The objective of this session is to gather case studies and scientific contributions connected to sustainable management of groundwater and its protection from degradation and deterioration, e.g., due to over-exploitation, competition for water resources, natural or anthropogenic contamination, and climate change. Contributions are invited on, but not limited to, the following subjects: (i) the use of environmental tracers (chemical species and isotopes) for investigating natural processes and human impacts on water resources, (ii) the assessment of hydrogeological budgets for the evaluation of water availability, and (iii) methods for preventing, managing and mitigating harmful environmental impacts related to groundwater, as well as (iv) identifying major existing challenges and critical issues. Contributions may span from local, to regional, to continental scale studies.
The Regional Groundwater Flow Commission (RGFC) of the International Association of Hydrogeologists (IAH) is sponsoring the session.
Orals: Mon, 4 May, 08:30–12:30 | Room 3.29/30
Agricultural intensification has led to persistent nitrate (NO₃⁻) accumulation in the vadose zone (VZ)–groundwater system, yet the long-term fate of this NO₃⁻ remains insufficiently understood. This study develops a high-resolution coupled modeling framework that integrates a multiple-column VZ model (MCM) with a MODFLOW-MT3D groundwater model. The framework reconstructs NO₃⁻ dynamics over four decades (1982–2022) in China’s Guanzhong Plain, captures the complete transport chain from agricultural inputs and VZ processes to riverine discharge, and has been validated against multi-source observations. The results show that the mean NO₃⁻ leaching fluxes increased sharply after 1987. Correspondingly, the VZ NO₃⁻ storage increased nearly tenfold, from 670 kt in 1982 to 7,631 kt in 2022. Pronounced spatial heterogeneity was observed, with VZ NO₃⁻ residence times exceeding 100 years in peripheral thick-loess areas, but only 10–27 years in central thin-loess zones. Groundwater NO₃⁻ concentrations exhibited a spatial pattern closely consistent with leaching distributions, while groundwater NO₃⁻ storage showed a turning point around 1988, decreasing to 3,190 kt before increasing to 3,328 kt by 2022. This pattern reflects the delayed but direct transmission of NO₃⁻ from the VZ to groundwater. Over the study period, the average groundwater discharge to the Yellow River was 4.2 × 10⁸ m³ yr⁻¹, while the NO₃⁻ export via this discharge decreased from 77 kt to 12.7 kt. When combined with irrigation return flows, this reduction forms a “closed N cycle” that enhances subsurface NO₃⁻ accumulation. This coupled framework provides a transferable approach for quantifying NO₃⁻ storage, residence times, and release dynamics in intensively cultivated regions. It provides critical insights into legacy N risks and facilitates the development of long-term groundwater protection strategies.
How to cite: Gong, Y., Niu, L., and Jia, X.: Long-term nitrate legacy in the vadose zone–groundwater system: Integrated modeling of intensive agriculture impacts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7711, https://doi.org/10.5194/egusphere-egu26-7711, 2026.
Groundwater protection has for decades been high on the Danish political agenda with implementation of national environmental action plans since the 1980’ies and a comprehensive groundwater mapping program in 2000 targeting vulnerable areas in need of further protection at a municipally level. Successful effect on improving groundwater quality due to effectful national agricultural nitrogen regulations has been documented with monitoring data in the first two decades until around year 2000. Since then, groundwater protection in Denmark has had negligeable effect e.g. seen in minor improvements on lowering nitrate concentrations in groundwater, and recently on detection of new emergent contaminants in many monitoring and drinking water abstraction wells. In addition, concerning nitrate, new knowledge has questioned the current drinking water standard of 50 mg/l due to increasing evidence of health effects well below this standard.
This talk will give an overview on the state and trends of nitrate in Danish groundwater for evaluation of the effect of protection strategies and present an Innovation Fund Denmark project called PROTECT running from 2025-2029. PROTECT aims to provide tools and knowledge for holistic future protection of groundwater in conjunction with protection of nature, the aquatic environment, climate, and human health by integrating knowledge from geosciences, engineering, medical and social sciences.
How to cite: Hansen, B.: Groundwater protection in Denmark, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21749, https://doi.org/10.5194/egusphere-egu26-21749, 2026.
Managed aquifer recharge (MAR) is increasingly recognized as a key strategy to enhance groundwater sustainability, yet the use of stormwater as a recharge source remains limited, particularly in rural and agricultural settings. Key uncertainties persist regarding stormwater quality variability, treatment performance, and potential impacts on groundwater quality.
We present the technical design, operational testing, and hydrogeochemical assessment of a stormwater-based MAR pilot site implemented in November 2024 in Hüll (Hallertau region, Bavaria, Germany), an area characterized by intensive agriculture, recurrent local flooding, and strong groundwater demand for irrigation. The MAR system combines a stormwater retention basin for buffering flash-flood dynamics, treatment units, and recharge via an infiltration well targeting a highly heterogeneous Tertiary aquifer.
Initial results demonstrate robust system performance under variable stormwater conditions. The treatment units effectively reduce suspended solids and pesticide concentrations, enabling controlled recharge while minimizing risks to groundwater quality. Beyond quantitative water resource augmentation, the scheme shows potential qualitative benefits for agricultural groundwater systems.
How to cite: Augustin, L., Schultze, A., and Baumann, T.: Stormwater-based managed aquifer recharge in a rural agricultural catchment: Design, monitoring, and hydrogeochemical impacts from a pilot site in Bavaria, Germany, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1948, https://doi.org/10.5194/egusphere-egu26-1948, 2026.
Understanding how groundwater flow influences river networks is essential for sustainable management of water resources and associated ecosystems, particularly in humid regions where baseflow sustains low-flow conditions and ecological habitats. Continental statistical analysis of river networks suggest that groundwater may exert a distinct control on channel morphology and bifurcation angles. However, direct process-based evidence for these controls remains limited, constraining our ability to predict groundwater availability and the response of fluvial systems to climate and anthropogenic change. To address this gap, we conducted a series of controlled sandbox experiments in which representative bifurcated channels were pre-constructed in a uniform sediment layer. Channel upward evolution under constant and uniform groundwater seepage was monitored. Meanwhile, a planar groundwater flow model and a coupled fluid-solid mechanical model were developed and parameterized based on the experimental conditions to simulate subsurface flow fields and assess stability. The results show that groundwater seepage can systematically modify initial bifurcation angles and thus reorganize channel branches. For symmetric bifurcations, new developed channel trajectories follow equipotential lines, with outward divergence at 30°, near-axial extension at 72°, and pronounced inward deflection at 120°. In asymmetric bifurcations, the branch aligned with the dominant subsurface flow persistently captures more discharge and stabilizes a robust drainage structure. Steeper hydraulic gradients promote wider and more symmetrically developed channels. These findings provide quantitative support that persistent groundwater flow can override initial geometric control and actively shape drainage architecture. They are helpful for predicting zones of focused groundwater discharge and the changes in river network structure caused by climate change, and for improving process-based models used in sustainable groundwater management.
How to cite: Tang, Y., Liang, X., and Yin, Z.: Controls of Groundwater Seepage on Channel Bifurcation Evolution: Implications for Groundwater–Surface Water Interactions and Sustainable Drainage Management, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7479, https://doi.org/10.5194/egusphere-egu26-7479, 2026.
Arsenic (As) is referred as a potentially toxic element (PTE) and is commonly present in rocks, soils, and water. Bioaccumulation of As poses significant risks to human health. The World Health Organization (WHO) and the European Union have established a maximum guideline value of 10 μg·L−1 for As in drinking water. Elevated As concentrations have been reported in thermal spring- and ground- waters globally. The distribution of arsenic species, specifically trivalent arsenite [As(III)] and pentavalent arsenate [As(V)], in natural waters is primarily influenced by geochemical conditions such as redox and pH [1]. Under oxidizing conditions, such as those found in surface waters, As(V) predominates and is mainly present as oxyanions (H2AsO4−, HAsO42−). In mildly reducing environments, As(III) is the dominant species and remains mostly as neutral arsenious acid (H3AsO3) at typical natural water pH levels (<9) [1].
This study examines As speciation in the Almopia Basin, Central Macedonia, Northern Greece, an area known for the Pozar thermal baths. The main geological formations include Quaternary and Neogene sediments (alluvium, marls, conglomerates, sandstones), Cretaceous and Triassic carbonate formations (limestones, dolomites), schists, ultramafic and mafic rocks (serpentinites, peridotites, diabases), Pliocene and Upper Jurassic volcanic rocks (andesites, dacites, trachytes), and pyroclastic rocks (volcanic tuffs and clasts).
Twenty-six surface water and groundwater samples were collected from irrigation and drinking wells (16), natural springs (4), and surface water bodies (6) during the wet period in 2023. All samples were analysed for physical parameters (i.e., pH, EC, Temp, D.O., Eh), major ions (i.e., Ca2+, Mg2+, NO3- etc) and 72 trace elements (i.e., As, B, Cr, Fe, Mn etc) in accordance with all established analytical protocols. For As speciation, an additional sample from each site was filtered in situ using disposable cartridges and analysed for As [2]. Spatial distribution maps were generated using ArcGIS Pro, and descriptive statistics were calculated.
The results show that total concentration of (Astot) in the whole samples range from 8.4 μg·L−1 to 382 μg·L−1, whereas As(III) concentrations, analysed in the filtered samples as Astot range from 0.5 μg·L−1 to 25.2 μg·L−1. Trivalent As in the samples accounts for approximately 1.6% to 17.5% of the Astot. The prevalent presence of As(V) suggests mildly oxidizing hydrogeochemical conditions in the Almopia Basin. Quantifying As(III) and As(V) is essential because As(III) is significantly harder to remove from water, while As(V) responds readily to standard treatments. This research highlights the importance of As speciation analysis in groundwater, as it informs the selection of suitable remediation strategies and determines the necessity for pre-oxidation to convert As(III) to As(V).
[1] Cullen, W. R., & Reimer, K. J. (1989). Arsenic speciation in the environment. Chemical Reviews, 89, 713–764.
[2] Meng X, Wang W. Speciation of arsenic by disposable cartridges. Proceedings of the third International Conference on Arsenic Exposure and Health Effects, San Diego, CA, July 12–15; 1998.
How to cite: Psarraki, D., Papazotos, P., Vasileiou, E., and Perraki, M.: Arsenic Speciation as a tool for groundwater quality assessment and sustainable water management: Evidence from the Almopia Basin, Northern Greece, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22950, https://doi.org/10.5194/egusphere-egu26-22950, 2026.
Groundwater depletion increases the carbon cost of irrigation through two linked controls: falling water tables raise pumping lift and electricity-related CO₂ per unit of water, and extraction of HCO₃⁻-rich groundwater can add a geochemical CO₂ flux as dissolved inorganic carbon re-equilibrates during use. These mechanisms compound as depletion deepens, making intensively irrigated drylands especially sensitive. Mexico is a compelling Latin American case because it is among the region’s largest agricultural groundwater users, with primary irrigated production concentrated in arid-to-semiarid basins where GRACE indicates substantial storage declines. We quantified national groundwater-related CO₂ emissions for 2012, 2017, and 2021 by integrating GRACE groundwater storage anomalies (referenced to a 2002 baseline) with representative bicarbonate concentrations and electric pumping energy. GRACE anomalies intensified to < −75 cm by 2021 across arid to semi-arid, groundwater-irrigated basins of northern Mexico and the central plateau (major production regions in Chihuahua, Sonora, Zacatecas, Guanajuato, and San Luis Potosí—where groundwater HCO₃⁻ typically spans ~150–600 mg L⁻¹, consistent with these controls, state hotspots exceeded 3,200 t CO₂e yr⁻¹ for pumping (notably Chihuahua) and 900 t CO₂e yr⁻¹ for bicarbonate-associated emissions (Chihuahua and Sonora). Combined emissions increased from 2012 to 2021, dominated by pumping with a minor bicarbonate-associated component. Hierarchical clustering separated a high-emission irrigated-dryland group from a lower-emission group, indicating that depletion intensity and hydrochemical enrichment jointly structure the national pattern. In the global context, Mexico’s national pumping emissions are far below national inventories such as the USA irrigation estimate (12.6 Mt CO₂e yr⁻¹; 2018) and India’s groundwater-linked estimate (32–132 Mt CO₂ yr⁻¹; 1996–2016), while hotspot area intensities reported for northern/central Mexico are comparable to the USA per-area irrigation-energy benchmark. These results support integrating groundwater-driven emissions into water–energy planning and prioritizing mitigation that couples lower-carbon electricity for pumping with reductions in irrigation demand and shifts away from high water-demand cropping systems in the most depleted basins.
