoming ever more important. Stable isotopes of 18O and 2H are recognized as reliable tracers for determining water sources and tracing their movement within a catchment. The Isotope-Based Hydrograph Separation (IHS) is used to determine the mix of water sources in streams. However, when determining the snowmelts contribution to streamflow using IHS, uncertainties arise due to the lack of a clear and consistent snow sampling approach do define the isotope signal of snowmelt water for IHS calculations. To tackle these uncertainties, we did intensive sampling of snowfall, snowpack, and snow meltwater 18O isotopes at the Pallas catchment in Northern Finland. Our examination of different snow sampling strategies revealed potential biases in the IHS analysis. By employing samples directly from the snowmelt water 18O isotope value as an endmember in IHS, we determined the fractional contribution from streamflow was 59.6% (with a ±2% uncertainty). Yet, using alternate average weighted isotope values from either snowfall or mid-winter snowpack resulted in underestimations of snowmelt fraction by 17.8% and 22.6% respectively. In the absence of snowmelt samples, samples collected from the snowpack during high snowmelt period resulted in smaller biases (4.2 % lower snowmelt fractions). Our findings underline the importance of selecting the right snow sampling method for IHS, or any other ecohydrological analysis using stable water isotope tracers.

How to cite: Ala-aho, P., Noor, K., Welker, J. M., Mustonen, K.-R., Klöve, B., and Marttila, H.: Understanding snow meltwater fractional contributions to streamflow in a subarctic catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16018, https://doi.org/10.5194/egusphere-egu24-16018, 2024.

EGU24-16332 | Posters on site | HS2.2.1

Water stable isotope approaches for estimating water ages in the hydrological cycle 

Christine Stumpp, Hatice Türk, Selma Hajric, and Michael Stockinger

Water stable isotopes provide a tracer signal input into the hydrological cycle with every precipitation event over a certain area. Tracking this signal, its seasonal distribution, and its relative changes since that water fell as snow or rain, can provide information about water flow and transport processes in the critical zone or integrative information about them within catchments. Water stable isotopes combined with other approaches can also be used to estimate water ages, such as the transit or residence time of water. Knowing the distribution of transit or residence times and how they vary over time and space can further inform about flow paths and hydrological processes as well as time scales of solute transport and hydrochemical processes. In this talk, an overview of the importance of water ages in hydrology will be provided, and different methods will be introduced for estimating water transit or residence times based on water stable isotope data. Several examples will be shown where we used experimental data-based methods and hydrological modelling for estimating water ages in soils and in catchments. The importance of high-resolution isotope data will be emphasized for uncovering hydrological processes, their dynamics, and controlling factors.

How to cite: Stumpp, C., Türk, H., Hajric, S., and Stockinger, M.: Water stable isotope approaches for estimating water ages in the hydrological cycle, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16332, https://doi.org/10.5194/egusphere-egu24-16332, 2024.

EGU24-16911 | ECS | Posters on site | HS2.2.1

Study of stable isotope in daily precipitation for the lower Brahmaputra region at Guwahati. 

Madhusmita Nanda and Archana M Nair

This study analysed the stable isotopic composition of daily precipitation from a monitoring station established in Guwahati located near the bank of the lower Brahmaputra region. Between September 2022 and December 2023, the precipitation samples were collected for hydrogen and oxygen stable isotope analysis. The analysis was performed following the conventional analytical procedure for laser-based, off-axis integrated cavity output spectroscopy (ICOS) in Liquid Triple Isotopic Water Analyser (L-TIWA). The preliminary study helps to define Local meteoric water line (LMWL) in the Lower Brahmaputra region. The pre-monsoon samples show regression line with slope lesser and an intercept greater than Global meteoric water line (GMWL), but the monsoon samples are showing a trend line similar to GMWL. The smaller intercept difference in the pre-monsoon and monsoon rainwater samples indicates the moisture sources of precipitation in this region originating from the Indian summer monsoon more than the western disturbances. The enrichment of heavier isotopes in precipitation of different seasons might be the result of a complex interplay between atmospheric circulation, moisture sources, elevation effects, and transport processes. Further analysis by using air mass back trajectories models and GIS tools will be able to understand and correlate the diverse origin of moisture and observed daily isotopic variability.

How to cite: Nanda, M. and Nair, A. M.: Study of stable isotope in daily precipitation for the lower Brahmaputra region at Guwahati., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16911, https://doi.org/10.5194/egusphere-egu24-16911, 2024.

EGU24-17064 | ECS | Posters on site | HS2.2.1

Physiographic controls on fractions of new water in 12 nested catchments 

Turk Guilhem, Gey Christoph J., Schöne Bernd R., Hissler Christophe, Barnich François, Leonard Loic, and Pfister Laurent

In the context of global change, the characterization and quantification of the “changing pulse of rivers” is a pressing challenge. Over the past decades, rapidly increasing computational capabilities and the related complexity of numerical models have contributed significantly to improve flood forecasting systems. However, our understanding of the mechanistic causality – especially of extreme hydrological events – remains fragmented. Streamflow responses are notoriously threshold-bound and site-specific, thus making extrapolations to ungauged basins and projections into future climate scenarios difficult without physical evidence. There is thus still a need for inter-catchment studies across contrasted physiographic and climate settings, ideally spanning over large observation time intervals.  Here, we rely on a 13 year-long, fortnightly resolved precipitation and stream water δ18O isotope record from 12 nested catchments with different bedrock geologies (marls, sandstone, schists) and land cover in the Alzette River basin (Luxembourg). Located on the eastern edge of the sedimentary Paris Basin, our study area has a rather homogeneous semi-oceanic climate. The δ18O records varied between catchments – exhibiting both seasonal and interannual patterns during the 13 years of observations. The seasonal amplitude of the precipitation δ18O signal was strongly damped in stream water of catchments dominated by permeable bedrock geology and large storage volumes. This dampening effect was much less pronounced in catchments dominated by marly (and thus less permeable) bedrock with limited storage capacity.

 

Across the set of 12 nested catchments, stream responses to precipitation were highly variable. Runoff coefficients were typically highest in catchments dominated by less permeable bedrock, as opposed to catchments with permeable bedrock, exhibiting low runoff coefficients. We found that the fractions of new water (Fnew) determined via ensemble hydrograph separation (as per Kirchner, 2019), i.e., water less than two weeks ‘old’, were correlated to bedrock geology. In catchments with mixed (i.e., permeable and less permeable) bedrock types, we noticed an increase in Fnew with discharge – mirroring the domination of groundwater contributions from areas with permeable bedrock during low to medium discharge and the activation of fast flow paths in sectors dominated by less permeable substrate at higher discharge. Findings shed new light on the role of bedrock geology on fundamental catchment functions of water collection, storage, mixing and release. The latter largely determine the responsiveness of catchments to variability and/or changes in climate. This information is key for better anticipating catchment response to future changes in climate.

 

 

References:

Kirchner, James W. (2019). Quantifying new water fractions and transit time distributions using ensemble hydrograph separation: theory and benchmark tests. Hydrology and Earth System Sciences, 23, 303–349.

How to cite: Guilhem, T., Christoph J., G., Bernd R., S., Christophe, H., François, B., Loic, L., and Laurent, P.: Physiographic controls on fractions of new water in 12 nested catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17064, https://doi.org/10.5194/egusphere-egu24-17064, 2024.

EGU24-17342 | Posters on site | HS2.2.1

Evaluating the Vulnerability of Mountain Springs: A Case Study in Italy to Prioritize Conservation and Management Strategies 

Maria Battistel, Lucio D'Alberto, Giovanni Mario, Raffaele Marciano, Giuliano Dreossi, Alessandro Pozzobon, Barbara Stenni, and Mauro Masiol

This research introduces a methodology for evaluating the protection zone of vulnerable mountain springs using an hydrogeochemical approach. Mountain springs play a crucial role in maintaining the ecological balance and ensuring the well-being and resilience of communities residing in mountainous areas. These resources frequently serve as the primary freshwater supply in numerous mountainous regions, their impact extends beyond these areas by catering to diverse applications, including agriculture, farming, hydropower generation, artificial snowmaking, and industrial utilization.

Despite their importance, mountain springs are under increasing threat due to climate change and human activities and thus need to be preserved and managed to ensure a sustainable use and conservation. In this study, we assess the vulnerability of two mountain springs located in a karstic water system in the Northern Italy mountainous region. Particularly we analyze the hydrogeological and hydrogeochemical parameters of the two mountain springs, together with the oxygen and hydrogen isotopic composition (δ18O and δ2H) and d-excess of both the springs and the rainwater of the area. The considered parameters were continuously measured from September 2018 to September 2021. The main goal is to assess the geochemical and hydrological processes that control the springs water quality and the isotopic composition of precipitation and use them for formulating effective springs protection measures.  Our results show that the vulnerability of mountain springs is influenced by various factors that include the use of the resource, the meteorological conditions, and the hydrogeology of the area. We propose a method that integrates the Vulnerability Estimator for Spring Protection Areas index with the use of the water stable isotopes to identify springs’ protection zones that takes in consideration the recharge area of the aquifers feeding the springs. Our study contributes to the development of a framework for assessing the vulnerability of mountain springs and highlights the importance of integrating the geochemical characteristics and the anthropic pressure in the conservation and management of these critical freshwater resources. This study is part of Next Innovation Ecosystem Program "Interconnected Northeast Innovation Ecosystem (iNEST)" supported by the European Union.

How to cite: Battistel, M., D'Alberto, L., Mario, G., Marciano, R., Dreossi, G., Pozzobon, A., Stenni, B., and Masiol, M.: Evaluating the Vulnerability of Mountain Springs: A Case Study in Italy to Prioritize Conservation and Management Strategies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17342, https://doi.org/10.5194/egusphere-egu24-17342, 2024.

EGU24-18018 | Orals | HS2.2.1 | Highlight

Isotope applications in the Critical Zone across Europe: the latest activities of the WATSON COST Action 

Daniele Penna and Ilja van Meerveld and the WATSON Extended Core Group

The COST Action WATSON - Water isotopes in the Critical Zone: from groundwater recharge to plant transpiration (CA19120; www.watson-cost.eu) is an European network of researchers and stakeholders who use the stable isotopes of hydrogen and oxygen to trace water fluxes to better understand hydrological, hydrogeological, and ecological systems. WATSON currently includes more than 250 members from 38 countries. The Action aims to integrate and synthesize current interdisciplinary scientific knowledge on the use of the stable isotopes of water to understand the mixing and partitioning of water in the Earth’s Critical Zone. The network is organized into four working groups (WGs) that focus on major scientific challenges: 1) groundwater recharge and soil water mixing processes; 2) vegetation water uptake and transpiration; and 3) catchment-scale residence time and travel times. A fourth WG is in charge of the communication and dissemination activities.

WATSON started in 2020 and is currently in its final year. In this contribution, we synthetize the most recent results and the current and planned activities. WG1 is analyzing different isotope-based methods to calculate groundwater recharge in various environments, preparing training and educational material, and a review paper on isotope methods to assess groundwater recharge and subsurface mixing processes. WG2 is analyzing the data from two Europe-wide isotope sampling campaigns to estimate the sources of water uptake of beech trees and spruce trees. Moreover, WG2 is finalizing a review paper on isotope sampling, extraction, and isotopic analysis methods to study vegetation water use. WG3 is comparing different isotope-based methods to calculate transit times, and preparing training scripts and educational guidelines. WG4 is in charge of many dissemination and communication activities, including the monthly seminar series, updating the website and the social media accounts with the latest information, videos, and technical and scientific material. In addition, all WGs are involved in the preparation of an online, interactive, and open data-map showing locations where isotope samples have been collected.

The WATSON activities will conclude with a large, final online conference, where all WATSON members (and beyond) will be invited to share their knowledge, experience, findings, and recommendations in using stable isotopes to advance our understanding of water fluxes in the Critical Zone.

 

How to cite: Penna, D. and van Meerveld, I. and the WATSON Extended Core Group: Isotope applications in the Critical Zone across Europe: the latest activities of the WATSON COST Action, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18018, https://doi.org/10.5194/egusphere-egu24-18018, 2024.

EGU24-18336 | ECS | Posters on site | HS2.2.1

Snowmelt runoff characteristics in an alpine headwater catchment, Northern Japan Alps 

An Nakata, Maki Tsujimura, Mayu Fujino, Yuuri Kawabata, Koichi Sakakibara, and Keisuke Suzuki

It is important to understand the hydrological processes in the alpine headwaters, because the areas sustain the water resources in the down streams. In Japanese high mountain areas affected by Asian monsoon, there is large amount of precipitation in summer season, and is covered by vegetation even in the area with an elevation more than 2,000 m. We focus on snowmelt runoff processes in a Japanese alpine headwater catchment with different land cover conditions.We performed an intensive field monitoring at Mt. Norikura, a stratovolcano mountain, located at the southern end of the Northern Japan Alps with the maximum elevation of 3026m, specifically two headwater catchments, namely NR1 and NR2. The dominant area of NR1 is bare, whereas NR2 is covered by forest dominantly.We observed precipitation, temperature, and runoff of stream from 13th July to 11th October 2023. which includes snowmelt season. In addition, we collected stream water daily, and rainwater, snowmelt water, and spring water at the intervals of approximately two weeks. The concentrations of major inorganic solutions and stable isotopic ratios of oxygen and deuterium are determined on all water samples.The d-excess value of snowmelt water was higher than that of rainwater, whereas SiO2 concentration of groundwater/ spring water was higher than that of rainwater/snowmelt water. Therefore, we applied End Member Mixing Analysis(EMMA)to separate stream water into three components, rainwater, snowmelt water, and groundwater, using d-excess and SiO2 as tracers, focusing on snowmelt season. The EMMA results show that the snowmelt water contribution to the stream water was estimated to be 55% in NR1, whereas that in NR2 was estimates to be 25% in the beginning of snowmelt season, then the snowmelt component decreased gradually. The groundwater contribution to the stream water in NR1 was estimated to be 15%, whereas that in NR2 was estimated to be 75%.There results show that the effect of snowmelt water to stream water varies depending on land cover condition, snow cover and vegetation. The snowmelt component contributed to the stream water, even after the snow cover disappeared. This suggests that the snowmelt water would contribute to the stream water via the shallow groundwater nearby the stream in addition to the direct discharge.

How to cite: Nakata, A., Tsujimura, M., Fujino, M., Kawabata, Y., Sakakibara, K., and Suzuki, K.: Snowmelt runoff characteristics in an alpine headwater catchment, Northern Japan Alps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18336, https://doi.org/10.5194/egusphere-egu24-18336, 2024.

EGU24-18631 | Posters on site | HS2.2.1

Origins, flow paths, and mean travel times of water in an Australian alpine catchment 

Willem Vervoort, Claudia Keietel, Robert Chisari, Kellie-Anne Farrawell, and Alexander Buzacott

Understanding water origins, flowpaths, and the timescales over which precipitation becomes streamflow are critical for knowledge of the functioning of catchments. Catchments on the Great Dividing Range along the east coast of Australia are important sources of flows into Murray Darling basin for agricultural and drinking water use. This study collected a unique dataset that includes hydrometric measurements and samples of groundwater, surface water and precipitation between 2016 to 2020 to investigate hydrological processes in the Corin catchment, an alpine catchment in south-eastern Australia. Water samples were analysed for major ion chemistry and stable isotopes in water, and eight samples were selected for analysis of tritium activities. Major ion chemistry and stable isotope values were used to assess the relative contributions of water from two contrasting geological areas of the catchment to streamflow. Streamflow exiting the catchment had a consistently different chemical and isotopic signature compared to the groundwater found in the catchment valley. Instead, streamflow consistently resembled water originating from the slopes of the catchment that are underlain by a relatively younger geology. The mean travel times (MTT) of valley groundwater are likely to be in the decades, while baseflows are estimated to have a MTT of around 7 years. This work demonstrates the power of a multi-tracer approach to unravel the hydrological complexities of headwater catchments in south-eastern Australia.

How to cite: Vervoort, W., Keietel, C., Chisari, R., Farrawell, K.-A., and Buzacott, A.: Origins, flow paths, and mean travel times of water in an Australian alpine catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18631, https://doi.org/10.5194/egusphere-egu24-18631, 2024.

EGU24-19706 | Posters on site | HS2.2.1

Hydrogeochemical characteristics in an urbanized tropical watershed, Kuala Lumpur area, Malaysia 

Taiga Suzuki, Maki Tsujimura, Mariko Saito, and Sumire Torimaru

There is not enough data on the hydrogeochemical characteristics of groundwater-surface water interaction in the urbanized tropical watersheds. Tropical regions are generally characterized by high annual precipitation and groundwater recharge. Especially the coastal cities of southeastern Asia have larger hydraulic gradient and subsurface water flux due to high topographical gradient in the elevation recharge area. We focus on an urbanized coastal watersheds, Langat River and Klang River watersheds, Kuala Lumpur area, capital city, Malaysia and investigate the hydrogeochemical characteristics of river water and subsurface water with the multi-tracer methods using inorganic dissolved constituents and stable isotope ratios.
    The SiO2 concentrations and (Na+K)/(Ca+Mg) ratio of river water decreases from upstream to midstream in Langat River. The decrease seems to be caused by geological setting, granite in the upper reaches and schist in the middle reaches. The stable isotope ratios (δ18O & δ2H) of the river water are plotted along with the local meteoric water line, and tend to be enriched toward to downstream. In the upstream area, hot springs are distributed along the faults and rivers. They showed Na-HCO3 type quality and much higher SiO2 concentrations than that of river water. There are wetland and lake in the midstream, and they show a significant depletion of d-excess value, suggesting an evaporation from the water surface of lakes and wetland. Na+, Cl- concentrations and stable isotope ratios increase in downstream of Langar River, suggesting seawater intrusion. On the other hand, stable isotope ratios and inorganic dissolved constituents decrease in the downstream of Klang River. This would be caused by the process that deep groundwater with depleted isotopic ratios discharges to the stream.

How to cite: Suzuki, T., Tsujimura, M., Saito, M., and Torimaru, S.: Hydrogeochemical characteristics in an urbanized tropical watershed, Kuala Lumpur area, Malaysia, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19706, https://doi.org/10.5194/egusphere-egu24-19706, 2024.

EGU24-19892 | ECS | Posters on site | HS2.2.1

Role of Subsurface Water in Stream Runoff in an Alpine Headwater Catchment 

Mayu Fujino, Maki Tsujimura, Yuri Kawabata, An Nakata, Koichi Sakakibara, and Keisuke Suzuki

We conducted field surveys and water sampling from July through October 2023. We compared stream runoff and stream water quality in two watersheds with different land cover in an alpine headwater, Mt. Norikura, Japan. We performed observation in two watersheds, namely NR1 with dominant bare soil surface with limited vegetation cover, 21% of total area, and NR2 dominantly covered by vegetation, 51% in total area. Stream runoff in the NR1 decreased to 0 m after the snowmelt season and runoff occurred only after rainfall, whereas runoff occurred constantly during the observation period in NR2. The stable isotope ratios of hydrogen and oxygen (δ2H and δ¹⁸O) in stream shows variation close to that of precipitation in NR1, whereas those are stable in NR2. These results suggest that the transit time of water in NR2 is longer than that in NR1. The contribution ratio of the groundwater component to the stream runoff during the observation period was higher in NR2 (72.2%) than in NR1 (15.5%). In NR2, the contribution ratio of the groundwater component to stream runoff tends to be lower when API (Antecedent Precipitation Index) is higher. Additionally, the contribution ratio of snowmelt water component increases       with rainfall and decreases promptly. The results indicate that groundwater plays an important role for maintaining stream runoff in NR2 with high coverage of vegetation. Even in NR1, where the contribution ratio of groundwater component to stream runoff is low, the presence of groundwater table is necessary for the discharge of water that is in the subsurface zones.

How to cite: Fujino, M., Tsujimura, M., Kawabata, Y., Nakata, A., Sakakibara, K., and Suzuki, K.: Role of Subsurface Water in Stream Runoff in an Alpine Headwater Catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19892, https://doi.org/10.5194/egusphere-egu24-19892, 2024.

EGU24-20064 | ECS | Posters on site | HS2.2.1

Constraining stream water source dynamics in a high-latitude catchment using tracer-aided modeling 

Andrea Popp, David Gustafsson, Hjalmar Laudon, Charlotta Pers, Benjamin Fischer, and Tricia Stadnyk

Standard hydrologic model calibration and evaluation primarily rely on streamflow observations, which can hinder an accurate representation of physical processes generating streamflow. Recent studies demonstrate that using tracers such as stable water isotope data in addition to flow observations in model calibration considerably reduces parameter uncertainty and constrains stream water source dynamics (e.g., He et al., 2019; Popp et al., 2021; Stadnyk and Holmes, 2023). In this study, we demonstrate the capabilities of an isotope-aided HYPE model (Lindström et al., 2010) in the Krycklan Catchment Study in Sweden. To this end, we integrated the isoWATFLOOD model's isotope routine (https://github.com/h2obabyts/isoWATFLOOD) into the HYPE model and incorporated extensive time series of stable water isotope data collected from different water sources including precipitation, snow, and groundwater and stream water. Our goal is to deepen the process understanding of snow-dominated catchments undergoing rapid changes due to global warming.

References

He, Z., Unger-Shayesteh, K., Vorogushyn, S., Weise, S. M., Kalashnikova, O., Gafurov, A., Duethmann, D., Barandun, M., and Merz, B. (2019. Constraining hydrological model parameters using water isotopic compositions in a glacierized basin, Central Asia, Journal of Hydrology, 571, 332–348, https://doi.org/ 10.1016/j.jhydrol.2019.01.048.

Lindström, G., Pers, C., Rosberg, J., Strömqvist, J. and Arheimer, B. (2010). Development and testing of the HYPE (Hydrological Predictions for the Environment) water quality model for different spatial scales. Hydrology Research 41.3–4, 295-319.

Popp, A. L., Pardo‐Álvarez, Á., Schilling, O. S., Scheidegger, A., Musy, S., Peel, M., ... & Kipfer, R. (2021). A framework for untangling transient groundwater mixing and travel times. Water Resources Research, 57(4), e2020WR028362.

Stadnyk, T. A., & Holmes, T. L. (2023). Large scale hydrologic and tracer aided modelling: A review. Journal of Hydrology, 129177.

How to cite: Popp, A., Gustafsson, D., Laudon, H., Pers, C., Fischer, B., and Stadnyk, T.: Constraining stream water source dynamics in a high-latitude catchment using tracer-aided modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20064, https://doi.org/10.5194/egusphere-egu24-20064, 2024.

EGU24-20344 | ECS | Posters on site | HS2.2.1

Isotopic hydrograph separation in the Hydrological Open Air Laboratory, Austria 

Borbála Széles, Ladislav Holko, Juraj Parajka, Christine Stumpp, Michael Stockinger, Jürgen Komma, Gerhard Rab, Stefan Wyhlidal, Katharina Schott, Patrick Hogan, Lovrenc Pavlin, Peter Strauss, Elmar Schmaltz, and Günter Blöschl

Exploring the contributions of new and old water to runoff during precipitation events in agricultural catchments is essential for understanding runoff generation, solute transport, and soil erosion. The aim of this study was to compare two isotope hydrograph separation methods in the Hydrological Open Air Laboratory (HOAL) in Austria, a 66-ha large experimental catchment dominated by agricultural land use. The classical two-component (IHS) and the ensemble isotope hydrograph separation (EIHS) methods were applied to multiple events in May-October of 2013-2018 using δ18O and δ2H. The new water contributions obtained by the IHS during peak flow were compared with the average new water fraction from the EIHS. The results showed that EIHS provided average new water fractions during peak flows (0.46 for δ18O and 0.47 for δ2H) that were close to the averages obtained by IHS (0.48 for δ18O and 0.50 for δ2H). While the EIHS may be a more robust approach compared to IHS, as it relaxes some of the assumptions of IHS and it gives a reliable average of the new water contribution, the IHS can provide useful information on the new water contribution variability for individual events.

How to cite: Széles, B., Holko, L., Parajka, J., Stumpp, C., Stockinger, M., Komma, J., Rab, G., Wyhlidal, S., Schott, K., Hogan, P., Pavlin, L., Strauss, P., Schmaltz, E., and Blöschl, G.: Isotopic hydrograph separation in the Hydrological Open Air Laboratory, Austria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20344, https://doi.org/10.5194/egusphere-egu24-20344, 2024.

EGU24-21419 | Orals | HS2.2.1 | Highlight

Quantifying mountainous groundwater age and contributions to streamflow with environmental tracers and integrated hydrologic models 

Erica Siirila-Woodburn, Nicholas Thiros, Michelle Newcomer, Rosemary Carroll, Matthias Sprenger, P. James Dennedy-Frank, Daniel Feldman, Ken Williams, and Eoin Broide

Ongoing atmospheric warming and declines in snow are expected to continue with anthropogenic climate change, with unknown impacts on mountainous water budgets that provide out-sized water resources to lower elevations. In a headwater catchment of the Upper Colorado River Basin (USA), six years of high-frequency groundwater observations at a lower montane well show >1m decline in baseflow water table levels since 2016 with corresponding mean ages from environmental tracers (CFC-12, SF6, 3H, and 4He) ranging from decades to millennia. Meanwhile, 100+ years of observed streamflow with reconstructed precipitation estimates suggests a long-term decline in annual runoff efficiency, but with interannual variability that remains high. This begs the question, is old-aged groundwater buffering streamflow? Using an integrated hydrologic model that allows for three-dimensional groundwater interaction with surface-water and land-surface fluxes of water and energy, we quantify spatio-temporal trends in water partitioning in the East River Watershed over the recent, observational period. Over half of the simulated water years show basin-wide groundwater loss, especially after low-snow years. Simulated runoff efficiency is inversely related to groundwater storage efficiency (what we define as the annual change in subsurface storage expressed as a fraction of precipitation), suggesting an underlying physical mechanism linking the two responses. We test a conceptual model where relative declines in groundwater storage accompany either a) new water input (precipitation or snowmelt) bypassing groundwater, instead feeding streamflow and/or b) groundwater reserves that are consistently being drained, also effectively subsidizing streamflow. With a Lagrangian particle tracking method, we quantify the groundwater age distributions that contribute to streamflow under different conditions. Results show substantial old-aged groundwater exports that are invariant to contemporary snow or melt conditions. This is unlike the young-aged groundwater contributions to streams, which are more transient. Numerical experiments of +2.5 and +4 degrees C of surface air temperature show higher rain-to-snow fractions, higher evapotranspiration rates, and losses to total streamflow yield. Together, these changes result in declines in runoff efficiency by ~2-3% per degree C of warming. Notably, the model shows disproportionate impacts to the highest elevations of the watershed with warming (10-30% change in water table depth, with local changes as high as 5 m), suggesting these regions will be most impacted by a warmer climate. Ongoing work uses the transient particle tracking age distributions, precipitation and snow stable isotope measurements, and the convolution integral to predict streamwater stable isotope dynamics, which can be compared to measurements from the past ~6 years at biweekly frequencies. This comparison will better constrain model performance and improve understanding of future water budget partitioning under warming and low-to-no snow conditions.

How to cite: Siirila-Woodburn, E., Thiros, N., Newcomer, M., Carroll, R., Sprenger, M., Dennedy-Frank, P. J., Feldman, D., Williams, K., and Broide, E.: Quantifying mountainous groundwater age and contributions to streamflow with environmental tracers and integrated hydrologic models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21419, https://doi.org/10.5194/egusphere-egu24-21419, 2024.

EGU24-21802 | Orals | HS2.2.1

Variation of δD, and δ18O in springs and precipitation of Takoli gad watershed Uttarakhand in the lesser Himalayas 

Nitish Kumar, Satyabrata Das, and Abhayanand Singh Maurya

The environmental isotopes (δD and δ18O) in natural water play a crucial role as indicators for hydrological processes, serving as a significant method to track the moisture sources in mountainous watersheds. The current study presents the isotopic compositions (δD, and δ18O) of the springs, streams, and rainwater samples from the Takoli Gad catchment, Uttarakhand in the Lesser Himalayas. Our results show that the spring, and stream samples, with an average δD and δ18O values of (-60‰ ± 4.11‰) and (-8.81‰ ± 0.55‰), respectively, represent the most depleted isotopic compositions during the monsoon season. During post-monsoon and pre-monsoon seasons, isotopic compositions are enriched with an average of (δ18O = -8.44 ± 0.43‰, δD: -57.79 ± 2.43‰) and (δ18O = -8.10 ± 0.42‰, δD: -55.7 ± 3.07‰), respectively. The depleted isotopic compositions during the monsoon period suggest the impact of monsoon precipitation on spring waters. Additionally, evaporation from the spring water has led to an enrichment of isotopic compositions during the pre-monsoon season. This conclusion is reinforced by the highest d excess values observed in spring water during the monsoon (10.27‰ ± 1.47‰) and the lowest during the pre-monsoon (9.12‰ ± 1.75‰). Furthermore, The rainwater samples collected during the winter season have the highest d excess values (13.7‰ ± 5.4‰) in comparison to the same during pre-monsoon (9.9‰ ± 4‰) and monsoon period (9.2‰ ± 2‰). These highest d values of the precipitation during winter mostly correspond to the westerlies' effect. The mass balance equation, including δ18O and d-excess values, estimates that approximately 83% of the spring water budget is contributed by monsoon precipitation. Similarly, the δ18O-enabled altitude effect (0.06‰/100m) is found to be within range of other Himalayan catchments. However, the same is ~5 times lower in comparison to the altitude effect estimated using the precipitation of the region (0.3‰/100m). Also, our study suggests a significant role of evaporation in altering the δ18O-associated altitude effect in precipitation. Finally, the rainout percentage approximation (using both δ18O and δD compositions of the rainfall) estimates that ~32% ± 4% of the moisture is being removed from the cloud as the same is traversing in the region.

How to cite: Kumar, N., Das, S., and Maurya, A. S.: Variation of δD, and δ18O in springs and precipitation of Takoli gad watershed Uttarakhand in the lesser Himalayas, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21802, https://doi.org/10.5194/egusphere-egu24-21802, 2024.

EGU24-528 | ECS | Posters on site | HS2.2.3

The effects of future climate-induced adaptation of the root-zone storage capacity on modeled streamflow dynamics 

Magali Ponds, Markus Hrachowitz, Marie-Claire ten Veldhuis, Gerrit Schoups, Harry Zekollari, Sarah Hanus, and Roland Kaitna

Hydrological models play a vital role in evaluating future changes in streamflow. Despite the strong awareness of non-stationarity in hydrological system characteristics, model parameters are typically assumed to be stationary and derived through calibration on past conditions. Integrating the dynamics of system change in these models remains challenging due to uncertainties surrounding changes in future climate and ecosystems.
Nevertheless, studies show that ecosystems evolve in response to prevailing climate conditions. There is increasing evidence that vegetation adjusts its root zone storage capacity – considered a critical parameter in hydrological models – to prevailing hydroclimatic conditions. This adaptation of the root zone to moisture deficits is central to the water balance method. When combined with long-term water budget estimates from the Budyko framework, the water balance method offers a promising approach to describe future climate-vegetation interactions within process-based hydrological models

Our study provides an exploratory analysis of the role of non-stationary hydrological model parameters for six catchments in the Austrian Alps. More specifically, we investigate future changes in the root zone storage and their consequent impact on modeled streamflow. Using the water balance method, we derive climate-based parameter estimates of the root zone storage capacity under historic and projected future climate conditions. These climate-based estimates are then implemented in our hydrological model to assess their consequent impact on modeled past and future streamflow.
Our findings show that climate-based parameter estimations significantly narrow the parameter ranges linked to root zone storage capacity. This stands in contrast to the broader ranges obtained solely through calibration. Moreover, using projections from 14 climate models, our findings indicate a substantial increase in the root zone storage capacity parameters across all catchments in the future, ranging from +10% to +100%. Despite these alterations, the model performance remains relatively consistent when evaluating past streamflow, independent of using calibrated or climate-based estimations for the root zone storage capacity parameter. Additionally, no significant differences are found when modeling future streamflow when including future climate-induced adaptation of the root zone storage capacity in the hydrological model. Variations in annual mean, maximum, and minimum flows remain within a 5% range, with slight increases found for monthly streamflow and runoff coefficients.

In summary, our research shows that although climate-induced changes in root zone storage capacity occur, they do not notably affect future streamflow projections in the Alpine catchments under study. This suggests that incorporating a dynamic representation of the root zone storage capacity parameter may not be crucial for modeling streamflow in humid and energy-limited catchments. However, our observations indicate relatively larger changes in root zone storage capacity within the less humid catchments studied, corresponding to higher variations in modeled future streamflow. This points to a potential higher significance of dynamically representing root zone characteristics in arid regions and underscores the necessity for further research in these areas.

How to cite: Ponds, M., Hrachowitz, M., ten Veldhuis, M.-C., Schoups, G., Zekollari, H., Hanus, S., and Kaitna, R.: The effects of future climate-induced adaptation of the root-zone storage capacity on modeled streamflow dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-528, https://doi.org/10.5194/egusphere-egu24-528, 2024.

EGU24-973 | ECS | Orals | HS2.2.3

Model development for a water supply catchment in southeast Brazil 

Ana Clara de Sousa Matos, Marvin Höge, Thiago Victor Medeiros do Nascimento, Gustavo de Oliveira Corrêa, Francisco Eustáquio Oliveira e Silva, and Fabrizio Fenicia

Brazil faced a severe water crisis during the mid-2010s, resulting in water scarcity and water rationing in various cities. The Belo Horizonte Metropolitan Region was seriously affected. It is located in the southeastern part of the country and home to roughly 5 million people (Costa et al., 2015) and mining industry. The region’s water supply relies on a complex and integrated system, which combines a water abstraction at the Velhas river and three reservoirs. One of these reservoirs, named Serra Azul, reached a minimum of only 5,4 % of its total capacity during the crisis. Here, we demonstrate tools for improving the water management in this area, by developing a hydrological model suitable for mountainous regions with tropical climates. Our case study was the Serra Azul reservoir’s well-gauged catchment. We selected 12 gauges that cover several head waters and rivers section in the 260 km² area.  We used these discharge data (3-5 years), and available static catchments' attributes (e.g. subsurface properties), to adapt a flexible framework for conceptual hydrological modeling. Hence, we identified a suitable model structure using SUPERFLEX (Fenicia et al., 2014). The findings show that by including soil type, lithology and land cover as explanatory variables in the model, we obtained significant improvements in performance, e.g. the correlation between the base flow index estimated for observed and simulated time-series increased from 0.40 to 0.76. We also accounted for groundwater contributions to the streamflow, modelling the relation between the percentage of porous aquifer within each catchment and its flow magnitude. Thereby, we improved the average NSE and timeseries correlation considerably.  Overall, we successfully set up a parsimonious hydrologic model for water resources management in a region that is notoriously difficult to predict, where anthropic activities such as mining and agriculture have a decisive impact on the water cycle.

 

References:

Costa et al. Caracterização e Quadros de Análise Comparativa da Governança Metropolitana no Brasil: análise comparativa das funções públicas de interesse comum (Componente 2)-RM do Rio de Janeiro (Relatório de Pesquisa). (2015). Rio de Janeiro: Institute for Applied Economic Research–Ipea.

Fenicia et al. "Catchment properties, function, and conceptual model representation: is there a correspondence?." Hydrological Processes 28.4 (2014): 2451-2467.

How to cite: de Sousa Matos, A. C., Höge, M., Medeiros do Nascimento, T. V., de Oliveira Corrêa, G., Oliveira e Silva, F. E., and Fenicia, F.: Model development for a water supply catchment in southeast Brazil, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-973, https://doi.org/10.5194/egusphere-egu24-973, 2024.

ParFlow CONCN model is the first integrated groundwater-surface water modeling platform over the mainland of China with a resolution of 30-arcsec and a depth of 492 m. With the flexibility of reconstruction and prediction of groundwater and surface water states and fluxes, it is undoubtedly an efficient tool for scientific understanding on water cycle and decision making on water resources and thus to tackle China’s water crisis in the changing world. Nonetheless, the CONCN model may have broader significances to the hydrologic community. Model evaluation and comparison is a common practice in the geoscientific modeling communities, such as those of land surface and earth system models. Due to the challenges in aquifer parameterization and the expensive computing requirement, high-resolution, large-scale, 3D groundwater modeling or integrated hydrologic modeling with 3D groundwater component is still under development though becoming more active in the past decade. Several national-scale such integrated hydrologic models, for example, ParFlow models over CONUS, west Africa, and Germany, have been built at 1 km resolution or higher with satisfying performances. However, the wide extension of modeling in this category to other places worldwide or to global scale is limitedly explored, preventing the evaluation of modeling workflows at different places and comparison with models using other parameterization schemes. Here, we demonstrate the construction and the first-phase evaluation of CONCN model by leveraging global datasets. Global permeability (GLHYMPS 1.0) and hydrography (MERIT Hydro) products were helpful to build the model while global water table depth (Fan et al., Science, 2013 and Zeng et al., JAMES, 2018) and streamflow (GRADES-HYDRDL and CNRD v1.0) products were adopted to preliminarily evaluate the simulation results. In this data-poor modeling area, both the construction and evaluation of the CONCN model are impossible about five years earlier as most of these global datasets did not exist. Therefore, the CONCN model can be one of the pioneers to evaluate and then to improve the current workflow of the existing models and address the challenges in new modeling areas with hydrogeology, hydrography, and climatology unseen in existing models. We also expect our dilemma caused by lacking observations as many other modelers in China can push the data-sharing to constrain hydrologic models and to motivate the collaboration such as model intercomparison in the Chinese hydrologic modeling community, which are well developed in the global community.

How to cite: Yang, C., Condon, L., and Maxwell, R.: Building and evaluating the high-resolution, integrated groundwater-surface water ParFlow modeling platform of continental China (CONCN): leveraging global datasets in a data-poor region   , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2600, https://doi.org/10.5194/egusphere-egu24-2600, 2024.

EGU24-2729 | Orals | HS2.2.3

Study on the collapse characteristics and threshold behavior of the subsurface stormflow mechanism 

Yuanxin Song, Yanjun Zhang, Shanqi Li, and Jiahui Yang

Abstract: Subsurface stormflow is the dominant runoff generation mechanism during certain flash flood events. The collapse characteristics and threshold behavior are critical to the transition from the slow runoff stage to the rapid runoff stage and the relevant study is not only essential for hydrology theory but also for flash flood disaster prevention. In recent years, efforts have been made to explore the common principles of hydrological processes under strong spatial heterogeneity, but findings from field experiments and numerical studies were difficult to apply to the modeling process. Furthermore, we have yet to develop a deeper understanding of the mechanisms for the impact of complex factors on subsurface stormflow and lack a comprehensive understanding of the formation mechanism of threshold.
This presentation discusses how we plan to address this research gap. Firstly, around the phenomenon of “burst-block-burst” in the subsurface stormflow runoff generation process, rainfall-runoff simulation experiments were carried out and factor analysis was conducted to determine the main influencing factors of subsurface stormflow runoff generation. The main influencing factors include soil texture factors, collapse state factors, initial state factors, and other factors, and the influence of these four types of factors decreases in turn. In the second step, we constructed a field hydrological station in the Huanggou Watershed located in Hubei Province, China, collected the rainfall-runoff data, and found that the subsurface stormflow process shows a three-stage-double-threshold behavior: the water storage stage, the initial flow stage, and the rapid flow stage. In the third step, synthesizing the main influencing factors, the three-stage double-threshold process was quantified. Further, the three-stage subsurface stormflow-based model (TSSM) was developed and applied to the Huanggou Hillslope and the Huanggou Watershed. The results show that TSSM performed well, with NSEs of 0.82 and 0.67 in the calibration and verification periods of the Huanggou slope, and NSEs of 0.76 and 0.74 in the calibration and verification periods of the Huanggou Watershed, respectively.
This study elucidated the collapse characteristics and threshold behavior of subsurface stormflow and developed an effective simulation model, which contributes to increasing our understanding of three-stage subsurface stormflow and is beneficial for hydrologists to develop more realistic hydrological models.

Keywords: Subsurface stormflow; Collapse characteristics; Threshold behavior; Three-stage subsurface stormflow mechanism; TSSM

How to cite: Song, Y., Zhang, Y., Li, S., and Yang, J.: Study on the collapse characteristics and threshold behavior of the subsurface stormflow mechanism, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2729, https://doi.org/10.5194/egusphere-egu24-2729, 2024.

To represent the physical processes at hillslope scales for hyper-resolution land surface modeling, we propose a hierarchical, catchment-based spatial tessellation method. The land surface is divided into a hierarchical structure: catchments, height bands along hillslopes within a catchment, and land cover patches within a height band. This catchment-based structure explicitly represents hillslope drainage networks and can be applied at various resolutions determined by a pre-defined maximum height band size. The proposed tessellation method is superior to the conventional grid-based structure in representing land surface heterogeneity, resulting in a higher aggregation skill through the height band representation. The spatial variations in air temperature, leaf area index, saturated soil hydraulic conductivity, and soil porosity are generally lower within a height band than those in a conventional rectangular grid, reflecting the nature of topographic control on climate, vegetation, and soil distribution. The improvement in aggregation skill depends on resolutions and terrain slope angle, more pronounced at 1/6° model resolution and over steeper terrains. Finally, we demonstrate that our proposed catchment-based structure performs better than the grid-based structure through modeling tests over the Columbia River basin at resolutions of 1/2°, 1/6°, and 1/20° and a global test at 1/2° using the ILAMB model evaluation metrics.

How to cite: Lina, H. and Shupeng, Z.: A Catchment-Based Hierarchical Spatial Tessellation Approach to a Better Representation of Land Heterogeneity for Hyper-Resolution Land Surface Modeling , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3343, https://doi.org/10.5194/egusphere-egu24-3343, 2024.

EGU24-3356 | ECS | Posters on site | HS2.2.3

Effects of watershed subdivision based on soil and land use inputs on SWAT performance in a coastal Mediterranean catchment 

Mathilde Puche, Magali Troin, Dennis Fox, and Paul Royer-Gaspard

Assessing the benefits of increasing the discretization level of semi-distributed hydrological models is of great importance for hydrological applications. The impact of spatial discretization on model performance is investigated with the use of the Soil and Water Assessment Tool (SWAT) model when applied on a Mediterranean watershed (Argens, France). This study aims to explore how the spatial discretization (number of sub-basins and of hydrological response units (HRUs)) affects the model’s performance at simulating daily streamflows, and if the choice of soil and land use input datasets modifies model accuracy. Low and moderate resolution soil (5 km and 250 m) and land use (400 m and 100 m) maps are considered. Four SWAT input sets are created, each corresponding to a different combination of land use and soil datasets. Each input set is used to build 17 configurations with an increasing number of sub-basins (4, 12, and 18) and HRUs (from 4 to 320). The 68 models (4 input sets x 17 configurations) are evaluated on the 2001-2021 period using the Kling-Gupta efficiency (KGE) metric. Results indicate no influence of the number of sub-basins on SWAT performance. However, increasing the number of HRUs leads to a significant performance decrease (from 0.13 to 0.26 of KGE loss), regardless of the number of sub-basins and input datasets. The SWAT model is found to be more sensitive to soil dataset than to land use dataset. Despite significant differences in hydrological soil groups between the two soil maps, no clear impact on the derived hydrological properties is observed, such as the curve number. The observed decline in SWAT performance with an increasing number of HRUs is attributed to the calibration process rather than the soil and land use input datasets. This study suggests that, when the calibration of the semi-distributed SWAT model is not performed at the finer spatial HRU level, an increase in the spatial discretization does not lead to an improvement of the overall model accuracy.  Therefore, minimizing the number of HRUs during the watershed subdivision is recommended for getting optimal simulations of streamflow while dealing with the computational efficiency of SWAT.

