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Groundwater and water scarcity in dry regions: causes, processes, regional solutions

Groundwater is the world's most important, best protected and most exploited freshwater resource. It is intensively used by humans. It is also the primary source for drinking water supply and irrigation, hence critical to the global water-food-energy security nexus, especially in dry regions. Groundwater is sensitively to shifts in climate, which changes the hydrological cycle and thus groundwater recharge. Additionally, global changes such as population growth or changes in land use affect groundwater resources, both in terms of quantity and quality. Due to these changes, regions with high water stress are expected to expand globally. Beside regions that have already a water deficit, new regions, such as catchments in Central Europe with continental climate and decreasing precipitation in summer periods are likely to be subjected to water stress. The Mediterranean basin is also expected to become a major hot spot of water stress in the future.
Therefore, groundwater resources, especially in dry regions, need to be managed wisely, protected and especially used sustainably. In this session we invite contributions, which identify new consequences of a changing environment for better future management, protection, and sustainable use of groundwater. This implies adapted modelling techniques, such as coupling climate models with hydrological models, coupling climate models with soil water- and groundwater models. This includes also studies into groundwater quantity and quality changes and recharge mechanisms. In addition, we invite contributions from appropriate field observational studies.

Furthermore, the session asks for contributions that address regional strategies for groundwater sustainability, in detail that (i) unravel the combined action of topography, geology, climate, land use and anthropogenic forcing in controlling regional groundwater availability, quality and sustainability; and (ii) propose new methods (e.g., coupled modelling approaches) for assessing and managing regional groundwater systems in diverse climatic, hydrologic, socio-economic and institutional settings, and accounting for uncertainty; (iii) present appropriate field observational studies; (iv) address uncertainty and limited data availability due to a frequently associated data scarcity issue in dry regions, methodologies, strategies.

Co-organized by CL2
Convener: Martin Sauter | Co-conveners: Irina Engelhardt, Noam Weisbrod, J.C. Maréchal, Xavier Sanchez-Vila, Zhilin GuoECSECS, Taher Kahil, Ting TangECSECS
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Tue, 27 Apr, 15:30–17:00

Chairpersons: Martin Sauter, Zhilin Guo, Xavier Sanchez-Vila

5-minute convener introduction

Eleftheria Kalaitzaki et al.

In the Mediterranean region, climatic variations in conjunction to intensive agriculture deteriorates groundwater resources which are over-exploited to cover irrigation demands. A characteristic example is Messara Basin in the island of Crete, Greece. This work presents an integrated suitability assessment study for potential aquifer recharge that considers the availability of water resources, hydro-geological and geomorphological characteristics, climatic scenarios, soil properties and suitability, and socioeconomic analysis under the framework of a suitable aquifer recharge technique.

The most suitable technique for planning the aquifer recharge was selected according to the area characteristics. The spreading method was assessed as the most suitable technique based on the area characteristics that should typically have a source of excess water available nearby, be located in a relatively flat area with permeable soils and be underlined by an unconfined aquifer. A multi-criteria decision analysis method was applied to identify suitable sites for implementing aquifer recharge type spreading method. The methodology is based on a multicriteria matrix developed in accordance to a relative optimization (weighting) method in terms of hydrogeological and geomorphological criteria, and water availability (reservoir, river). Criteria combining a high relevance and high data availability, and providing unique information, selected to assess the suitability of aquifer recharge in Messara basin such as slope, land use, hydrogeology, rainfall, groundwater level, soil texture and distance to source water.

All the aforementioned factors were separately studied and analyzed and then were combined under the principles of the spreading method to provide by means of spatial maps the most appropriate locations in the study basin.

The outcome of this work is a simple framework methodology for selecting the most suitable recharge locations of the underlying aquifers and to demonstrate its socioeconomic and environmental advantages. The results of this work will assist local authorities to consider the applicability of aquifer recharge in the Messara valley while it consists a framework for efficient planning of similar applications in other Mediterranean regions.



This work was implemented in the framework of the research project Uncertainty-aware intervention design for Mediterranean aquifer recharge. The project: "Uncertainty-aware intervention design for Mediterranean aquifer recharge benefits from the support of the Prince Albert II foundation". http://www.fpa2.org



Special water secretariat of Greece, 2017. Integrated Management Plans of the Greek Watersheds, Ministry of Environment & Energy, Athens.

Varouchakis, E.A., 2016. Integrated Water Resources Analysis at Basin Scale: A Case Study in Greece. J. Irrig. Drain. E-ASCE 142(3), 05015012. DOI:10.1061/(ASCE)IR.1943-4774.0000966

How to cite: Kalaitzaki, E., Varouchakis, E., Corzo Perez, G. A., Diaz, V., Akoumianaki, O., and Karatzas, G. P.: An integrated method to study and plan aquifer recharge, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3898, https://doi.org/10.5194/egusphere-egu21-3898, 2021.

Radegonde Rusagara et al.