How to cite: Panday, D. P. and Kumar, M.: Hidden CO₂ from falling aquifers: National-scale pumping emissions and bicarbonate degassing in Mexico, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15765, https://doi.org/10.5194/egusphere-egu26-15765, 2026.
Slowly regenerating groundwater systems must be considered finite resources if withdrawal rates exceed their replenishment rates and changes in their hydrochemical composition and age structure become apparent. Various concepts have evolved to ensure the long-term availability and protection of groundwater resources, including groundwater stress, safe yield, and different definitions of renewable groundwater. Most of these concepts focus on the quantitative availability of groundwater. The most recent concept, "peak groundwater", describes the maximum total withdrawal rate from an aquifer before reductions in withdrawal rates become necessary due to effects of depletion, such as reduced well yields and water quality issues (1). Here, deterioration of groundwater quality is interpreted in terms of contamination. However, for mineral water, deterioration also requires changes to the original hydrochemical characteristics (2), which tightens the evaluation framework.
This study aims to determine the modified peak groundwater withdrawal for a fractured bedrock aquifer that has been used for mineral water production since the mid-1900s, until it ceased in 2020. We have been closely monitoring the system since the 1990s. The recorded data enables us to quantitatively assess the changes due to production, as well as the rates and extent of the recovery. To develop a 4D understanding of the aquifer, we combined the extraction rates from the last 30 years of production with a comprehensive geological model, hydraulic measurements, and hydrochemical analyses (wellhead and depth-resolved) were combined.
The aquifer has been explored by five wells, which are oriented along a fault zone. It exhibits stratification of mineralization, with increasing concentrations of total dissolved solids (TDS) and CO2 with depth. The presence of persistent trace chemicals and the decrease in TDS during production indicate that the mineral water in the upper part of the aquifer is being replenished by freshwater, forming a lens of freshwater on top of the mineral water. This effect is more pronounced at the center of the explored area and correlates with individual withdrawal volumes. Measurements taken after production ceased reveal a trend toward aquifer regeneration. While the aquifer has almost returned to its initial hydraulic state with some wells flowing freely, it is unclear whether the original hydrochemical composition will be re-established or if a new hydrochemical steady state will be reached. The latter would confirm the mining operation of a finite resource, whereas the former would suggest a temporary excess of peak groundwater with no lasting impact on long-term use.
(1) Bhalla, S., Cherry, J. A., Konikow, L. F., Taylor, R. G., & Parker, B. L. (2025). Peak groundwater: Aquifer-scale limits to groundwater withdrawals. Earth's Future, 13. https://doi.org/10.1029/2025EF006221
(2) Dietmaier, A. & Baumann, T. (2023). Assessing sustainable development of deep aquifers. Water Resources Management. https://doi.org/10.1007/s11269-023-03529-6
How to cite: Hegels, M. and Baumann, T.: Understanding and quantifying the depletion of a mineral water aquifer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3147, https://doi.org/10.5194/egusphere-egu26-3147, 2026.
Bank filtration is widely used for producing drinking water; however, the increasing contamination of surface waters by human-pathogenic viruses, particularly adenoviruses, poses growing challenges to the drinking water supply under climate-driven hydrological extremes. Conventional groundwater quality monitoring primarily focuses on bacterial indicators, while viral surveillance remains limited and is generally not available on-site. Therefore, we developed a novel, field-applicable immunofluorescence chip for the adenovirus monitoring in groundwater within the project VIRUMEX. The antibody-functionalized polymer bead–based virus detection system allows near real-time monitoring either directly in groundwater wells or via an autonomous flow-through setup. Experiments demonstrated full chip functionality under both laboratory and field conditions, which, in the first step, allows for the screening of virus-positive and virus-negative samples at low ng/mL adenovirus protein concentrations. Although subject to further refinement, the results demonstrate that the prototype chip enables reliable, rapid, and qualitative detection of adenoviruses, complementing conventional PCR-based monitoring.
How to cite: Vienken, T., Hossain, M., Hastreiter, N., Wegmann, M., Roggenbuck, D., and Engelhardt, I.: Development of a Field-Applicable Immunofluorescence Chip for Adenovirus Monitoring in Groundwater, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2194, https://doi.org/10.5194/egusphere-egu26-2194, 2026.
The Köprüören Basin, located in Kütahya Province (Western Türkiye), hosts long-standing silver mining operations centered in the Gümüşköy area, where a complex geological framework controls groundwater flow and the mobility of contaminants. The region comprises several stratigraphic units, including the Carboniferous–Permian Şahin Formation (phyllite, clay-schist, marble), the Permian–Triassic marbles of the Karaağaç Formation, the Middle–Upper Miocene dacitic–rhyolitic tuffites of the Tavşanlı Volcanics, the Lower Pliocene marls, sandstones, and tuffs of the Çokköy Formation, the Upper Pliocene limestone–dolomite alternations of the Emet Formation, and the Quaternary clastic sediments of the Bozyer Formation (Arık, 2002). Türkiye’s only silver deposit is developed within the basement rocks, Miocene volcanics, and Pliocene units, making the area of high economic importance. Modern mining activities in Gümüşköy began in 1987 with cyanide leaching, producing 122.4 tons of 99.9% pure silver annually, and ore production reached five million tons after 2009 (Sasmaz, 2011). While contributing to regional economic development, mining activities have generated significant environmental challenges in the basin. The collapse of one of the mine waste pools in 2011 caused the contaminated wastes to spread into surface-water systems. Geochemical investigations conducted in 2012 indicated that, in addition to natural geogenic sources, mining activities represented a major anthropogenic source of arsenic and other trace elements (Pb, Sb, Zn) through leakage from waste pools (Arslan & Çelik, 2015; Arslan, 2017). The hydrostratigraphic units of the basin were characterized in a recent study (Mohamed, 2025), analyzing the areal extent, thicknesses and hydraulic properties of the aquifers using data obtained from 68 wells. Accordingly, the most productive aquifer occurs within the limestone–marl alternations of the Upper Pliocene Emet Formation, with a thickness ranging from 12 to 223 m. Groundwater is abstracted from this aquifer for both irrigation and mining operations. Silver production consumes large amounts of water (1,713 m³ per ton of silver; Meißner, 2021), a substantial fraction of which is extracted from groundwater in the Köprüören Basin, further exacerbating pressure on local water resources. Recent declines in groundwater levels indicate that water use in the basin is unsustainable. Field reconnaissance in 2024 confirmed ongoing leakage from mine-waste pools, especially near drainage channels. Local reports of rising colon cancer cases suggest possible long-term exposure to trace elements. These findings highlight the continuing environmental and public-health risks and emphasize the need for monitoring, improved management, and sustainable water use in the Köprüören Basin.
References
Arık, F., 2002. Geochemical Modeling of Gümüşköy (Kütahya) Silver Deposit, PhD Dissertation, Selçuk University, Türkiye.
Arslan, Ş., 2017. Assessment of groundwater and soil quality in Köprüören Basin, J. African Earth Sci., 131, 1–13.
Arslan, Ş., Çelik, M., 2015. Pollutants in soils and surface waters around Gümüşköy mine, Bull. Environ. Contam. Toxicol., 95(4), 499–506.
Meißner, S., 2021. The Impact of Metal Mining on Global Water Stress and Regional Carrying Capacities—A GIS-Based Water Impact Assessment. Resources, 10(12), 120.
Mohamed, A.S., 2025. Characterization of the Köprüören Basin Aquifer System, Master’s Thesis, Ankara University.
Sasmaz, A., 2011. As, Ag, Pb, Sb and Tl Levels in Soil and Plants Around Gümüşköy Mining Area, TÜBİTAK Project CAYDAG-110Y003, Ankara.
How to cite: Arslan, Ş.: Impacts of Long-Term Silver Mining on Water Quality and Groundwater Sustainability in the Kopruoren Basin, Western Turkiye, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1205, https://doi.org/10.5194/egusphere-egu26-1205, 2026.
Abstract
Microplastics have become an emerging contaminant found in groundwater. Microplastics is a concern in areas where aquifers are the main source of drinking water. This study assessed the presence, characteristics and potential risk of microplastics in shallow coastal aquifers of Al-Qatif, Eastern Province of Saudi Arabia. Groundwater was collected from ten shallow wells (SW1–SW10), prepared and processed through density separation, oxidative digestion, stereomicroscopy, and Raman spectroscopy to isolate, characterize and identify microplastics. Eight polymer types were found: polyethylene terephthalate (PET), polyethylene (PE), polyamide (PA), polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP), polycarbonate (PC) and an acrylonitrile–butadiene–styrene polyethylene blend (ABS–PE). Total Microplastics concentrations ranged from 5 to 16 particles L⁻¹, with a mean of 8.6 particles L⁻¹. PE and PC are the most abundant polymers (2.0 and 1.5 particles L⁻¹, respectively), followed by PET, PA and PP. PS, PVC and ABS–PE were present at lower average concentrations but still contributed to the overall polymer mixture. Most MPs occurred as fibers and fragments with sizes between 25 and 520 µm.
To evaluate potential ecological risk, Contamination Factor (CF), Polymer Hazard Index (H) and Pollution Risk Index (PRI) were evaluated. Polymer Hazard index values were found to range from 21.4 to 985.9, and PRI values vary between 25.7 and 1384.2. Four wells (SW6–SW9) falls into the high-risk category (PRI ≥ 200), mostly because of the presence of highly risk hazardous polymers such as ABS–PE and PVC. SW3 and SW10 had a moderate risk while the other wells were assigned low risk. SEM and FE-SEM analyses indicated that microplastics had rough and porous surfaces which meant there were some inorganic elements associated with the MPs. Therefore, it could be suggested that the MPs may serve as a means of transport for other contaminants. The findings represent the first mapping of the extent of MP contamination in the groundwater of Al-Qatif and point out the necessity of continuous monitoring as well as proper handling of plastic waste and wastewater in arid and semi-arid areas.
Keywords: Groundwater; Al-Qatif; Microplastic; Saudi Arabia; Shallow well.
How to cite: Isa, I., Benaafi, M., and Baalousha, H. M.: Detection and characterization and risk of microplastic in groundwater in the Eastern Province of Saudi Arabia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8265, https://doi.org/10.5194/egusphere-egu26-8265, 2026.
In Mediterranean-type ecosystems, droughts are altering the availability of soil water, forcing vegetation to adjust its water uptake strategies. When soil moisture is depleted, a critical survival mechanism for phreatophytes is the shifting of water uptake from shallow soil layers to groundwater. However, sustainable water resources management often overlooks this mechanism. Consequently, quantifying the evapotranspiration (ET) fluxes due to a direct link between the aquifer and the atmosphere represents an important advancement in hydrological modeling.
We investigate this vegetation-induced water uptake at two sites with shallow water tables: San Rossore (Pinus pinea) and Castel Porziano (Quercus ilex). Preliminary analysis at these sites indicates a decoupling of ET from soil moisture availability during summer months, suggesting a contribution from deep taproots. To separate the sources of these fluxes, we combine high-frequency Eddy Covariance measurements with stable water isotopes analysis (𝛿18O, 𝛿2H ) of xylem, soil water, rainfall, and groundwater.
We propose a framework where isotope-derived ET fractions are used to conceptualise and calibrate unsaturated zone models. This approach not only refines estimates of net groundwater recharge but also improves the representation of vegetation feedback in Earth System Models, ensuring that transpiration from groundwater is accurately represented in climate scenarios for adaptation and water management studies.