How to cite: Puche, M., Troin, M., Fox, D., and Royer-Gaspard, P.: Effects of watershed subdivision based on soil and land use inputs on SWAT performance in a coastal Mediterranean catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3356, https://doi.org/10.5194/egusphere-egu24-3356, 2024.

EGU24-4058 | ECS | Orals | HS2.2.3

SCS-CN parameter determination from observed rainfall runoff data. A critical review. 

Konstantinos Soulis, Stergia Palli Gravani, and Dionissios Kalivas

One the most difficult challenges in applied hydrology is predicting runoff in ungauged or poorly gauged watersheds. Thus, simple approaches for runoff estimation are especially useful in hydrologic applications. A simple, well established, and widely used technique for predicting the direct runoff depths of rainfall events is the Soil Conservation Service - Curve Number (SCS-CN) method. Due to its straightforward but well-proven approach, readily available and well documented environmental inputs, and incorporation of numerous variables influencing runoff generation into a single CN parameter, it quickly rose to prominence among engineers and practitioners. Tables can be used to identify the CN parameter values corresponding to prevailing soil, land cover and land management conditions. However, it is always better to estimate the CN value using observed rainfall-runoff (P-Q) data when available. Estimating appropriate CN values for additional soil – land cover conditions and additional regions is also critical for extending and updating the method’s documentation given that the SCS-CN approach is extremely sensitive to variations in the CN values.

However, even when the CN value is determined from measured P-Q data, the estimated CN values vary substantially from storm to storm on any given watershed. For this reason, various methods to estimate the CN value characterizing each watershed have been proposed up to know, and many theories on the reasons behind the observed relationships between CN and P for each watershed have been stated. Though, after many years of research, there isn’t still a unique agreed method to estimate the CN values characterizing a watershed or a soil-land cover complex, while the proposed methods lead to different CN values and in many cases neglect spatial variability. Further, an increasing number of modified SCS-CN versions are continuously developed, and new parameters are introduced complicating the situation even more.

Accordingly, this study attempts to collect, categorize, and systematically analyze the huge number of studies on SCS-CN method published in the last 30 years. We selected this period as 30 years ago, in 1993, R.H. Hawkins published his emblematic study on the “Asymptotic determination of runoff curve numbers from data” (J. Irrigat. Drain. Div. ASCE, 119(2): 334–345). In this review study, specific attention is given to the methods focusing on CN value determination from measured P-Q data. The advantages and limitations of the various approaches are investigated, as well as trends and gaps in existing literature. The analysed methods are classified and the main paths are identified. Based on the obtained results, conclusions on the current status are being made, and the more promising approaches are highlighted.  Then, ideas on future research pathways towards the target of a unified CN values determination approach are discussed.

How to cite: Soulis, K., Palli Gravani, S., and Kalivas, D.: SCS-CN parameter determination from observed rainfall runoff data. A critical review., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4058, https://doi.org/10.5194/egusphere-egu24-4058, 2024.

EGU24-4385 | ECS | Orals | HS2.2.3

Can we identify dominant hydrological mechanisms in ungauged catchments? 

Cristina Prieto, Nataliya Le Vine, Dmitri Kavetski, Fabrizio Fenicia, Andreas Scheidegger, and Claudia Vitolo

Hydrological modelling of ungauged catchments, which lack observed streamflow data, is an important practical goal in hydrology. A major challenge is to identify a model structure that reflects the hydrological processes relevant to the catchment of interest. Paraphrasing a well-known adage, “all models are wrong, but some model-mechanisms (process representations) might be useful.”

We extend a method previously introduced for mechanism identification in gauged basins, by formulating the Bayesian inference equations in the space of (regionalized) flow indices principal components and by accounting for posterior parameter uncertainty. We use a flexible hydrological model to generate candidate mechanisms and model structures. Then, we use statistical hypothesis testing to identify the "dominant" (more a posteriori probable) hydrological mechanism. We assume that the error in the regionalization of flow indices principal components dominates the error of the hydrological model structure.

The method is illustrated in 92 catchments from northern Spain. We treat 16 out of the 92 catchments as ungauged. We use 624 model-structures from FUSE (flexible hydrological model framework). The case study includes real data and synthetic experiments.

The findings show that routing is among the most identifiable processes, whereas percolation and unsaturated zone processes are the least identifiable. The probability of making an identification (correct or wrong), remains stable at ~25%, both in the real and in the synthetic experiments. In the synthetic experiments, where the “true” mechanism is known, we can evaluate the reliability, i.e., the probability of identifying the true mechanism when the method makes an identification. Reliability varies between 60%-95% depending on the magnitude of the combined regionalization and hydrological error. The study contributes perspectives on hydrological mechanism identification under data-scarce conditions.

Prieto et al. (2022) An Exploration of Bayesian Identification of Dominant Hydrological Mechanisms in Ungauged Catchments, WRR58(3), doi:10.1029/2021WR030705.

How to cite: Prieto, C., Le Vine, N., Kavetski, D., Fenicia, F., Scheidegger, A., and Vitolo, C.: Can we identify dominant hydrological mechanisms in ungauged catchments?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4385, https://doi.org/10.5194/egusphere-egu24-4385, 2024.

EGU24-5237 | Posters on site | HS2.2.3

Exploring the Reciprocity Behavior Distributions in Space for Hydrogeological Parameters 

Zi-Jun Hsu, Hong-Ru Lin, and Jet-Chau Wen

Past studies of hydrogeological parameters of aquifers have not using drawdown data from multiple sets of sequential pumping tests (SPT) at the same site to characterize the interaction of hydrogeological parameters (such as transmittance, T and storage coefficient, S) distribution field. Therefore, the purpose of this study was to use the same site (well site at the northeast corner of Yunlin University of Science and Technology, Douliu City, Yunlin County) collected for many years (20xx,20xx..year, five groups in total) of SPT drawdown data. First, the interaction between the drawdown water levels from the same observation well and five sets of pumping tests was analyzed. Afterwards, this study used the numerical method of (hydraulic tomography, HT) to analyze the leakage data of five groups of SPTs., reverse calculation the distribution of T and S of five groups of SPT and a spatial comparison was performed, comparing the interaction between 5 sets of T and S distribution fields, discuss in different time and space background, interaction of distribution field of local hydrogeological parameters.

How to cite: Hsu, Z.-J., Lin, H.-R., and Wen, J.-C.: Exploring the Reciprocity Behavior Distributions in Space for Hydrogeological Parameters, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5237, https://doi.org/10.5194/egusphere-egu24-5237, 2024.

Hydrological losses play a significant role in determining the runoff coefficient, influencing the amount of precipitation that ultimately contributes to surface runoff. These losses are influenced by various characteristics, including rainfall, the physical and geographical attributes of the watershed (such as slope and land use), and the soil moisture content within the watershed.

Here, we evaluate the effect of the variability of the loss function on the amount of simulated runoff and the runoff coefficient in specific watersheds in Iran. The investigation entails the assessment of two distinct conditions. First, the runoff coefficient is calculated under the assumption of a constant loss, utilizing the φ index. Second, a variable loss function, derived from a soil moisture algorithm, is employed to determine the runoff coefficient.

Our analysis shows that the assumption of a variable loss function yields more realistic results. When the variable losses are considered, the simulated runoff coefficient is closer to the observed values and determines the runoff coefficient for all months, including those characterized by low rainfall. The constant loss φ index exhibits two significant practical limitations: the overestimation of runoff coefficient values, and an inability to estimate runoff coefficient during months with low rainfall. The study emphasizes the need for a variable loss function to provide more realistic results. Our findings suggest that utilizing the variable loss function within the soil moisture algorithm produces more accurate results. Thus, the application for improved forecasting of rainfall and runoff processes is recommended.

 

How to cite: Eslami, Z., Abdollahi, K., and Kirchner, J.: Analyzing the fixed or variable effect of considering hydrological loss functions on the runoff coefficient in continuous modeling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5982, https://doi.org/10.5194/egusphere-egu24-5982, 2024.

EGU24-6789 | Posters on site | HS2.2.3

High-resolution Spatial Mapping of Runoff Prediction for Micro-scale Surface Rainwater Harvesting 

Dongryeol Ryu, Sri Priyanka Kommula, Bharat Lohani, and Stephan Winter

Spatially distributed runoff information is one of the most critical inputs to determining suitable locations of rainwater harvesting (RWH) structures. The majority of hydrological assessments for siting RWH structures rely on empirical formula, such as the Soil Conservation Service – Curve Number method that combines soil type, land covers, land use practices, surface conditions, and antecedent moisture conditions with a weak basis on hydrological processes. In addition, runoff generation by topography is considered separately through the computation of flow accumulation.  As a result, the current practice of determining suitable RWH locations is done using arbitrary scores rather than the actual spatiotemporal estimate of runoff.

The present study employs a topography-based hydrological model, TOPMODEL, to explicitly generate runoff for an experimental catchment of 1800 ha located in Haryana, India. The catchment has been subdivided into 102 sub-catchments where sub-catchment-scale runoff was calculated using daily forcing data of 40 years (1980 - 2020) with other static inputs such as soil and topography data.  For topography input, a 1-m resolution digital elevation model (DEM) collected by a Light Detection and Ranging (LiDAR) was used. The input variables of the model were calibrated using ground-based discharge values.

The daily sub-catchment-scale runoff from TOPMODEL was aggregated to monthly, seasonal, and annual time scales to produce more detailed picture of water availability for harvest over wet and dry seasons. Finally, the runoff was converted to grid-based values using the flow accumulation scheme widely used on GIS tools. The final grid-based map at 1-m resolution contains the runoff information across the entire catchment at monthly, seasonal and annual time scales. The improved spatio-temporal representation of runoff using TOPMODEL in combination with flow accumulation scheme offers enhanced assistance to designing RWH structures tailored by the actual water volume available at candidate locations and its seasonal and interannual variability.

How to cite: Ryu, D., Kommula, S. P., Lohani, B., and Winter, S.: High-resolution Spatial Mapping of Runoff Prediction for Micro-scale Surface Rainwater Harvesting, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6789, https://doi.org/10.5194/egusphere-egu24-6789, 2024.

Flash floods, characterized by rapid streamflow response to rainfall, pose a significant natural hazard, particularly in small tropical watersheds (< 40 km2). Understanding the role of rainfall event characteristics, including amount, intensity, and spatial structure, is crucial for addressing and predicting flash floods. This study employs the WRF-Hydro® model with high-resolution (250-m, hourly) rainfall data and the Random Balance Designs – Fourier Amplitude Sensitivity Testing (RBD-FAST) method to investigate how rainfall impacts streamflow, specifically peak flow events, in seven watersheds on Oʻahu, USA.

Analyzing storm events from 2015 to 2020, we examined peak flow responses to corresponding rainfall event characteristics and estimated their contributions to model efficiency. In addition, (1) random redistribution of rainfall and (2) spatial shifting of rainfall were experimented with to assess the sensitivity of peak flow to rainfall event characteristics. Not only the rainfall amount and intensity but heavy rainfall areas (>= 25 mm) within an event also exerted a significant impact on peak flow, while other spatial features contributed varying degrees of influence. Notably, spatially shifting rainfall for at least 250-m in any direction highly affected event peak streamflow, emphasizing the importance of rainfall amount, intensity, heavy rainfall areas, total rainfall areas, and connectivity among rainfall areas.

Given the significance of rainfall's spatial heterogeneity, these findings underscore the benefits of incorporating rainfall spatial characteristics in probabilistic flood forecasting and the mitigation of flood risks. This research contributes valuable insights for enhancing flood prediction strategies in small tropical watersheds, providing a basis for informed decision-making and risk management.

How to cite: Huang, Y.-F. and Tsang, Y.: Sensitivity analysis of streamflow responses to varied rainfall spatial patterns in small tropical watersheds, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7129, https://doi.org/10.5194/egusphere-egu24-7129, 2024.

Recent advances in the application of machine learning techniques to estimate soil hydraulic properties using soil datasets have shown promising results. PedoTransfer Functions (PTFs) can facilitate the mapping of the complex relationship between soil properties and soil hydraulic properties, e.g., lateral hydraulic conductivity—a necessity for estimating lateral subsurface flow in spatially distributed hydrological models like wflow_sbm. The vertical-to-horizontal saturated hydraulic conductivity ratio (fKh0) is crucial for model calibration, but an established PTF is currently lacking. Our objective is to investigate the potential of ML algorithms in estimating PTFs for fKh0 prediction. First, optimized fKh0 across Great Britain (GB) resulting from a sensitivity analysis of the wflow_sbm model (Weerts et al., 2024) were used to train two ML algorithms; Random Forest (RF) and Boosted Regression Trees (BRT), using seven soil parameters from SoilGrids v1.0. Both algorithms effectively predicted fKh0 of 92 subbasins (i.e., test set of 25%) with high performance as compared against the optimized values, and RF slightly outperformed BRT. As a next step, we compared wflow_sbm simulated discharge results using uncalibrated fKh0 (default value of 100) and predicted values. The predictions notably improved wflow_sbm predictive accuracy by rising the median KGE from 0.55 (using uncalibrated fKh0) to 0.75 (using predicted fKh0). Following, we generated two globally distributed fKh0 maps, allowing us to further investigate the transferability of the ML-based PTFs. Therefore, we tested the predicted fKh0 across 559 gauge stations within the Loire basin in France. The utilization of either RF or BRT improved performance in around 75% of these subbasins with a KGE that was, on average, 0.06 higher. Furthermore, fKh0 prediction uncertainty and the impact of model spatial resolution were further analyzed. In conclusion, our study demonstrates the potential of ML methods to find relationships between soil properties and (model) soil hydraulic properties, which assists in parameter estimates for distributed hydrological models in gauged and ungauged basins.

How to cite: Ali, A. M., Imhoff, R. O., and Weerts, A. H.: Machine learning for predicting spatially variable lateral hydraulic conductivity: a step towards efficient hydrological model calibration and global applicability, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8347, https://doi.org/10.5194/egusphere-egu24-8347, 2024.

EGU24-8809 | ECS | Posters on site | HS2.2.3

The potential of empirical mode decomposition to evaluate hydrological model simulations 

Svenja Hoffmeister and Erwin Zehe

We explore the potential of the empirical mode decomposition (EMD), a signal-processing method, to evaluate hydrological model simulations. Usually, hydrological models are assessed in the time domain observing and comparing residuals on a point-to-point basis. An additional model evaluation in the frequency domain might provide useful and complementary insights about the model’s capability to reproduce dynamic system behaviour. EMD separates a signal (e.g. a soil moisture time series) into fast and slow oscillations based on a sifting process, in which subtracting the signals moving average from itself reveals the highest frequency oscillation. This allows for instance to analyse phase shifts of different signature modes (e.g. daily fluctuations) in different depths and by that to make assumptions on soil hydraulic properties such as the conductivity. Naturally, a model will always miss high-frequency components of the “real” signal as measurement devices used as model input already act as a filter of such. However, the ability to capture the lower frequency remains interesting as they include relevant hydrological processes. Advantages of EMD over traditional methods like Fourier or wavelet transform are that no prior assumptions are needed and that it works well for nonlinear or non-stationary signals.

We test the EMD method on soil moisture and matric potential time series of observations and a process-based hydrological model extracted for the same site and compare the phase shifts and spectral components. We want to test whether metrics such as the RMSE of frequency spectra help to further compare and elucidate different signals. First results underpin the potential of including EMD as a tool to quantify models from a different perspective. We observe difference in observation and model frequencies of soil water time series and can related certain intrinsic modes to hydrological processes.

How to cite: Hoffmeister, S. and Zehe, E.: The potential of empirical mode decomposition to evaluate hydrological model simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8809, https://doi.org/10.5194/egusphere-egu24-8809, 2024.

EGU24-9070 | Orals | HS2.2.3

Virtual Hydrological Laboratories to develop the next generation of conceptual models and support decision-making under change 

Dmitri Kavetski, Mark Thyer, David McInerney, Hoshin Gupta, Seth Westra, Holger Maier, Anthony Jakeman, Barry Croke, Daniel Partington, Margaret Shanafield, Craig Simmons, and Christina Tague

The ability of contemporary hydrological models to serve as a basis for credible prediction and decision making is increasingly challenged – especially as hydrological systems are pushed outside the envelope of historical experience. Conceptual models are the most common type of surface water hydrological model used for decision support due to reasonable performance in the absence of change, ease of use and computational speed that facilitate scenario, sensitivity and uncertainty analysis. Hence, conceptual models arguably represent the current "shopfront" of hydrological science as seen by practitioners. However, these models have notable limitations in their ability to resolve internal catchment processes and subsequently capture hydrological change. New thinking is needed to confront the challenges faced by the current generation of conceptual models in dealing with a changing environment. We argue that the next generation of conceptual models should combine the parsimony of conceptual models with our best available scientific understanding. We propose a strategy to develop such models using multiple hydrological lines of evidence. This strategy includes using appropriately selected physically-resolved models as "Virtual Hydrological Laboratories" to test and refine the simpler models' ability to predict future hydrological changes. This approach moves beyond the sole focus on "predictive skill" measured using metrics of historical performance, facilitating the development of the next generation of conceptual models with hydrological fidelity - i.e., that "get the right answers for the right reasons". This quest is more than a scientific curiosity – it is expected by environmental policy makers and broader stakeholders.

How to cite: Kavetski, D., Thyer, M., McInerney, D., Gupta, H., Westra, S., Maier, H., Jakeman, A., Croke, B., Partington, D., Shanafield, M., Simmons, C., and Tague, C.: Virtual Hydrological Laboratories to develop the next generation of conceptual models and support decision-making under change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9070, https://doi.org/10.5194/egusphere-egu24-9070, 2024.

EGU24-9082 | Orals | HS2.2.3

Assessment of a global hydrological service by application-based metrics 

Jonas Olsson, Yiheng Du, Kristina Isberg, Johan Strömqvist, and Yeshewatesfa Hundecha

The calibration and validation of hydrological models often involve a suite of established statistical metrics, which may not always match the needs of local stakeholders, thereby constraining the evaluative scope, particularly in the context of global climate services. This study introduces an alternative, complementary evaluation approach by formulating two types of application-based evaluation metrics (Du et al., 2024), representing model performance in terms of (i) temporal matching of the extreme quantiles and (ii) reproduction of the maximized split-sample difference in flow signatures. The introduced metrics are compared to conventional statistical metrics, at seven case study areas across the world, with three model settings representing different datasets and calibrations, generated from the global hydrological model World-Wide HYPE (WWH; Arheimer et al., 2020). The different performances found using application-based and conventional metrics, respectively, reveal their ability to uncover the models' capability in various aspects. Ultimately, the comprehensive analysis of conventional and application-based metrics allows us to delineate two scenarios for model application: generally applicable models, and conditionally applicable models. For example, in some areas the WWH model, when applied with global dataset and local calibration, is well capable of producing predictions for the timing of extreme quantiles and the relative difference in flow signatures, even though it may not excel according to conventional evaluation metrics. Consequently, this model can be classified as conditionally applicable, suitable for areas where local data is scarce, yet providing reliable information that can aid decision-makers in developing strategies for water resources management.

Arheimer, B., Pimentel, R., Isberg, K., Crochemore, L., Andersson, J.C.M., Hasan, A.,  Pineda, L. (2020). Global catchment modelling using World-Wide HYPE (WWH), open data, and stepwise parameter estimation. Hydrology and Earth System Sciences, 24, 535-559.

Du, Y., Olsson, J., Isberg, K., Strömqvist, J., Hundecha., Y., Silva, B.C., Rafee, S.A.A., Fragoso Jr., C.R., Beldring, S., Hansen, A., Uvo, C.B., Sörensen, J. (2024). Application-based evaluation of multi-basin hydrological models. Journal of Hydrology, under revision.

How to cite: Olsson, J., Du, Y., Isberg, K., Strömqvist, J., and Hundecha, Y.: Assessment of a global hydrological service by application-based metrics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9082, https://doi.org/10.5194/egusphere-egu24-9082, 2024.

EGU24-9140 | ECS | Orals | HS2.2.3

Towards an understanding of the hydrological processes of greenhouse horticulture districts 

Daniele la Cecilia, Accursio Venezia, Davide Maino, and Matteo Camporese

The occurrence of agricultural catchments covered by plastic greenhouses is growing worldwide. Horticultural greenhouse production allows for saving irrigation water at the farm scale, but also alters the natural hydrological cycle. Currently, these alterations are not accounted for in physics-based hydrological models. In this study, we aim to couple the greenhouse climate model KASPRO1, to estimate indoor crop transpiration from outdoor meteorological variables, with the integrated surface-subsurface hydrological model CATchment HYdrology (CATHY2) to simulate the stream discharge as well as the shallow groundwater depth in an agricultural catchment (11 km2) covered by plastic greenhouses in South Italy. The dynamic presence of greenhouses, along with bare soils and vegetated lands, is mapped with the Open field and Protected Agriculture land cover Classifier (OPAC3).

We first compare our simulations against indoor measurements of water use (drip- and sub-irrigation) and soil moisture dynamics at different depths at the plot scale. Next, we run CATHY at the catchment scale and compare the output against measured stream water level.

The aim of our study is to validate the capabilities of KASPRO and CATHY to provide high-fidelity spatially distributed dynamic simulations of evapotranspiration and irrigation fluxes, as well as soil moisture and groundwater flows. Such capabilities are essentials to understand the implications of plastic greenhouse districts on the hydrological cycle and thus making these models useful tools for a more sustainable management of agricultural catchments.

References

1 De Zwart, H.F., 1996. Analyzing Energy-Saving Options in Greenhouse Cultivation Using a Simulation Model. Landbouwuniversiteit, Wageningen.

2 Camporese, M., Paniconi, C., Putti, M., & Orlandini, S. (2010). Surface--subsurface flow modeling with path-based runoff routing, boundary condition-based coupling, and assimilation of multisource observation data. Water Resources Research, 46, W02512.

3 la Cecilia, D., Tom, M., Stamm, C., Odermatt, D., 2023. Pixel-based mapping of open field and protected agriculture using constrained Sentinel-2 data. ISPRS Open Journal of Photogrammetry and Remote Sensing 8. https://doi.org/10.1016/j.ophoto.2023.100033.

 

Acknowledgements: We thank the Consorzio di Bonifica in Destra del Fiume Sele for the continuous support in the MSCA-PF REWATERING project.

Funding: This project has received funding from the European Union’s Horizon Europe research and innovation under the Marie Skłodowska-Curie grant agreement No. 101062255

How to cite: la Cecilia, D., Venezia, A., Maino, D., and Camporese, M.: Towards an understanding of the hydrological processes of greenhouse horticulture districts, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9140, https://doi.org/10.5194/egusphere-egu24-9140, 2024.

EGU24-9217 | ECS | Posters on site | HS2.2.3

Testing the Adequacy of 7533 KGE Calibrated Conceptual Model Structures 

Diana Spieler and Niels Schütze

Discussions calling for more rigorous evaluation practices for hydrologic models have recently increased. In addition to the widely used aggregated objective functions, hydrologic signatures are becoming common evaluation metrics for testing the adequacy of hydrologic models for specific application purposes.

This work calibrates 7533 conceptual model structures using KGE as an objective function. These structures are evaluated based on their accuracy (KGE performance) and their adequacy. We defined adequacy as showing less than a +/- 50% percentage bias on inter- and intra-annual flow representation as well as on ten selected signatures. These signatures represent five aspects of the hydrological regime (magnitude, frequency, duration, rate of change, and timing). The large number of model structures, calibrated to the streamflow of 12 hydro-climatically differing MOPEX catchments, allows general insight into how well common conceptual model structures can represent observed hydrological behavior evaluated by signatures.

Results show that a large number of model structures perform accurately (high KGE performance) but almost none of these may be considered adequate (poor signature performance). In nine catchments not a single model can be considered adequate. In the remaining three catchments, only between 1 (0.1%) and 49 (0.7%) of all tested model structures are adequate according to all testing requirements. While inter-annual mean flow representation is typically represented well, the number of models able to represent intra-annual mean flow and/or individual signatures rapidly decreases.

This study presents overwhelming evidence that traditional single-objective function-based calibration is unlikely to return model structures that adequately represent complete hydrologic regimes. We therefore recommend that any model intercomparison or evaluation study needs to be constrained with additional data and/or evaluated by more meaningful metrics than traditional objective functions alone.

How to cite: Spieler, D. and Schütze, N.: Testing the Adequacy of 7533 KGE Calibrated Conceptual Model Structures, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9217, https://doi.org/10.5194/egusphere-egu24-9217, 2024.

EGU24-9701 | Posters on site | HS2.2.3

Using a regionalized distributed hydrological modelling approach for prediction low flow on ungauged French territory based on the training of artificial neural network  

Thomas de Fournas, Nathalie Folton, François Colleoni, and Killian Pujol--Nicolas

This study delves into the exploration of low-flow rivers, a crucial subject within the global river network. These rivers, characterized by reduced flows over significant periods, play an essential role in various ecosystems. They constitute a substantial portion of the global river network, spanning diverse regions, including arid, semi-arid, temperate, humid tropical, boreal, and alpine areas. The flow variations observed in these watercourses are influenced by multiple factors, including climate change and increased water withdrawals associated with human activities. Ungauged basins, where reliable flow data is not readily available, present a significant hurdle in hydrological modelling. The absence of direct measurements makes it difficult to understand and predict the flow dynamics of rivers and streams, particularly in regions with low flow watercourses. To overcome this challenge, the study leverages the SMASH platform (Spatially-distributed Modelling and ASsimilation for Hydrology), a versatile multi-model framework capable of handling the complexities associated with ungauged territories.

The model implemented within the SMASH platform draws inspiration from the GR model family, a collection of global and semi-distributed models developed over the past years at INRAE. SMASH is a flexible, spatially distributed hydrological modelling platform capable of operating at high spatial and temporal resolution in both gauged and ungauged catchments. It is designed to simulate flow hydrographs across all grid cells in the computational domain.

Additionally, it incorporates functionalities for parameter sensitivity analysis and methods for both uniform and spatially distributed parameter calibration with different objective functions.

The principal aim of this study is to test the performance of various hydrological model structures, inspired by the GR model on the SMASH platform in low flow context. The evaluation centers on calibration and validation processes, employing uniform calibration techniques and regionalization approaches over a comprehensive dataset spanning 40 years at a daily time step. This extensive evaluation aims to elucidate the efficacy of these models in reproducing the low flows, seasonnality and bilan of watercourses over a set of basins (100) covering France with differents hydrometeorologic catchments. Furthermore, the study introduces a novel dimension by leveraging an artificial neural network (ANN) to process catchment descriptors specific to France. The ANN facilitates the exploration of regionalization by establishing a meaningful correspondence between select catchment descriptors and model parameters.

The study will then conclude with a comprehensive comparison of all simulations, highlighting the best hydrological model structure and regionalisation.

How to cite: de Fournas, T., Folton, N., Colleoni, F., and Pujol--Nicolas, K.: Using a regionalized distributed hydrological modelling approach for prediction low flow on ungauged French territory based on the training of artificial neural network , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9701, https://doi.org/10.5194/egusphere-egu24-9701, 2024.

Land-surface evapotranspiration (ET) is a major component of the hydrologic cycle. It is a very attractive approach to estimate land surface ET by means of complementary relationship (CR). After 60 years of continuous exploration, the CR has developed from linear relationships to the present nonlinear ones. There are usually four boundary conditions (BCs) for the nonlinear CR, among which the first-order one in completely wet environments (dy/dxx=1) has been a debatable issue, including both the difference in values of dy/dxx=1, and the divergence in definitions of the independent variable x. It has always been a problem how to consider the advection effect in CR. The effect degree of advection from outside the region varies in the ET process at different spatial scales. In this paper, x denotes the ratio of equilibrium ET (ETe) to apparent potential ET (ETpa), y denotes the ratio of ET to ETpa, and x=1 is set as the benchmark with ETe as the lower limit of ETpa. According to the characteristics of ET processes at different spatial scales, we extend the value range of dy/dxx=1, and take dy/dxx=1=k (k≥0) to establish the generalized BC. The generalized CR model for ET is then proposed by using an exponential function, expressed as y=EXP[k/d(1-1/x^d)] (denoted by GCR-EXP; d>0), where k and d are model parameters. k is equal to 2 in the absence of advection, which is the most complementary case. When k < 2, warm advection plays a role, and the value of k gradually decreases as the advection influence increases. Brutsaert (2015) considered the effect of minimal advection, and used the potential ET (Priestley and Taylor,1972) as ET’s constraint to determine the first-order BC in completely wet environments for the polynomial model of CR, which is a case that fits quite well with a large number of observed data. When k = 0, the CR is no longer valid, and the ET is always equal to ETpa, which reflects the ET of a small wet surface. When 0≤x≤xmin, y is equal or approximately equal to 0. xmin and Priestley-Taylor coefficient α can be determined by the values of x at y close to 0 and to 1 in GCR-EXP model, respectively. For instance, the value of x at y=0.001 can be taken as the value of xmin. k reflects advection effects and the corresponding degrees of CR. Moreover, the GCR models, which satisfy the four BCs including dy/dxx=1=k, can be also expressed as a power-exponential function form and other ones besides the proposed exponential one (Supported by Project 41971049 of NSFC).

How to cite: Liu, W., Mu, Z., and Cheng, C.: Advection Effect and Boundary Condition in the Formulation of Generalized Complementary Relationship for Evapotranspiration, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10306, https://doi.org/10.5194/egusphere-egu24-10306, 2024.

EGU24-12273 | ECS | Posters on site | HS2.2.3

Exploring the Impact of Various Streamflow Products on Ice-Jam Formation  

Mohammad Ghoreishi, Shervan Gharari, Mohamed Elshamy, and Karl-Erich Lindenschmidt

Ice jams present a significant flood risk in communities located along northern rivers, especially during the breakup of ice cover, resulting in increased backwater levels and flooding beyond riverbanks. The accurate simulation of ice formation relies on precise streamflow data, a vital input for hydraulic models. This study aims to evaluate how different streamflow products influence ice formation, focusing on simulating ice-jam flooding of the Athabasca River at Fort McMurray, Canada, with the broader goal of assessing the suitability of global datasets for predicting such events at a local scale. In our investigation, we integrate MizuRoute, a river network routing tool, and RIVICE, a one-dimensional, hydrodynamic, and river-ice hydraulic model. By employing various large-scale runoff from different models and datasets, such as MESH, ERA5, and VIC among others, our goal is to comprehensively understand how each product impacts the formation of ice jams and the subsequent flooding events. The incorporation of these runoff products is particularly relevant to investigate utilizing global datasets for predicting ice-jam flooding at a local scale.

How to cite: Ghoreishi, M., Gharari, S., Elshamy, M., and Lindenschmidt, K.-E.: Exploring the Impact of Various Streamflow Products on Ice-Jam Formation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12273, https://doi.org/10.5194/egusphere-egu24-12273, 2024.

EGU24-12287 | ECS | Orals | HS2.2.3

How well does CLM5 simulate water and energy cycles over India? - A performance evaluation  

Chiru Naik Devavat and Dhanya Chandrika Thulaseedharan

Land surface processes exert a significant impact on local, regional, and global climate through intricate physical exchanges, including energy, water cycle dynamics, vegetation response, soil moisture variations, and heat fluxes between land and atmosphere. A comprehensive understanding of these processes necessitates the analysis of land surface states (e.g., soil moisture, temperature) and fluxes (e.g., evapotranspiration, runoff) over an extended period for various research fields such as hydrological process modeling, weather and climate forecast, drought/flood monitoring, and water resource conservation. However, the accuracy of analyses is hindered by the sparse and uneven distribution of in-situ measurements. To overcome this limitation, satellite-based data and land surface models are employed. While satellites provide continuous global data, they only capture surface-level conditions and have limited daily spatial coverage. Daily, multi-depth soil profile information is essential for understanding land condition dynamics and their impact on the water cycle and agriculture. The Community Land Model (CLM), specifically its latest version CLM5, stands as a pivotal tool for simulating biophysical and biogeochemical processes, including interactions with the atmosphere. Nevertheless, its efficacy in accurately simulating water and energy cycles over India, where local land surface changes are particularly pertinent due to sparse in-situ data remains to be evaluated. To address this gap, our study employs CLM5 to simulate the land surface process at a 0.1° resolution from 1980 to 2020 over India. The evaluation process is comprehensive, involving comparisons with diverse land surface datasets, encompassing in-situ, remotely sensed, and reanalysis measurements. For soil moisture, CLM5 demonstrates good agreement with in-situ data (correlation: 0.66 to 0.67) but exhibits wet biases when compared to in-situ and GLEAM. In the case of evapotranspiration and runoff, CLM5SP closely matches the patterns observed in GLEAM and GRUN datasets (correlation: 0.89 to 0.95 for evapotranspiration and 0.77 to 0.96 for runoff). However, it is noteworthy that CLM5SP tends to overestimate both evapotranspiration and runoff when compared to the reference datasets. The anticipated outcome of this study provides valuable insights into the capabilities of CLM5 simulations over India, offering applications and references for enhancing the model's characterization of water and energy fluxes in the future.

How to cite: Devavat, C. N. and Chandrika Thulaseedharan, D.: How well does CLM5 simulate water and energy cycles over India? - A performance evaluation , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12287, https://doi.org/10.5194/egusphere-egu24-12287, 2024.

Conducting highly standardized model intercomparison studies of hydrologic models across large scales is beneficial in various aspects such as improving model accuracy and robustness, informing decision making, addressing uncertainties, enhancing educational and outreach opportunities and facilitating model benchmarking among others. However, looking beyond streamflow for hydrologic models is required to ensure that models simulate the right results for the right reasons. Continental scale analyses provide further insights into which systematic limitations a model has.

In this study, seven models (GR4J-CemaNeige, HMETS, Blended-v1, Blended-v2, HBV-EC, HYPR, SAC-SMA) have been setup for more than 2500 watersheds across Canada and the US using the RAVEN modeling framework. The models are setup using a standardized set of meteorologic and geophysical datasets to inform the model regarding forcings, soil, landcover, and terrain. All models are calibrated with respect to daily streamflow (2001-2015) and are subsequently validated on an independent time period (1986-2000). Calibration was performed using 10 independent trials of the Dynamically Dimensioned Search algorithm each using a budget of 2000 model evaluations and Kling-Gupta Efficiency (KGE) as the objective function. Additional variables such as actual evapotranspiration (AET), surface soil moisture (SSM), and snow water equivalent (SWE) for the calibrated model setups were recorded and compared against independent gridded reference datasets (AET and SSM from GLEAM, SWE from ERA5-Land). 

The results (surprisingly) show that all tested models perform equally well for streamflow prediction (range of median KGE values across all sites during calibration period is [0.83, 0.87] and validation period is [0.46, 0.54]). 

Differences between models are most apparent for the auxiliary variables analyzed, i.e. AET, SSM, and SWE. The most interesting differences between the models lie in their abilities to predict AET, with median KGE being the highest for SAC-SMA (0.71), followed by GR4J-CemaNeige (0.65), while the lowest values were observed for HMETS (0.37) and HBC-EC (0.17). Indeed SAC-SMA showed highest performances across 51% of locations while the second-best model is GR4J-CemaNeige with best performance at 13% of locations. 

The SSM, evaluated using the Pearson correlation (r) coefficient, was predicted relatively well by all models (r ranging between 0.62 and 0.72); however, while most models had poorer predictions in the Rocky mountains and at higher latitudes, the SAC-SMA was definitely a better predictor of the temporal dynamics in SSM in these regions.

While the median performance for SWE prediction was relatively low across all models (median KGE between 0.23 and 0.40), poorer predictions mostly occurred in regions with low annual SWE, and predictions improved with increasing annual snow amounts. 

The study reveals novel insights regarding the consistent ability of a suite of models to predict streamflow, while clear ranking of models was apparent based on their ability to simulate spatially distributed variables like AET. Such differences likely arise due to model equifinality highlighting the value of model evaluation against multiple spatially distributed and lumped metrics, generating the correct streamflow for the right reasons.

How to cite: Mai, J. and Basu, N. B.: Beyond streamflow predictions: A continental scale hydrologic model intercomparison experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12485, https://doi.org/10.5194/egusphere-egu24-12485, 2024.

EGU24-12492 | Posters on site | HS2.2.3

Metrics that Matter: Calibration Choices and Their Impact on Signature Representation in Conceptual Hydrological Models 

Peter Wagener, Diana Spieler, and Niels Schütze

Hydrologists are generally aware that the choice of calibration metric will affect how their model reproduces catchment runoff. However, scientific literature mainly provides a theoretical or case study specific discussion of the topic and no general guidelines. This study thus aims to develop a broader picture by evaluating the influence of 8 different objective functions on the representation of 15 hydrologic signatures for 45 lumped conceptual models in 10 climatically diverse catchments.

The 10 selected catchments are a subset of the CARAVAN dataset (Kratzert et al. [2023]) chosen by using a k-means clustering algorithm based on climate indices (Willmott and Feddema [1992]). The 45 models are taken from the MARRMoT toolbox (Knoben et al. [2019], Trotter et al. [2022]) and only models performing over a specified benchmark are used for the analysis. The signatures that will be analysed represent different processes and aspects of the hydrological regime and the following 8 calibration metrics are investigated: KGE, NSE, log KGE, log NSE, NP-KGE (Pool et al. [2018], Split KGE (Fowler et al. [2018], SHE (Kiraz et al. [2023], DE (Schwemmle et al. [2021]).

Preliminary results show that the ability to reproduce specific signatures is clearly influenced by the chosen metric and therefore this choice should always be based on the specific goal of the prospective modelling study. Each metric has specific strengths and weaknesses that may be used to make a decision. However, the results vary based on climate conditions, the applied model structure and the investigated signature. It is therefore difficult to disentangle all interdependencies and develop more general guidelines with the limited catchment set used in this study. We speculate that very dominant processes shaping the general runoff generation in a catchment (such as snow melt) reduces the impact of the choice of calibration metric, and that more complex models typically are more consistent in process representation.

References:
Fowler et al. (2018): doi: 10.1029/2017WR022466
Gupta et al. (2009): doi: 10.1016/j.jhydrol.2009.08.003
Kiraz et al. (2023): doi: 10.1029/2023WR035321
Knoben et al. (2019): doi: 10.5194/gmd-12-2463-2019
Kratzert et al. (2023): doi: 10.1038/s41597-023-01975-w
Nash and Sutcliffe (1970): doi: 10.1016/0022-1694(70)90255-6
Pool et al. (2018): doi: 10.1080/02626667.2018.1552002
Schwemmle et al. (2021): doi: 10.5194/hess-25-2187-2021
Trotter et al. (2022): doi: 10.5194/gmd-15-6359-2022
Willmott and Feddema (1992): doi: 10.1111/j.0033-0124.1992.00084.x

Disclaimer: The first author conducted the presented research at TUD, now a PhD student at UofC

How to cite: Wagener, P., Spieler, D., and Schütze, N.: Metrics that Matter: Calibration Choices and Their Impact on Signature Representation in Conceptual Hydrological Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12492, https://doi.org/10.5194/egusphere-egu24-12492, 2024.

EGU24-12534 | ECS | Orals | HS2.2.3

Modelling the effectiveness of multiple natural flood management interventions at a large catchment scale 

Qiuyu Zhu, Megan Klaar, Thomas Willis, and Joseph Holden

While natural flood management (NFM) as a resilience flood mitigation strategy is widely used in the UK and Europe, there remains a lack of scientific evidence regarding its effectiveness. The primary uncertainties stem from two aspects: the determination of NFM effectiveness on flood mitigation is limited by the scale of impact assessment; and the combination of multiple NFM interventions implemented within a catchment which may result in flood synchronicity. We argue that the effectiveness of combined scenarios involving multiple NFM interventions within a catchment can vary.  We utilize a hydrological model that simulates both instream and terrestrial interventions at a large catchment scale. To demonstrate how scale and interventions interact to determine flood peaks, we integrated various NFM interventions and land cover changes within the upstream catchment into a model, including afforestation, soil aeration, catchment/floodplain restoration and hedge planting. We modelled existing and planned scenarios using a spatially distributed hydrological model, Spatially Distributed TOPMODEL (SD-TOPMODEL). In comparison to previous versions of TOPMODEL, we have improved the simulation efficiency to allow for the simulation of up to a 200-year return period flood event at a larger catchment scale (~84 km2); and simplified the model parameters which are not related to the effects of NFM interventions and retained three key parameters which are physically significant. Following extensive parameter calibration and validation, the model is stable, providing a reliable fit for flood peaks, with the Nash-Sutcliffe coefficient (NS) between modelled and observed discharge reaching up to 0.905. The modelling results illustrated the effectiveness of NFM interventions in reducing flood peaks at a large catchment scale. Further refinements will involve incorporating additional types of NFM interventions into our next coupled model. 

How to cite: Zhu, Q., Klaar, M., Willis, T., and Holden, J.: Modelling the effectiveness of multiple natural flood management interventions at a large catchment scale, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12534, https://doi.org/10.5194/egusphere-egu24-12534, 2024.

EGU24-13129 | Orals | HS2.2.3

Multi-basin calibration of the ECMWF land-surface model ECLand 

Stephan Thober, Juliane Mai, Cinzia Mazzetti, Gianpaolo Balsamo, Christel Prudhomme, Robert Schweppe, Matthias Kelbling, Sebastian Müller, and Luis Samaniego

Accurately and efficiently estimating parameters for spatially distributed environmental models is impossible without proper regularization of the parameter space. The Multiscale Parameter Regionalization (MPR, Samaniego et al. 2010) makes use of high-resolution physiographic data (i.e., physiographic data such as soil maps and land cover information) to translate local land surface properties into model parameters. MPR consists of two steps: first, the high-resolution model parameters are derived from physiographic data via transfer functions at the native resolution. Second, the model parameters are upscaled to the target resolution the environmental model is applied on. MPR has already been successfully applied to the mesoscale hydrologic model (mHM, Samaniego et al. 2010, Kumar et al. 2013). An agnostic, stand-alone version implementation of MPR (Schweppe et al., 2022) allows applying this technique to any land-surface model or hydrological model.