The lack of adequate information on groundwater recharge mechanisms in the basement rock area of Sahelian regions does not allow to estimate recharge rates. Thus, this study, which aims to improve the knowledge of the groundwater recharge mechanisms of the Tougou (catchment of 37 km2 representing a basement rock in Sahel of West Africa) aquifers was initiated. The first step was to characterize the geology in terms of geometry and structure. The ERT profile (1.2 km length) crossing perpendicularly the river and lithologs from 10 observation wells (Average depth: 25m) and 1 borehole (Depth: 60 m) were used to make the correspondence between geological and geophysical data. The second step was to characterize vertically and laterally aquifers recharge mechanisms under the ephemeral river and two river banks. Hence, hourly to daily groundwater levels, electrical conductivity, and temperature of groundwater have been measured in those 10 observation wells and 1 borehole (Period: 2016-2020). The river water levels and the rainfall were also collected. The cross-correlation function was used between the rainfall or river water levels and the hydraulic heads time series. The geological characterization showed from top to bottom:

  • Residual soils: 1 m to 2 m thick, present in the riverbed and on the right bank;
  • Laterite (lateritic clays and lateritic cuirass): 2 m to 14 m thick, absent in the riverbed and present on the two banks;
  • Laterally continuous clayey saprolite: 10 m to 22 m thick;
  • Weathered schist: 32 m thick in the river. A bedrock was found at a depth of 55 m.

This geological conceptual model was a grounding for interpreting the results incurred from other data collected. It was ascertained that the weathered schist aquifer below the river is semi-confined (Average water depth: 9.5 m < top: 25 m) and vertically recharged by the saprolite aquifer. Laterally, the clayey saprolite aquifer is recharged by two main flows from:

  • The river: the electrical conductivity and temperature of the groundwater in the clayey saprolite aquifer below the river vary at the same time as the water table increases during the rainy season. In addition, mean hydraulic head differences of +0.3 m and +2 m have been observed between the piezometer located in the river and respectively, the piezometer located at 20 m from the river on the left bank and other piezometers located on the right bank (up to 600 m from the river). A maximum good cross-correlation between hydraulic heads and river water levels rather than with rain was found in all piezometers, but mostly in the one located in the river (cross-correlation = 0.56). These indicate an indirect recharge process.
  • The left bank: An mean hydraulic head difference (+3 m) which is related to a transfer of hydraulic pressure from probably a nearby recharge area was noted between the piezometers located at 300 m and the riverbed.

For further studies, the information obtained will be used to estimate the recharge through different methods including numerical modeling.

How to cite: Rusagara, R., Koita, M., Plagnes, V., and Jost, A.: Improvement of Groundwater Recharge Mechanisms Knowledge in Rural Sahelian Zones: Case Study of Tougou Catchment, Burkina Faso, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-8933, https://doi.org/10.5194/egusphere-egu21-8933, 2021.

Paul Hepach et al.

Karst aquifers provided 9.2 % of the world’s population with fresh water in 2016 (Stevanović, 2019), but due to their dual flow behavior they are highly vulnerable to anthropogenic impacts and shifts in climate. In the near future, 52 out of 356 Mediterranean aquifers will be exposed to more extreme climatic conditions, which will enhance their water stress if the water usage is not adapted to available water resources (Nußbaum, 2020). Therefore, accurate and high resolution numerical - and empirical models are essential to calculate the groundwater recharge and water availability in complex karst aquifers that cover ~ 14 % of the earth’s ice free land (Stevanovic, 2019).

During the last decades, several empirical equations have been developed to calculate the recharge for Israel´s most important source of freshwater, the Western Mountain Aquifer (WMA). These equations calculate annual groundwater recharge of the entire 1.812 km2 recharge area based on annual or monthly precipitation data. We analyzed the applicability of several new methods, such as Soil & Water Assessment Tool (SWAT), HydroGeoSphere (HGS) and Hydro- / Pedo- Transfer Functions (HPTF) to estimate groundwater recharge with  a higher resolution as this is essential to calculate proper water fluxes though the vadose zone of karstic aquifers when precipitation is affected by a high variability in space and time.

The hydrologic balance models,  e.g. SWAT (Neitsch et al., 2009),  calculate the water balance on a daily basis for specified Hydrologic Response Units (HRUs), while generalized HPTFs (Wessolek et al., 2009) use soil-, land cover-  and climate data to calculate  annual percolation rates on a coarse grid, in our case 500 m grid size. The dual continuum model using the code HGS (Brunner et al., 2011) is able to simulated based on Richards’s flow equation down- and upward water fluxes in the unsaturated zone accounting for both, a rapid flow component though the high permeable conduit and a slow flow component through the rock matrix.

The comparison of these empirical and new methods for groundwater recharge estimation show significant differences for hydrological extreme years, while results are similar during years with precipitation rates near the average value. For example, the empirical equation of Guttman & Zukerman (1995) gives  highest recharge values of all approaches during wet years, while the equation of Abusaada (2011) and the SWAT-model calculates  highest recharge values of all approaches during  dry years. Overall, the mean recharge ranges from 120 to 177 mm/a which equals 25 – 37 % of the average precipitation between 1990 – 2018.

These recharge rates are calculated based on IMS climate data. However, for recharge values used in water resources management regional climate projections are needed. For Israel a high resolution CORDEX-MENA climate projection (Hochman et al., 2018) is available for RCP4.5, showing an increase in temperature and decrease of precipitation during the winter of 2.5 °C and 40 %, respectively. Based on these climate projections the  SWAT-model estimates, that the average groundwater recharge for 2050 – 2070 will be 16 % lower than the reference period between 1980 – 2000.