How to cite: Gelsinari, S., Alessandri, A., and Penna, D.: Decoupling ET from soil moisture: Tracing groundwater uptake in Mediterranean forests using stable isotopes to inform land surface models., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17454, https://doi.org/10.5194/egusphere-egu26-17454, 2026.
Much of the world's population, as well as sensitive ecosystems, are dependent on groundwater systems recharged from adjacent mountain ranges. Despite this dependency on groundwater, our understanding of the processes controlling groundwater flow, including recharge, discharge, and storage in mountainous areas, is very limited. In addition, while uptake of groundwater by deep-rooted plants is potentially a significant groundwater discharge pathway, this process represents another large gap in our knowledge about groundwater in mountainous areas.
At Springbrook, in the Gold Coast hinterland, Australia, commercial water extraction is occurring next to a UNESCO World Heritage Listed rainforest, and the local community relies on groundwater for domestic supply. Yet, there is very minimal monitoring data that can be used to assess water availability and sustainably manage this resource. To address this data gap, a water monitoring network has been set up in close collaboration with the local community, First Nations representatives and government collaborators. Monitoring at Springbrook has provided insights into interactions between springs, groundwater, local creeks and deep-rooted vegetation. These insights are informing changes in water management policy.
We are now scaling up the water monitoring network to develop an integrated monitoring network which includes climate, soils, water, vegetation and endangered species monitoring over an altitudinal gradient. The monitoring network is currently being used to support environmental science teaching activities. A visualisation platform has been developed to share information about the monitoring more widely and to help support community engagement and science to policy translation.
How to cite: Reading, L.: Collaborative monitoring for sustainable water management in a Mountainous Region in Australia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4860, https://doi.org/10.5194/egusphere-egu26-4860, 2026.
The sandy soil region of northwestern Europe often experiences excess water during winter and water scarcity during summer, causing a compromised hydrological balance. Lowering of groundwater levels by anthropogenic interventions such as intensive drainage and groundwater abstraction threatens land use and biodiversity that are dependent on phreatic groundwater. Current spatial planning hardly considers natural soil-water systems, rendering these landscapes unsustainable for the future. This calls for a paradigm shift in which land use is guided by the potential of natural systems to sustainably support human needs.
Understanding how landscapes function under minimal human influence is crucial for understanding the natural processes, reversing declining trends and developing climate-robust land-use strategies. Therefore, we studied the Chaamse beek catchment (southern Netherlands) to develop a spatially explicit, quantitative understanding of the natural soil-water land use system and to assess the impact of human interventions over the late Holocene (2000 BCE till now) For this, we reconstructed palaeogroundwater levels using a regionally calibrated numerical model, which consists of MODFLOW (saturated zone) and MetaSWAP (unsaturated zone) for the time slices 2000 BCE, 0, 500, 1500 and 1850 CE. Topography, land use, hydrological features, and soils were reconstructed for each time slice and human interventions (e.g., ditches, artificial structures, abstraction wells) were chronologically removed (from present to past) to simulate increasingly natural conditions and evaluate their effects on groundwater dynamics. Model results were evaluated against historical maps.
Results show that removing drainage ditches (simulating conditions prior to 1500 CE) substantially increases areas with shallow groundwater (0-50 cm). These areas become even larger when removing abstraction wells. Notably, the model successfully simulated the presence of swamps at locations where they historically existed, as verified by historical maps from 1850 CE. These findings provide quantitative insights into human-modified hydrological systems and support the development of nature-based solutions, water buffer zones, and adaptive land-use planning for climate-resilient management of sandy catchments. By constraining hydrological models with palaeogroundwater reconstructions, future forecasting and scenario-based water management strategies can be made more robust.
How to cite: Chaulagain, L., H.J. Candel, J., de Louw, P., van der Meij, W. M., Larsen, A., and Wallinga, J.: Modelling the cumulative effects of Late-Holocene anthropogenic activities on phreatic groundwater levels , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3858, https://doi.org/10.5194/egusphere-egu26-3858, 2026.
According to European and Czech legislation, the quantitative status of groundwater must be regularly assessed, and a water management balance of groundwater quantities must be carried out. Good quantitative status of groundwater, assessed at the level of groundwater bodies, is defined based on the groundwater level (GWL), where the GWL in a groundwater body ensures that the available capacity of the groundwater resource is not exceeded by the long-term average annual abstraction.
However, the development of GWL in Quaternary hydrogeological zones (HZs), which in the Czech Republic correspond to groundwater bodies, can vary significantly over time depending on their recharge potential and the extent of their use. Groundwater may flow in from slopes, be drained from underlying aquifers, recharge directly from precipitation, or—due to groundwater abstractions (GA)—flow in from rivers. Furthermore, groundwater level development in individual monitoring wells varies depending on local hydrogeological conditions, distance from abstraction sites, proximity to rivers, and other factors. Consequently, neighboring wells within the same HZ may exhibit very different GWL trends. Establishing simple criteria for assessing the quantitative status of long-term and intensively managed Quaternary HZs is therefore challenging.
To address this, all Quaternary HZs were divided into smaller, more manageable units called subzones. The division was based on the presumed extent of influence of large abstraction sites and the arrangement of boundary conditions. For each subzone, a specific general GWL (sGWL) was determined by averaging standardized monthly GWL values from all wells within the subzone. For each subzone, the minimum sGWL (sGWLmin) and the development of GA were assessed for the most significant drought periods. The most severe drought occurred in 2015–2020, closely followed by droughts in 1990–1994 and 2003–2004. In contrast, GA during 1990–1994 was approximately double that of 2015–2020 and likely caused sGWLmin in many subzones to fall below the level observed in 2015–2020. The drought period of 2003–2004 had GA levels between those of 1990–1994 and 2015–2020.
The comparison was carried out under the assumption that during the driest period, 2015–2020, GA were not restricted due to drought. If higher GA in earlier drought periods caused sGWLmin to fall below its level in 2015–2020, GA influenced the quantitative status of the subzone. If, however, higher GA in earlier drought periods did not cause sGWLmin to fall below the level observed in 2015–2020, GA did not affect the quantitative status of the subzone. By comparing minimum sGWLmin during drought periods with varying historical GA magnitudes, volumetric and level-based criteria were established under which the groundwater status of a subzone can be considered good. This methodology was applied to 65 of 75 subzones. For the remaining 10 subzones with insufficient GA and GWL monitoring data, a specific approach was adopted. Based on the assessment of the quantitative status of subzones, the quantitative status of the HZs was subsequently evaluated.
How to cite: Nol, O., Burda, J., Zrzavecky, M., and Zabka, V.: Use of Minimum Groundwater Levels and Groundwater Abstractions for Assessing the Quantitative Status of Quaternary Groundwater Bodies in the Czech Republic, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10447, https://doi.org/10.5194/egusphere-egu26-10447, 2026.
Regional confined aquifers are becoming increasingly strategic as water pressures intensify worldwide. These aquifers are often found as part of multi-layer systems within extensive groundwater basins. Long response time scales challenge conventional approaches of sustainable management: hydraulic perturbations might propagate slowly and management decisions must be informed by the timing on which the impacts of climatic or anthropogenic stresses fully materialize.
Using a synthetic numerical model of a multi-layer system, we investigate response times across a wide range of hydraulic diffusivity scenarios spanning the diversity of real-world contexts. In particular, we highlight the critical role of leakage through confining units, an often-overlooked process that strongly governs how the groundwater basin adjusts to a given stress. To connect these dynamics with management decisions, we apply a constrained optimization framework to estimate sustainable yields. Here, we define the sustainable yield as the maximum pumping rate that meets specified drawdown or flow constraints within a given planning horizon.
Our findings show that the vertical diffusivity of confining units exerts an important control on response times of confined aquifers and that, in some cases, analytical solutions may significantly overestimate these times by ignoring leakage processes. In low-diffusivity regional systems, response times can span well beyond typical planning horizons, making them relevant for long-term management decisions. Crucially, the choice of planning horizon becomes a determining factor in defining sustainable abstraction volumes. Our approach explicitly quantifies this relationship, providing an informative basis for sustainable management decision-support.
This work underscores the need for a paradigm shift away from steady-state notions of groundwater sustainability. Effective management of regional groundwater systems requires adaptive strategies that recognize delayed responses and the long-term consequences of our decisions, which may unfold over decades, centuries, or even longer. What is considered sustainable depends not only on the magnitude of pumping impacts, but also on the timing of those impacts relative to human and management timescales.
How to cite: Marin Rivera, C. F., Pryet, A., and Goncalves, J.: Transient response in large groundwater basins: Implications for sustainable management, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5647, https://doi.org/10.5194/egusphere-egu26-5647, 2026.
Groundwater resilience is a key factor for water security and climate change adaptation in densely populated regions. This study proposes a robust methodology to estimate gravitational groundwater storage (Sethi and Di Molfetta, 2019) in unconfined and deep aquifers within the plain sector of the Metropolitan City of Turin (2,600 km2). This assessment was performed in response to a recent regulation issued by the Italian National utility authority ARERA, which introduced an extensive set of indicators for evaluating service quality and sustainability at province or larger scale. In this framework, it is necessary to estimate freshwater availability (including both surface and groundwater bodies) and withdrawals at the large scale. If on the one hand the estimation of surface water and some type of withdrawals are relatively straightforward, the evaluation of the overall groundwater availability is challenging, and requires a detailed knowledge of aquifer properties, three-dimensional extent, recharge and discharge fluxes which is in most cases not available. This work proposes a simplified approach to meet this target and its application to the plane of the Metropolitan City of Turin (North-Western Italy).
The methodology involves a high-resolution GIS-based approach (250 × 250 m) and assumes the presence of two main groundwater bodies, namely an unconfined (shallow) aquifer and a confined (deep) aquifer. Two hydrogeological surfaces bound the domain: the water table of unconfined (shallow) aquifer (WTSA) from De Luca et al. (2020) and the interpolated surface of well bottoms (ISBW) drilled in the confined aquifer, derived from 340 active wells operated by the local water utility SMAT. An additional intermediate surface, the base of shallow aquifer (BSA), separates shallow and deep aquifers and was previously derived from an extensive historical set of borehole core analyses.
The groundwater storage is estimated as the volume of gravitational water in the two compartments, accounting for impermeable layers and effective porosity. In particular, permeable volumes are determined using depth-dependent granulometry maps, while gravitational groundwater volume is calculated using effective porosity values reported in regional literature.
Results indicate that gravitational groundwater reserves amount to approximately 7.68 km3 for the shallow aquifer and 17.57 km3 for the deep aquifers, assuming intermediate values of effective porosity. When porosity variability is considered, total estimates range between 10 and 40 km3.
Although subject to epistemic uncertainties related to surface interpolation and the assumption of special uniform porosity, this preliminary assessment provides a solid and transferable methodological foundation for water resource governance and regulatory compliance under European and Italian environmental legislation.
References:
Bove, A., Casaccio, D., Destefanis, E., De Luca, D., Lasagna, M., Masciocco, L., Ossella, L., & Tonussi, M. (2005). Idrogeologia della pianura piemontese. Idrogeologia della pianura piemontese. Regione Piemonte Direzione Pianificazione delle Risorse Idriche, Mariogros Industrie Grafiche S.p.A., Torino.
De Luca, D. A., Lasagna, M., & Debernardi, L. (2020). Hydrogeology of the western Po plain (Piedmont, NW Italy). Journal of Maps, 16(2), 265-273. https://doi.org/10.1080/17445647.2020.1738280
How to cite: Sethi, R., Pigozzi, G., Amendola, A., Brussolo, E., Burzio, E., Casasso, A., Cocca, D., Colombano, D., De Luca, D., Egidio, E., Lasagna, M., and Tosco, T.: Assessment of groundwater storage to estimate water availability for the Metropolitan City of Turin (NW Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22580, https://doi.org/10.5194/egusphere-egu26-22580, 2026.