In this study, we apply MPR to optimize parameters for the land-surface model ECLand (Boussetta et al. 2021) of the ECMWF Integrated Forecasting System. ECLand is calibrated at multiple locations simultaneously to provide an improved representation of river discharge at a global scale. We demonstrate the flexibility of the MPR approach by optimizing different transfer functions including the default one used in ECLand. In particular, we will discuss how specific choices in the calibration setting (i.e., chosen model parameters and ranges, basin locations, transfer function) affect the obtained ECLand model performance.

 

References:

Samaniego L., Kumar, R., and Attinger, S.: “Multiscale parameter regionalization of a grid-based hydrologic model at the mesoscale”, Water Resour. Res., 46, 2010.

Kumar, R., Samaniego, L., and Attinger, S.: “Implications of distributed hydrologic model parameterization on water fluxes at multiple scales and locations”, Water Resources Res, 2013

Schweppe, R., Thober, S., Müller, S., Kelbling, M., Kumar, R., Attinger, S., and Samaniego, L.: MPR 1.0: a stand-alone multiscale parameter regionalization tool for improved parameter estimation of land surface models, Geosci. Model Dev., 15, 859–882, https://doi.org/10.5194/gmd-15-859-2022, 2022

Boussetta S, Balsamo G, Arduini G, Dutra E, McNorton J, Choulga M, Agustí-Panareda A, Beljaars A, Wedi N, Munõz-Sabater J, de Rosnay P, Sandu I, Hadade I, Carver G, Mazzetti C, Prudhomme C, Yamazaki D, Zsoter E. ECLand: The ECMWF Land Surface Modelling System. Atmosphere. 2021; 12(6):723. https://doi.org/10.3390/atmos12060723

How to cite: Thober, S., Mai, J., Mazzetti, C., Balsamo, G., Prudhomme, C., Schweppe, R., Kelbling, M., Müller, S., and Samaniego, L.: Multi-basin calibration of the ECMWF land-surface model ECLand, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13129, https://doi.org/10.5194/egusphere-egu24-13129, 2024.

EGU24-13230 | Orals | HS2.2.3

An Improved Representation of The Variable Contributing Area Concept in Hydrologic and Land Surface Models 

Tricia Stadnyk, Mohamed Ismaiel Ahmed, Martyn Clark, and Alain Pietroniro

Hydrologic modelling in the low-lying, flat prairie or arctic pothole regions is challenging because of variable contributing areas that modify the transformation of local runoff into streamflow. Most hydrological and land surface models fail in predicting prairie hydrology due to overlooking or inadequately representing the variable contributing area dynamics. In this study, we develop an open-source, model-agnostic version of a revised formulation of the recently developed Hysteretic Depressional Storage (HDS) model. This revised formulation accounts for the hysteretic relationship of pothole depressions and its effects on streamflow generation. The revised HDS model is implemented and tested with two different hydrological models of varying complexity (MESH and HYPE). The modified hydrological models are tested on a number of prairie pothole basins in Canada. Results show improved simulations of the streamflow response in the tested basins. Importantly, the modified models replicate the known hysteretic relationships between depressional storage and contributing areas in that region. The open-source HDS implementation approach is designed for use in hydrologic or land surface modelling systems, enabling improvements in simulating the complex hydrology and streamflow regimes globally.

How to cite: Stadnyk, T., Ahmed, M. I., Clark, M., and Pietroniro, A.: An Improved Representation of The Variable Contributing Area Concept in Hydrologic and Land Surface Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13230, https://doi.org/10.5194/egusphere-egu24-13230, 2024.

EGU24-13626 | ECS | Orals | HS2.2.3

How can spatial parameter sensitivity analysis enhance streamflow calibration routines in hyper-resolution hydrological models? 

Luiz Bacelar, Hongli Liu, Guoquiang Tang, Noemi Vergopolan, Naoki Mizukami, Andy Wood, and Nathaniel Chaney

Efficiently modeling water and energy fluxes across spatial scales has historically involved grouping landscapes based on hydrological similarities. The HydroBlocks (HB) modeling framework, using unsupervised machine learning of high-resolution environmental datasets, emerges as a robust tool for representing heterogeneity in Land Surface Models (LSMs). This framework effectively discretizes complex gridded LSMs, such as Noah-MP, into spatially unstructured Hydrological Response Units (HRUs), facilitating the modeling of hydrological processes at hyper-resolution (10-100 m) with computational efficiency suitable for continental and global simulations. However, extending process-based hydrological models to such scales does not inherently ensure heightened simulation accuracy. For operational purposes, especially in flood warning systems, calibrating new LSMs remains imperative. Therefore, this study proposes a spatial parameter sensitivity methodology based on the pyVISCOUS algorithm, with the potential to facilitate HRU-level parameter calibration and enhance the application of hyper-resolution resolving LSMs for real-time streamflow prediction.

Our investigation delves into the relationship between spatial parameter sensitivity and model discretization across the Contiguous United States (CONUS), mainly focusing on surface and subsurface runoff states. Two clustering architectures were used to generate HB HRUs for an ensemble of simulations varying Noah-MP LSM parameters. The simplified HB configuration clusters HRUs based on terrain and hillslope variations, while the formal HB incorporates finer-scale land heterogeneity from high-resolution land cover and soil properties maps. Results reveal that saturated hydraulic conductivity was considered the most sensitive parameter for runoff production independent of the HRU grid configuration. The infiltration controlling parameter REFDK was ranked as the second most important in first-order sensitivity and had a higher spatial impact (% of HRUs) over the experiment with a higher level of clustering small-scale heterogeneity. Lower sensitivities were found in HRUs classified as urban areas, while soil properties parameters demonstrate reduced sensitivity near streams, where the floodplain remains closer to saturation. We intend to demonstrate that excluding the least sensitive HRU groups within a defined parameter range from calibration could potentially minimize computational costs while preserving physically realistic spatial patterns of LSM fluxes and states at field-scale resolutions, mitigating artifacts introduced by conventional methods (e.g. constant parameter multiplier over subbasins).

How to cite: Bacelar, L., Liu, H., Tang, G., Vergopolan, N., Mizukami, N., Wood, A., and Chaney, N.: How can spatial parameter sensitivity analysis enhance streamflow calibration routines in hyper-resolution hydrological models?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13626, https://doi.org/10.5194/egusphere-egu24-13626, 2024.

Abstract
Study region: Typical basin in humid areas in the Huaihe River 
Study focus: Accurate flood forecasting is essential for making timely decisions regarding flood control and disaster reduction. The theory of watershed runoff generation and convergence serves as a crucial foundation for flood forecasting, while the calculation of runoff is necessary to simulate flood discharge. Identifying watershed runoff generation mechanisms has been a challenging task, particularly under complex underlying surface conditions. To improve the accuracy of flood simulation, this study examines the underlying surface information in the watershed, such as particle composition and content, soil bulk density, geological slope, land use, and other spatial attributes, aiming to analyze the mechanisms of runoff generation. In the study of sub-watersheds, various combinations of runoff generation mechanisms are identified to determine the patterns of runoff. Subsequently, a semi-distributed hydrological model is developed, which incorporates both saturation-excess and infiltration-excess runoff, utilizing the information obtained from the underlying surface. The model is validated using rainfall-runoff data from 14 events at the Xiagushan watershed. 
New hydrological insights for the region: The analysis of the fundamental physical conditions of the underlying surface of the watershed revealed that 69.70% of the area is prone to saturation-excess runoff, with an additional 30.30% of the area being susceptible to infiltration-excess runoff. The model considers the spatial distribution of runoff patterns by incorporating complex underlying surface information and demonstrates high accuracy in simulating flood events (NSE= 0.87, Epeak = 12.08%, Wpeak = 13.16%, Tpeak = 0.14 hours, R2 = 0.90). The model is straightforward, practical, and exhibits promising potential in terms of timeliness and applicability, thus lending itself well to further application in other watersheds, contributing to the scientific foundation of flood warning and forecasting efforts.

How to cite: Hu, C., Liu, C., Niu, C., and Yu, Q.: Construction of a semi-distributed hydrological model considering the combination of saturation-excess and infiltration-excess runoff space under complex substratum, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14494, https://doi.org/10.5194/egusphere-egu24-14494, 2024.

EGU24-15260 | Posters on site | HS2.2.3

Extreme low flow estimation: added value of piezometry to constrain the asymptotic behavior of a lumped rainfall-runoff model 

Joël Gailhard, Antonin Belin Mergy, Matthieu Le Lay, and Alexandre Devers

The adaptation to climate change of thermal power plants necessitates the identification and characterization of high impact hazards. Extremely low river flow is one of these situations. The estimation methods traditionally used today still rely on extreme value theory (i.e., statistical adjustment on few observations and/or simulations), but these methods suffer from numerous limitations. Recent developments now make it possible to consider another approach, based on hydro-climatic simulations: extreme low flow quantiles are estimated by coupling a climate generator and a hydrological model. A first proof of concept was recently tested on a single basin and showed significant potential (Parey et al. 2022). Areas for improvement were also identified, both on the climate generator and the hydrological model.

The purpose of this work was then (i) to extend this first proof of concept to a larger number of basins and (ii) to quantify the sensitivity of the simulation chain (i.e., extreme low flow quantiles estimation) to the parameters of the hydrological model (in our case, the MORDOR-SD daily lumped rainfall-runoff model, Garavaglia et al. 2017).

A dataset of 33 catchments, each of them being associated with at least one piezometer, was selected to investigate whether the MORDOR-SD model could be constrained by piezometric time series to improve low flow simulations. By performing calibrations using only streamflow information we first confirmed that a particular state of the model was well correlated with piezometry in most studied catchments (the level of the so-called « deep » store, dedicated to the baseflow component).

A multi-objective calibration approach was then implemented, optimizing both (i) flow simulation with 4 criterions focusing on different streamflow signatures and (ii) eventually one supplementary criterion base on the affine correspondence between the deep storage level of the model and piezometry (i.e., calibration with or without piezometric information).

The results led us to propose a classification of the 33 basins based on two indices. The first index characterizes the importance of the baseflow in the streamflow (BFI = baseflow index). The second index characterizes the a priori representativity of the piezometric time series during low flows (Cor QMNA/ZMNA, index also used in Andreassian & Pelletier 2023).

For 14 out of the 33 basins (BFI > 0.7), piezometric information was almost neutral and did not lead to a significant improvement: the streamflow information was sufficient to constrain the low flow simulations. For 11 out of the 33 basins (Cor QMNA/ZMNA < 0.6 and BFI < 0.7), piezometric information was misleading and degraded the results: we assume that the piezometric information was not sufficiently relevant. Ultimately, only 8 out of the 33 basins (Cor QMNA/ZMNA > 0.6 and BFI < 0.7) emerged as interesting case studies. For these 8 watersheds, the piezometric information appears relevant to be included in the calibration process to derive a physics-based extrapolation of extremely low flow quantiles.

How to cite: Gailhard, J., Belin Mergy, A., Le Lay, M., and Devers, A.: Extreme low flow estimation: added value of piezometry to constrain the asymptotic behavior of a lumped rainfall-runoff model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15260, https://doi.org/10.5194/egusphere-egu24-15260, 2024.

EGU24-15445 | ECS | Posters on site | HS2.2.3

Introducing WSFS-P, Process-based Version of the Watershed Simulation and Forecasting System (WSFS) in Finland 

Meseret Menberu, Juho Jakkila, Noora Veijalainen, Kristin Böttcher, Stefan Fronzek, Vesa Kolhinen, Paula Havu, Nasim Fazel, Miia Kumpumäki, Ari Koistinen, and Markus Huttunen

This study introduces the WSFS-P model, an evolution of the well-established national WSFS (Watershed Simulation and Forecasting System) hydrological model. This new model represents a significant shift, moving from a conceptual WSFS hydrological model framework to a more physically based, and process-oriented approach (WSFS-P). WSFS-P is a two-layer semi-distributed hydrological model developed at the Finnish Environment Institute (Syke) in order to offer more detailed physical representations in hydrological forecasting and research. This hydrological model incorporates a number of sub-models that cover a wide range of hydrologic processes, including precipitation, snow dynamics, evapotranspiration, lake evaporation, soil moisture, groundwater, river routing, and ice thickness. The model utilizes meteorological inputs such as precipitation, temperature, relative humidity, air pressure, net radiation, cloudiness, and wind speed to deliver a comprehensive and detailed simulation of the hydrological cycle. The WSFS-P aims to enhance the accuracy and effectiveness of hydrological forecasting and research in Finland by leveraging spatially distributed data, such as Corine land use, altitude, and Finnish soil database. This model covers the entire Finnish mainland and transboundary catchments but excludes islands and smaller coastal catchments. This study assesses the WSFS-P model in 58 different catchments in Finland that were selected to cover diverse hydrological characteristics, reliable data, and minimal influence from lake regulation. The selected catchments feature a variety of catchment sizes and topographical and land-use patterns, including forests and agricultural areas, and have varying soil types and distinct climatic conditions. Several catchments are characterized by numerous lakes typical to Finland. Additionally, the study provided a comprehensive examination of five specific catchments to highlight the model’s effectiveness. The preliminary results demonstrate the model’s capabilities in predicting water availability, contributing to efficient water resource management and enhanced flood and drought prediction in Finland. This study aims not only to introduce the WSFS-P model but also to validate its operational readiness for diverse hydrological conditions.

How to cite: Menberu, M., Jakkila, J., Veijalainen, N., Böttcher, K., Fronzek, S., Kolhinen, V., Havu, P., Fazel, N., Kumpumäki, M., Koistinen, A., and Huttunen, M.: Introducing WSFS-P, Process-based Version of the Watershed Simulation and Forecasting System (WSFS) in Finland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15445, https://doi.org/10.5194/egusphere-egu24-15445, 2024.

EGU24-16034 | ECS | Orals | HS2.2.3

Developing perceptual models of hydrologic behavior across the North American continent 

Wouter Knoben, Martyn Clark, Ying Fan, Hilary McMillan, Jordan Read, and Katie van Werkhoven

The North American continent is home to a wide range of different hydro-climates. A key research gap is that there is currently limited understanding on the spatial variability of dominant hydrologic processes across these different hydro-climates. This limited understanding makes it difficult to select computational models that faithfully represent the hydrologic processes across such large domains, yet faithful representation of the different hydro-climatic behaviors is critical for accurate numerical prediction.

Here we present progress on a synthesis of dominant hydrologic processes under different combinations of climate-terrain-human forcings, engaging the broader community of catchment and Critical Zone scientists. The product from this research will be a continental “Hydrologic Mosaic”, with each landscape in the mosaic described by a set of perceptual and conceptual models. In this first step, we produce a continental map of hydrologic landscapes defined through the juxtaposition of hydroclimate, terrain and geology, and vegetation, land use, and management. We will define hydrologically meaningful indicators of terrestrial hydrology that concisely describe a location’s (i) hydroclimate (e.g., aridity, snow fraction, energy/water seasonality), (ii) topography and geology (e.g. depth to bedrock, soil porosity, topographic slope), and (iii) vegetation, land use and management (e.g., vegetation type, agricultural drainage, reservoir size), and calculate values for these indicators for each location on the continent. We then use clustering analysis to create a manageable number of representative hydrologic landscapes.

This work functions as a starting point in a wider project, where these initial hydrologic landscapes will be refined through interactions with regional experts. Together, we will develop perceptual (sketches and descriptions) and conceptual (box-and-arrow diagrams) of the dominant processes in each hydrologic landscape. These conceptual diagrams will contribute to large-domain modeling efforts by allowing targeted model selection and comparison efforts for each hydrologic landscape.

How to cite: Knoben, W., Clark, M., Fan, Y., McMillan, H., Read, J., and van Werkhoven, K.: Developing perceptual models of hydrologic behavior across the North American continent, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16034, https://doi.org/10.5194/egusphere-egu24-16034, 2024.

EGU24-16116 | ECS | Posters on site | HS2.2.3

Can we parameterise Subsurface Stormflow in a conceptual simulation model using flow duration curve percentiles for calibration? 

Tamara Leins, Nikolai Späth, Christian Reinhardt-Imjela, and Andreas Hartmann

Subsurface stormflow (SSF) is an important runoff-generation process, especially in humid, mountainous regions. It can play a major role in flood generation and contaminant transport at the catchment scale. However, as it is a subsurface and heterogeneous process, its monitoring can be very challenging. In turn, the identification of SSF parameters in hydrological models is a difficult task and is often affected by equifinality.  Our study uses the HBV-light model, a conceptual model at the catchment scale, to simulate SSF (and catchment discharge) at a catchment in the Ore Mountains in Saxony, Germany. To see whether it is possible to improve the identifiability of SSF parameters by looking at different flow conditions separately, we divide discharge data according to flow duration curve (FDC) percentiles. We then calibrate the conceptual model several times, each time using only discharge data within one percentile of the FDC. Using a Monte Carlo based calibration, we select the same number of behavioural parameter sets for every FDC percentile based on the Kling-Gupta-Efficiency as an objective function. With a regional sensitivity analysis as well as a GLUE uncertainty estimation, we analyse and compare the parameter sets and discharge simulations of the different percentile calibrations. In this way, we analyse whether there is more information content on SSF hidden in a specific part of the FDC and thus, SSF parameters and processes become better quantifiable.

How to cite: Leins, T., Späth, N., Reinhardt-Imjela, C., and Hartmann, A.: Can we parameterise Subsurface Stormflow in a conceptual simulation model using flow duration curve percentiles for calibration?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16116, https://doi.org/10.5194/egusphere-egu24-16116, 2024.

EGU24-16210 | Posters on site | HS2.2.3

rechaRge – a package for integrated groundwater recharge modelling in R 

Yannick Marcon and Emmanuel Dubois

[9:56 AM] Emmanuel Dubois

The project introduces the new R package, rechaRge, dedicated to open-source groundwater recharge (GWR) models. The goal is to facilitate the simulation of GWR estimates for researchers, professionals, and stakeholders, for both hydrogeologists and non-hydrogeologists, by providing all the tools for state-of-art modelling and the available GWR models in a single R package. The package includes functions for data preparation (utility functions), automatic calibration, sensitivity analysis, and uncertainty analysis, all integrated directly in the R environment. A first open-source GWR model, the HydroBudget model, is also incorporated in the package. The model’s excellent performance allowed for the simulation of large datasets of spatially distributed and transient GWR in several projects in Canada, ranging from small watershed scale (few km2) to regional scale (thousands of km2). Sensitivity analysis, calibration, and uncertainty for the models were greatly facilitated by the utility functions of the package. At the region scale, GWR was simulated within a global change context with a spatial resolution of a 500 m x 500 m and a monthly time step for up to 150 years and 24 scenarios. Moreover, the rechaRge package is a collaborative effort and developers of open-source GWR modelling codes are warmly invited to publish their models in this package and take advantage of the existing functions.

How to cite: Marcon, Y. and Dubois, E.: rechaRge – a package for integrated groundwater recharge modelling in R, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16210, https://doi.org/10.5194/egusphere-egu24-16210, 2024.

EGU24-18302 | Orals | HS2.2.3

Recession discharge from compartmentalized bedrock hillslopes: hydrogeological processes and solutions for model calibration  

Clement Roques, Ronan Abhervé, Etienne Marti, Nicolas Cornette, Jean-Raynald de Dreuzy, David Rupp, Alexandre Boisson, Sarah Leray, Philip Brunner, and John Selker

Due to the difficulties of gathering relevant data of groundwater systems and the lack of fundamental physically-based understanding on the processes involved, the representation of groundwater flow heterogeneity in catchment- to regional-scale hydrological models is often overlooked. We often limit the representation of groundwater with simplified homogeneous and shallow aquifers where effective hydraulic properties are derived from global-scale database. This raises questions regarding the validity of such models to quantify the potential impacts of climate change, where subsurface heterogeneity is expected to play a major role in their short- to long- term regulation.

We will present the results of a numerical modelling experiment designed to explore the role of the vertical compartmentalization of hillslopes on groundwater flow and recession discharge. We found that, when hydraulic properties are vertically compartmentalized, streamflow recession behaviour may strongly deviate from what is predicted by groundwater theory that considers the drainage of shallow reservoirs with homogeneous properties. We further identified the hillslope configurations for which the homogeneous theory derived from the Boussinesq solution approximately holds and, conversely, for those for which it does not. By comparing the modelled streamflow recession discharge and the groundwater table dynamics, we identify the critical hydrogeological conditions responsible for the emergence of strong deviations. We further present new solutions to better represent subsurface heterogeneity in catchment-scale models and calibrate hydraulic parameters that properly capture the groundwater and streamflow dynamics.

How to cite: Roques, C., Abhervé, R., Marti, E., Cornette, N., de Dreuzy, J.-R., Rupp, D., Boisson, A., Leray, S., Brunner, P., and Selker, J.: Recession discharge from compartmentalized bedrock hillslopes: hydrogeological processes and solutions for model calibration , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18302, https://doi.org/10.5194/egusphere-egu24-18302, 2024.

EGU24-19135 | ECS | Orals | HS2.2.3 | Highlight

New modelling paradigm linking groundwater, surface water and rainfall-runoff relationship shifts under multi-year drought 

Keirnan Fowler, Dominic Regan-Beasley, Michael Nixon, and Glen Walker

While there is little opposition to the idea that groundwater can play a central role in rainfall-runoff response, there is little consensus on how this should be modelled. Here, we present modelling supporting a recently advanced hypothesis that links groundwater-surface water interactions with observed shifts in the relationship between rainfall and runoff in south-east Australia.  While many approaches assume a direct and simplistic relationship between groundwater head and baseflow, evidence arising from a multi-year drought in Australia challenges traditional notions. GRACE and bore data during the Millennium Drought (1997-2010) show multi-year declines in groundwater storage, of such severity that we might expect the baseflow to cease, giving a flashier regime.  In reality, the shape of the hydrograph is mostly unchanged, but other changes abound: a year of given rainfall generates less runoff today than it did pre-drought (ie. shift in rainfall-runoff relationship). In other words, during and after the drought we see a hydrograph of similar shape to before, but diminished. While many Australian hydrologists are convinced that groundwater played a key role in this behaviour, it is unclear how these observations can be explained by existing hypotheses or modelling methods for groundwater surface-water interaction, and new paradigms are required.

The hypothesis explored here is that these observations can be explained by leaky bedrock in headwater catchments, which facilitates gradual groundwater export from upslope areas to downslope areas (within the same catchment).  Upslope areas subject to groundwater decline then see groundwater-surface water decoupling and reduced runoff. The hypothesised leakage is slow enough to go unnoticed during wetter periods, but in drier periods recharge may be too low to balance the export, leading to reduced groundwater levels and groundwater surface-water decoupling. When wetter conditions resume, the groundwater deficits may take a while to be replenished, delaying recovery of rainfall-runoff relationships (as observed in Australia).  In downslope areas, the drained water may contribute to streamflow, but may also be lost to evaporation and transpiration, particularly in drier catchments with flatter valley bottoms of alluvium or colluvium. In such catchments, the net effect of these processes is to allow groundwater originating from upslope to supplement evaporative budgets downslope rather than increasing streamflow.

We advance this hypothesis, firstly by presenting evidence of its applicability in south-east Australia; and secondly by building and testing improved numerical models that incorporate a simplified representation of these processes. Modelling results show improved performance when tested across several catchments affected by rainfall-runoff relationship changes, and improved realism such as multi-year declines in simulated groundwater storage, consistent with observations.  These results suggest a promising avenue for further research relevant to a variety of water resource applications including climate change impact assessment.

How to cite: Fowler, K., Regan-Beasley, D., Nixon, M., and Walker, G.: New modelling paradigm linking groundwater, surface water and rainfall-runoff relationship shifts under multi-year drought, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19135, https://doi.org/10.5194/egusphere-egu24-19135, 2024.

EGU24-19742 | ECS | Posters on site | HS2.2.3

Predicting reservoir inflows with an advanced SWAT+ model calibration in the Tagus River headwaters (Spain) 

José Manuel Rodríguez-Castellanos, Alejandro Sánchez-Gómez, Silvia Martínez-Pérez, and Eugenio Molina-Navarro

The Tagus River is the longest in the Iberian Peninsula and its basin is highly managed: it is the most populated and subject to the Tagus-Segura water transfer, which sends an annual average of 330 hm3 to southeast Spain. Its starting point is a hyper-reservoirs' system (Entrepeñas-Buendía-Bolarque) located in the basin´s headwaters sector. The total inflow to this reservoir system has decreased by 50% in the last decades, mostly as a consequence of the already noticeable impacts of climate change, and this situation will be further aggravated in the future. Thus, both gaining knowledge about the hydrological behaviour of the Tagus River headwaters and developing reliable tools to predict inflows to this reservoirs' system are highly relevant tasks to aid for a sustainable water resources management in coming years.

In this work, we set up a highly detailed catchment model with SWAT+ in the Tagus River headwaters. Before calibration, two additional tasks were addressed: 1) HRUs were grouped into three classes with varying lithology and permeability (carbonate, detrital of high and medium permeability, detrital of low permeability), and 2) two hydrological indices, the runoff rate and the baseflow index, were obtained for eight subbasins that have streamflow records. Three sets of parameters were designed, one for each HRU geological class, and then a complex calibration procedure was addressed. A soft calibration, narrowing parameters´ ranges to reproduce the hydrological indices realistically, was followed by a multi-site hard calibration of the streamflow in eight subbasins. During hard calibration, the streamflow simulation performance and the accuracy of the model reproducing the runoff coefficient and the groundwater contribution were considered. Afterwards, a best simulation was chosen and tested with an initial validation of the daily streamflow produced in each reservoir watershed, obtaining both statistically and graphically satisfactory results. After some final modifications in the model, a second and final validation on the monthly inflows into the hyper-reservoirs system was done, successfully reproducing the observed records, with NSE, R2 and PBIAS values of 0.86, 0.88, 2.5% in Entrepeñas and 0.89, 0.91 and -8.5% in Buendía.

The SWAT+ calibration approach followed in this work is novel because it takes into account the heterogeneity in the hydrogeological properties of a catchment to parameterize it, optimizing the parameters values at a geological class level and evaluating the model performance at subbasin level, which implies a higher spatial calibration resolution that the usual one in SWAT studies. As a result, the model not only simulates accurately subbasins with uniform geological properties,  but the entire Tagus headwaters,  including those subbasins  with  mixed  geology, thus resulting  in a model that accurately simulates reservoir inflows. By performing a multi-site calibration on smaller subbasins, results are more accurate, and the model represents more realistically local hydrological conditions. For that reason, this methodology helps also to understand how specific environmental conditions might affect all hydrological model process, thus also helping in water management decision making.

How to cite: Rodríguez-Castellanos, J. M., Sánchez-Gómez, A., Martínez-Pérez, S., and Molina-Navarro, E.: Predicting reservoir inflows with an advanced SWAT+ model calibration in the Tagus River headwaters (Spain), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19742, https://doi.org/10.5194/egusphere-egu24-19742, 2024.

EGU24-19765 | ECS | Orals | HS2.2.3

Application of the new SWAT+ water allocation module in the Tagus River basin 

Alejandro Sánchez-Gómez, Jeffrey Arnold, Katrin Bieger, Nancy Sammons, Silvia Martínez-Pérez, and Eugenio Molina-Navarro

SWAT+ is a completely restructured version of the SWAT model. It includes new capabilities, and the possibility of modelling water resources management is particularly relevant. A new water allocation module allows to allocate water for different purposes inside and outside a basin. Reservoir management can be modelled using decision tables that define which actions occur under different scenarios. Despite the relevance of these novelties, there is a lack of studies demonstrating accurate simulations of reservoir outflows using decision tables in SWAT+, and there are to date no publications regarding the water allocation module.

The Tagus River basin (Spain) is the most populated (11 million inhabitants) basin on the Iberian Peninsula and its water resources management is highly controversial. This basin is a clear example of the importance of including anthropogenic water management in the modelling process, since it is intensively regulated by more than 50 reservoirs, several water transfers, and irrigation. Therefore, the water allocation module (for simulating water transfers and irrigation) and decision tables (for reservoir management and irrigation) were used in a detailed model of the Upper Tagus River Basin (UTRB), where most of the water demands of the basin are located.

Firstly, more than 30 reservoirs were introduced to the model and their management was analyzed using observed data. Different decision table structures were created considering the properties of the reservoirs (purpose, storage, etc.) and then adapted to each of the reservoirs. A satisfactory simulation of reservoir storage and outflow was achieved in most of the cases, demonstrating the reliability of the model and the adequacy of this approach.

There are numerous water transfers in the UTRB, of which the Tagus-Segura water transfer (TSWT) is the most relevant one. Some transfer water from one reservoir to another, while two of them divert water outside the modelled basin. In addition, water is transferred from reservoirs to water treatment plants and subsequently released to selected receiving channels. All these transfers were modelled using the SWAT+ water allocation module and for most of them the modelled volumes matched the observed ones well.

The agricultural water demand was estimated from the River Basin Management Plan. To simulate the irrigation, all demand objects within the UTRB (irrigated agricultural lands, 282 objects) and their respective sources (closest channel to those objects, 118 sources) were identified. An irrigation decision table was developed for the basin, allowing to simulate a demand close to the calculated and to supply enough water to meet more than 80% of this demand.

This works presents a novel approach to simulating water resources management in a highly regulated river basin using SWAT+. Results shows a satisfactory simulation of different management actions (reservoirs, irrigation, water transfers inside and outside the basin, wastewater discharges). Further work on the water allocation module will boost even more the application of SWAT+.

How to cite: Sánchez-Gómez, A., Arnold, J., Bieger, K., Sammons, N., Martínez-Pérez, S., and Molina-Navarro, E.: Application of the new SWAT+ water allocation module in the Tagus River basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19765, https://doi.org/10.5194/egusphere-egu24-19765, 2024.

EGU24-19807 | ECS | Orals | HS2.2.3

Simulations of energy and water balances with WRF and WRF-Hydro models: the role of model coupling and parameterizations 

Ioannis Sofokleous, Adriana Bruggeman, Corrado Camera, Hakan Djuma, Mohsen Amini Fasakhodi, and George Zittis

We tested the widely used atmospheric WRF (Weather Research and Forecasting) model in a coupled mode to the hydrological model WRF-Hydro. The coupled WRF/WRF-Hydro model adds the simulation of horizontal surface and subsurface flow of water relative to the standalone WRF. We conducted simulations for the Mediterranean island of Cyprus and 31 small mountainous river basins for the hydrological year 2011-2012. We found higher soil moisture (20%), more evapotranspiration (33%) and a small increase in rainfall (3%) for the coupled WRF/WRF-Hydro model, compared to the WRF model without horizontal flows. We also forced WRF-Hydro with observed rainfall and five different set-ups of WRF and examined the modelled streamflow. The WRF set-ups were adapted from combinations of different microphysics, cumulus cloud, planetary boundary layer and surface layer schemes. We found that WRF-Hydro with observed rain underestimated the average streamflow by 6%, during a two-year simulation (2011-2013). The best of the five WRF set-ups showed a 19% underestimation of the average streamflow, thus, an optimized ensemble of WRF set-ups is needed to model the streamflow. Our study suggests that the coupling of WRF with the WRF-Hydro model can improve land-atmosphere simulations. We will also present the calibration of parameters of the land surface component of the coupled model with observations of soil moisture and transpiration that could further enhance the ability of the model to represent the different parts of the combined terrestrial-atmospheric water cycle.

How to cite: Sofokleous, I., Bruggeman, A., Camera, C., Djuma, H., Amini Fasakhodi, M., and Zittis, G.: Simulations of energy and water balances with WRF and WRF-Hydro models: the role of model coupling and parameterizations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19807, https://doi.org/10.5194/egusphere-egu24-19807, 2024.

EGU24-21063 | Orals | HS2.2.3 | Highlight

The sociology of modelling: how we shape a perception together 

Lieke Melsen

Science, despite its status as objective and searching for truth, is inherently a social activity. Research is conducted by scientists that collaborate, work in teams, get advised by their supervisor, get funding to study particular questions, know one another from earlier projects, and so on. In these social interactions, we together define what we consider important to study, or what we deem unimportant. This occurs at multiple levels: Funding agencies, for example, have the power to determine which research questions should be addressed. As hydrological modelling community, we have implicitly agreed that discharge is the main variable of interest - focusing on other fluxes or states is often presented as an advancement.  And at the modelling team level, we often (implicitly) agree on a modelling vision. From interviews with modellers from different teams, it for example became apparent that one team had the modelling vision to `keep things as simple as possible’. Given this vision, the modeller was inclined to choose the simpler parameterization over a more complex one to describe the same process. In another team, ‘scale invariance’ was considered more important, and therefore process representations were selected based on their scalability. Therefore, if we want to “advance” process-representation in models across spatial and temporal scales, the theme of this session, we should acknowledge that different researchers have different perceptions of what advancing comprehends, that there is no objective measure to define advancement, and that the first step probably is, that we have to clarify and express our modelling vision.

How to cite: Melsen, L.: The sociology of modelling: how we shape a perception together, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21063, https://doi.org/10.5194/egusphere-egu24-21063, 2024.

EGU24-678 | ECS | Posters on site | HS2.2.5

Overland flow and shallow subsurface flow generation in a small pre-Alpine catchment: insights from tracer experiments 

Anna Leuteritz, Victor Gauthier, and Ilja van Meerveld

Near-surface flow pathways are important runoff processes in humid catchments with low permeability soils and provide fast transport of water and solutes from the hillslopes to the stream network. To improve our understanding of the spatial variability in solute transport and mixing in overland flow and shallow subsurface flow, we conducted tracer experiments on trenched runoff plots in a small headwater catchment underlain by Gleysols in the Swiss pre-Alps.

We applied a line of NaCl tracer to the surface of 14 small (3 m2) runoff plots and continuously measured flow rates and electrical conductivity in overland flow and shallow subsurface flow during natural rainfall events. In addition, we conducted tracer experiments during artificial rainfall on two large (>80 m2) trenched plots. Uranine and NaCl were applied as a line tracer at various distances from the trench after overland flow and subsurface flow had reached a steady state. NaBr was applied into the subsurface (at ~20 cm depth) and deuterium-enriched water was applied via the sprinklers. Samples of overland flow and shallow subsurface flow were collected at intervals ranging from 1 minute to 1 hour during several hours. We also continuously measured the rainfall rate, flow rates and electrical conductivity of overland flow and shallow subsurface flow, and soil moisture content.

The breakthrough curves from the small-scale experiments highlight the high spatial variation in overland flow and subsurface flow generation across the catchment, and the importance of mixing with shallow soil water for both overland flow and shallow subsurface flow. The results of the big plot experiments confirm the significant mixing of overland flow and subsurface flow. Maximum velocities, calculated from the first arrival of the tracers, were very high and ranged from 6x10-3 to 2x10-2 m s-1 for overland flow and 3x10-3 to 1x10-2 m s-1 for subsurface flow. Runoff generation in the large mixed forest plot was faster than for the large grassland plot and occurred primarily via macropores and soil pipes. In contrast, at the large meadow plot solute transport appears to be dominated by flow through the soil matrix.

How to cite: Leuteritz, A., Gauthier, V., and van Meerveld, I.: Overland flow and shallow subsurface flow generation in a small pre-Alpine catchment: insights from tracer experiments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-678, https://doi.org/10.5194/egusphere-egu24-678, 2024.

EGU24-704 | ECS | Orals | HS2.2.5

Near surface runoff generation in a pre-Alpine headwater catchment 

Victor Gauthier, Anna Leuteritz, and Ilja van Meerveld

Near-surface flow pathways can be important contributors to runoff in headwater catchments with low conductivity soils. However, the high spatio-temporal variability and connectivity between surface flow and shallow subsurface flow makes it difficult to study these processes. As a result, they are still poorly understood, especially for well vegetated humid catchments. The TopFlow project, therefore, aims to enhance our understanding of the generation and connectivity of overland flow and shallow subsurface flow in a pre-Alpine headwater catchment with low permeability Gleysols.

We installed 14 small (1 by 3 m) runoff plots at different topographic locations to cover the range in slope, vegetation, and wetness conditions across the catchment. At each plot, we measured overland flow (including biomat flow) and shallow subsurface flow from the rooting zone during two snow-free seasons. In addition, we collected groundwater, precipitation and soil moisture data. We also installed two larger plots (8 by >10 m), where we collected data during natural rainfall events and sprinkling experiments. Specifically, we conducted experiments to determine the surface flow path lengths and celerity of overland flow and shallow subsurface flow.

Overland flow and shallow subsurface flow occurred frequently on most plots (on average for 40% of the 26 rainfall events for which data were collected) but the spatial and temporal variability in overland flow and shallow subsurface flow generation was high. The timing and relative importance of overland flow and subsurface flow varied as well. Runoff ratios increased with increasing soil moisture storage and precipitation, and were generally higher for sites with a higher Topographic Wetness Index. Runoff ratios were sometimes larger than 1, indicating the importance of connectivity between subsurface and surface flow. Flow path lengths and celerity also differed for the plots and can be explained by differences in soil characteristics and wetness conditions. Overall, these results highlight the importance of fast near surface flow pathways for runoff generation and its high spatial and temporal variability.

How to cite: Gauthier, V., Leuteritz, A., and van Meerveld, I.: Near surface runoff generation in a pre-Alpine headwater catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-704, https://doi.org/10.5194/egusphere-egu24-704, 2024.

The growing demand for water resources is exacerbated by the impacts of climate variations, uneven rainfall distribution, and population growth. In the global inventory of water resources, rivers in mountainous regions contribute significantly to the available water supply. The subsurface aquifer system in these mountainous watersheds plays a crucial role in the hydrological cycle, serving not only as a primary source for downstream rivers or aquifers but also as a vital replenishment source during periods of drought. Due to its remote location and limited manpower, a comprehensive understanding of the hydrological functions of groundwater within the mountain system remains a challenge. Accordingly, this study selected the alpine watershed of Beinan River in eastern Taiwan, characterized by minimal human activities, to delineate groundwater flow paths and evaluate potential contribution of groundwater to water resources to address the existing gaps in understanding. Through long-term streamflow and groundwater level analyses combined with hydraulic tests and tracer experiments, the objective of this study focuses on delineating the subsurface flow paths from weathered soils and regolith to fractured bedrock and characterizing their associated hydraulic properties in this alpine hydrogeological setting. The results show that the main contributor to streamflow is shallow groundwater, particularly during the dry season. Rainfall infiltration is primarily observed in the weathered soils and regolith manifesting as the mountain front recharge (MFR). The groundwater flow in the bedrock is predominated influence by the fractures and its sources can be traced back to distant hillslopes. The water budget within the entire alpine system is preliminary quantified based on the long-term data and hydraulic parameters obtained from the field tests. The results obtained in this study can provide as a reference for developing conceptual models and fundamental frameworks for quantifying the water budget in alpine environments.

Keywords: alpine hydrogeology, groundwater flow path, fractured flow, water budget, Taiwan

 

How to cite: Lee, Y. H. and Chiu, Y. C.: Hydrogeological Study and Tracing of Groundwater Flow Paths in the Beinan River Basin within Eastern Taiwan's Alpine Catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3788, https://doi.org/10.5194/egusphere-egu24-3788, 2024.

EGU24-4376 | Orals | HS2.2.5

Spatio-temporal variability of hydrological connectivity through interflow 

Julian Klaus, Philipp Schultze, and Rhett Jackson

Interflow is lateral subsurface flow in hillslopes during and after precipitation events moving above a restrictive layer of lower hydraulic conductivity soil and rock. Interflow thus becomes more important in steeper hillslopes with a high contrast between the hydraulic conductivities of the layers that impede vertical water movement. However, the travel distance of a water parcel downslope in a perched water body is limited due to potential percolation of water through the impeding layer. This potential travel distance of interflow can be described with the concept of "Downslope Travel Distance" (DTD) that applies to temporary, perched groundwater in hillslopes. The determination of this downslope travel distance in catchments is possible with available topographic and subsurface data. Yet, how this interflow connects to the catchment outlet is poorly understood and depends on the spatio-temporal extension and contraction of the stream network. 

This presentation introduces the concept of DTD and employs calculations based on published data from various catchments and landscapes. In these catchments, DTDs ranged from about just one meter to over several hundred meters. Yet, the DTDs on must hillslopes with data are less than 50 m and less than 30% of the hillslope length showing that most shallow perched water percolates through the impeding layer before contributing to valley water or streamflow via interflow. In a subsequent step, we illustrate the spatial and temporal variability of the area connecting to the catchment outlet via interflow and thus contributing to discharge in different catchments. While soil properties and topographic characteristics generally remain stable over short periods, the wetted stream network undergoes notable changes both in the short and long term. Consequently, the pronounced variability of the area connecting to the catchment outlet via interflow is observable and characteristic for individual catchments. Lastly, we emphasize the present significant constraints of experimental studies and data concerning hillslopes in different landscapes, underscoring the necessity for revisiting research on runoff generation at the hillslope scale.

How to cite: Klaus, J., Schultze, P., and Jackson, R.: Spatio-temporal variability of hydrological connectivity through interflow, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4376, https://doi.org/10.5194/egusphere-egu24-4376, 2024.

EGU24-4588 | Posters on site | HS2.2.5

Identifying the source areas of subsurface stormflow through the analysis of depth profiles of water-soluble organic matter 

Peter Chifflard, Christina Fasching, Yvonne Schadewell, and Florian Leese

The hydrological dynamics of hillslopes, particularly subsurface stormflow (SSF), exhibit intricate variability in space and time. Existing studies are often confined to single slopes or limited storm events, resulting in uncertainties when applying findings to other slopes or catchments. To address this, a comprehensive understanding of hillslope hydrological dynamics and factors influencing spatial and temporal SSF patterns is essential for upscaling and model validation. Linked to hillslope hydrology is the export of organic carbon to streams, yet spatial carbon sources remain unclear due to limited knowledge of SSF flow paths within slopes.

We propose a hydro-biogeochemical approach, measuring water-soluble organic matter (WSOM; concentration, absorbance, and fluorescence) at 480 locations across 100 hillslopes in four contrasting catchments (Sauerland, Ore Mountains, Black Forest, Alps). This approach aims to establish empirical relationships between landforms, bedrock, and soil properties, quantifying spatial variability and stability of subsurface hydrological processes (e.g., flow directions, transit times, hydrochemical and biochemical composition).

Distributed sampling of WSOM along soil profiles (6 samples per profile) will assess vertical and lateral subsurface flow paths in unsaturated and saturated zones, aiding spatial discretization of SSF source areas.

Preliminary results will provide depth profiles of WSOM in the four catchments spanning low to high mountain ranges (Sauerland, Ore Mountains, Black Forest, Alps), facilitating the detection of SSF source areas.

How to cite: Chifflard, P., Fasching, C., Schadewell, Y., and Leese, F.: Identifying the source areas of subsurface stormflow through the analysis of depth profiles of water-soluble organic matter, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4588, https://doi.org/10.5194/egusphere-egu24-4588, 2024.