How to cite: Hepach, P., Banusch, S., Bresinsky, L., Somogyvári, M., Bucchignani, E., Sauter, M., and Engelhardt, I.: Comparison of methods for recharge estimation and prediction in karstic aquifers under Mediterranean Climate, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11825, https://doi.org/10.5194/egusphere-egu21-11825, 2021.

Lysander Bresinsky et al.

Present methods to quantify recharge in karst aquifers in many cases rely on spatially and temporally aggregated precipitation values, neglecting the highly erratic, non-linear nature of infiltration dynamics that give rise to a dual-domain behavior with a slow diffuse and fast focused recharge component. Here, we demonstrate the applicability of integrated surface-subsurface flow models to simulate diffuse and preferential infiltration within the large scale Western-Mountain-Aquifer (WMA) in Israel and the Palestinian territories. A semi-arid climate region with a highly pronounced seasonality of precipitation and intense short-duration rainfalls, such as the Mediterranean region, emphasizes the importance of understanding and accounting for the complex dynamics of dual-domain infiltration and partitioning of the precipitation input signal via spatially discretized overland flow processes.

We apply HydroGeoSphere as a dual-continuum flow simulator for transient variably-saturated water flows, discretizing the rock matrix and secondary porosity (i.e., conduits and fractures) as separate overlapping continua. Flow is respectively computed via the Richards' equation with volume-averaged van Genuchten parameters, assuming that the Richards' equation is valid for both domains. The presented model accounts for surface flow via the two-dimensional Saint-Vénant equations under nonexistent inertial forces. We apply precipitation directly to the overland flow continuum and naturally account for the partitioning into Horton overland flow and percolating water. However, modeling of unsaturated flow through the conduit/fracture continuum with the van Genuchten parameterization is often limited, as the Richards' equation describes flow solely in terms of capillary forces, leading to high matric suction in the matrix continuum as a result of the smaller pore spaces (and hence constant exchange from the fracture continuum to the matrix system). In a natural system, non-linear transfer processes govern the transfer between fracture/conduit and matrix flow, such as inertia-driven infiltration (i.e., droplet, rivulet, and film flow) that initially retains itself from equilibration of capillary pressure heads and avoids instant matrix imbibition. This study demonstrates parametrization strategies to allow for infiltration through the fracture/conduit continuum using small-scale process-based simulations. Further, we offer procedures that help to achieve convergence of complex catchment-scale variably-saturated simulations.

How to cite: Bresinsky, L., Kordilla, J., Engelhardt, I., and Sauter, M.: Distributed modeling of groundwater recharge in a semi-arid carbonate aquifer using the integrated surface-subsurface flow simulator HydroGeoSphere, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14446, https://doi.org/10.5194/egusphere-egu21-14446, 2021.

Nahed Ben-Salem et al.

Groundwater is a valuable resource throughout the world. It supplies the needs of many sectors everywhere. Providing high spatial resolution groundwater data is important for climatic, hydrological and agricultural applications, to ensure sustainable groundwater management. The scarcity of high-resolution groundwater data over large scales at the required accuracy is a significant limitation for such applications. This study was undertaken in the Mediterranean region, which is recognized as one of the world's most sensitive regions to water scarcity due to both climate change and consistently increasing anthropogenic pressures. Groundwater is considered a strategic freshwater reserve in the Mediterranean region; however, its status remains poorly characterized. This study investigates the feasibility of downscaling outputs of three global groundwater models (Reinecke et al. (2019), de Graaf et al. (2017) and Fan et al. (2013)) to higher resolution.

Steady-state results of the three models were compared with in-situ groundwater level observations, and an aggregation method was developed for downscaling. Observations from a long-term groundwater monitoring network over different regional studies around the Mediterranean were employed. Results showed that there is a significant discrepancy between the three compared model outputs. More specifically, the de Graaf et al. (2017) model presents a deeper water table than Reinecke et al. (2019) and Fan et al. (2013), while de Graaf et al. (2017) generally shows more significant variability in simulated water table depth. A detailed comparison between simulated and measured water table depth of different Mediterranean aquifers having different climatic, geologic and anthropogenic conditions will be presented.

The results of this work will contribute to advance the understanding of how to combine large-scale groundwater modelling with local in-situ data as a crucial tool to improve groundwater management in data-scarce regions.

This work was supported by the German Federal Ministry of Education and Research (BMBF, Germany, Grant 01DH19015) under the Project Sustain-COAST, co-funded by EU PRIMA 2018 programme.



  • ­ Reinecke, R. et al. Challenges in developing a global gradient-based groundwater model (G3M v1.0) for the integration into a global hydrological model. Model Dev 12, 2401-2418 (2019).
  • ­ de Graaf, I. et al. A global-scale two-layer transient groundwater model: Development and application to groundwater depletion. Water Resour 102, 53-67 (2017).
  • ­ Fan, Y. et al. Global patterns of groundwater table depth. Science 339, 940-943 (2013).

How to cite: Ben-Salem, N., Reinecke, R., Gómez-Hernández, J. J., Karatzas, G., Rode, M., and Jomaa, S.: Groundwater assessment in the Mediterranean region: Regional modelling and in-situ data across scales, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9792, https://doi.org/10.5194/egusphere-egu21-9792, 2021.

Rafael Chavez Garcia Silva et al.

