EGU General Assembly 2024  

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 x_min 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 x_min 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 x_min proposed by Crago et al. (2016) (the Crago’s x_min values) and the results show that the range of variation for the Crago’s x_min values is smaller than that for the x_min values obtained by inverse method from the models (the inversed x_min values) in the interannual process. The inversed x_min values of RCR-C2016 are mostly larger than that of RCR-S2017, while the Crago’s x_min values are in between these two values. The empirical function for x_min 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 x_min is expressed only using the AI. Cross-validation results show that the rescaled CR models combined with x_min 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.

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 0.1^o×0.1^o 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.

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.

Rainfall interception loss (E_i) is one of the biggest unknowns in the global hydrological cycle. As a dynamic process, E_i 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 E_i over large scales, and its sensitivity to non-stationary climate variability renders E_i 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 E_i, as well as the driving mechanisms behind its variability.

Here we explore the estimates of E_i 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 E_i 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 E_i. 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 E_i variability. We find that E_i, 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 E_i 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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, ET₀^vert, 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 (R_S) for the study area. Using VPD and R_S, 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 (R_S 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 16^th 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.

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.

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.

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.

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.

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, R_C, 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 R_C 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 R_C and adds useful information in that R_C values can also be established at ungauged locations, with R_C values higher than 1.6 in various regions especially over western Canada. An evaluation of the level of confidence for R_C , 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.

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.

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.

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.

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.

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.

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.

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 L_w (or the remote sensing reflectance R_rs), necessitating high-level expertise and expensive material.

One of the most robust methods to measure L_w is the skylight-blocked approach (SBA), which allows L_w 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 L_w) 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.

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 K_d,PAR, a measure of light penetration, and the Secchi depth (Z_SD), 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, K_d,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.

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.

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.

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.

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.

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.

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.

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 (θ_crit). Knowledge of θ_crit is important for improving land surface, hydrological and crop models and predicting hydroclimate extremes such as droughts and heatwaves. However, the quantification of θ_crit and the factors that impact θ_crit are still not well understood. Here we used precise lysimeter observations to quantify θ_crit 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 θ_crit 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 θ_crit 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 θ_crit with the same soil and vegetation but under different weather conditions, which can provide implication on changes of θ_crit under global warming. We would expect a dependence of θ_crit 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 θ_crit (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 θ_crit. In addition, an increase in θ_crit 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 sciences, 13(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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 (E_pot) 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 E_pot 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 E_pot 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 E_pot time series. First analyses show that the differences between the two P time series are relatively minor, whereas the seven E_pot 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/E_pot 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 E_pot 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 (pH_IEP) 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.

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.

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.

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.

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.

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.

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.

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.

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.