EGU24-5045 | ECS | Posters on site | HS2.2.5

Insights into Subsurface Stormflow Dynamics using multitracer approaches 

Jonas Pyschik, Alexey Kuleshov, Christina Fasching, Peter Chifflard, Theresa Blume, Luisa Hopp, and Markus Weiler

Subsurface stromflow (SSF) is an important runoff generation mechanism in hillslope catchments. However, since the process occurs below ground, it is difficult to observe and measure. So far, the dynamics and thresholds of SSF occurrence remain elusive.

To gain insights into the mechanisms and to determine SSF quantities and their dynamics, we installed three SSF trenches in a first-order catchment in the Black Forest, Germany. We selected hillslopes with different landuse and topography and excavated slope-perpendicular trenches to bedrock (approx. 15 m wide, 2.5 m deep). The trenches are split by soil depth to collect subsurface flow from a top and from a bottom layer. The flow is channeled to tipping buckets for measuring discharge, and autosamplers for semi-continuous water sampling. The water samples are then used to measure multi tracers like stable water isotopes, dissolved organic carbon as well as major anions and cations.

In November and December 2023, the catchment experienced three extreme, multi-day rainfall events. The generated subsurface discharge showed distinct differences in volume among the trenches (up to 100% of upslope-area-corrected flow volume). Most flow (70-90%) occurred in the lower trench sections. Top layer flow was only activated during peak discharge in the bottom layer. Using the multitracer approach, we can gain first insights into the dynamics of the different natural tracers and relate them to the observed subsurface flow variations, possible flow pathways and transit times. Ultimately, we aim to compare these findings to data from three other trenched research catchments to gain a more general understanding of the underlying subsurface stormflow generation mechanisms.

How to cite: Pyschik, J., Kuleshov, A., Fasching, C., Chifflard, P., Blume, T., Hopp, L., and Weiler, M.: Insights into Subsurface Stormflow Dynamics using multitracer approaches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5045, https://doi.org/10.5194/egusphere-egu24-5045, 2024.

Sensitivity analyses are an important component of modeling test, which represents the process of evaluating the sensitivity of groundwater flow to changes in hydraulic parameters. This can useful to understand the operating rules of the groundwater system. The major research area including regulating the transport of hydrogeological contamination, planning groundwater protection measures before land development and managing groundwater resources.

In this study, we choose to use the adjoint equation method to conduct the sensitivity analysis of the simulation field, which is used to analyze the sensitivity of the head to the model parameters (transmissivity and storativity) in the case of pumping under a two-dimensional transient heterogeneous groundwater parameter field. we will also consider the spatial correlation of the parameter field, which is often ignored in previous literature. In groundwater sensitivity analysis, spatial correlation can effectively improve the efficiency of the analysis and reduce the total computational cost in the adjoint equation method.

And then we will perform dimensionless analysis on the analytical solution that has been derived. This will make the analysis method no longer affected by the physical meaning, so that the equation can be applied to different situations without the need to re-derive or calculate, thus increasing the application range of the model.

The results will be numerically verified with the VSAFT2 numerical model, which is developed based on the adjoint method. A multi-well work area will be created that can simultaneously calculate the sensitivity coefficient change rate of multiple observation wells and a single pumping well. This will help to more effectively simulate the water flow and sensitivity at the field pumping site, and effectively expand the results of previous literature that only studied dual-well experiments. 

How to cite: Kuo, J.-T. and Wen, J.-C.: Analysis and Research on Hydraulic Characteristic Parameters and Related Sensitivity Changes of Groundwater Layers during Pumping Tests, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5114, https://doi.org/10.5194/egusphere-egu24-5114, 2024.

In this work, the parallel and fully integrated coupled hydrologic model Parflow-CLM was used to simulate the water and energy fluxes in a 4.2 km2 mountainous headwater catchment in the Odenwald, Germany, for a period of three years at hourly resolution. First, to establish the most time-efficient configuration of the model able to describe the observed discharges of the catchment, different definitions of the numerical domain for a fixed set of parameters along with different horizontal and vertical grid resolutions were compared. Second, with the purpose of achieving a calibrated state of the model, hydraulic soil parameters such as saturated hydraulic conductivities, Van Genuchten parameters, Manning coefficients, and anisotropy factors were optimized. In addition, the influence of the spin-up period was investigated, whereby an spin-up period of eight years was required for each simulation, despite the high computational effort involved, as the different model configurations result in different initial conditions. Finally, computational efforts, subsurface and surface storages, and statistical error measurements related to observed streamflow will be presented, aiming to provide some recommendations to the community about the required complexity for the calibration of complex integrated hydrological models.

How to cite: Muñoz-Vega, E., Bogena, H., and Schulz, S.: Influence of geometry, grid resolution, initial conditions and hydraulic soil parameters for the integrated coupled hydrological model Parflow-CLM, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6830, https://doi.org/10.5194/egusphere-egu24-6830, 2024.

Streamflow represents the hydrological output behavior of the catchment system and can elucidate the physical processes of other hydrological variables, such as rainfall–runoff processes and storage–discharge dynamics. Understanding streamflow dynamics not only enhances comprehension of complex hydrological processes and influencing factors, but also aids in estimating potential hydrological conditions in ungauged areas. In this study, we explored the differences in the flow duration curve (FDC) structure of streamflow components, ranging from slow to fast, using multiple hydrograph separation. Additionally, we analyzed the recession index and recession parameters of individual recession segments to characterize the storage-discharge dynamics based on the linear and nonlinear reservoir assumptions, respectively. We applied an analytical probabilistic streamflow model to determine which structure better aligns with the model’s physical basis, assuming streamflow generation from groundwater discharge when a sequence of rainfall events increases soil moisture beyond the retention capacity. It also provides estimations of optimal recession parameters for comparison with individual recession segment results. The recession analyses and multiple streamflow components separation revealed differences in dominant recession index, recession parameters, and streamflow complexity between catchments, highlighting their relationships with catchment characteristics. Recession parameters from FDCs with different components demonstrated the storage–discharge mechanisms associated with changes in streamflow components. The conformity of multiple streamflow component structures to the model’s basic assumptions can be evaluated through the model performance, contributing to an understanding of streamflow component structures in catchments and their relevance to specific streamflow generation mechanisms.

How to cite: Huang, C.-C., Yeh, H.-F., and Yang, Y.-S.: Effect of Streamflow Component Structure on Characterizing Storage–Discharge Dynamics in an Analytical Probabilistic Streamflow Model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6990, https://doi.org/10.5194/egusphere-egu24-6990, 2024.

EGU24-7599 | Posters on site | HS2.2.5

Revealing spatial patterns of lateral hydraulic conductivity through sensitivity analysis of wflow_sbm  

Albrecht Weerts, Awad mohammed Ali, ruben Imhoff, and Willem van Verseveld

Moving toward high-resolution gridded hydrologic models asks for novel parametrization approaches. The use of transfer functions and advances in scaling and regionalization play an important role to ensure flux matching across scales. However, for some processes no transfer functions are yet available or simplified approaches, such as a fixed vertical-to-horizontal saturated hydraulic conductivity ratio, are being used. To get insight into the spatial variability of the vertical-to-horizontal saturated hydraulic conductivity ratio we performed a sensitivity analysis on one parameter of the wflow_sbm model across England, Wales and Scotland exploiting the CAMELS-GB dataset. The wflow_sbm models were setup using reproducible workflows based on HydroMT (https://deltares.github.io/hydromt/stable/) for each CAMELS-GB basin.  To investigate the sensitivity to rainfall forcing all derived wflow_sbm models were first run using a default ratio of 100 with both EOBS and CEH GEAR rainfall data. The sensitivity analysis was only based on the high quality CEH GEAR rainfall dataset. In the sensitivity analysis, the vertical-to-horizontal saturated hydraulic conductivity ratio was varied over a large range from 1 – 10,000 and results were assessed using the non-parameteric KGE (which focuses more on recession/baseflow performance). Even with a fixed uniform vertical-to-horizontal saturated hydraulic conductivity ratio results show a big impact of the precipitation forcing on the model results.  The uncertainty analysis shows that wflow_sbm model results have a high sensitivity to the vertical-to-horizontal saturated hydraulic conductivity ratio. For the optimal ratios, we obtain high KGE values (median=0.84). In addition, when plotting the optimal ratios across the GB clear patterns emerge that seem to coincide with geological features. The resulting optimized lateral saturated hydraulic conductivity values seem realistic when compared with literature values. When compared to Grid2Grid model results the wflow_sbm model shows similar performance for most stations. However, for parts in the south of the England where the geology consists of chalk, the performance of Wflow_sbm is poor, but this is likely caused by the used soil depth map when constructing the models which limits the soil depth often to 30-60cm while it is known that the chalk below the soil is also hydrologically active. 

How to cite: Weerts, A., Ali, A. M., Imhoff, R., and van Verseveld, W.: Revealing spatial patterns of lateral hydraulic conductivity through sensitivity analysis of wflow_sbm , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7599, https://doi.org/10.5194/egusphere-egu24-7599, 2024.

EGU24-8263 | ECS | Posters on site | HS2.2.5

Performance assessment of a conceptual model to simulate fluxes in the unsaturated zone to better represent runoff and infiltration processes 

Veethahavya Kootanoor Sheshadrivasan, Jakub Langhammer, Lukáš Vlček, and Václav Šípek

In continuation to the previously presented methodological approach to estimate vadose zone boundary fluxes titled “A novel conceptualization to estimate unsaturated zone mass-fluxes and integrate pre-existing surface- and ground- water models” at the EGU GA 2022, and the performance assessment thereof showcased at the EGU GA 2023, titled “Performance assessment and Benchmarking of a conceptually coupled groundwater - surface-water model”, this study aims to assess the performance of the proposed methodology to couple surface- and ground- water models aims to investigate its local performance in a soil-column by comparing the results of a controlled simulation with that of HYDRUS-1D.

 

To recap, the initial study presented a conceptual numerical scheme that aimed to adequately estimate the in- and out- fluxes of the Unsaturated Zone (UZ) with the primary aim of coupling existing groundwater (GW) and surface-water (SW) models. It was expected that such a numerical scheme would provide a viable alternative to solving the computationally expensive Richard’s model for cases where description of fluxes within the UZ and the spatial description of the soil moisture were not in the interest of the modeller. Examples of such cases would be efforts to model the hydro(geo)logical effects of various climate-scenarios, efforts to estimate GW recharge dynamically, and efforts to design integrated watershed management design structures and systems, among others.

 

The model, and in effect, the methodology, established its capacity to simulate the fluxes of the UZ for the Tilted-V theoretical catchment setup during its comparison against the physically based ParFlow model, in the previous study. However, it also did demonstrate certain crucial shortcomings that arose from the nature of the coupling scheme (loose coupling - where the models ran consecutively until the end of a timestep, exchanged information, and continued so and and so forth until the end of the simulation period) used to couple the two GW and SW models.

 

In this study, the authors aim to more effectively assess the methodology, by attempting to simulate a real-world scenario of transport of water fluxes in the subsurface of a Spruce/Beech Stand in a Peatland experimental site in the Bohemian Forest region of Czechia. The model setup involves the simulation of fluxes in a 1D soil profile using the said methodology and also using the HYDRUS-1D modelling software and comparing the results of the two models and the results with observations. It is expected that such a setup should provide a robust assessment of the methodology. The discussion shall be an extensive analysis of the obtained results.

 

The authors also hope that the study fosters discussions to unify the polarising modelling approaches as outlined in Markus Hrachowitz er al., 2017.

How to cite: Kootanoor Sheshadrivasan, V., Langhammer, J., Vlček, L., and Šípek, V.: Performance assessment of a conceptual model to simulate fluxes in the unsaturated zone to better represent runoff and infiltration processes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8263, https://doi.org/10.5194/egusphere-egu24-8263, 2024.

EGU24-8814 | ECS | Orals | HS2.2.5

Integrating High-Resolution Tracer Data with Soil Moisture and Precipitation Dynamics to Characterize Streamflow Age Distribution in a Headwater Catchment 

Hatice Turk, Markus Hrachowitz, Karsten Schulz, Peter Strauss, Günter Blöschl, Christine Stumpp, and Michael Stockinger

The partitioning of rainfall into different hydrological components, such as lateral subsurface flow,  overland flow, and soil water storage, is essential for understanding and predicting streamflow responses and contaminant transport. This study investigates flow processes within shallow sub-surface layers and streamflow responses in an agricultural headwater catchment by utilizing high-resolution data of oxygen (δ18O) and hydrogen (δ2H) stable isotopes of water. We used weekly data from grab and event streamflow samples (ranging from 15 minutes to 2 hours based on the anticipated event length) in a tracer-based transport model to estimate water travel times and examine how catchment characteristics and climate factors influence storage water release and travel time distributions with a StorAge Selection function approach. We tested two conditions for the activation of preferential flow paths: i) based on soil moisture only, and ii) based on both soil moisture and precipitation intensity. The results show that calibrating a tracer-based transport model, coupled with soil moisture and precipitation intensity data, improve the tracer simulation of quick responses in stream flow (increase in Nash-Sutcliffe Efficiency from 0.21 to 0.51) and can greatly enhance the accuracy of streamflow age distribution estimates in headwater catchment compared to using soil moisture data only. Particularly in summer months with intense precipitation, the catchment shows dominant infiltration-excess overland flow processes resulting in young water to reach to the stream. The results also demonstrate that during wet conditions, a significant portion of event water bypasses through fast flow paths. These results highlight the importance of tracer data in understanding the interplay between catchment characteristics, rainfall intensity, and water storage release.

How to cite: Turk, H., Hrachowitz, M., Schulz, K., Strauss, P., Blöschl, G., Stumpp, C., and Stockinger, M.: Integrating High-Resolution Tracer Data with Soil Moisture and Precipitation Dynamics to Characterize Streamflow Age Distribution in a Headwater Catchment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8814, https://doi.org/10.5194/egusphere-egu24-8814, 2024.

Non-perennial streams, i.e., rivers that periodically cease to flow, are the focus of increasing research attention. Understanding how the spatiotemporal dynamics of runoff generation drives expansions and contractions of their active stream network is still challenging, due to the complex interplay among climate, topography, and geology. In this context, experimental data on the spatiotemporal variations of the wet channels of a river network are very valuable to study the joint variations of active stream length (L) and discharge at the catchment outlet (Q) and to analyze the processes driving such complex L-Q patterns. However, experimental data usually do not provide insights on what happens below the catchment surface; therefore, important insights can be gained by integrated surface-subsurface hydrological modeling (ISSHM), whereby the spatial configuration of the wet channels, the corresponding catchment discharge and the processes that drive the wetting and drying of different portions of the stream network can be simulated across the whole surface-subsurface continuum. In this study, we used CATHY (CATchment HYdrology) to simulate the stream network dynamics of two virtual catchments with the same, spatially homogeneous, subsurface characteristics (hydraulic conductivity, porosity, water retention curves, depth to bedrock) but different morphology (shape and slope). By running simulations under transient and steady-state conditions for different levels of antecedent catchment wetness, we investigated the role of topography, climate, and morphology on the resulting L-Q relation and on the processes that lead to the emergence of wet channels while comparing the numerical results with corresponding outcomes from simplified analytical formulations. Overall, we show that ISSHMs are useful tools to identify the main physical drivers of non-perennial streams, thanks to their capability of accurately describing the spatiotemporal variations of the storages and fluxes across the landscape, which eventually control network dynamics.

How to cite: Zanetti, F., Botter, G., and Camporese, M.: Looking below the ground: analyzing the processes that drive spatiotemporal variation of wet channels in dynamic river networks using a physics-based hydrological model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10046, https://doi.org/10.5194/egusphere-egu24-10046, 2024.

EGU24-10603 | Orals | HS2.2.5

Exposing Seasonal and Spatial Variability in Storage and Release Upstream of the Outlet 

Natalie Ceperley, Sabina Kurmann, Anna Meier, Martine Helfer, and Bettina Schaefli

Understanding the seasonal interplay of subsurface storage and release of water is critical to drought risk assessment in alpine environments because of the substantial carry-over effects of snow. Spatial variation across the catchment and its compartments governs the seasonal interplay and can shift dramatically according to annual fluctuations in snowfall. This analysis investigates the interaction between scale and yearly anomalies in assessing seasonal patterns of storage and release interpreted through the annual stable isotope signal (δ2H, δ18O, and δ17O) within the Vallon de Nant catchment in the Swiss Alps. We explore the limitation of simplifying catchment processes to a single outlet that integrates upstream water storage and release but overlooks nuanced variations within different compartments, including upstream springs, tributaries, near-surface groundwater, and vegetation (Larix decidua) and years with more and less snow.

Furthermore, using a mixing model, we explore the effects of seasonal precipitation dynamics by examining the summer-to-winter precipitation ratio based on the variation of stable isotopes (δ2H, δ18O, and δ17O) within these distinct compartments and across multiple observation years. Notably, our findings highlight a pronounced anomaly in the fraction of summer-to-winter precipitation within springs, particularly following the snow-drought year of 2022. This observation raises critical questions regarding the long-term sustainability of groundwater resources in alpine regions. To ascertain the broader implications of this drought-induced anomaly, we extend our investigation to include 51 National Groundwater Monitoring (NAQUA) sites across Switzerland to assess the potential recurrence of this phenomenon on a broader scale.

How to cite: Ceperley, N., Kurmann, S., Meier, A., Helfer, M., and Schaefli, B.: Exposing Seasonal and Spatial Variability in Storage and Release Upstream of the Outlet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10603, https://doi.org/10.5194/egusphere-egu24-10603, 2024.

Reliable quantification of subsurface dynamics in catchment hydrological models largely depends on good estimates of soil hydraulic properties which influence subsurface runoff generation, flows and storage. In most hydrological modelling concepts, the saturated hydraulic conductivity (Ksat) is a key parameter that controls the vertical transfer of water through the soil layers and the lateral subsurface flow. Ksat values are derived from direct measurements, literature, or available soil datasets, most of which do not reach depths beyond 2 or 3 m. This is one of the common motivations for limiting the soil column to shallow depths in most catchment models. This study investigates the model schematization of Ksat in an extended soil column, where Ksat measurements are absent, and the ensuing impacts on catchment hydrological functioning. The motivation is to determine a suitable modelling approach for catchments with deeper soil columns to sufficiently capture the subsurface, including the groundwater, and the feedback with the surface.

Different Ksat–depth relationships were conceptualized and implemented in the distributed hydrological model wflow_sbm. Most wflow_sbm applications so far have used a standard soil column thickness of 2.0 m and an exponentially declining Ksat with depth. The different Ksat schematizations were tested in the Dutch-German catchment Vecht where the model soil column was extended to capture the groundwater system.

The results reveal the impact of an extended soil column and the different Ksat schematizations on catchment water balance, surface and subsurface flows, and water table depths. Varying changes were observed among the different Ksat schematizations but all produced generally good, and in some cases improved, model performance when compared with observations of river discharge and water table depth. The results demonstrate the suitability of extending the soil column and applying the different vertical Ksat–depth relationships in catchment hydrological models.

How to cite: Mendoza, R., Weerts, A., and van Verseveld, W.: Assessment of saturated hydraulic conductivity-depth relationships and extended soil column thickness in catchment hydrological modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11384, https://doi.org/10.5194/egusphere-egu24-11384, 2024.

EGU24-11740 | ECS | Posters on site | HS2.2.5

Biological connectivity indicates hydrological flow pathways in the subsurface 

Yvonne Schadewell, Sören Köhler, Peter Chifflard, and Florian Leese

Extreme rainfall events are likely to increase in intensity and frequency due to climatic changes and therefore the forecast of flooding events will become more important in the following decades. The flow properties of rainwater in the subsurface play a critical role in the flood formation process, but the underlying mechanism of this subsurface stormflow (SSF) formation has not been fully understood so far. Here, we explore the viability of environmental DNA (eDNA) as an indicator for small-scale flow pathway reconstruction. eDNA comprises genetic signatures from organisms across the Tree of Life (ToL), from whole microorganisms to molecular traces of higher taxa, such as plants or animals. The degree of similarity of biodiversity patterns indicates biological and therefore, in principle, also hydrological connectivity. As part of the SSF Research Unit we characterised 3 trenched hillslopes in 4 catchment areas in Germany and Austria through eDNA ToL-metabarcoding. With this broad-range approach, we aim to understand whether and how eDNA diversity patterns can inform subsurface flow pathways. We found three-dimensional connectivity patterns of biodiversity indicating systematic barriers as well as pathways of hydrological connectivity within each hillslope. Variation between catchments reflects their geographic differences as well as geological peculiarities. Although our results support the potential of eDNA to identify flow pathways and enhance our understanding of SSF, we are still at the beginning of understanding the viability of eDNA as a tracer in hydrological research. Nonetheless, making use of such natural occurring tracers can extend our understanding of hydrological phenomena and can contribute to a more accurate flood prediction.

How to cite: Schadewell, Y., Köhler, S., Chifflard, P., and Leese, F.: Biological connectivity indicates hydrological flow pathways in the subsurface, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11740, https://doi.org/10.5194/egusphere-egu24-11740, 2024.

EGU24-12256 | Orals | HS2.2.5

Antecedent soil moisture conditions and receiving rainfall predict high streamflow in flashy watershed in Hawaiʻi 

Yinphan Tsang, Maxime Gayte, Yu-Fen Huang, and Yen-Wei Pan

Extreme events such as heavy precipitations and associated floods often have devastating consequences on societies and ecosystems. However, extreme rainfall alone is not the sole driver that results in high flow. Previous studies highlighted that annual maximum daily rainfall exhibits inconsistency with annual peak discharge in their occurrence timing in Hawaiʻi. The mechanism of runoff generation and, therefore, consequential storms and floods remain unclear. In this study, we investigated the linkage between extreme rainfall and high discharge events. Rainfall, soil moisture, and discharge data, in one watershed on Oahu and one on Maui were used in this study. We defined antecedent soil moisture conditions using Antecedent Soil Moisture Indexes (ASI) calculated from soil moisture data. We compared the timing of the occurrence of annual maximum hourly or accumulated (from three to twelve hours) rainfall and annual peak discharge. Then, we estimated the timing of high-flow events based on antecedent soil moisture conditions and maximum hourly rainfall. Multi-linear regressions were used to estimate high-flow event timing. Finally, we compared these estimates with the actual high-discharge events. We found out that the consistency between the timing of maximum rainfall and the timing of annual peak flow did not improve when we used hourly or accumulated hourly rainfall. Nevertheless, the consistency improved when we included antecedent soil moisture conditions by including ASI. We successfully estimated the occurrence timing of majority high-flow events at the site on Oahu and at the site on Maui. These accurate estimations emphasize the importance of incorporating soil moisture with hourly rainfall to estimate high discharge events and increase our understanding of flood events induced by extreme rainfall in Hawaiʻi.

How to cite: Tsang, Y., Gayte, M., Huang, Y.-F., and Pan, Y.-W.: Antecedent soil moisture conditions and receiving rainfall predict high streamflow in flashy watershed in Hawaiʻi, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12256, https://doi.org/10.5194/egusphere-egu24-12256, 2024.

EGU24-13242 | ECS | Orals | HS2.2.5

Controls on soil moisture variability on two Mediterranean hillslopes during dry and wet periods using wavelet coherence analysis 

Ilenia Murgia, Konstantinos Kaffas, Matteo Verdone, Francesca Sofia Manca di Villahermosa, Andrea Dani, Federico Preti, Christian Massari, Catalina Segura, and Daniele Penna

Although topography and evapotranspiration rates are the main determinants of soil moisture, climatic forcings play a crucial role. In the Mediterranean climate, the marked sensitivity of soil moisture to alternations between wet and dry periods exerts a strong control on hydrological and ecohydrological processes at the hillslope and catchment scales.

We monitored soil moisture in two hillslopes in the Re della Pietra experimental catchment, Appennine mountains, Tuscany, central Italy. The two hillslopes (HS1 and HS2) show different morphological characteristics, such as elevation (≅ 670m asl for HS1 and 940m asl for HS2), slope (≅ 26° for HS1 and 36° for HS2), and tree composition (fruit chestnut grove converted into coppice in HS1 and pure beech forest in HS2). For two years, soil moisture was measured in each hillslope, at three different positions and two different depths (15 and 30 cm) along a longitudinal transect. We used wavelet coherence analysis to evaluate the dominant factors controlling soil moisture variability in the two hillslopes during dry and wet periods.

Preliminary results reveal a clear coupling of soil moisture at 15 cm and 35 cm on both hillslopes during wet periods, indicating a relatively homogeneous soil water content across the two depths. Conversely, a decoupling occurs during dry periods when soil moisture values at 35 cm are greater than those at 15 cm, reflecting significant solar radiation, atmospheric demand, and tree water uptake from shallow soil layers. During dry periods, we observed significant differences in soil moisture between the two depths in HS1 compared to HS2, suggesting that local conditions affect hillslope-scale soil moisture response.

Ongoing analyses investigate the role of rainfall, solar radiation, vapor pressure deficit, and tree transpiration on soil moisture spatio-temporal variability on the two hillslopes.

How to cite: Murgia, I., Kaffas, K., Verdone, M., Manca di Villahermosa, F. S., Dani, A., Preti, F., Massari, C., Segura, C., and Penna, D.: Controls on soil moisture variability on two Mediterranean hillslopes during dry and wet periods using wavelet coherence analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13242, https://doi.org/10.5194/egusphere-egu24-13242, 2024.

EGU24-13275 | ECS | Orals | HS2.2.5

Seasonal variability of surface run-off, recharge and soil moisture dynamics in lowland catchments 

Mahdi Miri, Helena Galys, Christof Hübner, Martin Sauter, Felix Becker, and Irina Engelhardt

For an effective water resources management in regions faced with scarcity understanding infiltration dynamics in the unsaturated zone at a high temporal-spatial resolution is essential for quantifying stored water volumes in the vadose zone.

Our pilot-site (area 790 km²) is the Lower Spree catchment, located E of Berlin, Germany.This area is characterized by a continental climate and a low water supply compared to other German states. Increasing industrial water-use (e.g.Tesla factory) and increased irrigation demand causes conflicts over water availability for the different water user.Three aquifers(GWL 1 to 3)in the Lower Spree consist of sands and gravel-sands. Since 1980, the groundwater level in all aquifers has collectively dropped by 5m. The planned phase-out of coal mining up-stream of Berlin will reduce the discharge of the river Spree by 50-75%. With an average precipitation of 549 mm/y,average recharge decreases to 114 mm/y. Landuse varies between forests(46%) and grasslands(20%).The soil types range from Histosols and Fluvisol and are followed by an unsaturated zone's thickness varying from 5 to over 50m.  

We installed in pilot site 8 pressure-sensors in lakes, 12 pressure-sensors in streams, 8 pressure-sensors in groundwater observation wells and 21 Time Domain Reflectometry (TDR)sensors at various depths (25, 50 and 75 cm)in the unsaturated zone within different soil types and landuse.

Hydrological regimes,in ground and surface water, are affected by a high seasonal variability. Approximately 35% of the river discharge results from baseflow, which feed lakes and ecosystems. Comparison between coniferous forest-dominated and grassland-dominated areas shows that coniferous- forest plays a crucial role in attenuating streamflow variability.Lag-times between precipitation and discharge response are similar for both landuse(2-4 days).However, coniferous-forests result in decreasing river discharge during and immediately after precipitation.

Due to the shallow thickness of unsaturated-zone(<10m) in the southern, groundwater levels in both GWL 1 and 2quickly respond with a lag-time of 25-65 days to precipitation. The northern and central areas, characterized by a deeper unsaturated-zone(>15m)and the lag-time increases to 96-153 days.The groundwater flow system provides a highly relevant water resource for rivers and lakes and due reduced baseflow(35% of the discharge)and the short lag-time of a few days summer periods and droughts with limited precipitation results in a drying of streams and enormous lake level drop.5 streams dried from (May-August),also 7 streams and 5 lakes exhibited declining water levels from(winter-summer).

Soil Moisture Active Passive(SMAP)satellite estimates near-real time surface soil-moisture(5 cm-depth) and root zone soil-moisture(1 m-depth)with 9 km resolution.We compared SMAP with our measured soil moisture obtaining correlation-coefficients of(0.31-0.63).Higher soil-moisture values are observed in grassland and peat-soil.The soil-moisture curves indicate that the soils below coniferous-forests have a larger capacity to store and release water than those below in grassland.Based on these measurements we will be able to design a sophisticated water management concept:using the surplus of discharge during autumn,winter and store it our lakes.For the later infiltration into the unsaturated zone and groundwater we can identify regions with i)optimal storage capability of the vadose zone,ii)best protection of the artificially enriched groundwater from evapotranspiration loss.iii) maximum storage volumes,and iv) minimum discharge loss into lakes and streams.

How to cite: Miri, M., Galys, H., Hübner, C., Sauter, M., Becker, F., and Engelhardt, I.: Seasonal variability of surface run-off, recharge and soil moisture dynamics in lowland catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13275, https://doi.org/10.5194/egusphere-egu24-13275, 2024.

EGU24-14582 | ECS | Orals | HS2.2.5

Lessons from a decade-long drought and non-recovery: hydrological processes understanding and modelling 

Margarita Saft, Murray Peel, Timothy Peterson, Keirnan Fowler, Luca Trotter, and Hansini Weligamage

Prolonged changes in climatic conditions can induce unexpected shifts in catchment hydrologic functioning due to the indirect impact of catchment adaptation on streamflow. In a multiyear drought, streamflow can be reduced significantly more than expected from the typical response to the same annual precipitation. For example, the same annual rainfall in the first and the tenth years of a dry period is likely to result in significantly lower streamflow during the tenth year than in the first year. Such hydrological shifts were first detected in Australia during the Millennium Drought (1997 – 2009). Since then, similar shifts were also reported in studies from other continents. Subsequently, it was also discovered that catchments, once they shift their hydrologic behaviour, may not necessarily recover back to the pre-drought behaviour even after record-breaking floods and years of annual rainfall similar to the pre-drought conditions. Observed shifts not only challenge some common assumptions of long-term hydrologic functioning but also present an interesting practical problem as hydrological models tend to reproduce historic behaviour and systematically overestimate the streamflow when the hydrologic shifts occur. Here we present the results from a large collaborative project in Australia devoted to two questions (1) which hydrological processes are responsible for the observed shifts and (2) how to improve our hydrological models to provide robust predictions under non-stationary climate? We hope that the lessons from the Millennium drought and post-drought period will be helpful in the other parts of the world where similar hydrological shifts were or will be observed.

How to cite: Saft, M., Peel, M., Peterson, T., Fowler, K., Trotter, L., and Weligamage, H.: Lessons from a decade-long drought and non-recovery: hydrological processes understanding and modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14582, https://doi.org/10.5194/egusphere-egu24-14582, 2024.

EGU24-18248 | Posters on site | HS2.2.5

Spatial patterns and temporal dynamics of subsurface hillslope-stream connectivity 

Theresa Blume, Natasha Gariremo, Anne Hartmann, Alexey Kuleshov, Ilja van Meerveld, and Luisa Hopp

Subsurface hillslope-stream connectivity is a major control on runoff-generation and catchment storage dynamics. However, detecting this connectivity is challenging, as processes in the subsurface are not easily observable. Furthermore, we are faced with a high spatial variability as well as pronounced temporal dynamics.

In this context, we are investigating three catchments in German mid-mountain ranges: Black Forest, Ore Mountains and Sauerland. The experimental design consists of three trenched hillslopes per catchment as well as numerous observation wells and stream gauges along the stream. Water samples are taken at all locations during snapshot campaigns and are analyzed for major cations and anions to complement event-based sampling at the trenches and in the stream. This comparative design aims at moving beyond single-site insights to gaining a broader view of the process and its spatio-temporal patterns. First observations of these patterns based on physical and chemical signals of subsurface connectivity are presented.

How to cite: Blume, T., Gariremo, N., Hartmann, A., Kuleshov, A., van Meerveld, I., and Hopp, L.: Spatial patterns and temporal dynamics of subsurface hillslope-stream connectivity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18248, https://doi.org/10.5194/egusphere-egu24-18248, 2024.

EGU24-18826 | ECS | Posters on site | HS2.2.5

Influence of rainfall event characteristics on the subsurface stormflow response: a multi-site analysis 

Emanuel Thoenes, Bernhard Kohl, Markus Weiler, and Stefan Achleitner

In many natural landscapes, subsurface stormflow (SSF) is a runoff-producing mechanism which can substantially contribute to the storm hydrograph of a stream. Despite its importance, its complex and highly dynamic nature have hindered its conceptualization and integration in most hydrological models. The lack of general rules to describe SSF is partly linked to the fact that SSF studies are often conducted at only one specific site or analyze only a handful of storm events. In the quest to gain a better understanding of the processes governing SSF, multiple SSF-capturing trenches have been excavated on intensely instrumented hillslopes characterized by different land uses, geology, soils and climates. The trenches are 10-15 m wide and 2-3 m deep and are vertically divided into an upper and lower flow-capture zone, which allows to study SSF at different depths. At the sites, SSF was continuously recorded over a period of ca. 1.5 year, during which numerous rainfall events occurred. This study analyses how the different rainfall event characteristics (e.g. total rainfall, intensity, etc.) influence the SSF response and to what degree the relationships between rainfall and SSF event characteristics are affected by the initial subsurface conditions (i.e. initial trenchflow and initial water content).

How to cite: Thoenes, E., Kohl, B., Weiler, M., and Achleitner, S.: Influence of rainfall event characteristics on the subsurface stormflow response: a multi-site analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18826, https://doi.org/10.5194/egusphere-egu24-18826, 2024.

EGU24-22500 | Posters on site | HS2.2.5

Understanding low-flow periods based on river and aquifer recessions using a sequential groundwater-surface water modelling approach 

Lemuel Ramos, Daniel Paradis, Erwan Gloaguen, Louis-Charles Boutin, and René Lefebvre

Low-flow periods are a seasonal component of a river regime characterized by a reduction in discharge. This recession phenomenon is associated with water shortages and quality problems that are detrimental to communities and ecosystems that rely on groundwater-fed rivers. This paper presents a methodology to understand the dynamics of low-flow periods by utilizing the information contained in the response of the river-aquifer system during recessions. The methodology is developed and applied to the 5000 km2 Yamaska River watershed in Quebec (Canada), where critical low-flow conditions are frequently observed in winter and summer, and where the heterogeneous nature of the geology can lead to complex interactions between the rivers and the aquifer. Multiple water table and streamflow recession events recorded over a period of 20-50 years at 16 monitoring wells and 22 gauging stations were combined to obtain an averaged recession response at each location, referred to as the master recession curve (MRC). An MRC, which is minimally influenced by precipitation and evapotranspiration processes, contains important information about the flow and storage characteristics of an aquifer and its connection to rivers. Moreover, MRCs from wells and gauging stations provide complementary information. The recession-based analysis provided a tenable framework to disregard the surface modelling component at this stage since, during the depletion periods, the system is minimally influenced by atmospheric processes. A sequential modelling approach was devised to construct an integrated hydrological model using the HydroGeoSphere simulator to capture the groundwater-surface water interactions during low flows. First, the hydraulic characteristics of the subsurface were derived from the MRCs by history matching with the model in fully saturated mode. With the subsurface domain characterized, the rest of the processes were parameterized to capture the observed groundwater and surface water hydrographs using the fully integrated model. Beyond elucidating the low-flow dynamics, this methodology showcases efficiency due to its sequential strategy, alleviating the inherent computational burdens of setting up integrated models. This communication presents the outcomes from conceptual and numerical analyses, contributing to understanding hydrologic systems under low-flow conditions.

How to cite: Ramos, L., Paradis, D., Gloaguen, E., Boutin, L.-C., and Lefebvre, R.: Understanding low-flow periods based on river and aquifer recessions using a sequential groundwater-surface water modelling approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22500, https://doi.org/10.5194/egusphere-egu24-22500, 2024.

EGU24-164 | ECS | PICO | HS2.2.6

What is more important for model calibration: information on the discharge dynamics or information on the discharge volume? 

Franziska Clerc-Schwarzenbach, Ilja van Meerveld, Marc Vis, and Jan Seibert

Previous studies have shown that information on the discharge dynamics (e.g., variation in the water level) is valuable to constrain the parameters of a lumped hydrological model for some catchments, and that information on the discharge volume further improves model performance for most catchments. It has been suggested that for some catchments an estimate of the mean discharge already leads to a good model fit but so far, there have not been any systematic studies to test this. Therefore, it remains unclear for which catchments (i.e., for which regions or for catchments with specific characteristics) information on the discharge dynamics are most valuable for model calibration, for which catchments an estimate of the mean annual discharge is already sufficient, and for which catchments both data sources are needed for model calibration. Therefore, we used a subset of the Caravan large-sample dataset and assessed the value of water level measurements, estimates of the mean discharge, and both data sources together for the calibration of a simple bucket-type hydrological model. Preliminary results suggest that mainly climatic characteristics determine the relative value of the different data types for hydrological model calibration. This type of assessment of the value of data for a wide range of catchments allows for more optimal allocation of resources when it comes to obtaining limited data for the calibration of hydrological models for ungauged catchments.

How to cite: Clerc-Schwarzenbach, F., van Meerveld, I., Vis, M., and Seibert, J.: What is more important for model calibration: information on the discharge dynamics or information on the discharge volume?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-164, https://doi.org/10.5194/egusphere-egu24-164, 2024.

Risks to the planet's freshwater systems are currently subjected to soaring concern worldwide. We applied the coupled Social-Ecological Systems approach to study and systematize the risks due to ten major water related stressors (variability, overuse, groundwater, floods, droughts, organic pollution, salinity, eutrophication, drinking water, sanitation). We used gridded socioeconomic indicator data for the analysis of human exposure and its vulnerability (adaptive capacity) to these stressors in 540 river basin units covering the whole world. Among the stressors, lack of appropriate sanitation scored highest, followed by droughts and eutrophication. The large and densely populated Asian basins, Ganges-Brahmaputra-Meghna, Indus, and Yangtze, topped, followed with the largest African basins (the Nile, Niger, and Congo/Zaire). The other top-ten basins were Rajasthan Inner Basins, Huang, Hai, and Myanmar South Coastal Basins. The ranking changed when weighting the stressor data (on physical entities) with socioeconomic vulnerability data (on societal ones). Each included basin unit manifested a specific risk profile. For the basin units, we developed a typology using principal component and cluster analyses. This allowed us identification of the roles of vulnerability and population exposure in worldwide river basin risk framework and revealed distinctive basin clusters associable with the following characterizations: (1) too little water – high salinity – high variability – overexploited, (2) high organic pollution, eutrophic, flood prone – highly populated, (3) water abundant, (4) lacking infrastructure – low socioeconomic development. These clusters largely form a sequence as for instance there are basins that fall at the edge of (1), with many similarities already to (2), etc. The analysis provides a new perspective to comparison of world’s river basins and looking for novel learning opportunities for river basin management and risk reduction policies, especially in a multihazard-multirisk setting allowing the identification of the basin-specific risk profile and the roles of vulnerability and exposure.

How to cite: Varis, O.: Typology of world’s river basins regarding socio-ecological resilience to ten major water related risks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3507, https://doi.org/10.5194/egusphere-egu24-3507, 2024.

EGU24-3850 | ECS | PICO | HS2.2.6

Catchment Classification-Based Comparison of Hydrological Models to Inform Water Systems Analysis 

Saumya Srivastava, Leyang Liu, Abhinav Wadhwa, Gowri Reghunath, Venkatesh Budamala, Barnaby Dobson, Nagesh Kumar Dasika, and Ana Mijic

Choosing a suitable model and determining the best calibration method are complex processes. These can be simplified by comparing uncalibrated models and analyzing modeling results based on catchment characteristics. The amalgamation of these two stages forms "informing water systems analysis." This study examines the application of the Water Systems Integrated Modelling framework (WSIMOD), which is a comprehensive water systems model applied previously for catchments in the UK, and the Soil and Water Assessment Tool (SWAT), a commonly used hydrological model in India. The comparison is conducted using a catchment classification scheme based on physiography. This approach establishes a connection between the catchment characteristics and the model performances, providing valuable insights for the analysis of water systems. WSIMOD demonstrates superior performance compared to SWAT in its out-of-the-box configuration, particularly when simulating average flows. WSIMOD necessitates a greater amount of data preparation compared to SWAT, but it involves a less complex calibration process. The performance of SWAT is highly dependent on the characteristics of each catchment, necessitating the use of multi-site calibration. WSIMOD's performance is not significantly influenced by catchment characteristics, enabling regions within the same agro-ecological zone to share identical parameter values. The catchment classification analysis indicated that to enhance the accuracy of the SWAT model, it is necessary to select topography, precipitation, and soil parameters for calibration. Additionally, the infiltration rate and residence times of water should be further refined to improve the WSIMOD model. This proposed methodology facilitates and simplifies the processes of model selection and calibration.

How to cite: Srivastava, S., Liu, L., Wadhwa, A., Reghunath, G., Budamala, V., Dobson, B., Kumar Dasika, N., and Mijic, A.: Catchment Classification-Based Comparison of Hydrological Models to Inform Water Systems Analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3850, https://doi.org/10.5194/egusphere-egu24-3850, 2024.

EGU24-3872 | PICO | HS2.2.6

CAMELS-CZ: A catchment attribute database for hydrological and climatological studies using a large sample of catchments 

Michal Jenicek, Radovan Tyl, Ondrej Nedelcev, Ondrej Ledvinka, Petr Šercl, Jana Bernsteinová, and Jakub Langhammer

Hydrological methods based on the analysis of data from a large sample of catchments with different characteristics (large-sample hydrology; comparative hydrology) allow a comprehensive analysis of the hydrological regime and thus a description of hydrological variability and change in the components of the water balance. These methods provide insight into hydrological processes shaped by environmental and climatic factors and allow more general conclusions to be drawn. However, besides climate and runoff data, catchment attributes, such as geology, soils, topography and vegetation, are essential for effective hydrological behaviour analysis. For these reasons, the global hydrological community has recently developed a number of freely available large-scale datasets known as CAMELS (Catchment Attributes and MEteorology for Large-sample Studies), which provide catchment attributes, as well as hydrological and meteorological time series, in a comparable structure at national scales. The aim of this contribution is to present the current state of preparation of the CAMELS database for Czechia (CAMELS-CZ) as a reference data platform for analysis and modelling, using a large sample of catchments.

The database contains 389 catchments in Czechia maintained by the Czech Hydrometeorological Institute (CHMI) for which daily runoff data are available for at least 30 years. Catchments cover a variety of elevations (200–1600 m a.s.l) and runoff regimes (from pluvial to nival). Climate attributes were calculated from newly created daily climate grids (mean daily precipitation, mean daily air temperature) available in spatial resolution 1 km. Vegetation attributes are calculated based on Landsat data and the Corine Land Cover database. Soil texture database, hydraulic soil characteristics and geology maps are used for soil and geology attributes calculation. The subset of the catchments included in the upcoming CAMELS-CZ database has already been used for several purposes, mostly in mountain areas to analyse changes in snow cover and their influence on both low and high flows. For this subset, simulations of the conceptual hydrological model have been performed and used. The future goal is to prepare runoff simulations for all catchments included in the CAMELS-CZ database which will be publicly available for use among the hydrological community.