Contaminants of emerging concern (CECs) are increasingly detected in European waters, yet they are rarely studied jointly across wastewater, surface water, and groundwater at basin scale, limiting understanding of groundwater vulnerability. CECs comprise a heterogeneous group of mainly anthropogenic compounds, including pharmaceuticals, personal care products, food additives, pesticides, veterinary and industrial chemicals, and their transformation products. Here, we investigated the occurrence of 120 CECs in wastewater treatment plant (WWTP) effluents (n = 10), rivers (n = 27), and groundwater (GW; 42 wells and 6 springs) across the Besòs catchment (NE Spain). We combined non-parametric correlation analysis, principal component analysis (PCA) of major ions and CECs, and grouping strategies to assess shared sources and attenuation mechanisms across basin compartments.
Domestic and industrial CECs reached higher concentrations than pesticides across all compartments, and compounds ubiquitous in rivers and WWTPs were also detected basin-wide in GW. PCA of major ions showed that most river sites downstream of WWTPs plot between WWTPs and GW along the first two principal components (60–80% of ionic variance per sub-basin), with higher K and PO₄, whereas GW is characterized by higher Ca+Mg relative to Na+K and higher NO₃.
In most river sites and in 62% of groundwater, total CEC pollution was largely explained by a small group of 16 compounds with high detection frequency in rivers and peak concentrations exceeding 200 ng L⁻¹ in at least one river sample. In these sites, attenuation was primarily inferred to result from mixing between unpolluted waters and WWTP-impacted flows, with additional non-conservative processes. This interpretation is supported by systematic decreases in individual CEC concentrations from rivers to groundwater while maintaining CEC:sucralose ratios comparable to, but lower than, those measured in WWTP effluents. Consistent with PCA results, the ubiquitous occurrence of these compounds in groundwater was not accompanied by major ion shifts in 50–70% of sites per sub-basin, indicating dilutionof small volumes of polluted water with larger volumes of resident groundwater.
In contrast, 38% of groundwater sites showed total CEC pollution dominated by a larger group of 53 compounds with lower ubiquity and peak concentrations in surface water, including 23 CECs below detection limits in WWTPs and most river sites. Many of these compounds exhibited higher CEC:sucralose ratios in groundwater than in surface waters, suggesting inputs from subsurface sources rather than recent inflow from losing river reaches. At these sites, weaker relationships between CEC concentrations and hydrophilicity (log Dₒw) indicate reduced sorption control and a greater influence of desorption or legacy release from organic matter. PCA of selected CECs further showed co-variation among compounds sharing similar river ubiquity and peak concentration, highlighting common attenuation and release controls at sub-basin scale.
Overall, mixing, sorption, and degradation emerge as key processes controlling CEC persistence and protecting groundwater quality at basin scale under chronic wastewater pressure.
Acknowledgements: Financial support from MCIU/AEI/10.13039/501100011033, the European Union and NextGenerationEU/PRTR through grants CEX2018-000794-S, PCI2024-153452 (WATER4MED project, PRIMA) and CNS2023-144051. Doctoral fellowship from ”la Caixa” Foundation (ID 100010434), code B006133.
How to cite: Scrinzi, L., Santana, S., Mestanza, E., Jurado, A., Pujades-Garnes, E., and Pérez, S.: Drivers of Contaminants of Emerging Concern (CECs) concentration in aquifers and rivers of the Besòs basin (Catalunya, Spain), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22052, https://doi.org/10.5194/egusphere-egu26-22052, 2026.
Stable isotopes represent a powerful approach for investigating hydrogeological processes in groundwater. Using δ¹³C-DIC helps tracing carbon sources, quantify microbial activity (respiration), understand water-rock interactions and carbonate weathering, and determine DIC origin (organic matter mineralization, carbon dioxide dissolution, geogenic sources). Further, water-rock interactions can be effectively investigated using the ⁸⁷Sr/⁸⁶Sr isotopic ratio, a method based on the principle that the ⁸⁷Sr/⁸⁶Sr ratio in groundwater reflects the ⁸⁷Sr/⁸⁶Sr ratio of the hosting formation that was inherited at the time of rock formation, hence supporting the appropriate attribution of groundwater samples to a specific geological formation.
It is known that peat-rich fluvio-marsh alluviums promote anoxic conditions that enhance arsenic (As), iron (Fe), and manganese (Mn) release, while volcanic deposits and travertines also play a key role in controlling As in groundwater.
This study aims to elucidate how isotopes ratios can support groundwater quality patterns and biogeochemical processes interpretation in a medium size river basin with diverse lithological complexes, and eventually define hydrogeodiversity across the basin by combining geostratigraphy with hydrogeochemical information.
Between November 2024 and December 2025, more than 90 samples were collected in the Sacco River Valley. The study area has an extensive presence of alluvial and lacustrine deposits locally rich in peat (Pleistocene-Holocene), mainly alkali-potassic volcanic products intercalations from the Middle Latina Valley (Pofi and Ceccano eruptive centers) and the Albani Hill apparatus (Pleistocene), and travertine lenses (Pleistocene) connected to past hydrothermal systems. These lithological complexes host a large water table aquifer fed by local precipitation and by lateral flow from the carbonate mountains on the eastern side. A thick sequence of sandy-marly Flysch (Miocene) separates this groundwater body from a deeper groundwater system circulating in Meso-Cenozoic limestones. The sandy levels host themself a local circulation of groundwater.
Major and trace cations (ICP-OES/ICP-MS), anions (IC and titration for HCO3), and dissolved organic carbon (TOC analyzer) were analyzed at CNR-IRSA laboratories. Stable isotopes (δ¹⁸O, δ²H, δ¹³C-DIC) were determined at ISO4 s.r.l. (Turin, Italy) and ⁸⁷Sr/⁸⁶Sr at CNR-IGAG, at Sapienza University of Rome laboratories.
The collected groundwaters have a calcium-bicarbonate facies with a slight tendency to alkaline-earth facies. Average pH is neutral, though both strongly alkaline (9.57) and acidic (5.52) values were recorded. Encountered reducing samples were largely from alluvial deposits (41%), while oxidizing conditions dominate in volcanic rocks (48%). Higher variability for As (0.2-55 μg/L), Fe (43.4-6138 μg/L), and Mn (1.3-437 μg/L) was observed in reducing conditions.
Less negative/slightly positive δ¹³C-DIC values (-0.62 – 0.67‰) in few samples suggested deep CO₂ interaction and distinguished rainfall-fed waters from deeper circulating systems. Further, they might indicate where organic pollution is currently active. ⁸⁷Sr/⁸⁶Sr results were found generally consistent with the actual stratigraphic sequences observed in the sampled wells or inferred from available cartographic information, confirming its usefulness in the attribution of the samples to the appropriate aquifer (or a mixing among several of them).
Finally, hydrogeodiversity across the basin provides a framework to interpret the spatial variability of groundwater quality and the associated biogeochemical processes and ecosystems, also finalized to management purposes.
How to cite: Cisternino, A., Casentini, B., Amalfitano, S., Melita, M., Castorina, F., and Preziosi, E.: Using stable isotopes to investigate geochemical processes and hydrogeodiversity in a complex aquifer system , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21287, https://doi.org/10.5194/egusphere-egu26-21287, 2026.
Abstract
Community-scale defluoridation systems have been widely implemented in fluoride-affected, groundwater-dependent regions to mitigate and/or reduce the risks associated with exposure to excessive geogenic fluoride in drinking water [1, 2]. Performance of these systems is typically assessed by whether treated water meets a desired guideline threshold concentration (e.g., 1.5 mg/L fluoride, as prescribed by the World Health Organization) [3]. However, translating that threshold into practice requires a site-specific metric: the fluoride removal efficiency needed to reach the target from local source-water fluoride concentrations. Because this requirement varies across sites (and potentially seasons), treatment protocols should be set against the required removal rather than applying uniformly across all sites. Here, we quantify site-specific required removal targets and compare them with achieved/actual removal using paired pre- and post-treatment measurements. We applied this framework to 58 community water purification plants (CWPPs) in the Bankura and Purulia districts of West Bengal, India, to quantify required versus achieved removal across sites and identify where operational intensity (e.g., media choice, run time, regeneration frequency) should differ.
Pre-filter fluoride ranged from 1.6 to 8.2 mg/L. To meet the WHO guideline of 1.5 mg/L, required removal efficiencies were 11.8 to 81.7 % in Bankura (median 54.5 %) and 6.3 to 61.5 % in Purulia (median 28.6 %), with an overall median requirement of 33.3 % across both districts. Even for a stricter target of 1.0 mg/L, median required removal largely remained below 70 %. Together, these results show that many community systems do not need near-complete fluoride removal; they require a clearly defined, site-specific removal target that can range from moderate to very high. This spread is operationally consequential; a plant requiring ~30 % removal should not be managed with the same media choice, run time, or regeneration frequency as one requiring ~80 % removal.
Based on the required fluoride removal (derived from source-water fluoride and the selected threshold concentrations) and ideally tracked across seasons, this approach can tailor site-specific operation of the community defluoridation system, guiding adsorbent media choice for different sites, run times, monitoring and regeneration frequency, and maintenance scheduling. In doing so, it will help operators set realistic performance targets, detect underperformance early, and prioritize corrective actions where needed the most.
References
1. Khairnar et al. (2015). doi:10.7860/JCDR/2015/13261.6085
2. Osterwalder et al. (2014). doi:10.1016/j.scitotenv.2013.10.072
3. WHO (2022). Guidelines for drinking-water quality
Acknowledgements
This work was supported by the Australia-India Institute (Grant: 053139) and the Manchester-Melbourne PhD funding (Cookson Scholars) to AK. Additional support included contribution from The University of Manchester, UKRI (MR/Y016327/1) to LAR et al. We thank colleagues at the University of Manchester, IIT Kanpur, IIT Kharagpur, WBPHED staff, and communities in West Bengal for support with the project and field sampling. The views expressed are those of the authors.
How to cite: Kashyap, A., Richards, L. A., Reichman, S. M., Mumford, K. A., and Arora, M.: Identifying treatment protocols by translating required fluoride thresholds into site-specific removal requirements in community-based defluoridation systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19910, https://doi.org/10.5194/egusphere-egu26-19910, 2026.
The Farfa River is one of the most important tributaries on the left bank of the Tiber River, upstream Rome in Central Italy. Its water has a very high quality and a geochemical composition mainly associated with the calcium-bicarbonate facies, primarily due to the overflow of the Capore karst Spring, which is one of the main two spring supplying the city of Rome. In the final stretch toward the confluence with the Tiber River these geochemical characteristics completely change and according to the Regional Environmental Protection Agency's classification the river water quality status degrades from good to sufficient, suggesting that this may be due to potential pollution or contamination by human-related activities. This new study, using discharge and physico-chemical field measurements over four monitoring campaigns, together with the help of geochemical and multi-isotopic tracers (C, S, O, H) analyzed on water samples collected, reveals that this change is actually natural and related to the river's interaction with a group of springs, whose origin and recharge areas were largely unknown until now. The use of specific isotopes, such as 13C/12C and 34S/32S, has allowed to better understand the groundwater flowpaths, recharge areas and potential interactions with deep fluids upwelling along fault planes present in the study area.
How to cite: De Filippi, F. M., Eusepi, J., Franchini, S., Barbieri, M., and Sappa, G.: Multi-isotopic approach for the assessment of groundwater-surface water interactions in a complex hydrogeological and stratigraphic context: the case study of the middle Farfa River Valley (Rieti, Central Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-784, https://doi.org/10.5194/egusphere-egu26-784, 2026.