The Mediterranean region faces water security challenges with increasing water demand and climate change effects. Groundwater has become a key resource for water supply and economic development in the last decades, however, its budget remains poorly understood. The distribution of piezometric data in the Mediterranean has a very contrasting distribution. A large portion of them is not centralized and openly accessible, resulting in lack of detailed assessment of groundwater trends and their controlling factors at the regional Mediterranean scale. The objectives of this work are: i) the creation of a long-term and, possibly, the most comprehensive database for groundwater dynamics in the Mediterranean region, ii) the identification of trends and clusters on groundwater levels, and iii) the identification of the relationship between trends and climatic and hydrogeological drivers.

Over 10,000 time series of groundwater level have been collected from national and regional authorities and the literature. The data come from eight countries in the Mediterranean region and have been post-processed into a common format. A search for seasonal patterns and long-term trends is performed then clustered accordingly. Furthermore, the influence of controlling factors such as precipitation and hydrogeology on the groundwater dynamics and trends are assessed. Significant groundwater level changes have been identified at a regional scale and used to provide insight into groundwater level change drivers’ in the Mediterranean region. The database is the result of a unique joint effort between regional groundwater experts to collect groundwater status information in the Mediterranean region and will serve as the foundation for future research on the influence of anthropogenic drivers and the prediction of groundwater depletion hotspots.

This work was developed under the scope of the InTheMED project. InTheMED is part of the PRIMA programme supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 1923.

How to cite: Chavez Garcia Silva, R., Reinecke, R., Varouchakis, E., Gómez-Hernández, J., Rode, M., and Jomaa, S.: Long-term groundwater database and assessment for the Mediterranean region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10989, https://doi.org/10.5194/egusphere-egu21-10989, 2021.

Vineeth Vijayan and Parthasarathy Ramachandran

Strategies for sustainable ground water management are to be planned at regional scale. Urban ground water recharge is complex and dynamic. Various factors contribute to ground water level variation. Understanding the ground water recharge components is essential in planning and management of the water resources in any city. This study attempts to understand the spatiotemporal variations of an urban hard rock aquifer system in Bengaluru, India using REOF analysis and Kriging. Bengaluru meets its needs of water supply from river Cauvery. The water supply utility has an increasing block tariff to control the water demand in the city. But it measures only the use of surface water that is being supplied by the utility. Ground water, being a free resource, bridges the demand supply gap in the city. More than half of the water demand in the city is met through ground water. Hence it is essential to understand the components of ground water level variation in this hard rock aquifer system. Rotated empirical orthogonal function (REOF) analysis of monthly piezometric heads from 153 monitoring wells measured during 2015-2017 is used to identify the primary ground water recharge components. The major components of ground water level variation in the study area was identified as rainfall and pipeline leakage. Ordinary Kriging was used to regionalize the identified significant empirical orthogonal functions.

How to cite: Vijayan, V. and Ramachandran, P.: REOF analysis of ground water level variation in an Urban hard rock aquifer system, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13982, https://doi.org/10.5194/egusphere-egu21-13982, 2021.

Niranjan Naik et al.

Groundwater is an important natural freshwater resource and plays a significant role in the socio-economic development of any country. The Betwa River basin in central India has experienced severe exploitation of groundwater resource in the past few decades. About 80 % of groundwater in this region is extracted for the agriculture purpose. Also, the scarcity in rainfall throughout the year and seasonal flow in the Betwa River has increased the agricultural dependence on the groundwater. This has led the Betwa River basin into a major hot spot of groundwater depletion.

This study estimates the trend of groundwater level and storage change to assess the groundwater dynamics in the Betwa River basin. We used in-situ groundwater level data for a period between 1987-2018 to calculate the trend in groundwater level using the Seasonal and Trend decomposition using Loess (STL) method. Further, we performed the Ordinary Kriging to understand the spatial and temporal trends of groundwater during the pre-monsoon and post-monsoon. Eventually, we use the water table fluctuation (WTF) method to estimate groundwater storage in the study area. Our results suggest a decline in groundwater storage change as 701 and 626 MCM in the post and pre-monsoon period respectively from 2008-2018. During the same period, we observed that the Betwa basin has experienced about 3-5 m decline in the groundwater level.


How to cite: Naik, N., Beg, Z., Kumar, A., and Gaurav, K.: Groundwater dynamics in the Betwa River catchment in Central India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15373, https://doi.org/10.5194/egusphere-egu21-15373, 2021.

Philipp Nußbaum et al.

Approximately 10% of the global population rely on groundwater from karst aquifers. Due to complex karst structures, these aquifers have high infiltration capacities and hydraulic conductivities, which makes them vulnerable to pollution and, as prediction and management are complicated, overexploitation. As populations are growing and demand rises, we assess the current level of groundwater stress in karst aquifers with Mediterranean climates and their vulnerability (defined as the change in groundwater stress) to expected changes in temperature and precipitation on the global scale.

Our approach is based on a Groundwater Stress Index (GSI), which is calculated for 356 karst aquifers (as identified in the World Karst Aquifer Map) that have some of their area located in Mediterranean climate zones (Csa, Csb, and Csc after Köppen/Geiger). GSI are calculated from seven indicators: groundwater recharge, storage, and abstractions, surface runoff, climatic water balance, water-intensity of crops, and groundwater-dependent ecosystems. Each indicator is spatially and temporally averaged to describe a recent trend on aquifer level, resulting in one complex attribute table for the 356 aquifers. GSI is calculated as the average of the normalized indicators for each aquifer, ranging from 0 (no water stress) to 1 (extreme water stress).