How to cite: Jenicek, M., Tyl, R., Nedelcev, O., Ledvinka, O., Šercl, P., Bernsteinová, J., and Langhammer, J.: CAMELS-CZ: A catchment attribute database for hydrological and climatological studies using a large sample of catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3872, https://doi.org/10.5194/egusphere-egu24-3872, 2024.

EGU24-3944 | PICO | HS2.2.6

Large-sample hydrology lessons 

Wouter Berghuijs

The emergence of large-sample hydrology datasets has opened many new opportunities to derive more robust and more generalizable conclusions about hydrological processes and models. Here I showcase several examples of how large-sample hydrology can help unveil unknown hydrological behaviors, test and refine existing hypotheses, and challenge current modeling practices. Such advancements can include generating a better understanding of how climate, landscapes, and humans shape the diversity of hydrological conditions we encounter worldwide but can also focus on general emergent behaviors that are surprisingly similar between places. I also reflect on how large-sample hydrology datasets could evolve to become an even more productive playground for hydrology to advance.  

How to cite: Berghuijs, W.: Large-sample hydrology lessons, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3944, https://doi.org/10.5194/egusphere-egu24-3944, 2024.

EGU24-3984 | ECS | PICO | HS2.2.6

How catchment ecosystems globally manage root water access under different (climate) conditions 

Fransje van Oorschot, Ruud van der Ent, Tom Viering, Andrea Alessandri, and Markus Hrachowitz

The root zone storage capacity (Sr) is the maximum volume of water in the subsurface that can potentially be accessed by vegetation for transpiration. Sr is an essential characteristic of hydrological systems as it controls the partitioning of precipitation into evaporation and runoff. Understanding the influence of climatic and landscape characteristics on Sr is essential for predicting how different ecosystems will respond to disturbances such as human activities and climate change. While the magnitude of Sr on ecosystem scale is partly influenced by landscape characteristics such slopes, bedrock properties and soil characteristics, there is widespread consensus that it is primarily controlled by climate conditions (i.e., the temporal dynamics of water and energy availability) as vegetation optimizes its root system to sustain atmospheric water demand.

Several studies have identified the influence of various climatic variables on Sr, but for different regions conflicting influences of these variables on Sr appeared. So far, it remains unclear what aspects of the climate are most important controls on Sr on global scale. This research aims to bridge this gap by exploring how different climatic and landscape characteristics influence the magnitude of Sr globally. Based on discharge measurements in a large sample of catchments worldwide (~4000), we estimated the actual Sr using the memory method as in Van Oorschot et al. (2021, 2023). With a random forest model we were able to adequately predict Sr using various climatic and landscape characteristics. Analysis of the driving variables of the random forest model show that the precipitation inter-storm duration is the most dominant control on Sr, and positively influences Sr in all regions. On the other hand, the influence of mean precipitation on Sr is conflicting in different regions. We found that in water limited regions, increased mean precipitation leads to increased Sr, while in energy limited regions, increased mean precipitation leads to decreased in Sr. Furthermore, the developed model is used to extrapolate the catchment Sr estimates to a global gridded map of Sr ensuring coverage of data-scarce regions. This extrapolated map can be used for more adequate modelling of subsurface vegetation water availability in large scale hydrological and land surface models.

van Oorschot, F., van der Ent, R. J., Hrachowitz, M., and Alessandri, A.: Climate-controlled root zone parameters show potential to improve water flux simulations by land surface models, Earth Syst. Dynam., 12, 725–743, https://doi.org/10.5194/esd-12-725-2021, 2021.

van Oorschot, F., van der Ent, R. J., Alessandri, A., and Hrachowitz, M.: Influence of irrigation on root zone storage capacity estimation, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-2622, 2023.

How to cite: van Oorschot, F., van der Ent, R., Viering, T., Alessandri, A., and Hrachowitz, M.: How catchment ecosystems globally manage root water access under different (climate) conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3984, https://doi.org/10.5194/egusphere-egu24-3984, 2024.

EGU24-4626 | ECS | PICO | HS2.2.6

Global natural catchment classification based on hydrological similarity 

Huan Xu, Hao Wang, Pan Liu, Weibo Liu, and Chutian Zhou

Catchments are important in hydrology, and a catchment classification framework helps to understand the catchment hydrological behaviors, explain the differences between catchments, and predict in ungauged catchments. However, no research has yet established a global catchment classification framework.

We selected a group of hydrological signatures to represent catchment hydrological behaviors, and used the fuzzy clustering method to classify natural catchments. To explain the classification rules and the catchment attributes dominating the classification, we used decision tree and random forests, respectively. The results show that: the global natural catchments are divided into six classes by the fuzzy clustering method, most of the classes are extreme in at least one hydrological behavior, and the selected hydrological signatures can distinguish the catchment groups; The decision tree gives explicit classification rules, with an accuracy rate of over 93%, which reasonably explains the fuzzy clustering results and facilitates the judgment of catchment classes; The precipitation characteristics, aridity index and the lowest altitude of catchments are considered to be the dominant catchment attributes for catchment classification, among which the average daily precipitation is the most important; Compared with physiography, land cover, soil and geological factors, the relative importance of climate factors in catchment classification exceeds 50%; The global catchment classification pattern output by random forests is a comprehensive reflection of hydrological signatures and can better reflect the hierarchical differences in hydrological behavior among catchments in contrast to climate classification.

The validity of the proposed global classification pattern is supported by its consistency with regional studies conducted in Europe, the United States, and Australia. Furthermore, about 64.1% classification accuracy of catchment class and 62.0% simultaneous hit rates of eight hydrological signatures can be achieved by the random forests model, demonstrating the ability of proposed catchment classification in estimating the hydrological behavior of ungauged catchments. As the first step towards global catchment classification, this study developed a natural catchment classification method based on hydrological similarity using data-driven approaches, obtained a global distribution map, and laid the foundation for establishing a generally accepted global catchment classification framework.

How to cite: Xu, H., Wang, H., Liu, P., Liu, W., and Zhou, C.: Global natural catchment classification based on hydrological similarity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4626, https://doi.org/10.5194/egusphere-egu24-4626, 2024.

EGU24-5544 | ECS | PICO | HS2.2.6

Catchments deviate less from their own Budyko curves over time than previously thought 

Muhammad Ibrahim, Miriam Coenders, Markus Hrachowitz, and Ruud van der Ent

Quantification of precipitation partitioning into evaporation and runoff is crucial for predicting future water availability. Over longer time scales, the widely used Budyko Framework, which is a curvilinear relationship between evaporative index (i.e., actual evaporation over precipitation) and aridity index (i.e., potential evaporation over precipitation), robustly quantifies precipitation partitioning under prevailing climatic conditions. Global long-term records indicate that catchments generally follow Budyko curves; however, a narrow scatter around these curves have been demonstrated in various studies, raising questions about the framework's applicability. To address this, we quantified (based on historical long-term water balance data of over 2000 river catchments world-wide) the global, regional and local distributions of deviations from parametric Budyko curves, between multiple 20-year periods over the last century. This process resulted in four 20-year distributions of deviation for each catchment. On average, it was observed that in 73% of the catchments, the long-term median deviation values across these distributions were not significantly different from zero suggesting minimal to no median deviations. Furthermore, it is found that for majority of the catchments (78%) the four 20-year distributions of deviations are not significantly different to each other implying consistency in deviations among different 20-year periods. Our analysis revealed that, for 80% of these catchments, the long-term median deviations, for the last century, fall within the range of ±0.02 with a very narrow spread in Interquartile Range values. These findings demonstrate that while catchments do not precisely follow the expected Budyko trajectories, the deviations are small and quantifiable. Consequently, by taking into account these deviations, the Budyko Framework remains a valuable tool for predicting future evaporation and runoff under changing climatic conditions, within quantifiable margins of error.

How to cite: Ibrahim, M., Coenders, M., Hrachowitz, M., and van der Ent, R.: Catchments deviate less from their own Budyko curves over time than previously thought, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5544, https://doi.org/10.5194/egusphere-egu24-5544, 2024.

EGU24-5850 | PICO | HS2.2.6

Wastewater discharges and urban land cover dominate urban hydrology signals across England and Wales  

Gemma Coxon, Hilary McMillan, John P Bloomfield, Lauren Bolotin, Joshua F Dean, Christa Kelleher, Louise Slater, and Yanchen Zheng

Urbanisation is a critical driver of changes in streamflow. These changes are not uniform across catchments due to the diverse changes to water sources, storage, and pathways in urban river systems from impervious areas, abstractions, sewage networks, and sewage treatment plans. While land cover data are typically used to explain urbanisation, water management practices are poorly quantified. Consequently, urbanisation impacts are often difficult to detect and quantify, and the relative impact of these factors is currently poorly understood.

Here, we assess urban impacts on streamflow dynamics for a large-sample of catchments across England and Wales using data characterising water management practices and land cover. We quantify urban impacts on a wide range of streamflow dynamics (flow magnitudes, variability, frequency and duration) using random forest models. We demonstrate that wastewater discharges from sewage treatment plants and urban land cover dominate urban hydrology signals across England and Wales and have different impacts on streamflow dynamics. Wastewater discharges increase low flows and reduce flashiness in urban catchments, while urban land cover increases flashiness and frequency of medium and high flow events. We demonstrate the need to move beyond land cover metrics and include other features of urban river systems in large-sample hydrological analyses to quantify current and future drivers of urban streamflow.

How to cite: Coxon, G., McMillan, H., Bloomfield, J. P., Bolotin, L., Dean, J. F., Kelleher, C., Slater, L., and Zheng, Y.: Wastewater discharges and urban land cover dominate urban hydrology signals across England and Wales , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5850, https://doi.org/10.5194/egusphere-egu24-5850, 2024.

EGU24-6641 | ECS | PICO | HS2.2.6

EStreams: Building an integrated dataset of streamflow, hydro-climatic variables and landscape attributes for catchments in Europe 

Thiago V. M. do Nascimento, Julia Rudlang, Marvin Höge, Ruud van der Ent, Jan Seibert, Markus Hrachowitz, and Fabrizio Fenicia

High-quality datasets are essential to hydrological analysis1. Although many such datasets exist, their accessibility is typically time-consuming and often challenging. Recently, there has been a significant spread of large-sample hydrology (LSH) datasets. Many of these datasets are referred to as Catchment Attributes and MEteorology for Large-sample Studies (CAMELS) or derivations1–4, covering hydro-climatic and landscape static attributes and time series data. These data have collectively been made available5 including first extensionsbased on daily time series such as the Global Runoff Data Base (https://www.bafg.de/GRDC)6. Additionally, there have been collection efforts for global streamflow data indices and signatures7–9. However, such globally accessible dataset represent only a small fraction of what is currently available. 

Here we present EStreams, a new dataset and data-access catalogue of streamflow, hydro-climatic  variables and landscape descriptors for over 15,000 catchments in 39 European countries, set to be released in 2024. The data spans up to 100 years of streamflow data and includes several open-source catchment aggregated landscape attributes on topography, soil, lithology, vegetation, and land cover, as well as climatic forcing and streamflow time-series, hydro-climatic signatures and a catalogue of streamflow providers (“European streamflow data and where to find them”). EStreams offers both an extensive and extensible data collection along with codes for data retrieval, aggregation and processing. Our goal is to extend current large-sample datasets and take a step towards integrating hydro-climatic and landscape data across Europe.

References

1. Addor, N., Newman, A. J., Mizukami, N. & Clark, M. P. The CAMELS data set: Catchment attributes and meteorology for large-sample studies. Hydrol Earth Syst Sci 21, 5293–5313 (2017).

2. Coxon, G. et al. CAMELS-GB: hydrometeorological time series and landscape attributes for 671 catchments in Great Britain. Earth Syst Sci Data 12, 2459–2483 (2020).

3. Höge, M. et al. CAMELS-CH: hydro-meteorological time series and landscape attributes for 331 catchments in hydrologic Switzerland. Earth Syst Sci Data 15, 5755–5784 (2023).

4. Klingler, C., Schulz, K. & Herrnegger, M. LamaH-CE: LArge-SaMple DAta for Hydrology and Environmental Sciences for Central Europe. Earth Syst Sci Data 13, 4529–4565 (2021).

5. Kratzert, F. et al. Caravan - A global community dataset for large-sample hydrology. Scientific Data 2023 10:1 10, 1–11 (2023).

6. Färber, C. et al. GRDC-Caravan: extending the original dataset with data from the Global Runoff Data Centre (0.1) [Data set]. Zenodo https://zenodo.org/records/8425587 (2023) doi:10.5281/ZENODO.8425587.

7. Do, H. X., Gudmundsson, L., Leonard, M. & Westra, S. The Global Streamflow Indices and Metadata Archive (GSIM)-Part 1: The production of a daily streamflow archive and metadata. Earth Syst Sci Data 10, 765–785 (2018).

8. Gudmundsson, L., Do, H. X., Leonard, M. & Westra, S. The Global Streamflow Indices and Metadata Archive (GSIM)-Part 2: Quality control, time-series indices and homogeneity assessment. Earth Syst Sci Data 10, 787–804 (2018).

9. Chen, X., Jiang, L., Luo, Y. & Liu, J. A global streamflow indices time series dataset for large-sample hydrological analyses on streamflow regime (until 2022). Earth Syst Sci Data 15, 4463–4479 (2023).

How to cite: M. do Nascimento, T. V., Rudlang, J., Höge, M., van der Ent, R., Seibert, J., Hrachowitz, M., and Fenicia, F.: EStreams: Building an integrated dataset of streamflow, hydro-climatic variables and landscape attributes for catchments in Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6641, https://doi.org/10.5194/egusphere-egu24-6641, 2024.

Accurate meteorological forcings are a fundamental component for reliable hydrological modelling. Gridded meteorological products offer spatially distributed information facilitating hydrological model applications. In addition, they are often available at large scale (e.g. regional or continental scale), easing the application on large samples of basins, and generally enhancing the replicability of the experiments. Nevertheless, the accuracy of these products varies, and it must be rigorously assessed to ensure the validity of model simulations.

This study aims to evaluate the accuracy of four gridded meteorological products: three based on ground observations (E-OBS, SCIA, and ARCIS) and one reanalysis (ERA5-Land), across a large sample of over 150 catchments in three administrative regions of Northern Italy. To assess their reliability, we adopt an indirect evaluation method. This involves assessing the performance of a conceptual hydrological model, which is forced with each of the four gridded meteorological products, over the selected catchments.

The E-OBS dataset, developed by the ECA&D project, offers climatic variables at a 0.1° x 0.1° (~11 x 11 km) resolution from 1950 onwards across Europe. ERA5-Land is a global scale reanalysis dataset from ECMWF which provides data at a 9 x 9 km resolution from 1950. Finally, ARCIS (Pavan et al., 2019) and SCIA (Desiato et al., 2007) datasets are Italian meteorological products, respectively at 5 x 5 and 10 x 10 km spatial resolution, starting from 1961.

For the study catchments, four distinct meteorological forcings, including the daily time series of areal mean precipitation, temperature, and potential evapotranspiration, were estimated using each of the four gridded products. Daily streamflow data were collected from three different regional agencies managing hydroclimatic data and were manually validated.

The rainfall-runoff model used for the indirect validation is the CemaNeige-GR6J (Coron et al., 2023), a daily lumped and continuously simulating model. We investigate the performances of the model in simulating streamflow, in order to get insights on the reliability of the gridded products across the region and along the years.

Model performances are also analysed against catchment features (such as orography and presence of upstream reservoirs) and data set characteristics (such as gauge network density) to investigate whether certain conditions influence the representativeness of the gridded products and the corresponding streamflow simulations, enhancing our understanding of their applicability and limitations. 

References

Coron, L., Delaigue, O., Thirel, G., Dorchies, D., Perrin, C. and Michel, C. (2023). airGR: Suite of GR Hydrological Models for Precipitation-Runoff Modelling. R package version 1.7.4, doi: 10.15454/EX11NA, URL: https://CRAN.R-project.org/package=airGR.

Desiato, F., Lena, F., & Toreti, A. (2007). SCIA: a system for a better knowledge of the Italian climate. Bollettino di Geofisica Teorica ed Applicata, 48(3), 351-358.

Pavan, V., Antolini, G., Barbiero, R., Berni, N., Brunier, F., Cacciamani, C., ... & Torrigiani Malaspina, T. (2019). High resolution climate precipitation analysis for north-central Italy, 1961–2015. Climate Dynamics, 52, 3435-3453.

How to cite: Sarigil, G., Neri, M., and Toth, E.: An Indirect Validation of National and International Gridded Precipitation Products in Northern Italy through Rainfall-Runoff Model Application, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6800, https://doi.org/10.5194/egusphere-egu24-6800, 2024.

EGU24-7429 | ECS | PICO | HS2.2.6

River Flow Dynamics across Europe: Insights from continental to regional scales 

Julia Rudlang, Markus Hrachowitz, Thiago V. M. do Nasciamento, Ruud van der Ent, and Fabrizio Fenicia

River flow is affected by change in climate and land use. Today, we see many different magnitudes and directions of trends of change across European rivers with respect to streamflow, which affects water supply and hydrological extremes such as floods and droughts. Moreover, the drivers of change in streamflow and its temporal trends vary on multiple scales from local to regional to continental. 

In this study, we identify changes, trends and possible patterns of change in the hydrological response across the whole of Europe, as well as its underlying drivers. We do this by using multi-decadal streamflow data that was collected from more than 15000 European stream flow gauging stations in 39 European countries. This large-sample dataset, named EStreams and set to be published in 2024, provides valuable new perspectives on the hydrological response in Europe.

In the analysis, similar catchments across Europe were clustered into groups, based on their hydrological response, as characterised by a wide range of hydrological signatures. This allowed to identify the different controls of hydrological response between the groups, such as climate, landscape and seasonal water balance.

Furthermore, the high-resolution streamflow dataset used allowed for the opportunity to zoom in further and gave a meaningful look at the differences within the clustered groups. This ensured that it was possible to investigate the differences in hydrological responses that were primarily dictated by landscape characteristics, as within cluster catchments are assumed to have limited climate variability. 

Altogether, mapping out the different hydrological responses across Europe and the differences in hydrological response within nested sub-catchments gave a comprehensive identification and quantitative description of dominant landscape characteristics shaping the hydrological response within clusters of hydro-climatically distinct European regions.

How to cite: Rudlang, J., Hrachowitz, M., V. M. do Nasciamento, T., van der Ent, R., and Fenicia, F.: River Flow Dynamics across Europe: Insights from continental to regional scales, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7429, https://doi.org/10.5194/egusphere-egu24-7429, 2024.

EGU24-8081 | PICO | HS2.2.6

Introducing the BULL Database – Spanish Basin attributes for Unraveling Learning in Large-sample hydrology 

Javier Senent-Aparicio, Gerardo Castellanos-Osorio, Francisco Segura-Méndez, Adrián López-Ballesteros, Patricia Jimeno-Sáez, and Julio Pérez-Sánchez

Large-Sample Hydrology (LSH) plays a crucial role in understanding different hydrological processes, using large basin datasets as fundamental resources that allow researchers to explore multiple facets of hydrology (Addor et al. 2020). In recent years, multiple LSH datasets adapted to the national scale have been developed. We present BULL, a novel basin dataset for large-sample hydrological studies in Spain. BULL includes data from 503 watersheds, providing daily hydrometeorological time series (streamflow and climatic variables) and attributes related to basin characteristics. To collect these attributes, the recommendations included in the CARAVAN (Kratzert et al. 2023) initiative for the generation of a truly open global hydrological dataset have been followed. BULL covers the entire territory of Peninsular Spain, which is characterized by its wide climatic and hydrological variability, including catchments ranging from 100 km2 to 2000 km2. One of the main novelties of BULL to other national-scale datasets is the analysis of the hydrological alteration of the basins included in this dataset. The hydrological alteration is calculated by statistical comparison of the monthly flow values measured in the gauges and the flow values obtained from the Integrated System for Rainfall-Runoff Model (SIMPA) (Estrela and Quintas, 1996) developed by the Center for Hydrographic Studies (CEDEX), for the entire Spanish territory. This aspect is especially important in countries such as Spain, which is characterized as one of the countries in the world where rivers suffer from the highest levels of anthropization. The BULL dataset is made freely available to scientific users via the open-access repository Zenodo.

                           

References:

Addor, N., Do, H.X., Alvarez-Garreton, C. et al. Large-sample hydrology: recent progress, guidelines for new datasets and grand challenges. Hydrological Sciences Journal 65, 712–725 (2020). https://doi.org/10.1080/02626667.2019.1683182

Estrela, T., Quintas, L., 1996. A distributed hydrological model for water resources assessment in large basins. Proceedings of 1st International Conference on Rivertech. Vol. 96, pp. 861–868.

Kratzert, F., Nearing, G., Addor, N. et al. Caravan - A global community dataset for large-sample hydrology. Sci Data 10, 61 (2023). https://doi.org/10.1038/s41597-023-01975-w

How to cite: Senent-Aparicio, J., Castellanos-Osorio, G., Segura-Méndez, F., López-Ballesteros, A., Jimeno-Sáez, P., and Pérez-Sánchez, J.: Introducing the BULL Database – Spanish Basin attributes for Unraveling Learning in Large-sample hydrology, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8081, https://doi.org/10.5194/egusphere-egu24-8081, 2024.

Catchments descriptors are widely used in hydrological science to infer dominant hydrological processes, identify, and transfer information across catchments and scales. However, persistent use of descriptors aggregated as spatially-lumped values (i.e., catchment averages), without considering their spatial variability within catchments might hamper the efficiency of these tasks. In this study, we use interpretable machine learning to investigate the value of topographically enhanced catchment descriptors (i.e., weighting them using distance to outlet, distance and height to the nearest drainage and stream order) belonging to seven distinct categories (i.e., climate, topography, land use, geology, hydrogeology, soil physical properties, and soil water properties) for predicting mean values, variability and seasonality characteristics of hydrological droughts and runoff events occurred in 401 German catchments in the period 1979-2002.

We found that the spatially-differentiated catchment descriptors aggregated with topographical enhancing are able to predict droughts and runoff events characteristics more accurately than the lumped descriptors. The improvement is particularly promising for prediction of runoff event characteristics. Particularly, descriptors aggregated using height above the nearest drainage and stream order are essential for accurate prediction of variability of runoff events characteristics, while the proximity to the stream and to the outlet are more relevant for predicting their seasonality. In case of droughts, the descriptors weighted by the proximity to the stream improve the predictions of the variability and seasonality of duration and severity (i.e., deficit volume) of hydrological droughts. Moreover, we show that spatially-differentiated aggregation has the potential to identify the importance of descriptors that appeared irrelevant when aggregated in lumped way, particularly shading a light on the role of mean annual potential evapotranspiration and forest land cover descriptors for the prediction of mean values and seasonality of time scale of runoff events, and the role of groundwater yield and wetland land cover to predict the variability of time rise of runoff events. Our study highlights that development of the methods for spatially-differentiated aggregation has potential to disentangle the effects of different physio-geographical controls on event response in different catchments and to improve its predictability in ungauged locations.

How to cite: Ziani, C., Ribbe, L., Aala, S., and Tarasova, L.: The value of spatially-differentiated  catchments descriptors for predicting characteristics of hydrological events in German catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8259, https://doi.org/10.5194/egusphere-egu24-8259, 2024.

Large-sample hydrology aims to identify common patterns in the hydrologic behaviour of numerous catchments at the regional, continental and global scales. Large-sample datasets play a fundamental role in the context of large-sample hydrology as they collect data from multiple catchments and hydroclimatic variables.

This study focuses on the characterization of the water balance for 189 Spanish headwater catchments. The different ratios derived from the water balance equation will be calculated using multiple hydroclimatic datasets available for the Spanish domain for two consecutive and equally long periods: 1990-2005 and 2006-2020. Precipitation data will be extracted from a gridded dataset at 0.05º resolution from the Spanish Meteorological Agency (AEMET). Streamflow time series will be provided by the Spanish Center for Public Work and Experimentation (CEDEX). Evaporation data will be gathered from the Global Land Evaporation Amsterdam Model (GLEAM) versions 3.7a and 3.7b.

The results of this work will highlight the potential of using large-sample datasets to characterize the water balance for the Spanish catchments and will reveal key changes in their hydrologic behaviour during the last three decades.

ACKNOWLEDGMENTS: This study has been funded by a Humboldt Research Fellowship from the Alexander von Humboldt Foundation.

 

How to cite: Yeste, P. and Bronstert, A.: Large-sample evaluation of the water balance for the Spanish catchments using multiple hydroclimatic datasets, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8309, https://doi.org/10.5194/egusphere-egu24-8309, 2024.

EGU24-8643 | PICO | HS2.2.6

The value of hydrologic observatories for large sample hydrology and vice versa 

Thorsten Wagener, Gemma Coxon, John P. Bloomfield, Wouter Buytaert, Matthew Fry, David M. Hannah, Gareth Old, and Lina Stein

Hydrologic observatories have been a cornerstone of hydrologic science for many decades, advancing hydrologic process understanding with focused field observations and targeted experiments. Observatories present our key opportunity for achieving great depth of hydrologic investigation, most often at the headwater catchment scale. We address two main aspects concerning hydrologic observatories in this contribution: (1) While reviews of individual hydrologic observatories and observatory networks exist, no study has investigated the diversity of observatories to understand whether common aspects increase the likelihood of scientific success. We synthesise information from 80 hydrologic observatories and conduct 25 interviews with observatory leads to fill this gap. We find that scientific outcomes are most enhanced by involving scientific and stakeholder communities throughout observatory inception, design, and operation; by enabling infrastructure to be adjustable to changing ideas and conditions; and by facilitating widespread data use for analysis. (2) While observatories are key for advancing local hypotheses, the transferability of knowledge gained locally to other places or scales has often been difficult or even remained elusive. Headwater catchments in particular show a wide range of process controls often only understood if viewed in a wider regional context of climatic, topographic, or other gradients. We therefore must place observatories into the wider tapestry of hydrologic variability, for example through comparison with large samples of catchments, even though significantly less information is available to characterise these diverse systems. We provide some thoughts on how this connection could be improved through digital infrastructure, mobile observational infrastructure and a renewed focus on gradients and contrasts of controlling processes. We believe that there is a significant opportunity to enhance transferrable knowledge creation in hydrology.

How to cite: Wagener, T., Coxon, G., Bloomfield, J. P., Buytaert, W., Fry, M., Hannah, D. M., Old, G., and Stein, L.: The value of hydrologic observatories for large sample hydrology and vice versa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8643, https://doi.org/10.5194/egusphere-egu24-8643, 2024.

EGU24-11151 | PICO | HS2.2.6 | Highlight

A global dataset of near-natural basins for climate change detection 

Steve Turner, Jamie Hannaford, Lucy Barker, Harry Dixon, Adam Griffin, Amit Kumar, and Gayatri Suman and the ROBIN Network

As hydrological extremes become more severe in the warming world, impacts to livelihoods, infrastructure, and economies worsen. To attribute emerging trends to climate change, we need to remove the signal of anthropogenic activities, such as, the presence of dams, land-cover change, channelisation and the abstraction of water for public water supplies, industry and agriculture. These human disturbances can obscure climate change signals and distort trends in river flows and, in some cases, lead to a complete reversal of true, natural trends. 

There have been many studies of long-term changes in river flows around the world however, at a global scale (as represented by Intergovernmental Panel on Climate Change (IPCC) reports), confidence in observed river flow trends remains low. It can also be a challenge to integrate the results of various regional- and national-scale studies due to the different methods used, hampering consistent continental- and global-scale assessments. 

Identifying the problem, many countries have ‘Reference Hydrometric Networks’ (RHNs) which consist of natural or near-natural catchments. Globally, however, these types of catchment can be sparse in both their spatial and temporal nature and in order to provide real value to international assessments of hydrological change on a consistent basis (such as those undertaken by the IPCC), an integrated approach is needed. 

The Reference Observatory of Basins for INternational hydrological climate change detection or ROBIN initiative, is a worldwide collaboration to bring together the first global RHN. The network currently consists of partners from almost 30 countries spanning every continent, the first iteration of the ROBIN dataset is now available – a consistently defined network of near-natural catchments consisting of over 3,000 catchments.  

Here we will present the criteria for inclusion of river flow data in the ROBIN network, detail the quality control undertaken to prepare the dataset for analysis, and highlight data availability. Where data sharing allows, the dataset of daily mean river flow data at near-natural sites has been made openly available for the community to use as a resource to interrogate and conduct analyses on and alongside this the ROBIN team are undertaking the first, truly global analysis of trends in river flows using minimally disturbed catchments. 

Going forwards, whilst the first iteration of the ROBIN dataset has been published, it is our aim to continue network growth to increase the number of countries involved and add more catchments and even more diverse geographies to the dataset to continue developing this unique resource of river flow data. 

With the support of international organisations, including WMO, UNESCO and IPCC, ROBIN will lay the foundations for an enduring network of catchments, to support global assessments of climate-driven trends and variability in the future. 

How to cite: Turner, S., Hannaford, J., Barker, L., Dixon, H., Griffin, A., Kumar, A., and Suman, G. and the ROBIN Network: A global dataset of near-natural basins for climate change detection, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11151, https://doi.org/10.5194/egusphere-egu24-11151, 2024.

EGU24-12051 | ECS | PICO | HS2.2.6

Living among Artiodactyls - Current status and future plans of the Caravan dataset 

Frederik Kratzert, Nans Addor, Guy Shalev, and Oren Gilon

High-quality datasets are essential to support hydrological science and modeling. Several datasets exist for specific countries or regions (e.g. the various CAMELS datasets). However, these datasets lack standardization, which makes global studies difficult. Additionally, creating large-sample datasets is a time and resource consuming task, often preventing the release of data that would otherwise be open.

About a year ago, we released the Caravan (as in “a series of camels”) dataset, a community initiative that consists of 

  • a large-sample hydrology dataset which is derived from globally consistent data sources, and
  • open source code that facilitates the creation of Caravan extensions to new regions by leveraging cloud computing on Earth Engine.

On release, the Caravan dataset included 6830 gauges from 14 different countries with daily streamflow records (median record length ~30 years), 9 meteorological variables (from 1981 - 2020) in different daily aggregations, 4 hydrological reference states, and a total of 221 catchment attributes.

Since then, the dataset has been extended with several thousands of gauges in various, previously uncovered regions by different community members. Importantly, GRDC has joined the Caravan community effort and released a Caravan extension for 5357 watersheds (covering the period from 1950-2022) from the GRDC station catalog from 25 different countries. 

At this point, and with all extensions combined, the Caravan dataset now consists of 22494 gauge stations from 35 countries and contains a total of 660,382 years of streamflow records (median still at ~30 years).

With this submission, we want to reflect in more detail on the current state of the Caravan community efforts and share our thoughts and ideas for the future of Caravan. Additionally, we welcome interactions with owners of hydrological datasets interested in contributing to Caravan and discussions with users of large-sample datasets to understand the needs and desires for datasets and inform our future efforts. All information on Caravan can be found at https://github.com/kratzert/Caravan/

How to cite: Kratzert, F., Addor, N., Shalev, G., and Gilon, O.: Living among Artiodactyls - Current status and future plans of the Caravan dataset, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12051, https://doi.org/10.5194/egusphere-egu24-12051, 2024.

The question of what makes two catchments hydrologically similar is of fundamental importance for the understanding of catchment hydrology and for transferring hydrological information from gauged to ungauged catchments. In the regionalisation of rainfall-runoff model parameters, the definition of a similarity measure for identifying the donors basins as a function of catchment characteristics is an essential step for the most consolidated techniques. As demonstrated by a very large number of studies in the literature, conducted all around the world, the main controls of catchment similarity may change subtsantially across different hydroclimatic regions.

The recent availability of large-sample catchment dataset for rainfall-runoff studies in different hydroclimatic regions across the globe allows scientists to conduct comparative experiments for enhancing our knowledge about the factors that shape hydrological processes, including catchment similarity and regionalisation.

The aim of this study is to test how hydroclimatic characteristics in different regions of the world influence the main factors that control catchment similarity when regionalising rainfall-runoff model parameters, using a homogenised modeling protocol.

Two conceptually different bucket-type rainfall-runoff models are calibrated on more CAMELS-type large samples of catchments all around the world, characterised by different hydroclimates and data availability (i.e. streamgauge density). For each regional sample and for each model, one of the most consolidated parameter regionalisation approaches, based on the choice of a set of “most similar” donor catchments and on the transfer of the entire sets of model parameters from the donors to the target catchment, is applied in jack-knife cross-validation. Naturally, in such approach the choice of the donors (and therefore the regionalised model parameters) strictly depends on the catchment descriptors used to define the similarity measure between target and gauged basins.

Assuming that the higher is the similarity of the donors to the target catchment, the better is the model performance, the idea of the work is to assess which catchment features better represent similarity for the transfer of model parameters in each of the regional samples. In particular, it is interesting to analyse if and how such features change across different hydroclimates. In order to reach such goal, the regionalisation technique is implemented by including different typologies and combinations of climatic and/or morphological characteristics when defining similarity, therefore obtaining different donors and different regionalised model performances. The findings achieved in the different large samples are compared, mainly focusing on how the set of basin descriptors bringing to the best model performances varies across the different hydroclimatic regions.

How to cite: Neri, M. and Toth, E.: Exploring the controls of catchment similarity for the transfer of rainfall-runoff model parameters: a comparative study in different large-sample datasets around the globe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12411, https://doi.org/10.5194/egusphere-egu24-12411, 2024.

EGU24-12459 | PICO | HS2.2.6

FOCA: a new quality-controlled collection of floods and catchment attributes in Italy 

Pierluigi Claps, Giulia Evangelista, Daniele Ganora, Paola Mazzoglio, and Irene Monforte

In recent years, various national databases of geomorphoclimatic watershed attributes have been released. Relevant examples are the CAMELS datasets for countries such as the United States, Australia, Chile, Brazil, Switzerland, France, Germany, and the United Kingdom (now integrated into Caravan), and LamaH-CE. 

This work introduces FOCA (Italian FlOod and Catchment Atlas), a national-scale collection of 631 Italian basins that we fully characterized by providing more than 100 attributes related to geomorphology, soil, land cover, NDVI, climate, and extreme precipitation. The basins reported in FOCA are derived from a national-scale inventory of peak floods and annual maximum daily floods named "Catalogo delle Piene dei Corsi d'acqua Italiani", realized thanks to a data rescue initiative performed by merging recent data, already available in digital format, with historical information available on printed documents.

The selection of descriptors that we included in FOCA followed three main criteria: a) national spatial coverage; b) absence of regional or local distortions; c) adequate spatial resolution. Preference was given to local sources, resorting to global data only in specific cases. The inclusion of basin boundaries will allow users to assess additional descriptors using their models or datasets.

FOCA stands out from other national datasets due to its robust collection of geomorphological descriptors, computed using the r.basin algorithm of GRASS GIS and subjected to thorough quality controls. Another distinctive feature is the incorporation of extreme rainfall characteristics, evaluated using station data instead of reanalysis data — deviating from the approach often seen in the development of CAMELS datasets. For this purpose, the Improved Italian - Rainfall Extreme Dataset (I2-RED) has been used. I2-RED is a national collection of rainfall extremes measured by more than 5000 rain gauges from 1916 up to the present that was developed as the outcome of a data rescue project.

With this nationwide data collection, a wide range of environmental applications, with particular reference to flood studies, can now be undertaken on the Italian territory.

How to cite: Claps, P., Evangelista, G., Ganora, D., Mazzoglio, P., and Monforte, I.: FOCA: a new quality-controlled collection of floods and catchment attributes in Italy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12459, https://doi.org/10.5194/egusphere-egu24-12459, 2024.

EGU24-12781 | ECS | PICO | HS2.2.6

How does reservoir-regulation impact hydrological extremes in the Alps? 

Jonas Götte, Massimiliano Zappa, and Manuela Brunner

Low-flows and floods cannot be viewed as purely natural phenomena since their
occurrence and characteristics are influenced by water storage and regulation.
Reservoir-regulation has strong impacts on flow seasonality and can intensify
or attenuate hydrological extremes and change their duration. It is yet hardly
quantified how reservoir regulation affects low- and high flows in the Alps, where
most reservoirs are operated for hydropower production. We need a better un-
derstanding of the effect of reservoir-regulation on hydrological extreme events
in order to assess the readiness of current regulation schemes for the future.
However, the analysis of river flow and estimation of hydrological extremes is
challenging in regulated catchments, particularly in large-samples studies, where
detailed information about reservoir-regulation is missing.
In this study, we analyse how reservoir-regulation has changed the magni-
tude and frequency of hydrological extreme events in the European Alps. To do
so, we have compiled a dataset of discharge stations and reservoirs which in-
cludes reservoir characteristics such as the first year of operation or the storage
capacity. With this information, we distinguish between discharge time series
before and after reservoir construction for about 70 catchments in the European
Alps and calculate a normalized reservoir storage capacity for each catchment.
Then, we calculate flood return periods based on annual maxima discharges
and a generalized extreme value distribution and the minimum 7 day moving
average runoff (MAM7) for each time series. We compare flood and low-flow
characteristics before and after reservoir construction for each catchment to as-
sess the influence of reservoir-regulation on hydrologic extremes. Furthermore,
we analyse changes in the seasonality of hydrological extremes and evaluate how
it is affected by seasonal reservoir-regulation schemes.
Our preliminary results show that reservoirs affect both, low-flows and floods.
Annual low-flows have mostly increased since reservoir-construction, while their
variability has decreased. Annual maximum flows with low return periods (be-
low 10-years) have mostly decreased after reservoir-construction with catch-
ments with a larger normalized storage capacity showing a stronger effect of
reducing extreme flows. Consequently, we conclude that reservoirs operated for
hydropower production mostly have an alleviating effect on both low-flows and
floods.

How to cite: Götte, J., Zappa, M., and Brunner, M.: How does reservoir-regulation impact hydrological extremes in the Alps?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12781, https://doi.org/10.5194/egusphere-egu24-12781, 2024.

EGU24-13885 | ECS | PICO | HS2.2.6

A web-based watershed delineation tool and its application to delineate 24,000 watersheds across Canada 

Kasope Okubadejo, Juliane Mai, and Nandita B. Basu

Watershed delineation is the identification of the boundary of a drainage basin, representing the contributing area for a specific outlet. This application of hydrography is essential in the analysis of watershed behaviour and has historically been performed manually. The automation of delineation provides faster and more consistent results which can be more accurate and reproducible definitions of borders compared to the results of the manual delineation. There is a wide range of software and tools capable of performing watershed delineation automatically; all generally following the same steps – utilizing conditioned DEMs to create flow direction and accumulation rasters used in addition to a specified pour point that defines the extent of contributing area desired. These different tools and their results have been explored, addressing their similarities, contrasts, and complications. Using this analysis, selected methods have been included in a web application for watershed delineation for users to either delineate individual points selected on a web map or upload lists of points of interest The automatically delineated watersheds are then made available for download. One tool has been deemed most applicable and has been used to delineate more than 24,000 watersheds across Canada successfully. The presentation will include (1) the results of the comparison of the various tools tested, (2) a demonstration of the webtool as well as (3) the presenting the results of the large scale delineation task across Canada.

How to cite: Okubadejo, K., Mai, J., and Basu, N. B.: A web-based watershed delineation tool and its application to delineate 24,000 watersheds across Canada, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13885, https://doi.org/10.5194/egusphere-egu24-13885, 2024.

The percentage of total impervious area (TIA) is a popular proxy for the level of urbanization, adopted in many applications ranging from water quality assessments in developed watersheds to regional modeling for flood prediction in ungauged basins. However, TIA cannot satisfactorily capture important interactions between land development and its impacts on runoff patterns and peak flows, such as the effects of the spatial distribution of impervious patches, or the distinction between directly and indirectly connected impervious areas. In other words, TIA cannot incorporate information on hydrologic connectivity.  However, during a storm, these differences may have major implications on the surface runoff volumes that are contributed to the stream network from the impervious portions of a watershed, as well as their travel times, ultimately leading to large variability in the hydrologic response. E.g., the occurrence of pervious areas along the runoff paths from impervious patches to the stream may significantly decrease water volumes from those patches, attenuating both their impacts on direct runoff and the risks of stream contamination from localized pollution sources. Many recent strategies for flood mitigation at the local scale (also known as best management practices, or BMPs) exploit the concept of impervious-area disconnection to reduce peak-flow volumes via marginal landscape changes.

Although several other urbanization descriptors have been proposed in the literature, there is no agreement yet on alternative indices that could replace the traditional TIA in hydrological applications, so it is still predominantly used. One reason may be that these alternative measures may be difficult to derive for a given case-study basin. Some require the topology of the watershed’s stormwater drainage network, which is rarely available, especially in the case of large-scale studies. Other methods analyze patterns in concurrent flow and precipitation series, attempting to implicitly determine the proportion of directly connected impervious area from runoff coefficients, under the assumption that it is this component of the basin’s surface that governs its hydrologic response when smaller storms occur.  But this approach comes with major uncertainties related to the potentially variable contributions from pervious areas, depending on their antecedent soil moisture conditions.

We propose a new GIS framework for deriving connectivity-based urbanization measures using the digital elevation model, land-use, and soil maps of a watershed. We analyze its correlation to other, established urbanization measures, and test its predictive power in regionalization approaches. Our new index can aid urban water management on many fronts, including the assessment of alternative candidate BMPs on the overall connectivity of a watershed, enhancing the accuracy of regional models for prediction in ungauged basins (PUBs), and the analysis of the relationships between urbanization and water quality. The proposed methodology uses easily available datasets and can be implemented using Google Earth Engine and other open-source software, thus ensuring broad applicability irrespective of the study scale, as well as consistent analyses across different regions.

How to cite: Dell'Aira, F. and Meier, C. I.: Beyond Total Impervious Area: A New GIS Framework for Characterizing Urban Basins in Water Resources Management Applications incorporating Hydrological Connectivity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14235, https://doi.org/10.5194/egusphere-egu24-14235, 2024.