Posters on site: Mon, 4 May, 16:15–18:00 | Hall A
Morocco is among nations facing high to extremely high-water stress in the world under climate change whose impacts include reduced precipitation, higher temperatures, and evapotranspiration. This pressure is exacerbated by changes in land use and cover, such as agricultural extensification and urbanization, which reduces recharge and increases water demand. However, effective management of water resources, particularly groundwater, remains difficult because of the scarcity of in situ measurements and the low quality of the available data. In this regard, our study aims to downscale GRACE satellite-derived Total Water Storage Anomalies (TWSA) from their native coarse resolution (3°) to a finer resolution (0.04°), followed by Groundwater Storage Anomalies (GWSA) extraction. This is achieved by using machine learning models and hydrological variables that are strongly correlated with TWSA, including precipitation, evapotranspiration, soil moisture, and runoff. The performance of four machine learning models in capturing the spatial details of TWSA is then evaluated, namely, Convolutional Neural Network (CNN), Random Forest (RF), XGBoost, and Gated Recurrent Unit (GRU). Then the results generated by the model with the best results are analyzed spatially and temporally to better understand the trends, the availability, and the influence of LULC changes on groundwater resources. RF delivered the best performance by achieving an R² of 0.92 and an RMSE of 0.61 cm. The RF based TWSA estimates showed strong agreement with ground measurements across different spatial and temporal scales. And the analyses highlight the importance of integrating hydrological and land use factors into groundwater modeling and demonstrate that machine-learning-based downscaling can effectively capture groundwater variability and help bridge the gap between satellite observations and local scale sustainable water management.
How to cite: Mercha, M., Bahi, H., and Sabri, A.: Spatio-temporal analysis of groundwater from machine learning based GRACE downscaling in the Moroccan context, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-645, https://doi.org/10.5194/egusphere-egu26-645, 2026.
Arsenic (As), a naturally occurring metalloid in the Earth's crust, poses a significant environmental and public health concern due to its mobilization into groundwater. In India, As contamination primarily originates from the Himalayan region, where As is bound to different minerals like pyrite and iron oxy(hydr)oxide. Inorganic As predominantly exists in two forms—arsenite [As(III)] and arsenate [As(V)]—with As(III) being more mobile in a dynamic system. This process leads to elevated arsenic (As) levels in groundwater, particularly in the low-lying Indo-Gangetic delta plains. A seasonal investigation was done in the Laksar region to evaluate geomicrobiological parameters in groundwater. As concentrations frequently increased in all aquifers (3.5-78 µg/L), surpassing the WHO permissible limits. Hydrochemical analysis revealed that the groundwater was predominantly of Ca-HCO₃ type. As concentration showed a significant correlation with Mn and Fe, suggesting their importance in influencing As mobilisation. Arsenite-oxidizing bacteria (AOB) in groundwater play a critical role in the biogeochemical cycling of As by oxidizing As(III) to the less toxic As(V), thereby holding a potential for bioremediation. Out of ~158 bacterial strains isolated, 28 isolates demonstrated the ability to oxidise As(III). These isolates efficiently oxidised ~1.13 mM As(III) in cultured conditions, with biomass-normalised oxidation rates ranging from 0.2 to 1.13 mM As(III) mg⁻¹ d⁻¹. The major isolated bacteria belong to the genera of Acinetobacter, Stenotrophomonas, Brevundimonas, and Pseudomonas. These strains were further evaluated in a microcosm setup to determine their efficacy in As bioremediation under simulated groundwater conditions. The results highlight the potential of AOB as a sustainable and cost-effective alternative to conventional As remediation methods, which are often expensive and generate secondary waste in groundwater. The application of such bacteria could significantly mitigate As contamination in affected regions, providing a sustainable and eco-friendly solution to a pressing global issue.
How to cite: Ali, S., Basu, S., and Singh, R.: Bioremediation of Arsenic-Contaminated Groundwater Using Arsenite-Oxidizing Bacteria from the Upper Gangetic plains of Laksar region of Haridwar, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-816, https://doi.org/10.5194/egusphere-egu26-816, 2026.
Arid endorheic basins are increasingly dependent on deeper groundwater resources, making it essential to assess their renewability and long-term response to climate and pumping pressures. In the Bahira Basin (central Morocco), deep low-salinity groundwater is being exploited as the shallow aquifer has become extremely saline (up to 60,000 µS/cm). To explore the recharge rate and resilience of this deeper resource, a multi-tracer approach was conducted. Major ion chemistry, stable isotopes (δ18O, δ²H, δ13C), noble gases isotopes (He and Ne), and radiocarbon (14C) were analyzed in 19 groundwater samples. The deeper aquifer shows moderate salinity (500-3,000 µS/cm) and isotopically depleted δ¹⁸O-δ²H values, suggesting recharge from higher elevations and cooler climatic periods. Substantial radiogenic ⁴He enrichment (> 4x10-6 ccSTP/g) indicates very low recharge rates and long residence times. Radiocarbon analyses further support this interpretation, as most samples have 14C values below the detection limit (<1.12 pMC), corresponding to apparent ages >35 ka. These results suggest that modern recharge is extremely limited across most of the basin. However, a few wells near identified recharge areas show atmospheric He and Ne signatures and measurable 14C (~35 pMC), indicating the presence of a recent recharge mixed with older groundwater. These localized recharge zones illustrate the spatial heterogeneity of groundwater replenishment. Overall, our findings reveal the low renewability on human timescales and limited resilience under increasing abstraction pressures. The integration of geochemical, noble gas, and radiocarbon tracers proves essential for assessing aquifer vulnerability and supporting more informed groundwater governance in arid, data-scarce regions.
How to cite: El-Azhari, A., Ait Brahim, Y., Barbecot, F., Warr, O., Pinti, D. L., and Bouchaou, L.: Limited Groundwater Recharge and Long Residence Times in Salinized Endorheic Arid Aquifers: Evidence from Stable Isotopes, Noble Gases, and Radiocarbon Dating, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-845, https://doi.org/10.5194/egusphere-egu26-845, 2026.
The Danube-Tisza Interfluve (DTI) region, one of the most arid areas in Hungary, is threatened by the ongoing decline in groundwater levels driven by the combined impacts of climate change and human activities, including improper land use, excessive groundwater abstraction, and the existing drainage canal networks. One of the emerging solutions is the application of Natural Water Retention Measures (NWRM) (i.e., surface water retention techniques), which can utilize abandoned channels, oxbow lakes, and canals originally designed for draining the region. These measures intend to enhance the water resilience of different landscapes. While these measures have been used globally, their impacts on the shallow groundwater systems are rarely monitored. This study aims to evaluate the effectiveness of a canal-based water retention measure in Bátya Municipality, located in the southern part of DTI, by assessing the changes in the groundwater level and hydrochemical parameters in the near-surface aquifer. The research integrates electrical resistivity tomography (ERT) surveys, soil analyses, water chemistry analyses, and water level monitoring through wells to characterize the subsurface conditions and investigate the physical and chemical effects of infiltration. The results provide key insights into the infiltration processes related to canal-based water retention and its spatial influence on the groundwater resources in the study area. Furthermore, the study contributes to the understanding of how NWRMs can enhance groundwater recharge to help buffer the anthropogenic and climate change impacts on shallow groundwater systems. This work is funded by the LIFE LOGOS 4 WATERS project of the European Union and carried out in collaboration with the General Directorate of Water Management (GDWM). The study is also supported by the János Bolyai Research Scholarship of the Hungarian Academy of Sciences.
How to cite: Garas, A., Berecz, A., Szijártó, M., Mádl-Szőnyi, J., Kovács-Baksi, A., and Simon, S.: The Effectiveness of Water Retention in Canals in the Danube-Tisza Interfluve Region, Hungary, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1036, https://doi.org/10.5194/egusphere-egu26-1036, 2026.
The importance of securing stable water resources has become increasingly evident due to growing spatiotemporal uncertainty in precipitation and the more frequent occurrence of prolonged droughts caused by intensifying climate change. In this context, groundwater dams have gained prominence as an alternative water resource with low evaporation losses and high climate resilience. However, the independent operation of groundwater dams may have limitations in ensuring mid- to long-term water supply stability. Therefore, the development of an integrated water resource management system that considers conjunctive use with other water sources―such as surface water, bedrock wells, and artificial recharge facilities―is required.
The objective of this study is to demonstrate core technologies for a networking system linking groundwater dams and bedrock wells. The Ssangcheon watershed in Sokcho City, Republic of Korea―where two groundwater dams are currently operated for domestic water supply―was selected as the study area. Comprehensive analyses of geological structures, aquifer distributions, and hydrological conditions were carried out. The hydraulic and geological properties along with hydrochemical types of both alluvial and bedrock groundwater were characterized. Water balance analysis was performed to quantify available water resources within the watershed and to assess surface water–groundwater interactions.
To assess water supply stability, we conducted scenario-based simulations of integrated groundwater dam and bedrock well operations, focusing on drought and high-demand conditions. In addition, deep learning models based on Long Short-Term Memory (LSTM) networks for one-step prediction and an encoder–decoder LSTM architecture for multi-step prediction were developed to predict groundwater levels in support of the integrated operation of the Ssangcheon Dam.
The results indicate that integrating groundwater dams with bedrock wells substantially improves both water supply reliability and water quality protection. Moreover, AI-based groundwater level prediction techniques proved to be effective tools for proactive water resource management and the development of smart water management systems. This study offers a practical framework for water resource diversification, providing a foundation for developing sustainable and climate-resilient management strategies.
This work was supported by the Management Technology for Groundwater Dams in Water Supply Vulnerable Areas Program of the Korea Environmental Industry & Technology Institute (KEITI), funded by the Ministry of Environment (MOE) (RS-2025-01842973).
How to cite: Kim, Y., Seo, J. Y., Kang, J.-H., Kim, B., and Lee, S.-I.: Water Resource Diversification through Integrated Management of Groundwater Dams and Bedrock Wells, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2179, https://doi.org/10.5194/egusphere-egu26-2179, 2026.
The severe drought experienced during the summer of 2022 in the Western Alps brought unprecedented attention to water availability issues in Alpine regions traditionally considered rich in water resources, such as the Aosta Valley (Western Alps, Italy). This event highlighted the vulnerability of mountain groundwater systems to climate-driven extremes and emphasized the need for a deeper and more robust understanding of groundwater availability, particularly in densely populated alluvial plains where water demand is concentrated.
The Aosta alluvial plain represents a strategic hydrogeological system, supporting drinking water supply, ecosystem services, and an increasing interest in low-enthalpy geothermal applications. Despite its importance, the deep structure of the aquifer system and the depth to bedrock beneath the plain remained largely unconstrained until recently, limiting the reliability of conceptual and quantitative groundwater models and the capacity to anticipate future water scarcity scenarios.
Within a regional-scale program (UE-FESR Project: “Geothermalp”) aimed at enhancing sustainable groundwater and geothermal resource management, an integrated deep exploration campaign was carried out, combining advanced geophysical investigations with deep continuous-core drilling. Geophysical surveys were employed to characterize the geometry of Quaternary deposits and to delineate the bedrock surface, providing a framework for the optimal positioning of two deep boreholes. The boreholes reached depths between approximately 300 and 350 m and, for the first time beneath the Aosta plain, intersected the crystalline bedrock, yielding unprecedented direct information on lithostratigraphy, hydrogeological properties, and groundwater occurrence at depth.
The integration of indirect geophysical data and direct borehole observations revealed a hydrogeological structure significantly more complex than previously assumed. Previously unknown deep groundwater bodies were identified, hosted within permeable sedimentary units and in structurally controlled zones near the alluvium–bedrock interface. Based on the first interpretations, these groundwater bodies appear to play a key role in the vertical connectivity of the aquifer system and in the redistribution of groundwater flow at depth, suggesting multi-level circulation patterns rather than a single shallow aquifer system.
The first results have important implications for sustainable groundwater management in Alpine environments. They provide a stronger scientific basis for assessing groundwater availability under increasing climatic stress, protecting deep groundwater resources from overexploitation, and evaluating the compatibility between drinking water supply, geothermal exploitation, and ecosystem preservation. More broadly, the study demonstrates how integrated deep investigations can substantially improve hydrogeological knowledge and support informed decision-making in mountain regions facing emerging water scarcity challenges.
How to cite: Bertolo, D., Stra, M., Paganone, M., Lodi, L., Simonetto, F., Tognetto, F., and Grappein, B.: Deep groundwater exploration in an Alpine alluvial plain: first insights for sustainable water and geothermal resource management in the Aosta Valley, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4002, https://doi.org/10.5194/egusphere-egu26-4002, 2026.