Aquifers are then grouped based on similarities in two classification parameters – degree of karstification (P1) and land cover (P2). Comparison of aquifers with similar classification parameters allows to focus more directly on the relationship between groundwater stress and climate, disregarding relatively constant influences. For each group (e.g., well-developed karst, primarily agriculturally used), we plot calculated GSI values with current temperature and precipitation data. By investigating four Shared Socioeconomic Pathways (SSPs) until 2100, we identify aquifers that mimic future climate conditions for others with similar P1 and P2. We then measure the difference in groundwater stress accompanied by altered climatic factors. This change is interpreted as vulnerability to climate change.

This approach, which relies on present-day observed conditions, allows us to predict the effect of a changing climate without the need to develop a complex numerical model, which requires large amounts of data and functional understanding of aquifer behavior. While analysis is currently ongoing, we expect both groundwater stress and vulnerabilities to be high. Predicted climate zone shifts by Beck et al. (2018) indicate that, out of 356 karst aquifers with Mediterranean climates, 52 could move to more extreme arid climate zones by 2100.

Results will be visualized in the form of vulnerability maps that may serve as an “early-warning system”. For particularly threatened aquifers, we will derive recommendations for more sustainable management by suggesting strategies to lower groundwater stress. This is done by taking a closer look at the aquifer’s indicator values and identifying factors that currently contribute the most to groundwater stress.

How to cite: Nußbaum, P., Somogyvári, M., Conrad, C., Sauter, M., and Engelhardt, I.: Calculating groundwater stress and climate change-induced vulnerability of karst aquifers on a global scale, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-929, https://doi.org/10.5194/egusphere-egu21-929, 2021.

Gabriel Rau et al.

Determining subsurface hydraulic and geomechanical properties crucially underpins groundwater resource investigation and management. While standard practice relies on active testing, passive approaches require less effort and cost but are underutilised. We present the new Python package named HydroGeoSines (HGS) which quantifies hydraulic and poroelastic subsurface properties using the groundwater response to natural forces (such as Earth tides and atmospheric pressure changes) embedded in standard measurements. All implemented methods are drawn from the peer-reviewed literature. The package includes basic handling of time series, such as joining and aligning records and handling gaps. HGS uses standard atmospheric and groundwater pressure records to estimate the Barometric Response Function (BRF) groundwater state of confinement, hydraulic conductivity, specific storage, barometric efficiency (BE) and porosity. If Earth tides are required, they can be calculated on-the-fly using the PyGTide package which is based on ETERNA and included. HGS allows easy compensation and correction of pressure or hydraulic heads from barometric pressure or Earth tide influences. Further, HGS includes import from and export to common data formats as well as visualisation of data and results. We demonstrate the use of HGS using example datasets from around the world. Since HGS unlocks sophisticated methods for use by anyone with Python skills, we anticipate that it will support subsurface investigations and add value to standard monitoring practice.

How to cite: Rau, G., Schweizer, D., Turnadge, C., Blum, P., and Rasmussen, T.: A new Python package to estimate hydraulic and poroelastic groundwater properties using standard pressure records, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4679, https://doi.org/10.5194/egusphere-egu21-4679, 2021.

Zsóka Szabó et al.

In the Duna-Tisza Interfluve area, groundwater levels have declined significantly in the last decades, due to anthropogenic activities (e.g. water abstraction, canalization, and forestation) and climate change. In the past, several replenishment plans have been prepared, involving large, cross-regional technical investments, but have not been implemented due to the lack of adequate financial resources and environmental concerns. The aim of this study is to demonstrate a local scale solution by experimental research, which has several environmental and economic benefits and could contribute to ease the water shortage of the area.
Three approaches were used during the experimental research: (i) on-site field observations and measurements, (ii) time series analyses of the monitored data and (iii) transient numerical simulations to understand on-site processes. A field experiment was set up to lead rainwater from the roof of a family house to the dug well in the yard. Furthermore, two observation wells were established where the water level, temperature and electrical conductivity were recorded every half hour. Water samples were taken from the dug well and the monitoring wells for laboratory measurements. Precipitation was measured on a daily basis. The effects of shallow water injection on water level and water quality have been monitored for a year and the project is planned to be continued for at least one more year. In the second step, geomathematical methods have been applied to analyze time-series data and assess the effects of injected water on water levels and water quality. Moreover, a transient MODFLOW model was built (i) to evaluate the impact of the injected roof water on the groundwater level, (ii) to separate the influence of natural infiltration from the injected water, and (iii) to better understand the seasonal differences related to artificial and natural infiltration processes.
The obtained results can help to understand the effects of rainwater harvesting through shallow well infiltration, provide background information for further numerical simulations and contribute to expand the design of similar systems on settlement and regional level. In the Duna-Tisza Interfluve, rooftop rainwater harvesting and Managed Aquifer Recharge can be effective tools for climate change adaptation and increasing groundwater resilience.

This research is part of a project that has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 810980.