EGU24-14923 | PICO | HS2.2.6

A few hundred catchments later – lessons learned from modeling large catchment samples 

Jan Seibert, Ilja van Meerveld, Marc Vis, Franzisca Clerc-Schwarzenbach, and Sandra Pool

Traditionally, hydrological models are applied to one or a few catchments because preparation of the input and calibration data for a more extensive set of catchments is challenging. The availability of data sets with hydrometeorological time series for large numbers of catchments has been a game changer in hydrological catchment modeling in recent years. One example are the CAMELS data sets with the basic data to run hydrological models for several hundreds of catchments in various countries. In several recent studies, we have used these data sets for bucket-type modeling of a large number of catchments in different regions. In this presentation, I will discuss some of our main findings:

  • Variability of results: Simulation results vary considerably between catchments, making it pertinent to apply a model to a large number of catchments for robust results.
  • Uncalibrated model performance: Simple bucket-type models can provide surprisingly good results for some catchments even when not calibrated. This needs to be considered when we assess model performances.
  • Prediction in ungauged catchments: It can be challenging to improve simulations for ungauged catchments by regionalization as it is not obvious how to choose the most suitable donor catchments. Thanks to data sets with a vast number of potential donor catchments, we found that almost perfect donor catchments seem to exist in most cases. However, the challenge remains to identify them.
  • Model structure: For some catchments, a simplified soil routine with only one free parameter (instead of three) outperformed the standard model version.
  • Value of data: Large samples of catchments allow us to evaluate the value of different data types: a limited number of streamflow gaugings and other data types, such as stream level, stream width or water level class data, can be informative for streamflow simulations.

How to cite: Seibert, J., van Meerveld, I., Vis, M., Clerc-Schwarzenbach, F., and Pool, S.: A few hundred catchments later – lessons learned from modeling large catchment samples, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14923, https://doi.org/10.5194/egusphere-egu24-14923, 2024.

EGU24-14974 | PICO | HS2.2.6

GRDC-Caravan: extending the original dataset with data from the Global Runoff Data Centre 

Claudia Färber, Henning Plessow, Simon Mischel, Frederik Kratzert, Nans Addor, Guy Shalev, and Ulrich Looser

Large-sample datasets are essential in hydrological science to support modelling studies and global assessments. The Global Runoff Data Centre (GRDC) is an international data centre operating under the auspices of the World Meteorological Organization (WMO) at the German Federal Institute of Hydrology (BfG). Established in 1988, it holds the most substantive collection of quality assured river discharge data worldwide. Primary providers of river discharge data and associated metadata are the National Meteorological and Hydrological  Services of WMO Member States.

As the awareness for open data and reproducibility has increased in recent years, GRDC is working to simplify data provision to its users and to comply with the FAIR (findable, accessible, interoperable, reusable) principles. GRDC data and products are accessible online for non-commercial use (https://grdc.bafg.de). However, there are still hurdles on the way to a completely open and free exchange of data such as restrictive data policies and a lack of data standardisation.

Caravan is a community initiative to create a large-sample hydrology dataset of meteorological forcing data, catchment attributes, and discharge data for catchments around the world (Kratzert et al. 2023). Compared to existing large-sample hydrology datasets, the focus on Caravan is to use globally consistent forcing and attribute data to facilitate global studies. Additionally, Caravan provides the code to derive community extension on Earth Engine with as little as catchment boundaries and streamflow data required. The vision of Caravan is to provide the foundation for a truly global open source community resource that will grow over time.      

This dataset is the 6th extension to the original Caravan data set. It is based on a subset of hydrological discharge data and station-based watersheds from GRDC, which are covered by an open data policy (Attribution 4.0 International; CC BY 4.0). The dataset covers stations from 5357 catchments and 25 countries, spans 1950 – 2023, and is already publicly available on Zenodo: https://zenodo.org/records/10074416

 

Reference:

Kratzert, F., Nearing, G., Addor, N. et al. Caravan - A global community dataset for large-sample hydrology. Sci Data 10, 61 (2023). https://doi.org/10.1038/s41597-023-01975-w

How to cite: Färber, C., Plessow, H., Mischel, S., Kratzert, F., Addor, N., Shalev, G., and Looser, U.: GRDC-Caravan: extending the original dataset with data from the Global Runoff Data Centre, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14974, https://doi.org/10.5194/egusphere-egu24-14974, 2024.

The field of hydroclimatology is witnessing a transformative era with the convergence of various technologies and methodologies aimed at enhancing research reproducibility and collaboration. Within this context, hydroclimatic datasets have emerged as fundamental tools for unraveling the interplay between climate and hydrology, resonating across geographical boundaries. Particularly, the exploration of large-scale datasets can shed light on hydrological differences and similarities across diverse catchments, serving both scientific and educational purposes. Efforts to enhance the availability of such datasets are ongoing globally, with the introduction of initiatives like CAMELS (catchment attributes and meteorology for large-sample studies). Despite this collective global effort to unravel hydroclimatic complexities, and the abundance of online hydrologic databases, valuable information remains fragmented and scattered across different platforms. Much local data is still presented and documented in languages other than English, impeding the transfer of knowledge between local and international communities. For example, a considerable portion of open hydrologic data provided by Swedish governmental authorities is solely accessible in Swedish, hindering its integration into pan-European or global research.

Therefore, we here introduce the community-accessible CAMELS-SE dataset, which covers 50 catchments in Sweden spanning a wide range of hydroclimatic, topographic and environmental catchment properties. The dataset includes daily hydroclimatic variables (precipitation, temperature, and streamflow) over a 60-year period (1961-2020), and information on geographical location, landcover, soil classes, hydrologic signatures, and regulation for each catchment. Data was collected from various sources, such as the Swedish Meteorological and Hydrological Institute (SMHI), the Swedish Geological Survey (SGU) and several Copernicus products provided by the European Environment Agency (EEA). The compiled, spatially-matched, and processed data is publicly available online through the Swedish National Data Service (https://snd.gu.se/en). CAMELS-SE adds a new region to the list of existing CAMELS datasets, offering a valuable resource for studying hydrological processes, climate dynamics, environmental impacts and sustainable water management strategies in Nordic regions.

How to cite: Teutschbein, C.: Introducing CAMELS-SE: Connecting 60 Years of Hydroclimatic Observations with Catchment Attributes for 50 Sites in Sweden, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15238, https://doi.org/10.5194/egusphere-egu24-15238, 2024.

EGU24-17667 | ECS | PICO | HS2.2.6

CAMELS-DE: Benchmark dataset for hydrology – significance, current status and outlook 

Alexander Dolich, Pia Ebeling, Michael Stölzle, Jens Kiesel, Jonas Götte, Björn Guse, Sibylle Haßler, Mirko Mälicke, Larisa Tarasova, Ingo Heidbüchel, Corina Hauffe, Hannes Müller-Thomy, and Ralf Loritz

CAMELS datasets are recognized in the hydrological community as consistent and comprehensive benchmark datasets for hydrological and meteorological analyses. CAMELS stands for "Catchment Attributes and MEteorology for Large-sample Studies”. CAMELS datasets link landscape and catchment attributes (e.g. land use, geology, soil properties), hydrological time series (e.g. water level, discharge) and meteorological time series (e.g. precipitation, air temperature) in a large number of catchment areas. They clearly indicate the uncertainties and processing of individual variables and thus enable the comparison of models and data in different landscapes, but also contribute to the general understanding of hydrological processes across landscapes. This is crucial for assessing the consequences of the climate crisis and improves the basis for water resource management decisions. Although CAMELS datasets are intensively used in other countries, such a dataset is still lacking for Germany.

This contribution highlights the crucial importance of consistent and easily accessible benchmark datasets for hydrological research and education. We discuss both the challenges faced so far in compiling the dataset and the future ambitions of the project. In addition, an overview is given of the scope of the first version of the CAMELS-DE data set, which will include around 2,000 measuring stations with daily time series of discharge and water level with an average length of nearly 50 years in mainly small and medium-sized catchments. Also included are the landscape and catchment attributes as well as meteorological time series. A key focus is on the easy availability and straightforward import of data into programming environments. We discuss how such benchmark datasets not only increase efficiency in the use of environmental data, but also play a key role in ensuring the reproducibility of research results. Especially in the age of machine learning learning, they form an indispensable basis for modern, data-driven hydrology. By integrating CAMELS-DE into the research landscape, we want to emphasize that data publications and benchmark datasets are much more than a by-product of a doctoral thesis, but rather the basis and key to modern environmental science.

How to cite: Dolich, A., Ebeling, P., Stölzle, M., Kiesel, J., Götte, J., Guse, B., Haßler, S., Mälicke, M., Tarasova, L., Heidbüchel, I., Hauffe, C., Müller-Thomy, H., and Loritz, R.: CAMELS-DE: Benchmark dataset for hydrology – significance, current status and outlook, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17667, https://doi.org/10.5194/egusphere-egu24-17667, 2024.

EGU24-17964 | ECS | PICO | HS2.2.6

Framework development and flag-based quality control for a national scale dataset using UK's Historical 15-Minute Flow Data 

Felipe Fileni, Hayley J. Fowler, Elizabeth Lewis, Fiona McLay, and Longzhi Yang

The United Kingdom has an extensive repository of 15-minute flow data dating back to the 1930s, yet this wealth of information has remained decentralized within respective measuring authorities responsible for localized quality control. Consequently, the absence of standardization has resulted in heterogeneous data records. Several discrepancies can be observed, ranging from minor issues such as having different decimal places, to bigger issues such as having duplicate records with different values or having different quality codes in the data.

In the aim of producing a quality assured and consistent 15-min flow dataset for the whole UK, data has been requested from all UK measuring authorities. The data collected laid the groundwork for the development of a quality control framework, featuring both traditional, amply academically used and UK specific quality control flags. These flags have been used to standardise the data and produce a quality assured 15-min flow dataset for the UK.

More than 1000 stations and tens of thousands of years of data have been passed through different flags aiming to identify data and stations that have suspicious data. 14 flags have been generated in the framework. The flags vary in complexity and aim to provide better understanding of the data.  Even simple flags, such as detecting negative values serve multiple purposes: from identifying tide-influenced stations characterized by negative flows, to using the flag to remove/replace the negative values for hydrological analysis.  Conversely, complex hydrology flags such as identifying large flow events preceded by large rainfall events or identifying the relationship between the high flow of stations in the same river can be used for an enhanced comprehension of hydrological systems at a national scale.

This presentation aims to elucidate the flags that have been applied to the data; spotlight interesting case studies discovered in the quality control process; and showcase the versatile applications of the flags in data selections for specific hydrological analysis. In this PICO we want to emphasize the pivotal role that appropriate data selection has in shaping robust conclusions in the field of large sample hydrology.

How to cite: Fileni, F., J. Fowler, H., Lewis, E., McLay, F., and Yang, L.: Framework development and flag-based quality control for a national scale dataset using UK's Historical 15-Minute Flow Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17964, https://doi.org/10.5194/egusphere-egu24-17964, 2024.

High-quality observational data is critical for driving, evaluating, and calibrating geo-environmental models, particularly data-driven models. The quality and availability of such data greatly influence the output of these models. Over recent decades, numerous national, regional, and global observational datasets have been developed for catchment-scale hydrological modeling. However, the regional and national datasets often differ widely in data sources, formats, and variables, making their use challenging and time-consuming. Furthermore, existing global datasets do not include all available data sources and thus have limited coverage. In this presentation, we introduce a harmonized, comprehensive database that amalgamates existing national, regional, and global datasets into a unified, user-friendly resource. Our database consists of daily streamflow observations, daily time series of 10 meteorological variables, climatic and physiographic attributes, and catchment boundaries for over 28,000 catchments worldwide. These catchments range in size from 2~km$^2 to 1300~km$^2 (mean 150~km$^2$) and the number of daily streamflow observations per catchment ranges from 200 to 18,000 (mean 400). The meteorological data covers precipitation, temperature, humidity, radiation, and wind speed for each catchment. We included precipitation estimates from 17 state-of-the-art products such as CHIRPS, ERA5, GSMaP, IMERG, MSWEP, and SM2RAIN. To explore the database and retrieve data, we have developed a straightforward Python-based Application Programming Interface (API). All related code will be open sourced and accompanied by extensive documentation and usage examples. We anticipate this database will be an invaluable resource for various hydrological studies, including model calibration, evaluation, inter-model comparisons, and the assessment of different forcing datasets.

How to cite: Abbas, A. and Beck, H.: A large sample harmonized database of daily streamflow, meteorological data, and catchment attributes for over 28,000 global catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19406, https://doi.org/10.5194/egusphere-egu24-19406, 2024.

EGU24-1225 | ECS | Posters on site | HS2.2.9

A Long-term Spatial Runoff and Flood Prediction Method in Higher Accuracy 

Jiaqing Wang, Jianshi Zhao, and Quanjun Wang

When predicting future long-term runoff using hydrological models, the large uncertainty associated with general circulation models (GCMs) pose significant limitations. Additionally, current accurate long-term runoff predictions are restricted to specific locations with gauge stations, hindering basin-wide water resource planning and management. To address these challenges, this study proposes a hybrid Hydrological model, Empirical Orthogonal Function analysis, Gaussian Process Regression (HEG) model, which demonstrates higher accuracy in daily runoff prediction across the entire basin compared to the traditional multi-model ensemble mean method, with KGE improved by 0.09~0.11, and NSE improved by 0.08~0.32). Moreover, to enhance the estimation of future extreme flood risks which are of great concern of the public but are often predicted with high uncertainty, the model incorporates uncertainty interval information into prediction and is called HEGU model. Evaluations conducted in the topographically and climatically diverse Brahmaputra River Basin confirm the effectiveness of the HEGU model. The relative error of peak discharge (REPD) is reduced to an average of ~46% of that obtained through the ensemble mean method, while the correlation coefficient (CC) for flood volume estimation during the monsoon period increases from -0.054 to 0.645. Furthermore, the HEGU model demonstrates the potential to improve overall runoff prediction accuracy across the basin when the data quality of extremely few grids in the high-fidelity dataset is enhanced. The enhancement can be achieved through the incorporation of additional runoff gauge stations, remote sensing data, and other data augmentation techniques. These findings underscore the practical significance of the HEGU model, indicating its high effectiveness and applicability in real-world future hydrological projection and water resource management scenarios.

How to cite: Wang, J., Zhao, J., and Wang, Q.: A Long-term Spatial Runoff and Flood Prediction Method in Higher Accuracy, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1225, https://doi.org/10.5194/egusphere-egu24-1225, 2024.

EGU24-1606 | ECS | Posters on site | HS2.2.9

Integrated Approach to Mekong River Flow Modeling: Data Gaps and Climate Trends 

Khosro Morovati, Keer Zhang, and Fuqiang Tian

The transboundary Mekong River, spanning approximately 4800 km with numerous tributaries and floodplains, serves as a vital resource for power generation, fisheries, and agriculture. Despite its significance, the river's productivity faces disruption due to inadequate cooperation among riparian countries regarding data sharing, the uneven distribution of gauging stations, and data gaps for many parts of the river length. This disparity poses challenges in accurately modeling the river's natural runoff, flow characteristics, and the flooded area, navigating through mountainous and relatively flat terrains.

To address this, we have developed an integrated modeling framework comprising a physically-based hydrological model and a hydrodynamic model. For 2500 km of the Mekong River’s mainstream, a highly accurate hydrodynamic model was developed. The produced velocity, water level, and discharge data were compared with gauging stations with continuous data records, showing high accuracy with NSE exceeding 0.93. Additionally, a point-by-point comparison of the yielded water level and discharge data by the hydrodynamic model was conducted with the low-resolution recorded data for stations lacking continuous time series data. Results indicated a high accuracy with an average NSE greater than 0.91, demonstrating the model's precision in capturing the dynamic behavior of the Mekong River.

The hydrodynamic model's results were then used to fill data gaps in stations with significant data deficiencies, allowing the production of reliable data and sufficient gauging network distribution for the entire basin. These datasets, combined with recorded gauging data, served as the calibration stations for the developed physically-based hydrological model. This calibration aimed to assess the impacts of climate change on natural runoff, encompassing not only the mainstream but also tributaries and lake floodplains of the Mekong River. Findings revealed a discernible declining trend in natural runoff within the Mekong River over the specified four-decade period.

This enhanced modeling capability is particularly crucial for accurately simulating dynamic river flows with insufficient continuous data. Our comprehensive approach contributes to a more precise understanding of the Mekong River's complex hydrological dynamics, supporting informed decision-making for sustainable resource management.

How to cite: Morovati, K., Zhang, K., and Tian, F.: Integrated Approach to Mekong River Flow Modeling: Data Gaps and Climate Trends, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1606, https://doi.org/10.5194/egusphere-egu24-1606, 2024.

EGU24-4402 | ECS | Posters on site | HS2.2.9

A comprehensive method based on machine learning schemes in predicting river flow, case study: Po River 

Golmar Golmohammadi, Babak Razdar, Kourosh Mohammadi, Giovanna Grossi, and Saman Javadi

River flow forecasting has been the focus of many researchers for many years.  The methods evolved from simple statistical methods to highly sophisticated mathematical models.  In recent years, due to the advancement of computers and artificial algorithms, new methods have become increasingly reliable and easier to use.  One of the promising artificial intelligence methods is the Extreme Gradient Boosting (XGBoost) model.  XGBoost is a scalable, distributed gradient-boosting decision tree machine learning library.  It provides parallel tree boosting and is the leading machine learning library for regression, classification, and ranking problems.  Three different algorithms of XGBoost were used in this research and the results were compared.  These algorithms were Random Search, Grid Search, and CatBoost. The proposed models were conducted in a station located Pò River basin which is the longest river in Italy, and it flows from the Cottian Alps and ends at a delta projecting into the Adriatic Sea new Venice.  The data were divided into training and validation sets.  The statistical indicators included mean square error, Nash-Sutcliffe efficiency, and mean absolute error were calculated for each set to compare the efficiency of each algorithm.  These indicators showed that XGBoost using random search algorithm had better performance, although the other algorithms were also acceptable predictions.  In general, the XGBoost model could be used as a reliable tool to forecast the river flow at locations with enough historical data.

How to cite: Golmohammadi, G., Razdar, B., Mohammadi, K., Grossi, G., and Javadi, S.: A comprehensive method based on machine learning schemes in predicting river flow, case study: Po River, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4402, https://doi.org/10.5194/egusphere-egu24-4402, 2024.

EGU24-4407 | ECS | Posters on site | HS2.2.9

 Daily Streamflow Simulations Improvement in Data Scarce Watersheds using different Optimization Techniques and Calibration Methods 

Khaoula Ait naceur, El mahdi El khalki, Abdessamad Hadri, Oumar Jaffar, Luca Brocca, Mohamed El mehdi Saidi, Yves Tramblay, and Abdelghani Chehbouni

Hydrological modeling is critical for effective water resources management, especially in developing countries such as Morocco where data are scarce. This study aims to improve daily river discharge predictions in 26 Moroccan catchments from 1993 to 2019. It evaluates the GR4J and MISDc models, focusing on optimizing their performances using four optimization techniques: Particle Swarm Optimization (PSO), the Nelder-Mead simplex algorithm (FMIN), Simulated Annealing (SA), and the Genetic Algorithm (GA). The two hydrological models are coupled with six calibration methods to provide the different ranges of uncertainties and to assess their consistency across diverse datasets. The methods include the split-sample or half-half method, the odd/even year method, as well as the calibration on a longer period than validation and vice versa. In addition, the Kling-Gupta Efficiency (KGE) and the relative bias were used as performance criterions. Due to the high elevation of some catchments studied and to the important amount of the snowmelt contribution in the river discharge at their outlets, a snow module incorporation was necessary to assess whether snowmelt impacts runoff or not. The outcomes demonstrate that all algorithms were able to successfully calibrate the GR4J and MISDc models (-0.26<median KGE< 0.34). However, FMIN and PSO demonstrated greater consistency in their performance across all calibration methods and proved to be the most computationally efficient algorithms, making them the best choices in situations requiring both time effectiveness and performance. Despite its slower speed, GA's robustness makes it a viable option under less time-sensitive conditions. The relative bias metric indicates that for the GR4J model, the FMIN, PSO, and GA had comparable and balanced performance, while SA showed greater variability. For the MISDc model, FMIN showed a tendency to slightly underestimate the discharge, while GA and PSO showed higher biases in some cases. In addition, MISDc significantly outperformed GR4J in simulating runoff across all catchments, making it a suitable choice for our region. The integration of a snow module in both models enhanced their performance in some larger pluvio-nival catchments, illustrating the complexity of snow dynamics in hydrological modeling and the need for high resolution data as well as ground measurements.

Keywords: River discharge prediction, GR4J, MISDc, Moroccan catchments, Optimization methods, Data scarcity.

How to cite: Ait naceur, K., El khalki, E. M., Hadri, A., Jaffar, O., Brocca, L., Saidi, M. E. M., Tramblay, Y., and Chehbouni, A.:  Daily Streamflow Simulations Improvement in Data Scarce Watersheds using different Optimization Techniques and Calibration Methods, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4407, https://doi.org/10.5194/egusphere-egu24-4407, 2024.

The Salt Dilution Tracer method has been used in some form for >100 years (Allen and Taylor, 1923, Østrem, G. 1964, Moore, D 2004).  Recently, the method has undergone a renaissance as techniques and equipment have been improved, facilitating lower dosing (<100g/cms) and increased accuracy.  This paper studies the impact and best practices for filtering, extrapolation, and interpolation of the breakthrough curve to reduce uncertainty, and more importantly, extend the tail of the slug injection signal if the measurement is ended early.  By extrapolating, the user can leave the field in as little half the time, while introducing only +/- 5% uncertainty.  We examine different fitting models (gamma, SCS Unit Hydrograph, χ2, etc) and fitting methods.  An online fit/fill/filter tool is presented and happiness of user is optimized.

How to cite: Sentlinger, G. and Anderson, Z.: Fitting, Filling, and Filtering of Salt Dilution Breakthrough Curves for Reduced Field Time, Increased Accuracy, and Optimized Happiness, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4685, https://doi.org/10.5194/egusphere-egu24-4685, 2024.

EGU24-4937 | Orals | HS2.2.9

Flexible and physically based stage–discharge rating curves using a "double-Manning" approach 

Andrew Wickert, Jabari Jones, and G.-H. Crystal Ng

Rating curves translate between river stage (i.e., water level) and water discharge. They are applied ubiquitously for stream monitoring, water-resource estimation, and flood forecasting. However, they are calculated using a basic empirical power-law fit that lacks flexibility to robustly represent channel–floodplain structure or to adapt to changing hydraulic geometry or roughness. Furthermore, such empirical fits require many measurements of stage and discharge. Gathering these measurements is expensive and might not be possible if the channel and/or floodplain evolve before a sufficient range of flows may be measured.

To address this deficit with a similarly simple but physically grounded approach, we present a strategy based on Manning's equation. This "double-Manning" approach implements Manning's equation within and above the channel and a power-law relationship – analogous to a generalized Manning's equation – for flows crossing the floodplain. We demonstrate that the double-Manning equation can effectively fit field data and, in the process, accurately estimate bankfull width, bankfull depth, channel Manning's n, and Manning-style power-law parameters for floodplain-flow characteristics. For sites lacking exhaustive field data, the physical basis of the double-Manning approach enables rating-curve creation using a combination of stage–discharge data and common field measurements of the channel and floodplain. Such rating curves may be adjusted as the channel and floodplain evolve to predict how geomorphic change might affect flow depth and flood inundation.

The double-Manning approach may be run as a forward (predictive) or inverse (fit to data) model. Documented, open-source code may be acquired from GitHub (https://github.com/MNiMORPH/doublemanning) and Zenodo.

How to cite: Wickert, A., Jones, J., and Ng, G.-H. C.: Flexible and physically based stage–discharge rating curves using a "double-Manning" approach, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4937, https://doi.org/10.5194/egusphere-egu24-4937, 2024.

EGU24-5805 | ECS | Posters on site | HS2.2.9

IRIS: Global Reach-Scale River Surface Slopes from the ICESat-2 Satellite  

Daniel Scherer, Christian Schwatke, Denise Dettmering, and Florian Seitz

We present the latest version of the global reach-scale “ICESat-2 River Surface Slope” (IRIS) dataset, which comprises average and extreme water surface slopes (WSS) derived from observations of the ICESat-2 satellite between October 2018 and August 2023 as a supplement to 130,283 reaches from the “SWOT Mission River Database” (SWORD). To gain full advantage of ICESat-2’s accurate and unique measurement geometry with six parallel lidar beams, the WSS is determined across pairs of beams or along individual beams, depending on the intersection angle of spacecraft orbit and river centerline. Combining both approaches maximizes spatial and temporal coverage. IRIS can be used to research river dynamics, estimate river discharge, and correct water level time series from satellite altimetry for shifting ground tracks. Additionally, we compare IRIS with observations from the recently launched SWOT mission. 

How to cite: Scherer, D., Schwatke, C., Dettmering, D., and Seitz, F.: IRIS: Global Reach-Scale River Surface Slopes from the ICESat-2 Satellite , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5805, https://doi.org/10.5194/egusphere-egu24-5805, 2024.

EGU24-6865 | ECS | Orals | HS2.2.9

Monitoring river morphology with Sentinel 2 data: limitations and opportunities across scales  

Elisa Bozzolan, Simone Bizzi, Andrea Brenna, Nicola Surian, and Patrice Carbonneau

Satellite imageries are starting to become for geomorphologists a new tool to monitor medium-large river dynamics at high revisit time (weekly or daily). The Sentinel 2 mission, in particular, provides without charges a multi-spectral image of the earth surface at 10 meters resolution every 5 days (cloud cover permitting). Machine learning algorithms can then classify these images, automatically discriminating those river macro-geomorphic features, i.e. water, sediment and vegetation, that describe how a river responds to different hydrological impulses and boundary conditions. When using these tools (Sentinel 2 images + machine learning algorithm), it is important to first identify what geomorphic processes we can reliably detect, i.e. what are the applicability boundaries dictated by the spatio-temporal resolution of these images. In a dynamic, braided reach of the Sesia River (Northern Italy), we assessed how this inherent uncertainty associated with S2's spatiotemporal resolution can impact the interpretation of the active channel (a combination of sediment and water) delineation and evolutionary trajectory. The analysis demonstrates that water is ∼20% underestimated whereas sediments are ∼30% overestimated. These under- and over-underestimations are not random but a function of the mixed pixels present in each classified macro geomorphic unit. Nevertheless, the results show that these spatial errors are an order of magnitude smaller than the geomorphic changes detected in the 5 years analysed, so the derived active channel trajectory can be considered robust. Within these newly assessed applicability boundaries, in the Po River basin we started to explore in similarly dynamic river reaches new geomorphic indicators able to describe river responsiveness to seasonality and to different flood regimes.

How to cite: Bozzolan, E., Bizzi, S., Brenna, A., Surian, N., and Carbonneau, P.: Monitoring river morphology with Sentinel 2 data: limitations and opportunities across scales , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6865, https://doi.org/10.5194/egusphere-egu24-6865, 2024.

The 4DMED-Hydrolog ESA project aims at developing a high-resolution (1km) and consistent reconstruction of the Mediterranean terrestrial water cycle by using the latest Earth Observation (EO) products. We exploit here the synergy between available EOs to better estimate the terrestrial water cycle components (i.e., precipitation P, evaporation E, water storage dS and river discharge RD). The obtained, more accurate, representation of our environment is intended to feed decision support systems, in a changing climate, for a more resilient society. Among the water components, RD is strategic because it integrates many water-related processes. Unfortunately, in situ RD measurements are very sparse spatially. This paper presents a new approach for the mapping (i.e., spatially continuous estimate) of RD based on indirect EOs and a water budget balance constraint. First, satellite estimates of P, E, and dS are corrected, at the basin scale, using RD from a gauge network. Second, the water budget is balanced at the grid level using a horizontal flow direction information from topography. This approach is therefore based on satellite products and in situ measurements, without the use of any dynamical model. This methodology is used over the Po and Ebro basins. We use the new P, E, and dS data products, at high spatio-temporal resolution (1km and daily), developed in the 4DMED project. The resulting RD mapping is evaluated using a leave-one-out experiment, resulting in a mean KGE of 0.6 over the Ebro, to be compared to 0.5 for a river dynamical model such as Continuum. The spatially continuous RD is, by design, closer to the in situ measurements. Such work combining EO datasets to optimize, at high spatial resolution, to optimize our monitoring of the water cycle opens new doors for hydrology, water management, agriculture, as well as natural hazards predictions and response.

References:

  • Pellet, Aires, Yamazaki, Zhou, Paris, A first satellite-based mapping of river discharge over the Amazon. Journal of Hydrology,  10.1016/j.jhydrol.2022.128481, 2022.
  • Pellet, Aires, Yamazaki, Satellite monitoring of the water cycle over the Amazon using upstream/downstream dependency. Part I: Methodology and initial evaluation. Water Resources Res., 57, e2020WR028647, 2021.
  • Pellet, Aires, Yamazaki, Papa, Satellite monitoring of the water cycle over the Amazon using upstream/downstream dependency. Part II: Mass-conserved reconstruction of total water storage change and river discharge. Water Resources Research, 57, e2020WR028648, 2021.
  • Pellet, Aires, Munier, Papa, Long-term estimate of the water storage change in the large Himalayan river basins from water budget closure, HESS, 5194/hess-24-3033-2020, 2020.
  • Pellet, Aires, Munier, Optimisation of satellite observations to study the water cycle over the Mediterranean region, HESS, 5194/hess-2018-319, 2019.
  • Pellet, and Aires, Analyzing the Mediterranean water cycle via satellite data integration, Pure Appl. Geophys, 10.1007/s00024-018-1912-zpp, 2018.
  • Munier, Aires, A new global method of satellite dataset merging and quality characterization constrained by the terrestrial water cycle budget, RSE, 2017
  • Munier, Aires, Schlaffer, Prigent, Papa, Maisongrande, and Pan, Combining datasets of satellite retrieved products. Part II: Evaluation on the Mississippi Basin and closure correction model, JGR, 10/2014, 10.1002/2014JD021953, 2015
  • Aires, Combining datasets of satellite retrieved products. Part I: Methodology and water budget closure, J. Hydrometeor., 10.1175/JHM-D-13-0148.1, 2014

How to cite: Pellet, V. and Pellet, V.: Satellite-based mapping of river discharge at very high spatio-temporal resolution over the Ebro and Po basins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7740, https://doi.org/10.5194/egusphere-egu24-7740, 2024.

EGU24-9754 | Posters on site | HS2.2.9

An ADCP large-scale international intercomparaison: Sault-Brénaz 2023 

Aurélien Despax, Blaise Calmel, Jérôme Le Coz, Alexandre Hauet, and David Mueller

In the last decades, Acoustic Doppler Current Profilers (ADCP) has become the most widely used tool for measuring discharge of rivers and canals. Discharge is a key information for many risk studies, structures dimensioning and even impact assessments. These values must therefore be correctly estimated. Quality assurance and quality control (QA/QC) procedures have been established to ensure that hydrological services share the best practices. Also, to ensure that ADCP tools are working properly, services has to regularly check that the equipment is properly calibrated.

The lack of references value most of the time makes the task difficult. To make sure that ADCP is properly calibrated, interlaboratory testing are frequently organized. Large-scale intercomparaisons are particularly interesting because of the diversity of models and practices but it also makes them more complicated to organize. The Sault-Brénaz intercomparaison was definitively a big one with more than 120 European participants with 16 RiverPro, 15 M9, 15 StreamPro and 12 RS5 for a total of 160 measurements with 1870 transects among 4 sessions. Due to hydrological conditions, the protocol had to be adapted. Measurements took place on small straight canal of the Rhone river with a discharge of around 2m3/s.

Following QA/QC procedures, participant had to post-process their data with the QRevInt open-source software. QRevInt provides many quality filters and computes uncertainty following OURSIN method. Then, to compute interlaboratory results, the QRame software has been used. This open-source software has been developed to apply QRevInt with default settings to a set of ADCP discharge measurements and to retrieve post-processed discharge and uncertainty results. When the dataset is actually an ADCP interlaboratory experiment, the empirical discharge uncertainty, for a given number of transects taken in the average, can be computed by application of the standard interlaboratory method.

Results show that discharge varied slightly over time, particularly between sessions. To exploit further all the discharge results, different approaches to homogenizing data were tested. This issue of varying discharge over time is a common issue for interlaboratory experiments. A generalizable solution would enable experiments in extended conditions. Also, interlaboratory experiments permit to validate uncertainty computations. The greater the number of intercomparisons and the wider the measurement conditions, the more robust uncertainty models will be.

How to cite: Despax, A., Calmel, B., Le Coz, J., Hauet, A., and Mueller, D.: An ADCP large-scale international intercomparaison: Sault-Brénaz 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9754, https://doi.org/10.5194/egusphere-egu24-9754, 2024.

EGU24-11189 | ECS | Posters on site | HS2.2.9

A Contactless Rapid Rating Curve Assessment Based On Drone-borne Measurement 

Xinqi Hu, Ye Tuo, Karl Broich, Fabian Merk, and Markus Disse

Rating curve relationship is vital to hydrological studies, such as flood control and other water-related decision-making processes. Traditionally, rating curve are estimated by using single- or multiple-gauging observations, which is time-consuming, costly, and lacks spatial resolution. Hydraulic models are usually a reliable method to quickly derive the stage-discharge relation for discharge estimation, especially for assessing more reliable high-flow rating relations in extrapolation beyond gauge observation. To establish such models, hydraulic parameters such as water surface elevation, bathymetry, and bed roughness are needed, but they are mostly not available in remote and inaccessible regions. Drone-borne hydrometric monitoring technologies can be deployed to address this problem.

As one of the primary objectives of the Horizon Europe UAWOS project, which is dedicated to developing an Unmanned Airborne Water Observing System for providing key hydrometric variables at high spatial resolution/coverage, and data-based products/services to enhance management and decision-making, this work centers on integrating hydraulic modeling with the unmanned airborne water observing system to establish the rating curve relationship. Water surface elevation data is derived by radar altimetry, bathymetry data by water penetrating radar and sonar, and Doppler radar for surface velocity. By utilizing the surface velocity and water surface elevation data, in conjunction with shallow-water equations, a bathymetry estimation algorithm is used to interpolate the bathymetry from the observed cross-section to the whole simulated river channel. We also come up with a method to directly retrieve the river roughness parameter from the UAV drone observation data.

As a whole, these methods collectively establish a framework that is easily to use to estimate the rating curve in remote regions. The study shows how information from high spatial resolution and coverage hydrometric variables derived by drone-borne hydrometric monitoring technologies can improve rating curve estimates from models.

How to cite: Hu, X., Tuo, Y., Broich, K., Merk, F., and Disse, M.: A Contactless Rapid Rating Curve Assessment Based On Drone-borne Measurement, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11189, https://doi.org/10.5194/egusphere-egu24-11189, 2024.

EGU24-12507 | Posters on site | HS2.2.9

Towards a comprehensive optical workflow for monitoring and estimation of water levels and discharge in watercourses 

Jens Grundmann, Xabier Blanch, André Kutscher, Ralf Hedel, and Anette Eltner

Coping with natural disasters such as floods places special demands on the emergency units. From the point of view of command-and-control operators, observations of watercourses are desirable in the event of flooding in order to obtain an accurate picture of the situation. Optical measurement methods using cameras offer thereby advantages as they do not require water contact and hence can be used safely. Therefore, the project "KIWA: Artificial Intelligence (AI) for Flood Warning" (http://kiwa.hydro.tu-dresden.de/) is developing AI-based tools for the robust quantification of water levels, flow velocities and flow rates from surveillance cameras.

In this article, we present the workflow for an exclusive optical measurement of time series of water level and discharge from single images and short video sequences. The basis is a high-precision (i.e., at centimetre level), georeferenced 3D terrain model of the measurement site including the riverbed. The terrain model is created using the structure-from-motion (SfM) technique and georeferenced via ground control points (GCPs) measured with a multiband GNSS receiver. To determine the water level, the water area in the single images is automatically segmented using AI based on convolutional neural networks (CNNs) and then intersected with the terrain model. Changes of the camera geometry influence the measurement accuracy during long-term observations. Therefore, the GCPs are automatically detected in the individual images with an adapted AI-based keypoint detector to frequently update the estimated camera orientation. To estimate the discharge, the water surface flow velocity is determined using short video sequences and applying the particle tracking (PTV) method, whereby the segmented water area narrows down the search area for the particle detection. Afterwards, the "OptiQ" modelling approach is used to derive the discharge times series based on the PTV measurements. Thereby, data filtering and error correction methods are used to achieve continuous time series. 

The methods were developed at three different measuring gauges, whose cameras record single images and videos every 15 minutes over several months. The accuracy of the water level measurement is in the centimetre range, even at night with the support of infrared emitters. Depending on the water level, there are deviations in the flow rate, which average less than 10%.

How to cite: Grundmann, J., Blanch, X., Kutscher, A., Hedel, R., and Eltner, A.: Towards a comprehensive optical workflow for monitoring and estimation of water levels and discharge in watercourses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12507, https://doi.org/10.5194/egusphere-egu24-12507, 2024.

EGU24-14090 | ECS | Orals | HS2.2.9

Optimizing Flood Control: A Comprehensive 3D Computationsl Fluid Dynamic Study of the Comite Diversion Channel in the Comite and Amite River Basins 

Christopher Denney, Gaurav Savant, Abigail Grant, Tate McAlpin, and Keaton Jones

To address the escalating challenges posed by extreme weather events and the critical importance of water management, this presentation focuses on innovative methodologies in streamflow monitoring and prediction. Specifically, we present a comprehensive study undertaken to enhance flood mitigation in the Comite and Amite River Basins of central Louisiana.

In response to the imperative need for effective flood control, a 12-mile diversion channel has been designed to redirect flow from the Comite River into the Mississippi River. Our research, commissioned by the United States Army Corps of Engineers, New Orleans District, aims to quantify the impact of design modifications on crucial flow parameters within the diversion structure. We employ advanced three-dimensional, multiphase computational fluid dynamics (CFD) modeling techniques, utilizing the open-source OpenFOAM library with the interFoam finite volume solver.

The study evaluates the alignment of the diversion channel by analyzing flow diversion, velocity profiles, and streamlines within the channel and the associated hydraulic control structure. Special emphasis is placed on understanding the dynamics of the drop structure flow, interactions with upstream drainage features, and potential sediment accumulation risks. Our model, validated through perturbations in turbulence models, boundary roughness, and grid independence studies, provides valuable insights into the performance of the diversion structure under various flow conditions. 

In conclusion, our findings underscore the importance of informed engineering decisions for fostering climate resilience in riverine regions. By providing insights into the dynamics of the diversion channel and quantifying uncertainties associated with flow parameters, this study offers actionable solutions to enhance streamflow monitoring efficiency in the face of evolving hydrological challenges.

How to cite: Denney, C., Savant, G., Grant, A., McAlpin, T., and Jones, K.: Optimizing Flood Control: A Comprehensive 3D Computationsl Fluid Dynamic Study of the Comite Diversion Channel in the Comite and Amite River Basins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14090, https://doi.org/10.5194/egusphere-egu24-14090, 2024.

EGU24-14133 | Orals | HS2.2.9 | Highlight

Measuring stream discharge using audible sound 

Marek Zreda

Before we see a stream we can hear it. The discharge of that stream can be inferred from measurements of its sound. Sound pressure level is proportional to the energy of the flowing water and is related to discharge by a sound-discharge rating curve. Measurements with a hand-held sound level meter take seconds to acquire, allowing for high-resolution, long-term monitoring of stream discharge, campaign surveys, and ad hoc measurements. Sound measurements correlate well with the standard stream gauge data over the full range of discharges studied, from 0.02 m3/s to 33 m3/s. The following characteristics make the method an attractive alternative to the standard stream gauging: the instrumentation is simple and inexpensive; field deployment requires no built infrastructure; the instrument is suitable for rapid or emergency deployment; the measurements are non-invasive and non-contact, made at a distance from the stream, using a stationary or roving instrument; the acoustic response curve is linear; and the interfering sound sources are either negligibly small or easily removed.

If there is enough time, attendees will be able to create their own sound-discharge rating curve using their cell phones and the Decibel-X app to measure sound intensity. The conference room's audio equipment will provide sound clips of an actual stream along with the independently measured discharges.

How to cite: Zreda, M.: Measuring stream discharge using audible sound, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14133, https://doi.org/10.5194/egusphere-egu24-14133, 2024.

EGU24-15519 | ECS | Posters on site | HS2.2.9

Exploring the relative scale of uncertainty in high-resolution soil moisture remote sensing products towards model integration  

Pietro Stradiotti, Wouter Dorigo, and Luis Samaniego

Soil moisture (SM) is a fundamental hydrological variable for understanding processes in the land-atmosphere, biological, or geophysical domains and an output of many hydrological or land surface models. It is peculiar in that its variability reflects distinct hydrological processes moving from the field scale, where local topography plays a role, to the regional scale, where meteorological forcing is the main control. Correctly representing this variety of processes is a complex modeling task often alleviated by integrating information from well-established Earth Observation (EO) systems, which produce SM data with near global coverage at coarse (10-25 km) resolution. Still, the increasing need for fine scale (1 km, 1 day) simulations of the water cycle is to be met by EO data of similarly high resolution. 

High resolution satellite-based SM data is now available from several sources. 1km datasets are multiplying following simultaneous efforts to retrieve SM from backscatter measurements of the Sentinel-1 mission with various inversion models. At the same time, physical or statistical relationships are leveraged to down-scale coarse resolution products by ingesting data from distinct observational sources, coming from the mentioned Sentinel-1 or the optical domain. However, while products of the first type are confronted with the limited sensitivity of C-band microwave to SM and reduced spatial and temporal availability, down-scaled products might retain much of the original signal and fail the fine-scale process representation. The question of which of these resources can preferably be integrated to reliably improve high-resolution modelling is therefore an open one. 

In this study we perform a round robin (i.e., inter-comparative) assessment of the most prominent high-resolution SM products in the EO landscape. While adapting validation and error characterization techniques and tools (e.g., the Quality Assurance for SM service) that are routinely used at the coarse scale, we address the partial lack of 1km scale reference measurements through the application of an emerging high resolution validation framework. Such a framework demonstrates that metrics for high resolution benchmarking can be reliably retrieved with only sparse, point-scale measurements. The first results suggest that the true spatial SM heterogeneity might explain a minimum noise tradeoff between coarse- and high-resolution EO products. This work is a fundamental step to assess the current state-of-art in EO and its maturity for integration in high-resolution water cycle modelling.

How to cite: Stradiotti, P., Dorigo, W., and Samaniego, L.: Exploring the relative scale of uncertainty in high-resolution soil moisture remote sensing products towards model integration , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15519, https://doi.org/10.5194/egusphere-egu24-15519, 2024.

EGU24-16356 | Posters on site | HS2.2.9

Sharing perceptual models of uncertainty – on the use of soft information about discharge data uncertainty 

Ida Westerberg and Reinert Huseby Karlsen

Many hydrologists face the situation that they have no, or very limited, information about the uncertainty in the discharge data they are using. Data uncertainty is rarely communicated by monitoring agencies and data providers – and is often not available on request. This means that data users typically treat data as if they are error-free, whereas in reality there can be large uncertainties and errors.