Climate change poses a major challenge to sustainable groundwater management, especially in island territories. In this context, the development of innovative tools for characterising aquifers is essential to reduce their vulnerability. Currently, 3D geological modelling allows the geometric properties of geological bodies to be defined, making it possible to infer their structure, volumes and determine the availability of their groundwater resources. These three-dimensional models also form the basis for implementing numerical flow simulations, providing valuable geoscientific information for the proper management of aquifers.
Within the framework of the GENESIS project, this work presents the first 3D geological model of the volcanic island of Gran Canaria (Canary Islands, Spain). The 3D model was created using GeoModeller software, based on the island's Digital Terrain Model, surface geological maps, geological cross-sections and lithological data from boreholes and wells. The geological model obtained covers the entire surface of the island of Gran Canaria and includes a geological sequence of six main formations representing the most important volcanic edifices and geological and hydrogeological structures on the island, including the Caldera Tejeda, the remains of the Roque Nublo stratovolcano and the island's characteristic radial ravine system.
The 3D geological model will serve as the basis for the development of the first hydrogeological model of the island of Gran Canaria. This new information will be key to improving knowledge about the island's aquifer and implementing nature-based solutions (NbS), creating new management strategies to tackle climate change.
How to cite: Baquedano-Estévez, C., Martínez-León, J., Jiménez, J., Sariago, R., Meixueiro-Ríos, G., Santamarta, J. C., and García-Gil, A.: Construction of a 3D geological model to reduce the vulnerability of groundwater resources to climate change: the case of Gran Canaria (Canary Islands, Spain), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4771, https://doi.org/10.5194/egusphere-egu26-4771, 2026.
The main task was to assess the existence of significant declining trends at monitoring objects of the state groundwater hydrological network. The evaluated parameters included groundwater levels and spring discharges in Quaternary and Pre-Quaternary groundwater bodies of Slovakia. Two time periods (2014-2023 and 2018-2023) were evaluated and subsequently compared with each other to identify potential differences in trends. Time series of mean annual values as well as mean annual minimum values from a total of 1455 monitoring sites were evaluated (including 1113 boreholes and 342 springs). To identify the presence of a significant declining trend, all time series were tested using the non-parametric Mann-Kendall statistical test. If the dataset followed a normal distribution, the parametric ANOVA method was also applied. For better comparison the results were visualized using map presentation. If there was one significant declining trend found, groundwater quantity status was classified as being at risk. If there were two or more declining trends in one category (average/minima) found, the groundwater body was classified as having a poor quantitative status. Finally, 17 groundwater bodies were classified at risk and five groundwater bodies in poor quantitative status for period 2014 - 2023. However, for shorter period 2018 – 2023 only two groundwater bodies were found in poor quantitative status and four groundwater bodies were classified at risk. There was an improvement in the quantitative status of three groundwater bodies declared in comparison to longer period (from poor to good quantitative status) – SK2000200P (Intergranular groundwater of the western part of the Vienna Basin), SK200220FP (Fractured and intergranular groundwater of the northern Central Slovak Neovolcanic Area), SK200240FK (Fractured and karst-fractured groundwater of the Malá Fatra), SK200290FK (Fractured and karst-fractured groundwater of the southern slopes of the Low Tatras). In addition, 15 groundwater bodies classified at risk in longer period improved their quantitative status to good quantitative status in short period 2018-2023. Classifications of both periods define the groundwater body SK2002300P (Intergranular Groundwater of the Eastern Part of the Danube Basin and the Ipeľ Basin) in poor quantitative status and two groundwater bodies at risk SK2000400P (Intergranular groundwater of the eastern part of the Vienna Basin) and SK200590FP (Fractured and intergranular groundwater of Neovolcanic rocks).
How to cite: Janečková, L., Slivová, V., Kandrík, R., Chriašteľ, R., and Hagara Pivarčiová, L.: Significant declining trends of groundwater level and spring discharge and their comparison between two periods (2014-2023 vs 2018-2023), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6541, https://doi.org/10.5194/egusphere-egu26-6541, 2026.
Groundwater temperature has been used in the past as an environmental tracer for studying changes to groundwater quality, water flow and ecosystem health. Groundwater thermal plumes originating from subsurface geothermal energy use, urban infrastructure, waste disposal sites or mining activities can significantly impact groundwater systems. As such, continuous monitoring of groundwater temperature can be crucial when the aim is rapid detection of changes to the local thermal groundwater regime early on.
Here we demonstrate the suitability of Fibre Optic Distributed Temperature Sensing (FO-DTS) for tracing the arrival and propagation of heat plume-related temperature signals in steel and plastic-lined steel blind tubes. The use of blind tubes is increasingly being considered when monitoring the subsurface of waste processing and waste management areas including landfills and nuclear waste sites. For our laboratory experiments, plastic tanks filled with saturated sand were equipped with different blind tube configurations and a FO-DTS system (Silixa XT-DTS) and subjected to periodic heating and cooling to monitor dispersive heat transport under various thermal conditions along the blind tube. Laboratory experiments were supported by heat transport modelling.
Experimental results showed that the FO-DTS setup was well suited to detect temperature changes along the blind tube wall as low as 0.1oC at high temporal resolution. Detectability of the thermal signal was not significantly impaired by the plastic-lining where this was present inside the steel tubes. We observed that the lag of the thermal signal through the blind tubes was typically less than two minutes and that only little smearing of the temperature signal along the blind tube walls occurred, which was further confirmed by modelling results. As such, the experimental setup has the potential to be further developed into an effective on-site monitoring system, which will help to support decision making in contaminated site management and ultimately lead to an improved management of groundwater resources.
How to cite: Schneidewind, U., Rivett, M., Heneghan, J., Herbert, A., Haverson, L., Simcox, E., and Krause, S.: Using Fibre Optic Distributed Temperature Sensing for Detecting Groundwater Plume Thermal Anomalies, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7006, https://doi.org/10.5194/egusphere-egu26-7006, 2026.
Understanding the relative contribution of climatic recharge and groundwater abstraction to piezometric variability is essential for managing the stressed Doñana/Almonte-Marismas aquifer system. Traditional correlation-based approaches (Pearson, Spearman, cross-correlation) have shown limited ability to represent the intuitive differences observed among piezometric series. This work proposes the use of wavelet analysis to characterize the temporal–frequency relationships between rainfall and piezometry and to explore if these results can qualitatively separate climatic and pumping influences.
We analyze long-term piezometric records (1999-2025) together with monthly rainfall data. This time window was chosen because agricultural groundwater exploitation intensified markedly from the late 1990s, defining the modern hydrodynamic behavior of the aquifer. Time series are standardized and detrended, and raw rainfall is used to exploit the ability of wavelets to isolate frequency-dependent relationships. Selected piezometers represent contrasting hydrogeological conditions, including recharge-dominated areas or zones affected by stable intensive pumping.
Two wavelet-based metrics are computed: (i) wavelet coherence, which measures the shared variance between rainfall and groundwater levels across time and scale; and (ii) contribution, defined as the percentage of piezometric signal energy attributable to rainfall within selected temporal bands (1 year, 1–5 years, > 5 years).
Future work includes calculating contributions across all long series in the aquifer and evaluating the feasibility of spatializing these metrics for both the unconfined and confined sectors. By quantifying rainfall-driven variability across scales, wavelet analysis provides a robust framework to distinguish natural recharge signals from non-natural dynamics (e.g., pumping effects) in complex, non-stationary aquifer systems.
How to cite: Guardiola-Albert, C., Aguilera, H., Naranjo-Fernández, N., Ruiz-Bermudo, F., Serrano-Reina, J. A., and Gómez-Fontalva, J. M.: Exploring Wavelet–Based Approaches to Characterize Piezometric Variability in the Doñana Aquifer, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7046, https://doi.org/10.5194/egusphere-egu26-7046, 2026.
Ongoing climate change and increasing anthropogenic pressures are intensifying the challenges associated with the sustainable management of groundwater resources, particularly in Mediterranean regions characterized by pronounced climatic seasonality and recognized as climate change hot spots. Groundwater springs often represent a critical resource for local communities, serving both as a source of high-quality drinking water and as a key component of socio-ecological systems. Understanding the functioning, vulnerability, and resilience of the groundwater systems feeding these springs is therefore essential for effective and sustainable water management.
This study presents the first results of an ongoing investigation in the Municipality of Capannori (Lucca, Tuscany, central Italy), where publicly accessible springs are widely used for domestic water supply and have become the focus of increasing conservation efforts by local authorities. The collection of water from local springs represents a shared practice in this region that fosters a strong sense of community and reinforces the concept of water as a common good. Ensuring the sustainable management of these resources, therefore, requires a comprehensive understanding of groundwater systems, achievable through multidisciplinary approaches integrating isotopic fingerprinting with geochemical and hydrogeological tools.
A two-year monitoring programme started in April 2024 and involves 19 groundwater springs distributed across three hydrogeological sectors. Groundwater samples were collected for chemical and isotopic analysis (δ18O and δ2H), while temperature, pH, electrical conductivity and redox potential were measured in the field. Tritium and δ34S-δ18O-SO4 were determined on selected samples, and compositional data analysis (CoDA) was applied to the chemical dataset. In addition, a rain sampler was installed in February 2024 to collect monthly precipitation samples for isotopic analysis.
The results highlight pronounced chemical and isotopic heterogeneity among springs across the three hydrogeological sectors, reflecting the complexity of the groundwater systems involved. This heterogeneity points to distinct flow paths, water-rock interaction processes, and recharge dynamics, and suggests potentially different sensitivities of individual springs to hydroclimatic variability and anthropogenic pressures. From a management perspective, these differences imply that springs commonly perceived as part of a single resource may in fact exhibit contrasting levels of vulnerability under ongoing and future environmental change.
Stable water isotope data, together with deuterium excess, provide robust constraints on the recharge elevations of the aquifers feeding the springs, allowing the identification of recharge areas and the possible extent of recharge catchments. At the same time, part of the observed isotopic variability may reflect a climatic signal related to recharge seasonality rather than elevation alone. However, seasonal isotopic shifts were negligible across all springs, indicating well-mixed recharge systems and relatively slow groundwater circulation that dampens the pronounced isotopic variability of precipitation. Consistently, tritium values show no significant differences among springs (2.5-2.9 TU), indicating young groundwater with residence times not exceeding 5-10 years.
Overall, this study demonstrates how integrated isotopic and geochemical approaches can provide process-based insights that are directly relevant for groundwater protection and management under changing hydroclimatic conditions.
How to cite: Natali, S., Raco, B., Bucci, G. L., Delgado Huertas, A., Ferrari, M., Giorgi, C., Pasquetti, F., Stasi, G., and Zanchetta, G.: Integrating isotope hydrology and hydrogeochemistry to assess recharge processes and vulnerability of drinking water springs: the case of Capannori (Tuscany, central Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8005, https://doi.org/10.5194/egusphere-egu26-8005, 2026.
Endorheic basins with terminal lakes are particularly vulnerable to chemical pollution due to their closed hydrological nature, which promotes the retention and accumulation of contaminants. This study investigates the occurrence, sources, and environmental fate of contaminants of emerging concern (CECs) in the rural endorheic basin of Gallocanta Lake (Spain), one of the largest saline lakes in Europe and a protected Ramsar site. A spatially comprehensive sampling campaign was conducted in September–October 2024 across surface waters, groundwater, treated and untreated wastewater, and terminal water bodies. Non-target screening and semiquantative approaches based on liquid chromatography coupled to high resolution mass spectrometry (LC–HRMS) were applied to characterize complex contaminant mixtures across environmental compartments.
Multivariate analyses revealed clear chemical fingerprints associated with diverse sources, including effluents from rural wastewater treatment plants (WWTPs), untreated wastewater discharges, agricultural runoff, and natural stream waters. Primary-treated WWTP effluents showed variable and often limited removal of CECs, with selective attenuation of some pharmaceuticals but persistence or even enrichment of others, highlighting the limitations of basic treatment in rural settings. Terminal lakes exhibited the highest cumulative contaminant loads, reflecting their role as integrators of upstream pressures.