How to cite: Szabó, Z., Pedretti, D., Masetti, M., Ridavits, T., Csiszár, E., and Mádl-Szőnyi, J.: Experimental rooftop rainwater harvesting by shallow well infiltration – A case study from the Duna-Tisza Interfluve, Hungary, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7985, https://doi.org/10.5194/egusphere-egu21-7985, 2021.

Amit Pandey et al.

The study area located in the semi-arid western India is the tenth most populous Indian state with an estimated population of 60.3 million (~5% of Indian population) and population density of 308 persons/km2. About 42.6% of the population lives in the urban area and 57.4% in rural areas. Surface water paucity, seasonal availability and a varying amount of rainfall in this region make groundwater an important and most preferred source to fulfil the demand for drinking water, agricultural, industrial and sustain an important native terrestrial ecosystem. The over-dependency on groundwater leads to various problems related to quality and quantity of groundwater like a rapid decline of the water table, mining of static groundwater, seawater intrusion and groundwater contamination by geogenic and anthropogenic sources. Sustainable water management across the state must be underpinned by the clear understanding of groundwater recharge characteristics, relationship between recharge sources and groundwater, factors controlling the interaction between surface water and groundwater, deletion of the areas not receiving a freshwater influx. Shallow groundwater samples were collected during IWIN nation programme (2008 to 2013)  for the year 2009 to measure the stable isotopes of oxygen and hydrogen in groundwater from 205 locations during post-monsoon (November ) season and 207 locations in pre-monsoon season ( May-June) to understand the factors governing Spatio-temporal variation in isotopic composition and obtain insights about the spatially variable recharge characteristics and possible controlling factors. The oxygen and hydrogen isotopic values and their spatio-temporal variations in the study area demonstrate that (1) d18O depletion in post-monsoon GW compare to pre-monsoon infer the seasonal recharge of GW (2) d18O of post-monsoon GW ( -2.3‰) lie in between the d18O of pre-monsoon GW ( -1.9‰) and d18O of southwest monsoon rainfall (-4.1‰) indicates post-monsoon GW is the mixture of these two components (3) Seasonal variation in d18O deduce that 56% ( ~109773 km2) of the total land area (~ 196773 km2) shows seasonal GW recharge while 32% (62727 km2) is not receiving any freshwater influx (4) 36% of post-monsoon samples while 40% of the pre-monsoon samples have negative d-excess values and shows a decreasing trend with d18O infer evaporation of sub-surface water prior to recharge (5) Alluvial aquifer of north Gujarat has depleted d18O compare to adjacent high elevated hard rock aquifer indicates irrigation return flow of deep static water.

How to cite: Pandey, A., Padhya, V., and Deshpande, R. D.: Isotopic Characterization of groundwater in semi-arid Western India: Insights into Hydrogeological Processes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10826, https://doi.org/10.5194/egusphere-egu21-10826, 2021.

Henrik Schreiber et al.

The Chtouka plain in Morocco suffers from groundwater overexploitation and a significant increase in water salinity. In this study, a multidisciplinary approach combining water chemistry, stable isotopes of water (18O, 2H) and Transient Electromagnetic (TEM) method was used. The main objective was to identify the water salinity sources and the extension of the marine intrusion. Water samples were collected from wells and boreholes, springs, the Massa river and the main source of freshwater in the region, the Youssef Ibn Tachfine Dam. Geophysical (TEM) measurements (12 profiles comprising 83 measurement points) were carried out along the coastal zone and around the northern bank of the Massa river. The results show a spatial variability of water salinity, indicating rock-water interaction, seawater intrusion and anthropogenic influence. The interpretation of the TEM soundings allow to draw the front line of the marine intrusion in the aquifer. The results, compared to previous numerical simulations, show a significant progress of the marine intrusion into the coastal aquifer. The intrusion indeed reaches a distance of 2.5 km from the coast, far beyond models’ predictions. The local water authorities can use these results to improve their monitoring network and better assess the progress of the seawater intrusion.
Keywords: Water salinity, TEM geophysical method, chemical and isotopes tracers, marine intrusion

How to cite: Schreiber, H., Danni, S. O., Touab, A., Abourig, F., Montcoudiol, N., Ez-Zaouy, Y., Hssaisoune, M., and Bouchaou, L.: Study of water salinity in the Chtouka plain (Morocco) using TEM geophysical method, chemical and isotopes tracers, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12074, https://doi.org/10.5194/egusphere-egu21-12074, 2021.

Eduardo De Sousa et al.

Quantification of long-term hydrologic change in groundwater often requires the comparison of states pre- and post- change. The assessment of these changes in ungauged catchments is particularly difficult from a conceptual point of view and due to parameter non-uniqueness and associated uncertainty of quantitative frameworks. In these contexts, the use of data assimilation, sensitivity analysis and uncertainty quantification techniques are critical to maximise the use of available data both in terms of conceptualisation and quantification. This paper summarises findings of a study undertaken in the Lake Muir-Unicup Natural Diversity Recovery Catchment (MUNDRC), where a number of techniques were applied to inform both conceptual and numerical models. The MUNDRC is and small-scale endorheic basin located in southwestern Australia listed under the Ramsar Convention as a Wetland of International Importance and have been subject to a systematic decline in rainfall rates since 1970. Conceptual and numerical frameworks have been development to understand and quantify impacts of rainfall decline on the catchment using a variety of metrics involving groundwater and lake levels, as well as fluxes between these compartments and mass balance components. Conceptualisation was facilitated with the use a novel data-driven method relating rainfall and groundwater response running backwards in time, allowing the establishment of baseline conditions prior to rainfall decline, estimation of net recharge rates and providing initial heads for the forward numerical modelling. Parameter and predictive uncertainties associated with data gaps have been minimised and quantified utilising an Iterative Ensemble Smoother (White, 2018), while further refinement of conceptual model was undertaken following results from sensitivity analysis, where major parameter controls groundwater levels and other predictions of interest were quantified.