However, the absence of metadata and ‘hard’ information about data uncertainty does not mean that there is no information about the data uncertainty. Instead, we can use other types of ‘soft’ information to understand the likelihood that discharge data in a particular location are uncertain. For example, if high flows are of short duration (i.e., a few hours) and the rainfall-runoff lag time is short, it is practically quite difficult to manage to gauge high flows, leading to likely extrapolation of stage–discharge rating curves and large high flow uncertainty. A second example is if a river is ice-covered during the winter season, then most of the winter water-level time series is subjectively estimated, leading to substantial uncertainty in winter low flows. Such soft information about data uncertainty is well known by field hydrologists and data uncertainty experts but is not as commonly known in the wider hydrological community. In this presentation we focus on uncertainty in discharge data calculated from stage–discharge rating curves and aim to share – and to encourage sharing – of soft information about data uncertainty sources, to promote more informed decisions on data uncertainty in hydrological studies.

We summarize the soft information about discharge data uncertainty as a perceptual model of uncertainty. Our perceptual model divides the soft information into three categories: station characteristics, climate and flow regime, and catchment characteristics. For each category we present and describe different types of soft information, the uncertainty sources and impacts they can inform us about, and sources for each soft information type (e.g., photos, satellite images, land use). We find that soft information can inform us about three main types of uncertainty sources: uncertainty related to the hydraulic control, uncertainty related to incomplete gauging of the full flow range, and uncertainty due to measurement error.

Our generalised perceptual model can be seen as a smorgasbord of information about uncertainty sources, where the soft information can be considered as relevant to a particular dataset and can inform us if high or low data uncertainty is likely. We believe that a key benefit of the type of generalized perceptual model of uncertainty we present is to facilitate dialogue on, and understanding of, possible sources of observational uncertainties and their impacts.  We encourage others to complement our perceptual model of discharge data uncertainty based on experience from different regions and for other discharge monitoring techniques such as index-velocity stations or drone/camera-based methods.

How to cite: Westerberg, I. and Huseby Karlsen, R.: Sharing perceptual models of uncertainty – on the use of soft information about discharge data uncertainty, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16356, https://doi.org/10.5194/egusphere-egu24-16356, 2024.

EGU24-16913 | ECS | Posters on site | HS2.2.9

Characterizing the space-time evolution of wet channels in a non-perennial Mediterranean catchment exploiting a network of camera traps 

Simone Noto, Nicola Durighetto, Flavia Tauro, Salvatore Grimaldi, and Gianluca Botter

Non-perennial streams are those streams that periodically cease to flow in at least one point along their network. The research community well recognizes the importance of such watercourses for they have a global prevalence and provide diverse hydrological functions and ecosystem services. The spatiotemporal pattern of the active drainage network is anything but simple, sometimes showing a very complex pattern. Non-perennial streams, in fact, are often located in heterogeneous environments, in which the combination of climate, morphology, land cover, soil, substrate, and anthropic factors could play a role in the observed drying and wetting patterns. This work combined two techniques, with different spatiotemporal resolutions, to characterize the spatiotemporal extent of the stream network in a 3.7 km2 Mediterranean catchment of central Italy. The hydrological status of a set of nodes of the network was derived for the period 2020-2022 from sporadic visual surveys and, most importantly, through the analysis of sub-hourly images collected by 21 cameras distributed along a set of strategic nodes of the network. The latter technique is particularly promising to reconstruct the hydrological dynamics taking place in the target cross-section, as the temporal evolution of the underlying hydrological conditions (wet vs. dry), the water stage, and the corresponding discharge can be inferred from the automatic or manual analysis of the acquired images. The available experimental data  was combined exploiting the hierarchical principle, that postulates the existence of a Bayesian chain based on the local persistency of the nodes that dictates their drying/wetting order during stream retraction/contraction cycles. The results highlighted the complexity of the network dynamics in the study area: while the number of wet nodes decreased during the dry season and increased during the wet season, the local persistency of the nodes showed a highly heterogeneous and non-monotonic pattern, resulting in a dynamically disconnected network. The approach allowed the reconstruction of the entire river network and represented a useful tool to estimate the extent of its wet portion, even in case part of the network could not be inspected. This work represents a novel approach to reconstruct the extension of the wet portion of the stream network in difficult-to-access environments, where traditional techniques might be inadequate.

How to cite: Noto, S., Durighetto, N., Tauro, F., Grimaldi, S., and Botter, G.: Characterizing the space-time evolution of wet channels in a non-perennial Mediterranean catchment exploiting a network of camera traps, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16913, https://doi.org/10.5194/egusphere-egu24-16913, 2024.

EGU24-16956 | ECS | Orals | HS2.2.9 | Highlight

Improving the resolution of satellite precipitation products in Europe 

Paolo Filippucci, Luca Ciabatta, Hamidreza Mosaffa, and Luca Brocca

Climate change is increasing the challenges related to extreme weather events, shifting precipitation patterns, causing water scarcity and increasing the occurrence of natural disasters. Accurate and timely precipitation data are critical for understanding and mitigating these events, as well as for informing decision-makers. Specifically, Europe climatic and physiographic features make capturing fine-scale (1 km-daily) variations crucial to improve the precision of climate models and facilitate targeted adaptation strategies in this area.

This can be achieved by using the recent remote sensing technologies, which allow to systematically monitor wide areas without the need of maintaining ground networks. In particular, for satellite precipitation estimation, both the top-down and bottom-up approaches have been exploited in recent years to obtain information related to rainfall. Both the methodologies carry advantages and limitations. Their merging, coupled with high spatial resolution ancillary information, is therefore recommended to reach the final aim of detailed and accurate precipitation data.

In this study, the rainfall data obtained from IMERG Late Run and SM2RAIN ASCAT (H SAF) are downscaled and merged over the whole Europe. The downscaling is obtained by leveraging high spatial resolution statistical information from CHELSA product, while a triple collocation technique is applied to merge the two downscaled datasets. The resulting high resolution rainfall is subsequently compared against multiple products, including coarse resolution ones such as H SAF, IMERG-LR, ERA5, EOBS, PERSIANN, CHIRP, GSMAP, and high-resolution products like EMO, INCA, SAIH, COMEPHORE, MCM, 4DMED. These comparisons, spanning ground, model and satellite data, serve to assess its capabilities in estimating precipitation over Europe.

How to cite: Filippucci, P., Ciabatta, L., Mosaffa, H., and Brocca, L.: Improving the resolution of satellite precipitation products in Europe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16956, https://doi.org/10.5194/egusphere-egu24-16956, 2024.

EGU24-17533 | Posters on site | HS2.2.9

A Round Robin Exercise for an intercomparison of Snow Cover Area maps retrieved from Earth Observation 

Federico Di Paolo, Matteo Dall'Amico, Pietro Stradiotti, and Luis Samaniego

In Europe, the majority of the precipitation during winter falls as snow over 1.000 m altitude, and remains stored in the snowpack until the melting season, when it returns in the hydrological cycle and is partly used for irrigation and power generation. Snow cover estimation is then one of the main indicators necessary to evaluate water budget and plan water management, predict possible drought conditions, and drive operational flood prediction. 

The use of Earth Observation (EO) for Snow Cover Area (SCA) estimation has been improved during the last decade thanks to high resolution satellites such as the ESA Sentinels, having a pixel resolution of 10 m. Furthermore, diverse processing techniques, nowadays mature, are used by the different data providers to retrieve SCA and Fractional Snow Cover (FSC) maps from EO data.

The scope of our work is an intercomparison of different medium- to high-resolution EO-retrieved SCA/FSC maps over Europe; we use as a benchmark a vast dataset of in situ data coming from different sources and harmonized by Matiu et al. (2021). 

Regarding the dataset, SCA or FSC maps retrieved from multispectral Sentinel-2 and Landsat-8 images are considered, together with gap-filled maps evaluated integrating Sentinel-1 (Synthetic Aperture Radar) and/or Sentinel-3 (multispectral). A unique dataset of Sentinel-1-retrieved snow depth maps is also used in the exercise. Finally, for a continuity with a previous project on EO snow products, medium-resolution MODIS-retrieved SCA images have been added to our dataset.

The results can be used to correctly interpret the accuracy of the EO datasets as well as the processing methodologies. From the comparison it can be evaluated the possibility of merging the different dataset in order to enhance the temporal resolution to a sub-weekly effective revisit time.

How to cite: Di Paolo, F., Dall'Amico, M., Stradiotti, P., and Samaniego, L.: A Round Robin Exercise for an intercomparison of Snow Cover Area maps retrieved from Earth Observation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17533, https://doi.org/10.5194/egusphere-egu24-17533, 2024.

EGU24-19308 | Posters on site | HS2.2.9

Evaluation of remote sensing actual evapotranspiration products for hydrological modeling applications 

Matěj Orság, Milan Fischer, Almudena García-García, Jian Peng, Luis Samaniego, and Miroslav Trnka

Evapotranspiration (ET) is one of the main environmental variables for the study of land-atmosphere interactions due to its interconnection with the energy and water balance at the land surface. Despite the dedicated effort of the remote sensing community to estimate the magnitude of ET at global scales, the uncertainties and differences between products are still very large, especially when comparing ET products with different spatial resolutions. Here, we designed a round-robin experiment to determine the product or products most suitable for future integration in hydrological modeling. The evaluation is performed using eddy covariance measurements as reference and point-scale downscaling (PSD) benchmarking criteria to identify the added value of the high-resolution products. The eddy covariance measurements of latent and sensible heat fluxes are known to not close the surface energy budget. Therefore, the use of eddy covariance measurements as a reference could have important consequences for the later use of ET products in assimilation approaches. Therefore, two main strategies to deal with the energy balance closure problem are considered here. Firstly, we considered three energy balance closure scenarios – (i) assigning the energy balance residuum to sensible heat flux; (ii) distributing the residuum to both turbulent energy fluxes by preserving their ratio, i.e. Bowen ratio; (iii) assigning the entire residuum to latent heat flux. While the first case has no impact on ET, the two remaining ones lead to an increase in ET. Secondly, the use of the triple collocation method, which does not require a reference dataset, will be explored to complement these results. Despite these efforts to identify the best ET product for the integration of satellite ET products in hydrological models, we cannot conclude that the products reaching the best metrics in this evaluation will be the products adding more value to the assimilation approach. Therefore, further experiments should be designed to test if the products selected in the round-robin exercise are indeed improving the performance of hydrological models or on the contrary other ET products are more suitable for assimilation approaches. We acknowledge support from AdAgriF - Advanced methods of greenhouse gases emission reduction and sequestration in agriculture and forest landscape for climate change mitigation (CZ.02.01.01/00/22_008/0004635).

How to cite: Orság, M., Fischer, M., García-García, A., Peng, J., Samaniego, L., and Trnka, M.: Evaluation of remote sensing actual evapotranspiration products for hydrological modeling applications, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19308, https://doi.org/10.5194/egusphere-egu24-19308, 2024.

EGU24-19632 | Posters on site | HS2.2.9

Eddy covariance, scintillometer, and cosmic ray 1 km scale measurements at three sites (grassland, forest, and vineyard) in North-West Italy compared with CLM simulations 

Stefano Ferraris, Alessio Gentile, Davide Gisolo, Davide Canone, Stefano Bechis, Brendan Heery, Biddoccu Marcella, Giorgio Capello, Gerrit Maaschwitz, Alexander Myagkov, Enrico Gazzola, and Luca Stevanato

Water and energy balances have been monitored at a scale which is comparable with remote sensing one in three North-West Italy sites. One step has been to evaluate the performance of a land surface model, in this work the Community Land Model. The measurements taken at the horizontal hundreds meters scale are also compared with vertical profiles of local sensors of soil moisture.

At the grassland mountain site (2600 m asl) the eddy covariance data are taken from 6 years, while the 25 m high mast eddy covariance in the forest from 3 years. The scintillometer and cosmic ray in the vineyard have been installed from one year.

The main result is to have different land cover monitored at about 1 km scale, and to see that the uncalibrated simulations with CLM are following quite well the data in most cases. Also the comparison of cosmic ray and point soil moisture time series will be discussed. The future work will be the comparison with satellite data.

This work is a part of the project NODES which has received unding from the MUR-M4C2 1.5 of PNRR grant agreement no. ECS00000036

How to cite: Ferraris, S., Gentile, A., Gisolo, D., Canone, D., Bechis, S., Heery, B., Marcella, B., Capello, G., Maaschwitz, G., Myagkov, A., Gazzola, E., and Stevanato, L.: Eddy covariance, scintillometer, and cosmic ray 1 km scale measurements at three sites (grassland, forest, and vineyard) in North-West Italy compared with CLM simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19632, https://doi.org/10.5194/egusphere-egu24-19632, 2024.

EGU24-19935 | Orals | HS2.2.9

An evaluation of low-cost terrestrial LiDAR sensors for assessing geomorphic change 

Matthew Perks, Seb Pitman, Rupert Bainbridge, Alejandro Diaz Moreno, and Stuart Dunning

For process geomorphologists, accurate topographic data acquired at appropriate spatio-temporal resolution is often the cornerstone of research. Recent decades have seen advances in our ability to generate highly accurate topographic data, primarily through the application of remote sensing techniques. Structure from Motion Multi View Stereo (SfM-MVS) and LiDAR have revolutionised the spatial resolution of surveys across large spatial extents. Continuing technological developments have led to commercialisation of small form LiDAR sensors that are suited to deployment on both mobile (e.g. uncrewed aerial systems), and in fixed semi-permanent installations. Whilst the former has been adopted (e.g. DJI Zenmuse L1), the potential for the latter to generate data suitable for geomorphic investigations has yet to be assessed. We address this gap here in the context of a three-month deployment where channel change is assessed in an adjusting fluvial system. We find that the small form sensors generate change detection products comparable to those generated using an industry-grade LiDAR system (Riegl VZ-4000). Areas of no geomorphic change are adequately characterised as such (mean 3D change of 0.014m compared with 0.0014m for the Riegl), with differences in median change estimates in eroding sections of between 0.01-0.03m. We illustrate that this data enables accurate characterisation of river channel adjustments through extraction of bank long-profiles, the assessment of bank retreat patterns which help elucidate failure mechanics, and for the extraction of water surface elevations. Deployment of this emerging, new technology will enable better process understanding across a variety of geomorphic systems as data can be captured in 4D with near real-time processing.

How to cite: Perks, M., Pitman, S., Bainbridge, R., Diaz Moreno, A., and Dunning, S.: An evaluation of low-cost terrestrial LiDAR sensors for assessing geomorphic change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19935, https://doi.org/10.5194/egusphere-egu24-19935, 2024.

EGU24-22332 | Orals | HS2.2.9

Monitoring of infrastructure at risk of scour and other hydraulic actions 

Eftychia Koursari, John MacPherson, Hazel McDonald, Maggie Creed, Stuart Wallace, Hossein Zare-Behtash, Andrea Cammarano, and Kevin Worrall

Scour is a significant impact caused by climate change on infrastructure, while also being the most common cause of bridge failure worldwide. Approximately 60% of bridge collapses are a result of scour (Briaud and Hunt, 2006; Wardhana & Hadipriono, 2003).

Climate change has resulted in the increase of extreme weather events, such as wildfires and floods among others. Global warming is evident, sea levels are rising, and the frequency and magnitude of flood events is increasing. As the climate is changing, the risk of scour is expected to increase further.

Monitoring is crucial for the identification of scour taking place around a structure, its magnitude, as well as the rate of deterioration to allow owners and operators to establish when predetermined thresholds are at risk of being reached. Scour monitoring is crucial to safeguard infrastructure that could be exposed to scour action.

According to the Design Manual for Roads and Bridges BD 97/12 Standard entitled ‘The assessment of scour and other hydraulic actions at highway structures’, scour monitoring techniques can be divided in the following categories (Highways Agency, 2012):

  • Measuring the maximum scour level that has taken place;
  • Measuring scour development adjacent to a structure during high flow events;
  • Methods correlating with scour development, such as water level monitoring, flow velocity monitoring and weather warnings.

Scour monitoring techniques are mainly reactive. This study compares existing and emerging scour monitoring methods, exploring a combination of scour monitoring sensors at structures at risk of scour.  The introduction of a new, innovative sensing platform for scour monitoring is discussed, linking the new sensor package to the asset health management platform using telematics, enhancing the understanding of scour taking place through accurate visualisation. This method facilitates more proactive monitoring of scour, the collection of data necessary for the design and implementation of scour protection measures, and innovative, more accurate scour prediction.

References:

Briaud JL and Hunt BE (2006) Bridge scour and the structural engineer. Structure Magazine, December: pp. 57–61.

Highways Agency, Transport Scotland, Welsh Government and Department for Regional Development Northern Ireland, UK (2012) Design Manual for Roads and Bridges. Highway Structures: Inspection and Maintenance. Volume 3, Section 4, Part 21. BD 97/12. The Assessment of Scour and Other Hydraulic Actions at Highway Structures. The Stationery Office, London, UK.

Wardhana K and Hadipriono FC (2003) Analysis of recent bridge failures in the United States. J. Perform. Constr. Facil. 17 (3): 144–150. https://doi.org/10.1061/(ASCE)0887-3828(2003)17:3(144)

How to cite: Koursari, E., MacPherson, J., McDonald, H., Creed, M., Wallace, S., Zare-Behtash, H., Cammarano, A., and Worrall, K.: Monitoring of infrastructure at risk of scour and other hydraulic actions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22332, https://doi.org/10.5194/egusphere-egu24-22332, 2024.

EDF (Électricité De France) is the world's largest electricity generator, with an installed capacity of about 130 GW. In order to safely operate the plants, optimize natural resources and fulfill ecological requirement, EDF has installed, since 1946, a sensor network dedicated to the monitoring of hydro-climatologic parameters.

 

In the context of non-intrusive methods for measuring flood discharge (LSPIV, SVR[1]), understanding the depth-averaged to surface velocity ratio is crucial. The depth-averaged to surface velocity ratio is here called α. This study analyzes a substantial sample of gaugings data (current meters and ADCP methods), totaling around 6,500 observations collected at various EDF sites. For current meters measurements, three methods are employed to compute α : fitting of a log- and a power-law and using the measured surface velocity. For ADCP measurements, three methods are applied to approach α : fitting of power-power, constant-no slip and 3-point-no slip law by using the Qrame[2] application.

 

This study aims at creating an alpha coefficient database (classified by riverbed, hydraulic radius, etc.) directly usable for non-intrusive streamflow measurements. 


[1] LSPIV (Large-Scale Particle Image Velocimetry), SVR (Surface Velocity Radar).

[2] QRame (QRevint Adcp Massive Exctraction), INRAE, 2023.

How to cite: Perriaud, T., Morlot, T., and Hauet, A.: Velocity profile and depth-averaged to surface velocity in natural streams: a review over a large sample of rivers using current meters and ADCP measurements., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22428, https://doi.org/10.5194/egusphere-egu24-22428, 2024.

HS2.3 – Water quality at the catchment scale

The North American Great Lakes constitute a distinctive hydrological system comprising five interconnected lakes (Superior, Michigan, Huron, Erie, and Ontario) that together represent one of the planet's most significant freshwater reserves. Extensive environmental surveillance by federal, state, and provincial governments targets major water quality parameters such as temperature, pH, total dissolved solids, electrical conductivity, and dissolved oxygen, as well as concentrations of nutrients and major ions. However, trace element concentrations are more scarcely measured, and the comparatively little available data on trace element concentrations in the Great Lakes is typically older, discontinuous, or focused on historically contaminated areas. Consequently, the myriad of processes and sources involved in the distribution patterns of trace elements is poorly studied, and there remains a lack of understanding the natural baselines for these elements, including for the Rare Earth Elements (REE). The REE play a crucial role in various technological applications, including electronics, renewable energy technologies, and other high-tech industries. Because of their increasingly applications, REE are currently a significant concern, particularly in mining and industrialized areas, due to their enduring toxicity, radioactive properties, and the potential for bioaccumulation.

To understand the REE distribution pattern in the North American Great Lakes, we assessed REE concentrations in >70 surface water samples from Lakes Huron, Erie, and Ontario. The concentrations of dissolved REE, filtered at <0.22 µm, exhibited significant spatial heterogeneity across the lakes, with higher ΣREE values in Lake Huron (0.065±0.082 μg/L, n=27, 2022) than in Lake Erie (0.041±0.033 μg/L, n=14, 2021 and 2022) and Lake Ontario (0.033±0.041 μg/L, n=27, 2021 and 2022). Interestingly, there was no consistent upstream-to-downstream increase in dissolved REE concentrations within the basin, but dissolved REE levels decreased nearshore-to-offshore across all lakes. Enrichment of light REE over heavy REE, particularly in samples closer to the shore, was suggestive of riverine inputs and aqueous speciation modeling indicated strong control of speciation (hydrochemistry) on REE dynamics. Finally, we employed normalization and pattern-filling to assess REE enrichments in lake surface waters. Anomalies for Gadolinium (Gd), exceeding 20%, on average, across the lakes, were notably higher than for other REE but exhibited significant spatial variability, with enrichment observed especially in proximity to urban centers and in Lake Ontario. This research contributes valuable baseline data, enhancing our understanding of the dynamics of Rare Earth Elements in the Great Lakes and providing a foundation for further studies worldwide.

How to cite: Junqueira, T. and Vriens, B.: Rare Earth Elements Concentration Patterns in Surface Waters of Lakes Ontario, Erie, and Huron (North America), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1326, https://doi.org/10.5194/egusphere-egu24-1326, 2024.

EGU24-2137 | Orals | HS2.3.1 | Highlight

Increasing hydrologic connectivity contributes to browning of northern freshwater 

Stefano Basso and Heleen de Wit

Sustained increments of organic carbon concentrations in northern freshwaters have triggered concerns about the impacts of water browning and raised questions on the underlying mechanisms causing this phenomenon. In addition to the key role played by reduced sulfate deposition, hydrologic mechanisms have been put forward as possible concurrent causes of the observed trends of organic carbon concentrations. How the suggested hydrologic controls act is however still unclear. In this study we analyze long data series (> 30 years) of daily discharge and weekly to biweekly Total Organic Carbon (TOC) concentration for four reference acid-sensitive rivers in Norway, whose locations span the entire length of the country, to clarify hydrologic changes which may be promoting freshwater browning. In all cases we observe stable values of the slopes of double logarithmic relations between concentration and discharge, as well as a steady growth along the years of the intercepts of these relations. These joint observations enable sorting out previously proposed biogeochemical mechanisms for the observed trends of TOC concentrations (i.e., less sulfate deposition versus higher soil temperature). Decreasing ratios of concentration and discharge variability along the years, observed in all watersheds during the autumn season, point at growing stores of organic carbon produced in summer and suggest that the spatial distribution of the sources is becoming more homogeneous. In detail, analyses of the runoff frequency, which is typically higher in wetter and more hydrologically connected watersheds, suggest that sources are more homogeneously connected to streams than before. In fact, increasing trends throughout the years of the runoff frequency, as well as strong relations between runoff frequency and increasing concentrations of aquatic organic carbon, are detected in all cases. More connected sources together with more frequent runoff events, which multiply the chances for the organic carbon to reach streams, may hence contribute to the observed rise of organic carbon concentrations in northern freshwaters.

How to cite: Basso, S. and de Wit, H.: Increasing hydrologic connectivity contributes to browning of northern freshwater, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2137, https://doi.org/10.5194/egusphere-egu24-2137, 2024.

EGU24-2921 | Orals | HS2.3.1

Chloride Trends in the Fox River watershed: Stratton Dam to Illinois River  

Elias Getahun and Atticus Zavelle

Applying road salt to melt ice on urban roads and pavements has raised the chloride levels in streams and rivers in the U.S. over time, which can damage aquatic life. High chloride levels in the waterbodies of the Fox River watershed, where one-third of the land is urban, are mainly caused by road salt application for deicing. This study analyzed how the chloride levels changed over the years and seasons in the Fox River watershed – from Stratton Dam to Illinois River. The Seasonal Kendall Tau (SKT) method was used to estimate the annual and seasonal trends in chloride concentration at 44 monitoring sites on the Fox River and its tributaries for three time periods (2017–2021, 2012–2021, and 1997–2021), after conducting exploratory data analysis and assessing the data suitability. The chloride concentration in the watershed varied over time, space, and season. From 2012 to 2021, it declined or remained stable at most of the monitoring sites, but it rose slightly from 1997 to 2021. The 5-year trend from 2017 to 2021 was similar, except that some sites showed an increase in summer and fall. The chloride concentration along the Fox River and Tyler Creek showed a longitudinal pattern, decreasing from upstream to downstream in most seasons and periods, except for the 5-year annual and fall trends, which increased. Weighted Regression on Time Discharge and Season (WRTDS) models were developed to estimate the trends in flow-normalized chloride flux for one site on the Fox River and two sites on its tributaries with daily flow data. The resulting trends indicate that the chloride fluxes dropped significantly at the Fox River and Polar Creek sites, mainly in the winter of 2012–2021. However, the site on Blackberry Creek had an opposite trend of increasing chloride flux, except for the winter flux, which also declined. Trends in selected streamflow statistics including mean, 7-day minimum, and 1-day maximum flows were also analyzed for the three monitoring sites to provide insight into how hydrologic variability affects chloride trends. The trends in annual and seasonal flow statistics exhibited a steep slope for low flows but a gradual slope for high flows, indicating more variability in the low flow statistics during the periods of analysis. The changes in chloride concentration and flux were partly related to the changes in flow, but other factors affecting water quality, such as watershed conservation, may also play a role. Assessing trends over distinct periods provides a nuanced understanding of how mitigation strategies may influence water quality improvements through the years and serves as a crucial guide for initiatives aimed at enhancing the overall health of the Fox River ecosystem. Choosing deicing methods that balance cost, performance, and environmental impacts should be a vital part of a mitigation plan. Moreover, monitoring and evaluating trends can help assess the current status of chloride levels in the watershed and inform future actions.

How to cite: Getahun, E. and Zavelle, A.: Chloride Trends in the Fox River watershed: Stratton Dam to Illinois River , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2921, https://doi.org/10.5194/egusphere-egu24-2921, 2024.

EGU24-3559 | ECS | Orals | HS2.3.1

Deciphering pollution loads in the Middle-Lower Yangtze River by coupling water quality models with machine learning 

Sheng Huang, Jun Xia, Yueling Wang, Gangsheng Wang, Dunxian She, and Jiarui Lei

Pollution control and environmental protection of the Yangtze River have received major attention in China. However, modeling the river’s pollution load remains challenging due to limited monitoring and unclear spatiotemporal distribution of pollution sources. Specifically, anthropogenic activities’ contribution to the pollution have been underestimated in previous research. Here, we coupled a hydrodynamic-based water quality (HWQ) model with a machine learning (ML) model, namely attention-based Gated Recurrent Unit, to decipher the daily pollution loads (i.e., chemical oxygen demand, COD; total phosphorus, TP) and their sources in the Middle-Lower Yangtze River from 2014 to 2018. The coupled HWQ-ML model outperformed the standalone ML model with KGE values ranging 0.77–0.91 for COD and 0.47–0.64 for TP, while also reducing parameter uncertainty. When examining the relative contributions at the Middle Yangtze River Hankou cross-section, we observed that the main stream and tributaries, lateral anthropogenic activities, and parameter uncertainty contributed 15%, 66%, and 19% to COD, and 58%, 35%, and 7% to TP, respectively. For the Lower Yangtze River Datong cross-section, the contributions were 6%, 69%, and 25% for COD and 41%, 42%, and 17% for TP. The primary drivers of the anthropogenic pollution sources, in decreasing order of importance, were temperature (reflecting seasonality), date, and precipitation. This study emphasizes the synergy between physical modeling and machine learning, offering new insights into pollution load dynamics in the Yangtze River.

How to cite: Huang, S., Xia, J., Wang, Y., Wang, G., She, D., and Lei, J.: Deciphering pollution loads in the Middle-Lower Yangtze River by coupling water quality models with machine learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3559, https://doi.org/10.5194/egusphere-egu24-3559, 2024.

China has been a traditional aquaculture powerhouse, contributing over one-third of the global production. The Guangdong-Hong Kong-Macao Greater Bay Area stands out as a primary region for aquaculture. Pond aquaculture is a significant method employed in this area, benefiting from its geographical advantages with a widespread and numerous distribution of fish ponds within the Greater Bay Area. The primary production units for aquaculture ponds are predominantly household-based, decentralized, and lack a significant intensive production effect. Aquaculture personnel often rely on experiential judgment to assess water quality. In recent years, increased human factors and a lack of effective management in the aquaculture pond industry have exacerbated water pollution issues. This has resulted in a growing severity of water pollution problems, with governmental departments unable to conduct large-scale monitoring of aquaculture pond water quality. Dissolved oxygen serves as a crucial indicator reflecting the water quality of these aquaculture ponds. Only dissolved oxygen concentrations within suitable ranges can facilitate the growth of aquatic products; concentrations that are either too high or too low can adversely affect aquatic product growth. This study utilized Landsat 8/9 OLI satellite images, employing atmospheric correction based on Rayleigh reflectance. It combined machine learning and water body index methods to establish a dissolved oxygen Support Vector Regression (SVR) inversion model (R2=0.67). This model determined the trends in dissolved oxygen concentration changes and spatial distribution patterns in aquaculture ponds within the Greater Bay Area over the past decade. The results indicate that from 2013 to 2023, there was a marginal decrease of 0.04% in dissolved oxygen concentration. Concentrations decreased during 2014-2016 and 2018-2020, while they increased in other years. Seasonally, concentrations were higher in spring and autumn and lower in summer and winter. Summer exhibited the lowest dissolved oxygen concentration throughout the year, with the smallest concentration difference and relatively concentrated numerical distribution. Dissolved oxygen concentrations varied significantly in other seasons. Aquaculture ponds in low latitude coastal areas generally had lower dissolved oxygen concentrations, while those in northern mountainous and upstream river regions had relatively higher dissolved oxygen concentrations.

How to cite: Mao, K. and Yang, X.: Remote Sensing Retriving of Dissolved Oxygen Concentration in Aquaculture Ponds in the Guangdong-Hong Kong-Macao Greater Bay Area, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4925, https://doi.org/10.5194/egusphere-egu24-4925, 2024.

Dissolved organic carbon (DOC) in surface waters originates mainly from riparian soils, where several processes affect the mobilisation/immobilisation of organic compounds. Among these processes, iron reduction is thought to be of primary importance for DOC mobilisation and export to surface waters. However, this process can be inhibited by the presence of nitrate due to its higher redox potential than Fe(III), making microbial nitrate reduction thermodynamically favourable compared to iron reduction. In agricultural catchments, the groundwater is typically enriched in nitrate. Thus, rising water tables in riparian areas during the (winter) wet season may inhibit iron reduction and the subsequent DOC mobilisation in soil and surface water. In this study, we tested this hypothesis in a well-monitored agricultural catchment belonging to the OZCAR network, the so-called Kervidy-Naizin catchment (5 km²). We installed 21 zero-tension lysimeters in the riparian zone of the catchment along three transects to sample soil solution in organic-rich top soil horizons (15 cm below the soil surface), at weekly to fortnightly intervals (oct 2022 – jun 2023). We analysed DOC, nitrate, Fe(II) concentrations as well as dissolved organic matter (DOM) composition through its optical properties (3D fluorescence coupled with PARAFAC modelling) to obtain information about DOM sources and dynamics across the hydrological cycle. We found that DOC concentrations were positively correlated with Fe(II) concentrations both spatially and temporally. In contrast nitrate concentrations were negatively related to Fe(II) in the soil solutions during the winter period. These observations support the hypothesis that nitrate is an inhibitor of iron reduction and subsequent DOC mobilisation. Data on the optical properties of DOM show that the DOC mobilised by this process contains large proportions of organic molecules of microbial origin, probably derived from the processing of soil organic matter. In addition, the mobilisation of high amounts of DOC unrelated to iron reduction in some zero-tension lysimeters suggests that other controls, such as wet-dry cycles, may be equally important for sustaining organic compounds in soil solutions and surface waters.

How to cite: Dupas, R., Lambert, T., and Durand, P.: The influence of nitrogen and iron biogeochemical cycles on the production and export of dissolved organic matter in headwater catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5683, https://doi.org/10.5194/egusphere-egu24-5683, 2024.

EGU24-6339 | ECS | Orals | HS2.3.1

Quantifying the impacts of an exogenous dust input to the soil and stream chemistry of an upland Mediterranean watershed using a reactive transport modeling framework 

Celia Aranda Reina, Julien Bouchez, Jon K. Golla, Pierre-Alain Ayral, and Jennifer L. Druhan

In upland watersheds, depletion of essential nutrients due to physical erosion and chemical weathering can be compensated by exogenous inputs such as aeolian dust deposition. The presence and chemical composition of exogenous dust arriving in natural environments is commonly analyzed in soil profiles using a suite of geochemical and isotopic tracers. However, it remains an outstanding challenge to describe the impacts of dust on the reaction rates that produce these profiles and how this cascades into ecosystem function and water chemistry. As increasingly intense and episodic periods of drought and aridity are promoted by a warming climate, the role of dust production and deposition in Critical Zone structure and function requires improved modeling techniques to facilitate rigorous quantification and prediction. Here we present a newly developed process-based reactive transport framework by modifying the open source CrunchTope software in order to quantitatively interpret the impacts of dust deposition and solubilization in stream water chemistry, regolith weathering rates, and ecosystem nutrient availability. We describe two simulations: (1) a generic model demonstrating a simplified system in which bedrock uplift and soil erosion occur in tandem with solid phase dust deposition at the land surface; (2) a case study based on a small (0.54 km2) upland Mediterranean watershed located on Mont Lozère in the National Park of Les Cévennes, France. In the absence of an exogenous dust input, long-term field observations of calcium in stream water, rain, bedrock, soil, and plant samples cannot be produced from reactive transport simulations of the weathering profile. By adding a carbonate-rich depositional input consistent with the composition of Saharan dust, both stream water chemistry and elemental mass-transfer coefficients in the soil profile better align with field observations, suggesting that dust has become a significant input to this field site in the last ~10 ka. Over this period, the deposition of exogenous carbonates has introduced far more calcium into the system than what could be supplied by the Ca-poor granitic bedrock. This highly soluble carbonate also limits the reactive potential of infiltrating precipitation, ultimately inhibiting chemical weathering rates and hence the component of elemental export fluxes derived from local bedrock. This is the first demonstration of solid-phase dust deposition incorporated into a multi-component reactive transport framework. Our update to the CrunchTope source code allows us to show how dust incorporation affects geochemical cycling across upland watersheds beyond the prohibitive limitations of simplified steady-state assumptions, a feature that will allow further research of a variety of Critical Zone systems subject to the effects of environmental change scenarios. 

How to cite: Aranda Reina, C., Bouchez, J., Golla, J. K., Ayral, P.-A., and Druhan, J. L.: Quantifying the impacts of an exogenous dust input to the soil and stream chemistry of an upland Mediterranean watershed using a reactive transport modeling framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6339, https://doi.org/10.5194/egusphere-egu24-6339, 2024.

EGU24-6444 | ECS | Orals | HS2.3.1

Identifying nitrate-vulnerable zones for surface water pollution in Flanders based on the depth of the redoxcline and aquifer thickness 

Abdul Hadi Al Nafi Khan, Jan Vanderborght, Erik Smolders, and Jan Diels

As in other areas with intensive agriculture in Europe, Flanders struggles with bringing surface water quality in line with the EU Nitrates Directive. At about 25% of the 874 surface water measurement locations in Flanders monitored by the Flanders Environment Agency (VMM), the 90th percentile from monthly measurements conducted during 2018-2023 exceeded a NO3- concentration of 50 mg/L.

A large fraction of the nitrate that leaches out of the root zone is denitrified in the groundwater. However the denitrification rate varies spatially, so mitigation measures are best targeted to zones from where NO3- is transported to the surface water without undergoing significant denitrification in the aquifer. We used a novel methodology to predict NO3- concentrations in the outlets of small catchments that explicitly considers hydrochemical variation within aquifers and is based on the thickness of oxidized and reduced zones in an aquifer.

The depth of the redoxcline, the boundary between the oxidized and reduced zone, was determined from the phreatic groundwater monitoring network of VMM consisting of 2089 multilevel groundwater wells in Flanders. Analysis of the time series of hydro-chemical data (redox potential and dissolved NO3-, O2, Fe, Mn) allowed us to classify the filters as being in oxidized or reduced zone. For each well, the depth of the first ‘reduced’ filter was taken as the depth of the redoxcline.

Assuming a spatially uniform nitrate concentration in the groundwater recharge, the nitrate concentration of the water reaching the catchment outlet can be estimated as:

NO3- at catchment outlet = (thickness of oxidized zone / equivalent aquifer thickness ) × NO3-   in recharge water        (1)

This simple approach assumes that all nitrate is denitrified once the groundwater flowline crosses the redoxcline. Instead of the true aquifer depth, we used the aquifer's equivalent thickness, utilizing the Hooghoudt equation based on the average distance between watercourses. The nitrate input in the recharge water for this calculation was taken from VMM’s NEMO model, which provides the nitrate leachate from agricultural fields to groundwater.

Our investigation covered 68 small agricultural catchments (0.4-20.4 km²). The ratio of oxidized to entire aquifer thickness varied from 0.03 to 1, averaging 0.33. Therefore, on average, 33% of the agricultural areas would show high nitrate vulnerabilities because flowlines originating from there do not cross the redoxcline. However, the ratio of the average observed NO3- concentration in surface water to that in recharge water is 0.46, indicating an overestimation of denitrification. The estimated nitrate concentrations in surface water, calculated using Equation (1), showed a reasonable agreement with observed values (R2 = 0.32). A much lower R2 (0.08) is observed when replacing the ratio of thicknesses in Equation (1) with the average thickness ratio of 0.33. This suggests that the variation in nitrate concentration at the catchment outlet is predominantly governed by the relative thickness of the oxidized zone.

This method identifies nitrate-vulnerable areas along water courses in a catchment that can be used to better target mitigation measures across Flanders.

How to cite: Khan, A. H. A. N., Vanderborght, J., Smolders, E., and Diels, J.: Identifying nitrate-vulnerable zones for surface water pollution in Flanders based on the depth of the redoxcline and aquifer thickness, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6444, https://doi.org/10.5194/egusphere-egu24-6444, 2024.

In recent years, intensive agricultural practices have been adopted to enhance crop yields for food production. Therefore, the issue of agricultural non-point source pollution attracts attention due to the increasing use of fertilizer. The non-point source pollution control is diverse and difficult to manage because of the physical landscape and agricultural practices (e.g., topography, soil texture, farming, and irrigation). In addition, excessive fertilizer used to enhance crop yields would lead to land degradation. During a rainfall event, nitrogen and phosphorus from fertilizers would be washed into surface water and infiltrated into groundwater, resulting in the degradation of the aquatic environment.

In this study, the use of slow-release fertilizer, compared to the reference of conventional chemical fertilizer, and a constructed wetland were adopted at a pilot-scale study. During a 40-day growing cycle, Brassica Chinensis L.(Pak-Choi) was chosen as the model crop, and two types (i.e., chemical fertilizer and slow-release fertilizer) of fertilizers were applied under pre-designed conditions. Two simulated intense rainfalls were operated on the 26th and 33rd days, and the surface runoff was introduced to the constructed wetland for further nutrient removal. The soil and water samples from the soil and wetland were analyzed for nutrient concentration variation, and the nutrient distribution and removal efficiency were assessed. The results showed that the chemical fertilizer has a higher nutrient loss rate. The nitrogen (N), phosphorus (P), and potassium (K) contents in the soil increased rapidly after top dressing and decreased significantly after the simulated rainfall. In contrast, slow-release fertilizer has a relatively steady nutrient loss rate during the growing cycle. Meanwhile, the chemical fertilizer has a higher total N, P, and K loss via infiltration and runoff than slow-release fertilizer. For the wetland treatment, the N removal for chemical fertilizer and slow-release fertilizer after 15 days was 24.4 % (i.e., from 19.99 ppm to 15.11 ppm) and 29.5 % (i.e., from 20.81 ppm to 14.68 ppm), the P removal amount was 38.1 % (i.e., from 0.21 ppm to 0.13 ppm) and 87.5 % (i.e., from 0.08 ppm to 0.01 ppm), respectively. Opposing to the conventional chemical fertilizers, the use of slow-release fertilizers could reduce nutrient loss. The constructed wetland demonstrated a positive effect on removing the nutrients in neighboring water, which reduced the impact of agricultural non-point source pollution.

Keywords: Conventional farming, Best management practices, Slow-release fertilizer, Constructed wetlands

How to cite: Huang, C.-J. and Fan, C.: Non-point source pollution control in farmland by source-reduction strategies coupled with wetland treatment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7171, https://doi.org/10.5194/egusphere-egu24-7171, 2024.

Cover crops (CC) have shown promise in reducing nitrogen (N) leaching, but in semi-arid regions, they might compete with subsequent field culture for water availability. In Austria's Marchfeld region, which is intensively used for agriculture, nitrate levels in groundwater exceed threshold values due to N surplus and limited dilution of seepage water caused by low annual precipitation. Early sown CC with sufficient emergence and N uptake might reduce such groundwater contamination. Further, later tillage dates keep the N stored in the organic pool and reduce mineralisation during autumn and winter. However, CC induced changes in soil water availability could impact the follow-up crop.
This study investigates the impact of cover crop (CC) varieties with different i) seed compositions, ii) tillage dates and iii) on-demand irrigation on N leaching and soil water availability for subsequent field culture.

The randomized block trial included a) frosting CC – autumn conversion, b) frosting CC – spring conversion, c) a mixture of winter hardy and frosting CC – spring conversion and d) fallow plots. On-demand irrigation was performed at plots with same varieties to enhance CC emergence and simulate conditions of both wet and dry years. Within each plot soil moisture sensors and suction cups were installed. Some plots were equipped with matrix potential sensors. Monthly soil samples were analysed for plant available N and plant samples were taken twice. Evaporation was evaluated using four mini-lysimeters, one for each CC composition. STOTRASIM, which is a soil water and mass transport model was used to model the amount of seepage water of each plot and was calibrated on matrix potential measurements.

In general, the results show that all tested varieties of CC significantly reduce plant available nitrogen during winter compared to fallow. Despite the relatively low levels of leached N, in semi-arid regions even minor amounts pose a risk of groundwater contamination. Soil water content analysis revealed no significant differences between the CC varieties. The yield of the subsequent crop remained unaffected by the different CC.
While CC reduced N leaching and did not compete with the subsequent field culture, integrating practical considerations like phyto-sanitation, seedbed preparation, tillage methods, crop rotation and succeeding crop selection into CC practices is crucial to prevent adverse effects on subsequent field culture.

How to cite: Schmid, A., Scheidl, A., and Eder, A.: Cover crop varieties, tillage dates and irrigation on-demand: their impact on nitrogen and soil water dynamics in Austria’s semi-arid Marchfeld region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7589, https://doi.org/10.5194/egusphere-egu24-7589, 2024.