Particular attention was drawn on the insect repellent N,N-diethyl-meta-toluamide (DEET), due to its exceptional persistence and enrichment in Gallocanta Lake, reaching concentrations (>5,000 ng/L) far exceeding those in inflows (<1,000 ng/L). This pattern, resulting from the combination of compound stability and strong evapoconcentration under semi-arid conditions, will be discussed in detail, illustrating how moderate inputs can lead to disproportionately high accumulation in endorheic lakes.
Overall, the results demonstrate that endorheic basins act as hotspots for the accumulation of persistent CECs and emphasize the need to consider hydrological closure, in-lake processes, and rural wastewater management when assessing contamination risks and designing mitigation strategies.
How to cite: Marazuela, M. A., Carrizo, J. C., Diaz-Cruz, S., Jurado, A., Pujades, E., Pérez-Bielsa, C., and Causapé, J.: Occurrence and fate of emerging contaminants in rural endorheic basins: insights from the Gallocanta Lake Basin (Spain), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10091, https://doi.org/10.5194/egusphere-egu26-10091, 2026.
Groundwater is a strategic resource whose protection is essential to maintain its quality and prevent contamination processes. Delineating protection perimeters around abstraction points makes it possible to establish zones where potentially polluting activities are restricted, thereby reducing risk to the resource and supporting planning and the sustainable management of water supply.
In this work, the main approaches for determining protection perimeters are analysed and an operational methodology, implemented in a spreadsheet, is proposed to facilitate its application in environmental assessment and management contexts, taking into account the available hydrogeological data. The approach is developed and applied in the province of Valencia, with an emphasis on consistency between the regulatory framework and the definition of protection zones based on groundwater travel times.
The reference framework is established through a review of the applicable European and Spanish legislation for the protection of abstraction points, from the EU Water Framework Directive to basin-specific regulations, enabling the definition of the required zones, the criteria associated with travel times, and the activities subject to restrictions. Building on this basis, both analytical and numerical delineation approaches are examined: the former provide rapid solutions but rely on restrictive assumptions (homogeneous and isotropic media), whereas the latter are based on mathematical models (e.g., MODFLOW) capable of representing pumping-induced flow and estimating travel-time isochrones.
As a result, a replicable and transparent spreadsheet-based procedure is presented, integrating regulatory criteria and hydrogeological principles to support the delineation of protection zones, contributing to more traceable decision-making in contamination prevention and the sustainable management of groundwater resources.
How to cite: Iturriaga-Gosen, F., Rodrigo-Clavero, M.-E., Cassiraga, E., and Rodrigo-Ilarri, J.: Methodological framework for delineating wellhead protection areas for groundwater abstraction wells, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10864, https://doi.org/10.5194/egusphere-egu26-10864, 2026.
Groundwater overdraft has been occurring for decades in California’s San Joaquin Valley, an alluvial basin consisting of unconfined, semi-confined and confined aquifers. Excessive pumping of groundwater is exceeding the natural recharge of the aquifers; this is causing land subsidence which has a significant negative economic impact through infrastructure damage. A solution is to supplement natural recharge through managed aquifer recharge, which can be implemented by the spreading of water on the ground surface, or by the injection of water in wells. Because subsidence of the ground surface occurs primarily due to compaction in the confined aquifers, there is a need to prioritize recharge of the confined aquifers. This requires identifying locations where there are permeable pathways that can be accessed by recharge operations to reach the confined aquifers. Recent studies have shown that high resolution interferometric synthetic aperture radar (InSAR) data, when processed to extract seasonal deformation timing and amplitude information, reveal seasonal uplift patterns associated with natural recharge into the confined aquifers. We find coherent signals in three regions in the InSAR data from the 2017, 2019 and 2023 water years which represent “wet years”, i.e. the years with high volumes of precipitation and surface runoff. For each of the three regions, we used an interpolated 3D sediment-type model derived from airborne electromagnetic data to identify the permeable pathways that enter the confined aquifer. In two of the regions, pathways to the confined aquifer exist at the margins of the Corcoran Clay, the major confining aquitard of the valley. In the third region, the Corcoran Clay is thin and intersected by pathways of coarse material. The ability to utilize satellite imaging to inform the design of recharge operations can contribute significantly to achieving sustainable groundwater management.
How to cite: Zhang, S. and Knight, R.: Satellite imaging to identify pathways for recharge of the confined aquifers in California's San Joaquin Valley, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15172, https://doi.org/10.5194/egusphere-egu26-15172, 2026.
Rising rates of groundwater abstraction and associated aquifer depletion are a major global concern, threatening environmental integrity, water availability, and food security for future generations. Overexploitation reduces pore water pressure, increasing effective stress in aquifers. The extracted water coming from the compression of adjacent and intervening clay beds results in aquifer compaction and land subsidence, one of the most severe geotechnical consequences of groundwater withdrawal. This issue is prevalent in densely populated and developed areas, often located in unconsolidated Quaternary basins of alluvial, lacustrine, or shallow marine origin. Despite extensive research on land subsidence from groundwater overexploitation, the combined effects of intensified drought and anthropic pressure on aquifer deformation are still unclear. In Italy, land subsidence due to groundwater abstraction is observed particularly in agricultural areas. Increasing demand for irrigation and uncertain surface water supplies exacerbated by climate change, suggests the issue will persist.
Satellite Earth Observation data can enhance understanding of groundwater dynamics: phenological metrics from time series of biophysical parameters and vegetation indices can be used for crop mapping and irrigation needs, while differential SAR interferometry offers accurate quantitative measurements of surface deformation and land subsidence at high spatial and temporal resolution, serving as a proxy for evaluating groundwater abstraction effects. An ongoing research is here presented, with the aim to investigate the physical mechanism beneath the land subsidence, to identify key hydrologic and geotechnical principles driving land subsidence in target areas, in order to develop a predictive framework to estimate the irreversible volume loss of economically extractable groundwater. The workflow comprises a preliminary phase involving data collection and storage in a dedicated WebGIS platform, followed by the assessment of geological setting, a land use analysis, the analysis of dinSAR data and the trend analysis of groundwater head and withdrawals. The study was approached in two areas (Po Plain and Pontine Plain, Italy), sensibly differing among each other for both the density of available head and withdrawal data and the geological setting, to preliminary assess the relationship between land subsidence and groundwater withdrawal. The perspective of this research is to provide a scientific basis for authorities to plan effective mitigation and ensure sustainable groundwater management.
How to cite: Di Salvo, C., Pennica, F., Pedretti, L., Zucca, F., Mesina, C., and FIlipponi, F.: Integrating hydrogeological and earth observation data for the assessment of aquifers compaction and storage dynamics under groundwater abstraction, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17040, https://doi.org/10.5194/egusphere-egu26-17040, 2026.
Climate change is threatening both the quantity and quality of groundwater resources, as scarcer rainfalls and prolonged droughts reduce natural recharge and increase reliance on groundwater abstraction. In this context, Managed Aquifer Recharge (MAR) is a climate change adaptation measure that, through the intentional recharge of aquifers with excess surface water, provides water underground storage for later use (e.g., irrigation) and may improve groundwater quality (e.g. addressing saltwater intrusion or nitrate pollution).
The SeTe (Sécheresse et Territoires) project, funded by the EU Interreg ALCOTRA programme, involves the feasibility study and demonstration of MAR at three sites – Beinette, Tetti Pesio and Tarantasca – in the Cuneo plain, a large shallow alluvial aquifer in northwestern Italy. In this intensively farmed area, with a large seasonal mismatch between water supply and demand, groundwater use for irrigation is widespread and recent droughts and human pressures have caused severe aquifer depletion. This issue is particularly relevant in the SeTe test sites, where irrigation water is supplied through wells and semi-natural lowland springs (fontanili), drainage trenches excavated since the Middle Ages to reclaim the marshy lands conveying the drained groundwater to irrigation canals. As groundwater levels decline, many wells dry up, or show reduced yields, and fontanili discharge decreases or ceases. Experimental recharge trenches were built within the project to supply the aquifer by infiltrating water from canals when they are not used for irrigation. This water, which would otherwise flow into water courses, is infiltrated upstream the fontanili to raise local groundwater levels and enhance their drainage capacity.
After the geological, hydrological and hydrogeological characterization of the area carried out in the first year of the project, two infiltration trenches were completed in Beinette and Tetti Pesio by spring 2025. Then, the trenches were tested until the start of the irrigation season, while a full infiltration season was planned for winter 2025-2026.
Water levels in monitoring wells, fontanili and recharge trenches, as well as recharge flow rates, are continuously monitored through a monitoring network, also using LoRA-based systems to enable real-time data acquisition. Water chemistry monitoring is carried out to ensure that the infiltrated water is of higher quality than the groundwater, often affected by nitrate contamination.
Meteorological and hydrological data, including rainfall, snowfall and rivers flows, are integrated from the regional monitoring database to understand the overall system behaviour, with a focus on quantifying recharge and its beneficial effects on groundwater levels and fontanili discharge.
Despite operational challenges, such as clogging, the SeTe ALCOTRA project is demonstrating that with its cost efficiency, simple design and minimal environmental impact, MAR is a suitable strategy for aquifer recharge, supporting ecosystem services and economic activities.
Finally, public engagement, both with authorities and local communities – is a key aspect, as it can facilitate the adoption and dissemination of this type of infrastructure.
How to cite: Taramasso, M. A., Amendola, A., Gallia, L., Giordano, N., Algarotti, P., Gandolfo, M., Vigna, B., Fiorucci, A., Tosco, T., Sethi, R., and Casasso, A.: Managed Aquifer Recharge (MAR) using irrigation channels: experiences from the test sites of the SeTe-ALCOTRA project, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18110, https://doi.org/10.5194/egusphere-egu26-18110, 2026.
As climate change accelerates, extreme events like droughts and floods are becoming more frequent and severe across Europe, and pollution adds further strain on groundwater resources. Groundwater sustains ecosystems and provides most of the drinking water in Estonia and Latvia, making its sustainable and proactive management more important than ever. In practice, however, that kind of management is difficult to achieve. Current monitoring systems in Estonia and Latvia still operate on slow cycles of data collection and manual analysis, leaving little room for early intervention. Because of this, municipalities often find out about issues with groundwater quality and quantity when they have already escalated – when wells have run dry or contaminants have reached drinking water supplies. Even when data is available, it often requires expert interpretation, making it difficult to act quickly and prevent problems in time.
The cross-border 'HydroScope' project addresses these challenges by developing a groundwater early warning system for two pilot municipalities: Saaremaa (Estonia) and Dienvidkurzeme (Latvia). In these municipalities, telemetry systems tailored to local groundwater conditions are installed in monitoring wells, introducing real-time groundwater monitoring in Estonia for the first time and expanding the network in Latvia. Real-time digital spring systems complement the well monitoring network.
Machine learning models are developed to automatically detect patterns in real-time groundwater quantity and quality data and to generate short-term predictions. This information feeds into two municipality-specific early warning platforms. These platforms visualize insights from near real-time data in an easily interpretable way, along with recommendations for what actions to take under different scenarios – e.g. reducing water use if a groundwater drought is likely, or identifying potential contamination sources when thresholds are approached.
The ‘HydroScope’ project is a first step toward establishing a real-time groundwater monitoring paradigm in Estonia and Latvia, and also toward making that real-time data directly usable for local decision-making, thus supporting sustainable and proactive groundwater management practices.
The project HydroScope (EE-LV00250) is funded by the European Union through the European Regional Development Fund (ERDF) within the Interreg VI-A Estonia–Latvia Programme 2021–2027.
How to cite: Hints, L., Männik, M., Karro, E., Retiķe, I., Bikše, J., Tīrums, M., and Vīksna, A.: Improving local groundwater management in Estonia and Latvia through real-time monitoring and machine learning, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20039, https://doi.org/10.5194/egusphere-egu26-20039, 2026.