How to cite: De Sousa, E., Hipsey, M., and Vogwill, R.: Data assimilation, sensitivity analysis and uncertainty quantification in a semi-arid terminal catchment subject to rainfall decline, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14038, https://doi.org/10.5194/egusphere-egu21-14038, 2021.

Elisha Persaud and Jana Levison

Strategies for understanding regional groundwater contamination risk are often challenged by changing land use and climate conditions. Furthermore, index-based assessment methods are typically implemented in a static manner which inherently precludes possible changes in future contamination risk resulting from these dynamic conditions. It is perhaps equally important to consider the manner in which climate forcing and land use are represented. With regards to land use in particular, rural regions may have unique concerns; agricultural land use is commonly represented as a single land use class despite the complex land management practices that may be present and the subsequent implications for groundwater quality. This investigation demonstrates alteration of the conventional DRASTIC-LU methodology to assess mid-century changes in groundwater contamination risk through the treatment of recharge, depth to water table, and land use as dynamic factors. The potential influence of agricultural land use representation on DRASTIC-LU model performance and prediction is concurrently examined. The Upper Parkhill watershed in southwestern Ontario, Canada is explored as a case study for method application. Study results indicate that the inclusion of crop rotation and tile drainage data has the potential to improve model functioning. Moreover, predicted future changes in groundwater contamination risk may differ depending on the manner in which agricultural land use is represented. This investigation helps to resolve the influence of land use on groundwater contamination risk and provides a screening tool that may be used to support groundwater decision making.

How to cite: Persaud, E. and Levison, J.: Prediction of Future Groundwater Contamination Risk in Rural Agricultural Regions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-982, https://doi.org/10.5194/egusphere-egu21-982, 2021.

Mohd Usman Khan et al.

As contamination in groundwater has been reported from various regions of the Indian subcontinent but no data related to heavy metal contamination of groundwater has been reported for the Bahraich area in the Indo-Gangetic plains. We report the first dataset on arsenic contamination and groundwater hydrogeochemistry, in Bahraich. This includes concentrations of heavy metal such as As, Mn, and Fe, along with major cations (Na+, K+, Ca2+and Mg2+) and anions (F-, Cl-, NO3-, SO42- and PO43-), and dissolved organic carbon (DOC), along with various physico-chemical parameters such as EC, pH, and Eh from samples collected during two extensive field campaigns conducted during pre-monsoon, and post-monsoon seasons respectively. The combined use of geochemical modeling and multivariate statistical approaches such as principal component analysis (PCA) and correlation analysis (CA) suggest several processes affecting the geochemistry of groundwater including the lithological characteristics of aquifers and anthropogenic activities.

The groundwater of the study area predominantly belongs to the Ca-Mg-HCO3 type hydrochemical facies. HCO3/Na+ and Ca2+/Na+ signatures of groundwater indicate the influence of silicate weathering and carbonate dissolution processes with the insignificant role of evaporate dissolution mechanism. As concentration was found to range from 0.6 μg/L to ~100 μg/L with almost 40% of the collected samples exceeding the WHO defined limit of 10 μg/L for drinking water. 70 % of the groundwater samples were found to have very high Fe concentrations exceeding the WHO guideline of 0.3 mg/l in drinking water. Mn concentrations in the groundwater samples were relatively low with only ~10 % of the samples exceeding the WHO defined limit for Mn (400 μg/L). The majority of the groundwater samples were found to be anoxic in nature showing low NO3 & SO42- concentrations, high Fe & Mn and DOC concentrations, and negative Eh values.

Results from this study show that the reductive dissolution mechanism of iron oxyhydroxide is the dominant mechanism responsible for arsenic release in groundwater of the region, ruling out any role of sulfide oxidation and alkali desorption.



How to cite: Khan, M. U., Rai, N., and Sharma, M. K.: Geochemical modeling and multivariate statistical approach for assessing the groundwater quality, and mechanism of arsenic mobilization in Bahraich region, Indo-Gangetic plains, India, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1061, https://doi.org/10.5194/egusphere-egu21-1061, 2021.

Stefan Baltruschat et al.

Water-rock-interactions in the saturated and unsaturated zone govern the natural variability of CO2 in groundwater. However, anthropogenic pollutions such as excessive input of organic and inorganic fertilizers or sewage leakage can cause shifts in the carbonate-pH system in an aquifer. Additional dissolution of minerals and associated mobilization of harmful heavy metals are possible consequences. Anthropogenic groundwater pollution is especially an issue where a protective confining layer is absent. On the other hand, addressing an environmental hazard such as fertilizer input to a single parameter remain intricate due to the high number of possible competing reactions such as microbial-controlled redox reactions. To overcome these obstacles, machine learning based statistical methods become increasingly important.