EGU24-8959 | ECS | Posters on site | HS2.3.1

Valorization of agricultural residues through its transformation into sustainable filters for water treatment 

Águeda M. Sánchez-Martín, Sara Pérez Dalí, Tomás Undabeytia López, Jorge Marquez Moreno, Alba Dieguez-Alonso, Frank Behrendt, Germán Almuiña-Villar, and José María De la Rosa

Finding a sustainable solution to the increasing amount of organic waste generated, and reducing air, soil and water pollution are two most pressing environmental issues today. In both problems, agriculture plays a crucial role. Within this context, this study aims to valorize abundant agricultural waste via its transformation into activated carbon (AC), useful for the removal of emerging organic contaminants (EOCs) in water.
Thus, rice husk (RH) and almond shell (AS) were characterized, pyrolyzed and tested as feedstock for ACs to be used as water filters. In addition, chemical (with KOH) and physical activation (with water vapor) of the pyrolyzed materials were performed.
The elemental composition and physical properties were suitable in both cases (alkaline pH, high water retention capacity, Carbon content and Iodine index). The specific surface area (SSA-BET) increased significantly to values 600 m2 gr-1 on the ACs produced from physically activated and pyrolyzed RH.
Furthermore, adsorption tests of anti-inflammatory and antibiotic compounds in water showed that ACs produced from RH were able to adsorb up to 100 % of the these persistent EOPs, performing similarly to commercial AC.

 

Acknowledgements:
This study received financial support in the framework of the Project RICERES4CHANGE (grant TED2021-130964B-I00), by the Spanish Agency of Research (MCIN/AEI/10.13039/501100011033) and the European Union (Next Generation EU/PRTR funding).
A.M. Sánchez-Martín thanks The Spanish Ministry of Science and Innovation (MICIN) for her contract as Technical Support Personnel (PTA2021-020000-I). M. Arenas is thanked for this technical and analytical support.

How to cite: Sánchez-Martín, Á. M., Pérez Dalí, S., Undabeytia López, T., Marquez Moreno, J., Dieguez-Alonso, A., Behrendt, F., Almuiña-Villar, G., and De la Rosa, J. M.: Valorization of agricultural residues through its transformation into sustainable filters for water treatment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8959, https://doi.org/10.5194/egusphere-egu24-8959, 2024.

EGU24-9538 | Orals | HS2.3.1

German-wide analysis of high-frequency, continuous concentration-discharge relationships 

Jens Kiesel, Tobias Houska, Janosch Müller-Hillebrand, and Nicola Fohrer

High-frequency observations of solute and particulate concentrations (C) and associated discharge (Q) measurements allow the analysis of C-Q relationships on the event-scale. Together with catchment attributes and event properties, C-Q relationships can be used to disentangle the fine-grained dependencies between catchment properties, hydrologic processes and water quality.

We collected 72 high-frequency (sub-hourly), continuous C and Q time series across Germany in catchments ranging from 8 to 122.000km² (median of 6.051km²). Besides discharge at all 72 locations, the database contains water temperature (60 locations), turbidity (34), conductivity (59), oxygen (57), pH (53), ammonia (16), nitrate (22), phosphate (10) and chlorophyll (12) in varying lengths over a maximum period of 20 years. Event filters were used to extract single discharge events. Hysteresis indices and classes of each event were used to describe the C-Q relationships. Event properties such as season, magnitude, variability, length, antecedent conditions, rise- and fall characteristics and physical catchment characteristics were assigned to each C-Q relationship.

We used a Random Forest model to explain the hysteresis properties based on the event- and catchment characteristics. Particularly the variables turbidity and conductivity revealed spatio-temporal dependencies, which we relate to interplays of land use and soil characteristics. We further found that the C-Q patterns are significantly impacted by the identifiability and definition of the extracted discharge events across the heterogeneous catchments as well as the resolution and quality of the measurements of the different C variables.

How to cite: Kiesel, J., Houska, T., Müller-Hillebrand, J., and Fohrer, N.: German-wide analysis of high-frequency, continuous concentration-discharge relationships, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9538, https://doi.org/10.5194/egusphere-egu24-9538, 2024.

EGU24-9606 | Orals | HS2.3.1 | Highlight

Field scale optimization of woodchip bioreactors for nitrate removal from drainage water in the Netherlands 

Stefan Jansen, Inge Van Driezum, Joachim Rozemeijer, Arnaut Van Loon, and Frank Van Herpen

It is known from recent international research that woodchip bioreactors can be an effective measure to reduce emissions of nitrate from agricultural drainage water. In the Netherlands, up till now no experience was present with woodchip bioreactors. Therefore, a field pilot was started at an agricultural test location situated in a lowland catchment in the south of the Netherlands (Vredepeel). A woodchip bioreactor was installed to treat drainage water from 4 ha arable land on sandy soil. Nitrate was measured in the in- and effluent of the bioreactor to estimate nitrate removal efficiency over time. Also, water chemistry and discharge were monitored. 
With a series of sampling points in the woodchip bioreactor, biogeochemical processes in the reactor are investigated that can explain the performance of the reactor. The goal is to not only determine the removal efficiency, but also potential side effects and effects of temporarily limited flow rate (e.g. sulfide and ammonia production and oxygen demand). We aim to give practical guidelines for practical design and application for agricultural fields in sandy lowland catchments. In this contribution we will present the monitoring results of one drainage season.

How to cite: Jansen, S., Van Driezum, I., Rozemeijer, J., Van Loon, A., and Van Herpen, F.: Field scale optimization of woodchip bioreactors for nitrate removal from drainage water in the Netherlands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9606, https://doi.org/10.5194/egusphere-egu24-9606, 2024.

EGU24-10390 | Orals | HS2.3.1

Increasing stream water DOC concentrations in peat-affected catchments: insights from high-resolution water quality analysis 

Tobias Houska, Ingo Müller, Klaus Kaiser, Klaus-Holger Knorr, Maximilian Lau, Conrad Jackisch, and Karsten Kalbitz

Peatlands are an important natural terrestrial carbon sink. Any impact on the drivers of hydro-biogeochemical processes in these ecosystems can be particularly severe. Climate change and degradation by drainage and ditching are dramatically changing peatlands. Degraded peatlands turn from effective carbon sinks to emitters. They can also threaten drinking water supplies, as (heavy) metals can leach from degraded peatlands together with dissolved organic carbon (DOC). However, quantifying DOC fluxes from terrestrial to aquatic ecosystems is challenging. The hydro-biogeochemical processes at the soil-aquatic interface are not only complex but also occur at different spatial and temporal scales. These processes depend on a variety of constantly changing external conditions such as temperature, nutrient and oxygen availability. In addition, there is no sensor that can directly measure DOC concentrations in streams in situ.

Here we investigated the DOC concentration in two nested catchments of two adjacent streams in the Ore Mountains of southern Saxony, Germany. One stream is dominated by mineral soils, the other by (degraded) peat soils. Each of the four sites is equipped with YSI-EXO fDOM sensors. Other data include discharge, water temperature, turbidity and electrical conductivity. A machine learning algorithm (Random Forest) was trained to predict DOC concentration from the available data set (validation r² between 0.85 and 0.98). The 15-minute resolution DOC data were analysed for potential driving factors. Interestingly, the area-specific loads of the peat-dominated catchment with 3.4 g C m-2 a-1 were not significantly different from those of the mineral soil-dominated catchment with 1.8 g C m-2 a-1. However, the annual loads were almost twice as high as previously determined from monthly data. With the high-resolution DOC data, we can identify periods of extreme DOC concentrations (up to 40 mg l-1) after heavy rain events in summer and constant high DOC concentrations of 20 mg l-1 during snowmelt in winter. By applying the algorithm to DOC:DON ratios, we were also able to quantify the different sources contributing to streamwater DOM with plant-derived material from peat and microbially-derived material from the mineral soil.

Previous DOC measurements, mostly based on 2-week to monthly measurements, are likely to greatly underestimate the contribution of DOC to C fluxes in ecosystems. This is particularly important for C-rich ecosystems such as peatlands.

How to cite: Houska, T., Müller, I., Kaiser, K., Knorr, K.-H., Lau, M., Jackisch, C., and Kalbitz, K.: Increasing stream water DOC concentrations in peat-affected catchments: insights from high-resolution water quality analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10390, https://doi.org/10.5194/egusphere-egu24-10390, 2024.

EGU24-11237 | ECS | Posters on site | HS2.3.1

Using field deployable sensors to identify the inter-event predictability of Dissolved Organic Matter mobilisation in an urban river 

Hongzheng Zhu, Kieran Khamis, David M. Hannah, and Stefan Krause

Emerging sensor technology offers new opportunities to monitor different fractions of Dissolved Organic Matter (DOM) in high resolution. Concentration-discharge (C-Q) relationships (e.g. hysteresis or c-q slopes), derived from high frequency observation can offer insight into source mobilization and reactive transport processes of DOM. However, few studies have explored patterns in urban catchments, where understanding of storm event DOM responses under different hydrometeorological conditions remains elusive. To bridge this gap, we collected 2-years (15 min resolution) fluorescence data (humic-like fluorescence [HLF: Ex. 325 nm/ Em 470 nm] and tryptophan-like fluorescence [TLF: Ex 275 nm/ Em 350 nm]) in an urban headwater stream (Birmingham, UK). We used c-q slopes and two indices, the hysteresis index (HI) and flushing index (FI), to explore the inter-event variability in DOM dynamics. In addition, we assessed the hydrometeorological factors (e.g., antecedent conditions, temperature, discharge and rainfall characteristics) that govern DOM mobilisation and transport using statistical multiple linear regression. Our findings reveal pronounced seasonal variation in the behaviour of TLF and HLF. In warmer periods, the chemodynamic characteristics of both fluorescence peaks become evident. We observed a consistent counter-clockwise hysteresis pattern accompanied by flushing behaviour. The magnitude of discharge, antecedent temperature, and rainfall intensity were identified as key drivers of HLF and TLF flushing and hysteresis dynamics. Conversely, during colder months, a shift in DOM mobilisation was observed. For TLF, source limitation was apparent, characterized by clockwise hysteresis and a notable dilution. In contrast, HLF exhibited a more variability during this period, with complex hysteresis patterns and a combination of solute flushing and dilution. The magnitude of discharge and antecedent wetness were identified as the key factors influencing the solute behaviour in this cooler period. Our research indicates that the responses of DOM in urban rivers exhibit distinct responses to hydrometeorological conditions which were relatively predictable (i.e. low stochasticity within particular event types). However, variability in DOM composition and magnitude was pronounced between event types which has implications for managing urban rivers, specifically ensuring ecological health and resilience are maintained in the face of increasing climatic extremes.

How to cite: Zhu, H., Khamis, K., Hannah, D. M., and Krause, S.: Using field deployable sensors to identify the inter-event predictability of Dissolved Organic Matter mobilisation in an urban river, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11237, https://doi.org/10.5194/egusphere-egu24-11237, 2024.

EGU24-11516 | Posters on site | HS2.3.1

Integrating and managing nitrogen and phosphorus dynamics in agriculturally impacted inland waters via a stoichiometric nutrient management framework 

Daniel Graeber, Anika Große, Katja Westphal, Alexander Wachholz, Marc Stutter, Gabriele Weigelhofer, Thomas Alexander Davidson, Tom Shatwell, Andreas Musolff, Rohini Kumar, and Dietrich Borchardt

Agricultural nutrient management tends to treat nitrogen (N) and phosphorus (P) in surface waters as separate entities, potentially overlooking their strong interactions in biogeochemical cycles. This study proposes a unifying approach by integrating these nutrients through a stoichiometric nutrient management framework. This framework suggests two paradigm shifts in inland-water nutrient management: 1. It improves catchment and ecosystem-level understanding of N and P sources and effects via N : P ratio assessments of sources, transport and ecological effects, such as eutrophication. 2. It proposes that provision of organic carbon (OC) can increase the retention of N and P in agriculturally impacted inland waters, which can be assessed using C : N : P ratios. Provision of OC to modify C : N : P ratios may be reached through restoring natural OC sources. This can be done by focusing on areas such as wetlands, riparian forests, and bogs at catchment scale. Here, stoichiometric rules are utilized to assess the responses of key microbial processes, which includes examining how nutrients are assimilated by microbial primary producers and heterotrophs, as well as the process of denitrification. Understanding the secondary effects of wetted area development through the stoichiometric nutrient management framework will also support decision making for flood and drought protection based on such wetted areas. With these aspects, the stoichiometric nutrient management framework provides comprehensive understanding of nutrient dynamics, retention, and their ecological impacts in inland water catchments and ecosystems. In the presentation, we will present evidence supporting the comprehensiveness of the stoichiometric nutrient management framework. This evidence is based on a series of studies we conducted, including conceptual modeling, statistical modeling, ratio-based monitoring, and targeted proof-of-concept microcosm experiments. We conclude that the stoichiometric nutrient management framework could provide crucial strategies to mitigate current nutrient pollution issues in agriculturally-impacted inland waters, thereby aligning with the Water Framework Directive’s objectives for improving water quality.

How to cite: Graeber, D., Große, A., Westphal, K., Wachholz, A., Stutter, M., Weigelhofer, G., Davidson, T. A., Shatwell, T., Musolff, A., Kumar, R., and Borchardt, D.: Integrating and managing nitrogen and phosphorus dynamics in agriculturally impacted inland waters via a stoichiometric nutrient management framework, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11516, https://doi.org/10.5194/egusphere-egu24-11516, 2024.

EGU24-12746 | ECS | Orals | HS2.3.1

Sediment ponds; an effective mitigation measure for reducing nutrient export in agricultural drainage ditches?  

Linda Heerey, Owen Fenton, Fiona Regan, Blánaid White, Nigel Kent, and Karen Daly

The agricultural sector is a large contributor to poor water quality in our freshwater systems. One potential pathway for agriculturally sourced pollution to enter the freshwater environment is through drainage ditches, which can be either open surface drains or subsurface pipes, or a combination of both. While large scale tile-drainage systems with a central output point are common in some countries, Irish agricultural drainage networks tend to be comprised of a complex network of drains, each with varying levels of connectivity to freshwater systems. Recent research by Moloney et al. (2020) categorised these drains in terms of their connectivity, finding that those with a direct connection between a farmyard and river/stream were at the greatest risk for transporting the highest concentrations of nutrients (phosphorus and nitrogen). Therefore, to target the most ideal location to mitigate against nutrient transport through drainage ditches, drains with direct farmyard connectivity provide the most resource- and cost-effective option.

This study investigated the effectiveness of sediment ponds installed in drainage ditches which had a direct connection between a farmyard and a river. Three case study farms were selected, two in the south (Cork) and one in the south-east (Wexford) of Ireland. All ponds were installed by 2021, with sampling commencing in December 2022. Grab water samples were collected weekly (Wexford farm) and fortnightly (Cork farms) at multiple points upstream and downstream of the ponds, and were analysed for nitrogen, phosphorus and dissolved organic carbon. Sediment samples were extracted from within the drainage ditches in summer 2023 and analysed for Mehlich-3 P, pH, Morgan’s P and particle size distribution. Initial results suggest ponds provide limited attenuation of nutrients, with no significant decreases at the downstream sample points. While sediment phosphorus concentrations are marginally elevated downstream, suggesting potential accumulation in the soil, further sampling is needed to confirm this trend. This study provides valuable insights into nutrient dynamics within agricultural drainage ditches and contributes to a better understanding of the effectiveness of sediment ponds as a potential mitigation measure for nutrient retention.

How to cite: Heerey, L., Fenton, O., Regan, F., White, B., Kent, N., and Daly, K.: Sediment ponds; an effective mitigation measure for reducing nutrient export in agricultural drainage ditches? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12746, https://doi.org/10.5194/egusphere-egu24-12746, 2024.

EGU24-13731 | Orals | HS2.3.1 | Highlight

Memory and Management: Competing Controls on Long-Term Nitrate Trajectories in U.S. Rivers 

Kimberly Van Meter, Nandita Basu, and Danyka Byrnes

Excess nitrogen from intensive agricultural production, atmospheric N deposition, and urban point sources elevates stream nitrate concentrations, leading to problems of eutrophication and ecosystem degradation in coastal waters. A major emphasis of current US-scale analysis of water quality is to better our understanding of the relationship between changes in anthropogenic N inputs within watersheds and subsequent changes in riverine N loads. While most water quality modeling assumes a positive linear correlation between watershed N inputs and riverine N, many efforts to reduce riverine N through improved nutrient management practices result in little or no short-term improvements in water quality. Here, we use nitrate concentration and load data from 478 US watersheds, along with developed N input trajectories for these watersheds, to quantify time-varying relationships between N inputs and riverine N export. Our results show substantial variations in watershed N import-export relationships over time, with quantifiable hysteresis effects. Our results show that more population-dense urban watersheds in the northeastern U.S. more frequently show clockwise hysteresis relationships between N imports and riverine N export, with accelerated improvements in water quality being achieved through the implementation of point-source controls. In contrast, counterclockwise hysteresis dynamics are more common in agricultural watersheds, where time lags occur between the implementation of nutrient management practices and water-quality improvements. Finally, we find higher tile-drainage densities to be associated with more linear relationships between N inputs and riverine N. The empirical analysis in this study is bolstered by modeled simulations to reproduce and further explain drivers behind the hysteretic relationships commonly observed in the monitored watersheds.

How to cite: Van Meter, K., Basu, N., and Byrnes, D.: Memory and Management: Competing Controls on Long-Term Nitrate Trajectories in U.S. Rivers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13731, https://doi.org/10.5194/egusphere-egu24-13731, 2024.

 Cascade reservoirs construction has modified the nutrients dynamics and biogeochemical cycles, consequently affecting the composition and productivity of river ecosystems. Cascade reservoirs in different rivers typically exhibit distinct variabilities in the retention characteristics of different nutrients. The Jinsha River, as the predominant contributor to runoff, suspended sediment (SS), and nutrients production within the Yangtze River, is a typical cascade reservoir region with unclear transport patterns and retention mechanisms of nutrients (nitrogen and phosphorus). Therefore, we monitored monthly variations in nitrogen and phosphorus concentrations from November 2021 to October 2022. The results demonstrated that the concentrations and fluxes of total phosphorus (TP) and particulate phosphorus (PP) significantly decreased as they moved downstream along the cascade of reservoirs, primarily due to PP deposited with SS, while total nitrogen (TN) and dissolved total nitrogen exhibited opposing trends. Moreover, the positive average annual retention rates for TP and PP were 9.64% and 15.64%, respectively, in contrast to the negative averages of -8.38% for TN and -10.51% for particulate nitrogen. A higher proportion of TP and PP was retained by the reservoirs in the flood season compared to the non-flood season. Additionally, the variability in runoff-sediment and hydraulic retention time (HRT) of cascade reservoirs played crucial roles in the retention of TP and PP. A stronger relationship between HRT and TP retention rate during the flood season suggested that the cascade reservoirs could effectively transport or intercept TP downstream when HRT was either less than or greater than 5.3 days. Consequently, the HRT of these reservoirs could be managed to control nutrients delivery, which was of particular significance for watershed government institutions. This study enhances our comprehension of how cascade reservoirs influence the distribution and transport patterns of nutrients, offering a fresh perspective on nutrients delivery regulation. 

How to cite: Zeng, Q.: Impact of cascade reservoirs on nutrients transported downstream and regulation method based on hydraulic retention time, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14010, https://doi.org/10.5194/egusphere-egu24-14010, 2024.

EGU24-14984 | Orals | HS2.3.1

The establishment and use of local coastal water boards is tested in Denmark to find bottom-up solutions for RBMP 2027 

Jørgen Windolf, Kristoffer Piil, Torben B. Jørgensen, Hans E. Andersen, Tommy Dalgaard, and Brian Kronvang

The Danish EPA has in the 3rd River Basin Management Plan (RBMP) under the Water Framework Directive set target nitrogen loads for each coastal water for how to reach the reduction needed from coastal catchments to be implemented in 2027. In this context four locally based pilotprojects have been initiated to engages stakeholders to find local solutions for the RBMP. One of these new pilots are focusing on the Hjarbæk estuary situated in Limfjorden being one of the coastal water bodies in Denmark that needs the highest reductions in nitrogen loadings to be achieved before 2027 (ca. 65 %). This new project involving a coastal water board with all main stakeholders in the region being represented was initiated in February 2023 and has delivered proposals for 2 scenarios by the end of 2023 that can assure that the Hjarbæk estuary reach the target of achieving good ecological conditions.

Because of the high reductions in nitrogen loadings needed it is necessary to reduce all sources and both nitrogen and phosphorus to reach the goal. Focus in the RBMP has so far been to reduce the total nitrogen (TN) loadings. In the locally based scenarios phosphorus has gained greater focus. Our calculations show that every ton of phosphorus that is removed corresponds to removing 22 tons of nitrogen in Hjarbæk Fjord.  To be most cost-effective the effort will be carried out based on the principle of achieving the greatest possible effect per area unit. For that a detailed mapping of nitrogen (N) attenuation in the catchment have been conducted at a scale of ca. 15 km2 (ID15 sub-catchments) including mapping of both N-retention in groundwater and surface waters as well as N-delays in groundwater in Karst sub-catchments. The mapping shows huge differences in N-retention in both groundwater and surface waters within the ID15 sub-catchment (<20 % to >80 %).

The local engagement of stakeholders representing all sectors in the catchment and estuary have worked together to set up two scenarios that includes: i) marine mitigation measures such as mussel farming and eelgrass planting; ii) reductions in point source loadings; iii) use of a new portfolio of N mitigation measures to be adopted at source (e.g. catch crops, early seeding, set a side, afforestation, etc.); iv) use of transport mitigation measures from field to surface water (several types of constructed wetlands, riparian buffers and restored wetlands); v) the possible use of different phosphorus mitigation strategies in the catchment (lowering bank erosional P-losses, buffer strips, afforestation, etc.).

How to cite: Windolf, J., Piil, K., Jørgensen, T. B., Andersen, H. E., Dalgaard, T., and Kronvang, B.: The establishment and use of local coastal water boards is tested in Denmark to find bottom-up solutions for RBMP 2027, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14984, https://doi.org/10.5194/egusphere-egu24-14984, 2024.

EGU24-15329 | Orals | HS2.3.1

Redox driven mobilisation of DOC from riparian wetlands in Krycklan (N Sweden) after a drought experiment 

Benny Selle, Anja Hortmann, Klaus-Holger Knorr, and Hjalmar Laudon

Riparian wetlands are major sources of dissolved organic carbon (DOC) to streams. Increasing DOC concentrations were observed for many northern streams during the last decades, with potential implications for carbon (C) storages of wetland soils and streamwater quality. Drivers behind these trends, and particularly the significance of redox processes in wetland soils, are still incompletely understood. In soils, organic C is often associated with or bound to iron (oxy) hydroxides. These associations of iron (Fe) and organic C may immobilise and protect soil organic matter from mineralisation under oxic conditions. However, organic C can be remobilised if ferric Fe is reduced under anoxic conditions, a process which also increases pH further enhancing DOC solubility. Redox processes are therefore presumably important drivers of DOC dynamics in both wetland soils and the adjacent streams. We hypothesised that in-stream DOC concentrations are mainly driven by redox conditions within riparian organic soils, where DOC mobilisation is controlled by reduction of DOC associated Fe. We further propose that these DOC mobilising redox processes are particularly relevant for periods of rewetting of riparian soils, e.g. in autumn. In this study, were used monitoring data following a drought experiment conducted in summer 2017 in a sub-catchment of Krycklan in northern Sweden. For the experiment, a drought was simulated for a sub-catchment in Krycklan by damming a lake outlet that feeds a small stream. For the rewetting period after the drought experiment, daily time series of discharge, DOC and Fe feeding into the manipulated stream section were calculated from data measured at the top and the bottom of the stream section. Discharge was measured by flumes. From discharge time series, baseflow feeding into the stream section was computed using a baseflow separation filter. Time series of baseflow was assumed to represent average watertable dynamics in riparian wetlands. Both Fe and DOC concentrations were obtained from absorbances measured across different wavelength using a portable ultraviolet–visible probe. Adsorbances were converted into aquatic concentrations using a partial least-squares regression model calibrated on Fe and DOC concentrations measured in the laboratory. Furthermore, concentration time series were corrected for discharge and in-stream retention (for DOC only). We found that Fe increased with increasing baseflow with a time lag of 5d indicating delayed iron reduction in riparian areas in response to elevated watertables. Dynamics of DOC were weaker related to baseflow than to Fe, but DOC was significantly correlated to Fe. From rules to obtain directed acyclic graphs it can be inferred that changing baseflow - as a proxy of watertables in riparian wetlands - caused changing discharge corrected Fe concentrations in the stream, which can be understood as a proxy of Fe concentrations in riparian wetlands. Changing Fe concentrations caused changes of computed in-stream DOC concentrations, which can be seen to represent mobilised DOC pools in riparian wetlands. It is concluded that redox driven mobilisation of DOC is a plausible process for rainfall periods in autumn, when riparian soils are rewetted after summer.

How to cite: Selle, B., Hortmann, A., Knorr, K.-H., and Laudon, H.: Redox driven mobilisation of DOC from riparian wetlands in Krycklan (N Sweden) after a drought experiment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15329, https://doi.org/10.5194/egusphere-egu24-15329, 2024.

EGU24-15361 | ECS | Posters on site | HS2.3.1

Mitigation of nitrogen loss in rice fields through soil desaturation prior to re-irrigation and the application of controlled-release nitrogen fertilizer: a meta-analysis 

Sabi Kidirou Gbedourorou, Pierre G. Tovihoudji, Marnik Vanclooster, and Irénikatché P. B. Akponikpe

Water pollution by nitrogen residues from agricultural intensification has become a recurring problem, particularly in wetlands used for rice production. As a solution to remediate this issue, sustainable water and nutrient management are being explored. These practices involve matching water and nutrient availability with plant needs in space and time while ensuring production objectives are met. In this study, we performed a meta-analysis to synthesize the current knowledge on the effect of water and nutrient management practices on nitrogen losses and uptake by plants in rice cropping systems. Using a random effects model, we summarized the effect sizes of 103 observations from 27 peer-reviewed studies. Tree water management practices were evaluated: “Continuous Flooding” (used as control), “Alternate Wet and Dry (AWD)” and “Controlled Irrigation (CI)”. The response ratio (RR) of nitrate leaching and total nitrogen loss was negative for CI (-0.53 and -0.34, respectively) and AWD (-0.13 and -0.36, respectively). Regardless of water management practices (AWD or CI), desaturating the soil before re-irrigation reduced nitrate and total nitrogen losses. When considering the source of nitrogen input, water management practices involving desaturation of the soil before re-irrigating were effective in reducing nitrogen losses in urea-only applications. However, in the case of controlled release urea (CRF) applications, water management treatments (AWD or CI) were not necessary to reduce nitrogen losses, especially those due to ammonia volatilization. This result also indicates the effectiveness of CRF treatment in retaining the essential nitrogen component required for plant growth and development. Nevertheless, when nitrogen rates exceed 200 kg N/ha, adopting water management practices such as CI and AWD becomes necessary to decrease nitrate leaching and total nitrogen loss in rice fields. Regarding the rice grain yield, water management practices that involve reducing the amount of water (AWD and CI) have shown no significant effect on yield (RR 0.017 and -0.0001). In conclusion, AWD and CI water management practices have been shown to reduce nitrogen losses without compromising rice grain yield. Additionally, the application of CRF reduces nitrogen losses that may occur in a continuous flooding system.

Key-words: Water management; Nitrogen; Rice; Controlled release urea; Water pollution

How to cite: Gbedourorou, S. K., Tovihoudji, P. G., Vanclooster, M., and Akponikpe, I. P. B.: Mitigation of nitrogen loss in rice fields through soil desaturation prior to re-irrigation and the application of controlled-release nitrogen fertilizer: a meta-analysis, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15361, https://doi.org/10.5194/egusphere-egu24-15361, 2024.

EGU24-17087 * | Orals | HS2.3.1 | Highlight

Paludiculture: multifunctional land-use to decrease nutrient loading 

Jeroen Geurts, Marelle Van der Snoek, Christian Fritz, and Gert-Jan Van Duinen

To counteract soil subsidence and greenhouse gas emissions, groundwater levels in agriculturally used peatlands are increased in summer (e.g. by subsurface irrigation). This rewetting could lead to increased nutrient mobilization under anaerobic conditions in nutrient-rich soils, which will lead to eutrophication in ditches and lakes. However, rewetted peatlands can also be used to purify surface water and utilize the available nutrients by cultivation of wet crops like Typha and Phragmites, which is called “paludiculture”. These wet crops can provide raw materials for fiber based products (e.g. insulation and building materials). Paludiculture can also be implemented in multifunctional buffer zones along streams in sandy landscapes.

This multifunctional land-use can create a win-win situation that combines biomass production of wet crops with the provision of ecosystem services, such as peat preservation and water purification. To underpin what the water purification potential of paludiculture is, measurements have been done in several mesocosm experiments and field-scale paludiculture pilots within national and European projects (e.g. VIP-NL, KLIMAP, Carbon Connects and CINDERELLA). These pilots and experiments were used to learn how to cultivate paludiculture crops under different hydrological circumstances (water level and fluctuations), nutrient loads, water quality, soil types and field configurations. We quantified the nutrient uptake by Typha and Phragmites and the change in water quality between inlet and outlet in different situations. The results are also used to investigate which combination of factors will give the most efficient combination of water purification, nutrient uptake and biomass production.  In the end, this contributes to developing new ways of sustainable and economical feasible farming on wet peat soils and in brook valleys.

How to cite: Geurts, J., Van der Snoek, M., Fritz, C., and Van Duinen, G.-J.: Paludiculture: multifunctional land-use to decrease nutrient loading, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17087, https://doi.org/10.5194/egusphere-egu24-17087, 2024.

EGU24-17979 | Orals | HS2.3.1 | Highlight

Impact of drought on nitrogen concentrations in leaching water from agricultural areas in the Netherlands 

Marieke Oosterwoud, Harm Wismans, Astrid Vrijhoef, Richard van Duijnen, and Susanne Wuijts

Since the introduction of the EU Nitrates Directive (91/676/EEC), nitrogen concentrations have gradually declined. The recent summer droughts (2018-2020) in the Netherlands, have caused an increase in nitrogen concentrations in water leaching from agricultural soils, exceeding standards. It is expected that with increasing numbers of climate extremes, summer droughts will occur more often in the Netherlands. In order to develop possible strategies, it is important to better understand the underlying mechanisms and consequent impact of droughts on water quality. 


In rural areas of the Netherlands the water quality of shallow groundwater and surface water (leaching water) is strongly influenced by agricultural land use. The EU Nitrates Directive aims to protect waters against pollution caused by nitrates from agricultural sources. In the Netherlands, leaching of nitrogen to shallow groundwater and surface water is monitored for over 30 years by the Dutch Mineral Policy Monitoring Programme (LMM). Within the LMM, the Netherlands is divided in 4 main and 14 subregions based on soil type. The water sampling at participating farms, enables to analyse the effect of farming practices on water quality in the different LMM regions. 


Nutrients applied during the growing season can leach to shallow groundwater and surface water in the following autumn and winter. Summer drought inhibits the uptake of nutrients by crop, hampers the process of denitrification and leads to thickening of the soil moist and upper groundwater, leading to accumulation of excess nitrates in the soil. These excess nitrates can potentially increase nitrogen concentrations in leaching water in winter. Not every soil region responds similarly to a drought period. The aim of this study is to investigate why certain regions experience a stronger impact of drought on nitrogen leaching than others. 


We used monthly spatial Standardized Precipitation Evaporation Index data provided by the Royal Meteorological Institute (KNMI) over the period 1990-2022 to identify where (region) and when (year) summer droughts occurred. The LMM dataset was used to analyse the change in groundwater levels, nitrogen concentrations in leaching water and soil nitrogen surplus following a summer drought. Furthermore, we investigated the role of soil type and land use on the change in nitrogen concentrations in leaching water caused by drought.


Our findings reveal that the magnitude of the increase in nitrogen concentration in leaching water following a summer drought is determined by the duration and intensity of the drought. Furthermore, soil type and agricultural practices influenced the variation of the impact by droughts between regions. These results can be used to identify areas that are more sensitive to impacts of droughts on water quality based on their soil and land use characteristics and thus support the development of adaptation strategies by farmers, water authorities and national government. 

How to cite: Oosterwoud, M., Wismans, H., Vrijhoef, A., van Duijnen, R., and Wuijts, S.: Impact of drought on nitrogen concentrations in leaching water from agricultural areas in the Netherlands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17979, https://doi.org/10.5194/egusphere-egu24-17979, 2024.

The Nitrates Directive (91/676/EEC) obliges all EU Member States to protect groundwater and surface water against pollution caused by nitrates from agricultural sources. To meet this objective, the Netherlands has developed standards for the use of manure and inorganic fertilisers. Empirical models are used to evaluate these standards to ensure that they are consistent with the objectives of the Nitrates Directive. This study has evaluated field data over a period of 30 years to assess leaching fractions of nitrogen surplus for different soil types and land use (arable vs grassland).   The results serve as input for the empirical models.

The aim of this study was to calculate the part of the nitrogen surplus on arable land and grassland that leaches into ground and surface water (nitrogen leaching fraction). This is done for four regions characterised by different soil types (sand, loess, clay and peat). The sand region is herein divided in different groundwater depth regime classes (GRC’s) which are an indicator for the soil drainage condition. 

The type of soil and its usage impact specific soil microorganisms. These microorganisms are able to break down nitrate. The more denitrification takes place, the less of the nitrogen surplus, in the form of nitrate, reaches ground and surface water, resulting in a reduced leaching fraction. 

This study utilised monitoring data from the Minerals Policy Monitoring Programme (LMM). This long term monitoring programme monitors the agricultural practice and water quality on agricultural farms in the Netherlands since 1991 onwards. All farms in this study were randomly sampled and selected (about 750 farms over the whole period).

Nitrogen surplus was derived by subtracting nitrogen outputs from input at the farm level. Precipitation surpluses were used to calculate nitrogen loads from nitrate concentrations per soil region and land use (arable or grassland). This was done using year specific long-term median precipitation surplus based on fractions of crop types, soil types and GRC’s. 

The nitrogen leaching fraction is highest in dry sandy soils, followed by loess, clay and peat. Leaching fractions were found to be significantly higher on arable land than on grassland. The findings of this study closely align with prior research on leaching fractions from 1991 to 2014   even though input data was completely renewed.

The most remarkable change in input data from the former version was visible on Dutch soil and GRC maps: soil types and GRC’s have shifted over the monitoring period. Shallow peat soils located on sands have shifted, due to oxidation, to a more sandy soil, whereas groundwater tables have fallen. 

This method is, as far as known, unique because of the use of a large sample of random, shallow water quality measurements, aggregating to a long term leaching fraction, without the use of complex model instruments. This measurement-based method can be a helpful tool to derive environmentally sound N use standards to meet with the objectives of the Nitrate Directive.

How to cite: Brussée, T. and Oosterwoud, M.: Estimating nitrogen leaching fractions to ground and surface water on agricultural farms from long-term monitoring data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18419, https://doi.org/10.5194/egusphere-egu24-18419, 2024.

EGU24-18955 | ECS | Posters on site | HS2.3.1

Shifting nitrate seasonality along decades of anthropogenic impact in western European catchments 

Pia Ebeling, Rémi Dupas, Benjamin Abbott, Rohini Kumar, Sophie Ehrhardt, Jan H. Fleckenstein, Nils Turner, and Andreas Musolff

Nitrate pollution in streams, although attempts have been made to combat it, remains a persistent problem, especially in highly anthropogenically impacted landscapes such as Western Europe. Nitrate concentrations and discharge typically vary with the seasons, as does the vulnerability of water bodies to high nitrate inputs. However, the degree of variability and seasonal timing vary in space and time while nitrate inputs in catchments have undergone drastic long-term changes. The changing N sources and distribution in the catchments and their variable hydrological activation suggest that different nitrate seasonality has emerged across catchments over the decades. In this study, we hypothesize that nitrate concentrations respond faster to changes in input during the high-flow season than during the low-flow season, as shallow sources are typically activated during high flow and are the first to be affected by changes in management. To test this hypothesis, we propose a hysteresis approach of long-term nitrate seasonality during low- and high-flow seasons, which we applied in 290 catchments in Germany and France with nitrate and discharge time series of 20 or more years. Our results show that in the majority of catchments, nitrate and discharge vary synchronously with peaks in winter. Deviating average nitrate-discharge typologies could be linked to topography and hydroclimatic seasonality as well as to the regionally characteristic source heterogeneity and lithology in northwestern France. Contrary to our hypothesis, we found both types of trajectories with preceding high-flow and low-flow nitrate concentrations were equally present. We could exemplarily show high-flow concentrations responded first in an agricultural catchment and low-flow concentrations reacted first in a more point source intense catchment. However, across the large number of catchments, consistency was not observed suggesting higher complexity of interacting processes. In a further step, we plan to investigate the long-term trajectories of phosphorus to account for the ratios of the major nutrients affecting the resulting impact of land-stream transfer processes on eutrophication.

References: Ebeling, P., Dupas, R., Abbott, B., Kumar, R., Ehrhardt, S., Fleckenstein, J. H., & Musolff, A. (2021). Long-term nitrate trajectories vary by season in Western European catchments. Global Biogeochemical Cycles, 35, e2021GB007050. https://doi.org/10.1029/2021GB007050

How to cite: Ebeling, P., Dupas, R., Abbott, B., Kumar, R., Ehrhardt, S., Fleckenstein, J. H., Turner, N., and Musolff, A.: Shifting nitrate seasonality along decades of anthropogenic impact in western European catchments, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18955, https://doi.org/10.5194/egusphere-egu24-18955, 2024.

Diffuse pollution of shallow groundwater as a result of leaching of substances from agricultural soils has a negative impact on groundwater quality. In the drinking water sector, the focus has traditionally been on nitrogen (nitrate) and crop protection products, which are subject to strict standards. Geochemical buffering processes in the subsurface convert a large part of the nitrate load that leaches to groundwater from agricultural soils. However, these processes can often lead to an increase in the hardness (sum of the calcium and magnesium concentrations) of groundwater, which is undesirable for drinking water and domestic use.

Recent research shows that 70% of phreatic groundwater extraction locations in the Netherlands show a significant increasing trend in hardness. However, quantitative insight into the relationship between spatial characteristics (land use, soil type and geochemical composition of the subsoil) and hardness has so far been lacking. In this research we analyzed a long time series of data (since 1900) from shallow (< 25 m below ground surface) phreatic and semi-confined groundwater extraction locations in the Netherlands. The trends in hardness and partial pressure of CO2 (PCO2) and relationship with spatial characteristics of the extractions is presented.

A clear influence of agriculture activities in groundwater protection areas was observed; the hardness in agricultural-dominated extraction sites was 2.5 times higher compared to nature-dominated extraction sites, while the trend in the increase in hardness was almost 3 times higher. The trend is observed in both calcium carbonate-rich and calcium carbonate-poor soils. In carbonate-rich areas, the hardness of groundwater is determined by the addition of acid, from atmospheric deposition, agricultural activities such as fertilization and crop harvesting and by weak acid (CO2) contributions from root respiration and mineralization of organic matter. In carbonate-poor soils hardness sources are the use of calcium and magnesium salts and the application of manure on agricultural land. 

In carbonate-rich systems, slightly less than half of the groundwater hardness was found to be due to limescale weathering due to strong acid input, while slightly more than half of the hardness was due to weathering from CO2. Higher PCO2 levels and trends in agricultural-dominated extraction sites comparted to nature-dominated sites reveals an impact of intensive agricultural production on the CO2 production is soils, and thereby on groundwater quality, that have not been considered so far.

To minimize hardness as a result of soil acidification it is recommended to reduce nitrogen deposition, limiting nitrate leaching and limit the use of fertilizers that acidify the soil. To minimize hardness as a result of weak acid (CO2) weathering, more extensive agricultural practices to reduce root respiration should be adopted, and the degradation of soil organic matter can be limited by preventing (short-term) lowering of groundwater levels in organic rich soils. The results indicate that land use has a significant effect on the hardness and PCO2 in groundwater. Mitigating measures should consider an area-based approach, taking into account the land-use, soil type and geochemical characteristics of the subsurface to limit the impacts of increased hardness and PCO2 as a result of agricultural activities.

How to cite: Hockin, A., van der Grift, B., and Scheper, D.: Unexpected impact of agricultural land-use practices on the concentration and trend in hardness of groundwater abstracted for drinking water supply, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20251, https://doi.org/10.5194/egusphere-egu24-20251, 2024.

EGU24-20400 | ECS | Posters on site | HS2.3.1 | Highlight

Understanding hysteresis in high-frequency water quality data in rivers: adding value to targeted research using routinely collected operational data  

Josie Ashe, Emilie Grand-Clement, and Richard. E Brazier

Patterns and variability in the concentration-discharge relationship may be used to describe the complex interactions and combined effects of catchment processes affecting sources, mobilisation and transport of contaminants. Many concentration-discharge relationships display temporal variability on diurnal, event, seasonal and annual scales. This has been widely demonstrated through both routine regular sampling and targeted storm sampling.

The set-up costs of high frequency in-situ river and reservoir sensors is high, and operation and maintenance of a wide network is both time and resource intensive and the conditions for operation (e.g. environmental conditions, signal, power) are rarely ideal. Yet with technological advances and the growth in availability of high-frequency is-situ water quality sensors, the complexity of the water quality response to changes in flow, across multiple timescales, has become increasingly evident. The observed dynamics during events, and range of hysteresis patterns displayed, shows that the sources of contaminates, mechanisms for mobilisation, and transport times are highly variable both spatially and temporally. Furthermore, seasonal and interannual controls on catchment functioning are seen to result in pronounced differences in the behaviour of parameters between sites, and between individual events at the same site.

This study shows how routine high-frequency data, collected with an operational focus for source protection and in raw water at drinking water treatment works, provide opportunities when trying to identify sources and pathways for contaminants. Despite challenges, these data support the development of a baseline understanding for water quality within a specific catchment or region, and provide insight into catchment specific event-driven dynamics. In catchments where routinely collected data is the only source of multiannual high-frequency water quality data, these data may be crucial in building understanding of long term (decadal) variability and trends; in particular, gaining understanding the changing interactions and effects due to extremes in seasonal patterns across different years. However, the key limitations in the use of these data include undefined uncertainties and missing data, monitoring design, and limited metadata. Therefore, building on initial analysis of routine data, efficient monitoring campaigns for targeted research can be designed to investigate any previously unexplored or unidentified processes and pathways.

This study is part of a wider programme of research on the identification of sources and pathways for contaminants of concern in catchments supplying drinking water in the south west of the UK, and how water quality dynamics are impacted by meteorological and catchment conditions, including atypical events. It supports work on increasing resilience in drinking water source areas and reducing treatment demands and costs, through improving understanding of how water quality in rivers and reservoirs is affected by landscape and farm-based catchment interventions.

How to cite: Ashe, J., Grand-Clement, E., and Brazier, R. E.: Understanding hysteresis in high-frequency water quality data in rivers: adding value to targeted research using routinely collected operational data , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20400, https://doi.org/10.5194/egusphere-egu24-20400, 2024.