Groundwater potential zoning (GWPZ) using multi-criteria decision analysis (MCDA) and data-driven techniques has emerged as a vital tool for sustainable groundwater management, particularly in data-scarce coastal regions where surface water availability is limited and aquifers are vulnerable to overexploitation and seawater intrusion. Coastal aquifer systems are inherently heterogeneous and dynamically influenced by geomorphology, lithology, land use, and climatic conditions, making integrated decision-support frameworks essential for identifying zones with varying groundwater potential. In this context, the present study evaluates and compares six widely used subjective, objective and probabilistic MCDA techniques—Analytic Hierarchy Process (AHP), Fuzzy-AHP (F-AHP), Frequency Ratio (FR), Weight of Evidence (WoE), Entropy, and Multi-Influencing Factor (MIF), for analyzing groundwater prospect in a complex coastal alluvial setting. The study area with an areal extent of 6468.60 km2, comprises the Haldi–Kansabati–Subarnarekha interfluve located along the Bay of Bengal in the southern coastal region of West Bengal, eastern India. The region is characterized by a ‘Tropical Wet-and-Dry’ climate under the Köppen–Geiger classification and exhibits pronounced hydrogeological heterogeneity. The geological framework is dominated by younger alluvium (quaternary sediments) in the floodplains and deltaic tracts, followed by older alluvium (tertiary sediments) inland, coastal alluvium along the shoreline, and lateritic formations in the landward uplands. These formations exert strong control on groundwater occurrence, storage, and movement. Multiple groundwater-conditioning factors such as: ‘runoff coefficient’, ‘land slope %’, ‘drainage density’, ‘geology’, and ‘proximity to surface water bodies’ representing topography, hydrology, geology, land surface characteristics, and recharge conditions were integrated within the ArcGIS pro v3.4.2 environment to generate GWPZ maps using each of the six MCDA techniques. The resulting groundwater potential maps were classified into three categories—‘high’, ‘moderate’, and ‘low’ potential zones—using consistent classification criteria across all methods to enable inter-model comparison. Model validation was performed using observed pumping well yield (discharge) data, which were independently categorized into three classes: ‘low’ (<36 m³/hr), ‘moderate’ (36–90 m³/hr), and ‘high’ (>90 m³/hr). The predictive performance of each GWPZ model was quantitatively evaluated using Pearson’s correlation coefficient (r), and Receiver Operating Characteristic (ROC) curve-derived Area Under the Curve (AUC) statistics generated through the ArcSDM v5.00.22 toolbox in ArcGIS Pro v3.4.2. The validation results demonstrate notable variability in model performance. Among the six MCDA techniques, Fuzzy-AHP (F-AHP) exhibited the highest predictive accuracy with a correlation coefficient (r) of 0.912 and an AUC value of 0.853, followed by AHP (r=0.897; AUC=0.815), WoE (r=0.868; AUC=0.773), FR (r=0.809; AUC=0.724), MIF (r=0.778; AUC=0.702), and Entropy (r=0.727; AUC=0.683). The superior performance of the hybrid Fuzzy-AHP technique highlights its robustness in handling uncertainty and subjectivity while maintaining logical consistency. The F-AHP technique further sustains gradual transitions in factor importance when dealing with complex coastal hydrogeological systems. Overall, the study underscores the robustness of MCDA-based approaches, particularly F-AHP and AHP, for groundwater potential assessment in coastal alluvial environments and provides a comparative framework to support groundwater planning and management in similar vulnerable coastal regions.
How to cite: Naz, A., Ghosh, S., and Jha, M. K.: Comparative Evaluation of Multi-Criteria Decision Analysis Techniques for Groundwater Potential Mapping in a Coastal Alluvial Basin of Eastern India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21167, https://doi.org/10.5194/egusphere-egu26-21167, 2026.
Groundwater, a major source of available freshwater 1, is central to meeting the drinking water needs globally 2, and in the eastern Indian state of Bihar 3. Groundwater in parts of Bihar however, has elevated levels of geogenic inorganic contaminants 4, with more recent studies also indicating microbial contamination 5 and presence of antimicrobial resistance (AMR) genes 6 in shallow and deeper depth groundwater. However, studies investigating contamination of groundwater-derived household drinking water at the point of consumption (PoC), as compared to the point of source (PoS), are limited in Bihar. Paired water samples (n = 39) were collected from groundwater wells at the PoS, and the corresponding household drinking water containers at the PoC; and tested for arsenic (As), Escherichia coli (E. coli) and extended spectrum beta-lactamase (ESBL) producing E. coli (ESBL-Ec) - as an exemplar of inorganic chemical contaminant, microbial contaminant, and AMR indicator organism, respectively. Results indicate samples exceeding the 10 µg/L WHO provisional guideline value for As to be same (at 5 %) between PoS and PoC. However, presence of E. coli increased from 46 % to 59 % (McNemar’s p = 0.27) while that of ESBL-Ec rose from 10 % to 46 % (McNemar’s p < 0.01) between PoS and PoC samples. 74 % of the households reported collection and storage of water prior to consumption, of which 72 % reported the storage vessels to be covered, and another 69 % reporting cleaning of the container’s multiple times a day. However, more than half of the sampled households owned livestock within premises, had kids under the age of five, and just 13 % reported any kind of treatment (including boiling) being done to the groundwater prior to drinking. No improvement in water quality was observed from PoS to PoC for E. coli. On the contrary, deterioration in water quality from PoS and PoC was indicated based on ESBL-Ec (Wilcoxon signed rank test; p < 0.05). As expected of inorganic contaminants, no significant shift (at the 0.05 level) in overall concentration was observed for As between PoS and PoC. The results call for sustainable management of groundwater sources, and improvements in delivery and treatment of contaminated groundwater prior to consumption so that potable drinking water is ensured at the end-user stage.
References: [1] Weblink: https://portals.iucn.org/library/sites/library/files/documents/2016-039.pdf; [2] DOI: 10.1016/C2018-0-03156-4; [3] Weblink: https://nhm.gov.in/uhc-day/Session%202/NFHS-5%20State%20Factsheet%20Compendium_Phase-I%20%281%29.pdf; [4] DOI: 10.3390/ijerph17072500; [5] Roshan et. al., AGU 2025; [6] 10.1016/j.envpol.2024.124205. This work was supported by MR/Y016327/1 (to LAR et. al.,) and Cookson Scholarship (to AR).
How to cite: Roshan, A., Polya, D. A., Arora, M., Kumar, A., Ghosh, A., Glenny, A.-M., Sedighi, M., Reichman, S. M., and Richards, L. A.: From ground to home: Evidence, extent and potential controls on groundwater sourced household drinking water contamination in Bihar, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22704, https://doi.org/10.5194/egusphere-egu26-22704, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot A
EGU26-4336 | ECS | Posters virtual | VPS8
“Environmental implications of natural sources of arsenic and boron in hydrothermal bodies in the second biggest lake of México.”Tue, 05 May, 14:21–14:24 (CEST) vPoster spot A
Lake Cuitzeo is the second biggest lake in Mexico. It is placed in a semi-graben
structure, linked to volcanic rocks and fault systems. On the lake shoreline,
hydrothermal bodies emerge. These present arsenic and boron concentrations and
are used in thermal spas. Nevertheless, it is necessary to study the original and
behavior of these hydrothermal bodies, which provides information for the
sustainable management in order to benefit the local users.
The objective of this work is to determine the spatial distribution of the
hydrothermal manifestations, as well as their hydrogeochemical characteristics and
the temperature they reach at depth. The methodology consisted of sampling thermal wells and springs, along with laboratory determination of major ions and
trace elements. Subsequently, hydrogeochemical diagrams, isoline maps, and
geochemical indicators were used to understand their behavior. The results show
that the thermal sites have higher temperatures at depth and are associated with
the presence of faults.
Finally, the information compiled in this study may be useful for defining a safe and
feasible use of the geothermal resource for the communities inhabiting the study
area, whether for energy generation or for direct-use applications.
How to cite: Sierra Garcia, B. A., Olea, S., Israde Alcántara, I., Villanueva Estrada, R. E., Morales Casique, E., Zamora Martínez, O., Tadeo León, J., Gómez Vasconcelos, M. G., Avellán Denis, R., and Ramírez Serrato, N.: “Environmental implications of natural sources of arsenic and boron in hydrothermal bodies in the second biggest lake of México.”, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4336, https://doi.org/10.5194/egusphere-egu26-4336, 2026.
EGU26-13428 | ECS | Posters virtual | VPS8
Hydrogeological and Hydrochemical Characterization of Quarry Lakes in the Piedmont Alluvial PlainTue, 05 May, 14:24–14:27 (CEST) vPoster spot A
Quarry lakes, primarily located in alluvial plains, form as a result of the deepening of quarry excavations beyond the water table of the shallow aquifer.
They allow for full exploitation of the deposit without excessively damaging the landscape, limiting land consumption. Quarry lakes play also an important ecological and landscape role, because they provide (i) habitats for aquatic plants, aquatic animal species and birds, and (ii) recreational opportunities. Additionally, they contribute to management of water resources and mitigation of flood risks.
In the Piedmont region (NW Italy), quarry lakes are numerous and of considerable size due to the high market demand for concrete and aggregates. These quarry lakes are mostly located along the Po River, the main river of the region, and its main tributaries.
This study focused on six active quarry lakes and, primarily, a hydrogeological reconstruction of the surrounding areas was carried out. Lake water samples were collected in the summer and autumn of 2025 and analysed for hydrochemical composition. Field parameters, including pH, electrical conductivity, and water temperature, were also recorded.
The hydrochemical results, compared with data from the regional network of groundwater monitoring wells, reveal a strong correlation between lake waters, the surface aquifer, and watercourses. The chemical characterization of these quarry lakes supports the study of their photochemical activity, and the assessment of their potential use as nature-based basins for quaternary treatment of water, thus allowing to minimize the overexploitation of groundwater resources in a context of more frequent drought events due to climate change.
How to cite: Pigozzi, G., Bianco Prevot, A., Biasio, L., Carena, L., Cocca, D., De Luca, D. A., Egidio, E., Lasagna, M., and Mittaridonna, A.: Hydrogeological and Hydrochemical Characterization of Quarry Lakes in the Piedmont Alluvial Plain, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13428, https://doi.org/10.5194/egusphere-egu26-13428, 2026.
EGU26-15246 | Posters virtual | VPS8
Nitrate behavior in a groundwater flow system that discharges into the largest lakes of MexicoTue, 05 May, 14:27–14:30 (CEST) vPoster spot A
The nitrate input in the groundwater and surface water is the main source of contamination in many areas of the world. In Mexico, agricultural activities depending of groundwater and surface water. The groundwater flow system (GFS) is a single system with recharge and discharge zone were the interactions between surface and groundwater are present. In Mexico, the Cuitzeo GFS is a is one of the most agriculturally developed areas in central Mexico and includes the second and third largest lakes, lakes Cuitzeo and Patzcuaro.
The main object of this work is to analyze the nitrate behavior in groundwater and lake waters to understand the spatial changes over two years.
The methodology includes sampling of major ions of 39 sites, including wells, dugwells, springs, and lakes in the dry season for the years 2024 and 2025. Additionally, hydrogeochemical diagrams and spatial analysis were developed. The nitrate concentrations in this country are regulated by Mexican rules.
The results show that 11 sites exceed the permitted limit of concentrations according to these rules. Nitrates predominate in the zone of major population close to Morelia city and close to Lake Cuitzeo. Whereas ammonium is present close to the lake Patzcuaro. These distributions are in groundwater and surface waters, reflecting the same processes in both water bodies. This area presents a rapid expansion and intensification of berry and avocado cultivation, which have displaced local crops and driven unsustainable patterns of agricultural water use.
This study provided valuable information about the source and quantification of nitrate species contaminations, which can help to generate new management strategies.
How to cite: Llanos Solis, A. G., Olea Olea, S., Morales Casique, E., Zamora Martínez, O., Tadeo León, J., Goméz Vasconcelos, M. G., Avellán, D. R., and Ramírez Serrato, N.: Nitrate behavior in a groundwater flow system that discharges into the largest lakes of Mexico, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15246, https://doi.org/10.5194/egusphere-egu26-15246, 2026.