This study attempt to predict the CO2 concentration in groundwater from a multi-feature selection by using Random Forest. For this purpose, groundwater chemistry data (in situ measured bulk parameter, major ions, nutrients, trace elements and more) from more than 23000 wells and springs in Germany were collected and homogenized in a single database. Measured or calculated CO2 concentrationsare used to train the Random Forest algorithm and later to validate model results. Beside chemistry data, features about hydrogeology, soil characteristics, land use land cover and climate factors serve as predictors to build the “forest”. The intention of this study is to establish comprehensive CO2 predictions based on surface and climate features and to identify trends in local CO2 production. Gained knowledge can be used as input for groundwater quality management processes and adaptation policies.

How to cite: Baltruschat, S., Bender, S., Hartmann, J., and Nolte, A.: Estimation of groundwater CO2 concentrations on a catchment scale using Random Forest, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3458, https://doi.org/10.5194/egusphere-egu21-3458, 2021.

Hamish Johnson et al.

The environmental fate and transport of nitrogen and phosphorus nutrient species leached from agroecosystems are largely influenced by the hydrogeological setting, which dictates the distribution of groundwater flow pathways, residence times, and physio-chemical properties of the subsurface. Traditional conceptual models tend to oversimplify these relationships, and their application towards river catchment nutrient management promotes insufficient characterisation of hydrogeological heterogeneity, which is subsequently not accounted for. Until recently, very little hydrogeological information and conceptual understanding existed for groundwater systems within the postglacial basement terranes of Scotland and Northern Ireland, due to an abundance of surface water resources and prevalence of poorly productive bedrock aquifers. Recent research has demonstrated the role of geological heterogeneity in determining the contaminant transport behaviour of these hard-rock aquifers, where the presence of weathering and fracturing can potentially result in the rapid delivery of nutrients to rural water supplies and groundwater-dependent ecosystems.

We aim to further elucidate the role of hydrogeological setting in river catchment nutrient dynamics to improve agricultural sustainability in geologically heterogeneous agricultural regions. This will be achieved by developing conceptual models of nutrient fate and transport for two contrasting agricultural river catchments. Here, we present preliminary conceptual models based on a literature review of groundwater systems within the same geological terranes, analysis of hydrochemical monitoring data, and accounting for catchment-specific features through desk studies of geological and airborne geophysical surveys.

The River Ythan is a groundwater-dominated lowland catchment within Scotland’s arable belt, designated a Nitrate Vulnerable Zone due to the eutrophication of its estuary. This catchment is geologically complex, with a variably metamorphosed and sheared Precambrian basement with igneous intrusions ranging from ultrabasic rocks to granite. This complexity is enhanced by the significant preservation of Tertiary weathering profiles and an extensive but discontinuous cover of glacial deposits derived from the saprolites. The superficial deposits create a shallow aquifer system characterized by oxic, well-mixed groundwaters with high nitrate concentrations. The bedrock groundwater bodies feature lower nitrate concentrations with variable denitrification rates, resulting from the relationships between lithology, tectonics, and weathering.

Two upland headwater sub-catchments of the Upper Bann River (Co. Down, Northern Ireland) drain either side of the contact between a granodiorite laccolith and Lower Palaeozoic metasedimentary rocks within an elevated drumlinoid landscape. Here, diffuse phosphorus exports to surface waters have not experienced the same extent of decline observed in storm runoff phosphorus following the implementation of nutrient management policies. Anoxic groundwaters favourable for denitrification may result in the release of previously adsorbed (legacy) phosphorus following the reductive dissolution of Fe (hydr)oxides. These conditions are generated by (a) confinement by thick, drumlinised clayey tills; and (b) bedrock structures promoting deep groundwater flow.

The site-specific conceptual models will be further developed through multi-scale geophysical characterisation of hydrogeological heterogeneity and constrained by the catchment-scale distribution of residence times derived from stable (2H, 18O) and radioactive (3H) isotope compositions of groundwaters. These refined conceptual models can guide the development of numerical groundwater models and spatially targeted nutrient management.

How to cite: Johnson, H., Comte, J.-C., Ofterdinger, U., Cassidy, R., and Troldborg, M.: Preliminary conceptual models of groundwater and nutrient dynamics in typical agricultural river catchments underlain by hard-rock aquifers in Scotland and Northern Ireland: The River Ythan and Upper Bann River Catchments, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9281, https://doi.org/10.5194/egusphere-egu21-9281, 2021.

Aiyu Zhu and Chi-Yuen Wang

The interaction between the shallow and deep groundwater systems is important for a number of issues on water resources and the environment but is difficult to evaluate directly. Here we use two-dimensional numerical simulations to show that the tidal response of deep aquifers may be significantly affected by capillary force on the water table. We propose a criterion to evaluate the capillary effect and apply the model to interpret the tidal response of the Arbuckle aquifer in a USGS deep monitoring well in Oklahoma. Our study suggests that the shallow and deep groundwater systems may interact across thick layers of intervening aquitards and that the analysis of the tidal response of deep aquifers may be an effective means to evaluate such interaction.

How to cite: Zhu, A. and Wang, C.-Y.: Capillary effect on the tidal response of buried aquifers – an interaction between shallow and deep groundwater systems, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9316, https://doi.org/10.5194/egusphere-egu21-9316, 2021.

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