This session seeks to deepen our understanding of the full spectrum of qualitative and quantitative impacts of extreme hydroclimatic conditions on groundwater systems, and their representation through numerical modeling and data-driven approaches.
We welcome contributions that provide insights into innovative methodologies, field case studies, or novel perspectives investigating the qualitative and quantitative impacts that extreme hydroclimatic conditions exert on groundwater systems, with a specific focus on cold-climate hydrosystems, whose dynamics are strongly controlled by prolonged cold winters, warm summers, and variable presence of snowpack, soil frost, and permafrost. In particular, we welcome studies that address: (i) comparative analysis of methodologies and system responses across different spatial scales and climatic contexts; (ii) novel modeling frameworks including past, present, and projected variations of extreme hydroclimatic events; (iii) characterization and modeling of system memory, including how aquifers and subsurface catchments retain the effects of past events; (iv) analysis of aquifer systems recovery times; (v) evaluation of the consequences of combined climatic and anthropogenic stresses on groundwater systems; (vi) identification and assessment of potential mitigation and adaptation strategies.
By bringing together field observations, modelling studies, and theoretical approaches, this session aims to foster cross-disciplinary dialogue and advance predictive understanding of groundwater system resilience under accelerating hydroclimatic extremes.
Orals: Mon, 4 May, 08:30–10:15 | Room 2.17
Arctic hydrosystems are undergoing rapid change, driven by warming temperatures, shifting precipitation regimes, and increasing climate extremes. In Arctic coastal settings, these terrestrial and atmospheric pressures are compounded by ocean-driven change, including storm-surge inundation and saltwater intrusion that can introduce heat and solutes to tundra soils and near-surface aquifers. Despite the strong groundwater-surface water connectivity and pronounced seasonality that characterize cold-climate hydrosystems, we still lack a process-based understanding of how ocean variability interacts with coastal groundwater dynamics and the resulting ecohydrological and biogeochemical feedbacks.
Here we synthesize recent work from the Arctic Coastal Plain of Alaska that quantifies two-way interactions between ocean conditions (event to seasonal scales) and groundwater response, and links these dynamics to hydro-thermal and biogeochemical change. We combine year-round time series of groundwater and surface-water levels with multi-depth soil temperature profiles, electromagnetic surveys of subsurface electrical conductivity, and seasonal measurements of porewater chemistry and thaw depth across tundra environments spanning gradients in inundation frequency. Across sites, elevated porewater salinity and higher subsurface electrical conductivity were associated with vegetation degradation and thicker active layers. A year-long record of soil temperature profiles shows that inundation-driven shifts in vegetation and soil properties alter surface energy balance and increase soil thermal conductivity, yielding summer soil temperatures up to 10°C warmer than at undisturbed sites. These warming patterns cannot be explained by freezing-point depression alone, highlighting the importance of coupled ecological-hydrogeological-thermal feedbacks.
We further show that spatial variability in active layer thickness modifies surface-subsurface connectivity and water exchange, with implications for both saltwater intrusion pathways and the magnitude of coastal groundwater discharge. Our results demonstrate that coastal Arctic groundwater vulnerability emerges from interacting processes across hydrologic, thermal, and ecological domains, and that integrating geophysics, year-round monitoring, and porewater biogeochemistry is essential for anticipating how permafrost-bound coastlines will respond to continued warming and ocean change.
How to cite: Guimond, J., Spera, A., Elmstrom, E., Hung, J., Natali, S., and McClelland, J.: Drivers and consequences of changing groundwater dynamics in Arctic coastal systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2335, https://doi.org/10.5194/egusphere-egu26-2335, 2026.
In cold regions, snowmelt is an important source of groundwater recharge and spring streamflow. However, in a warming climate the factors governing snowmelt recharge dynamics are expected to change. The amount and timing of groundwater recharge may be altered through changes in air temperature and soil ice content, and the shift from less snow towards more winter rain. While declining snowpacks have been linked to reduced summertime low flows, the impact of a precipitation phase shift on groundwater resources is not well understood. This study investigates whether snowmelt is more effective than rainfall at recharging groundwater under future climate conditions in the Christmas Brook watershed of Eskasoni First Nation, Nova Scotia, Canada (45°57′45″N,60°34′59″W), where the local community relies on groundwater as a potable water source.
We monitored hourly precipitation, snow depth, groundwater level, soil moisture and temperature, and streamflow across three landscape types at differing topographic positions. We used field observations to calibrate the Simultaneous Heat and Water (SHAW) model, a one-dimensional critical zone model that simulates coupled heat, water, and solute transport through canopy, snow, residue, and soil as well as the consideration of freeze-thaw processes. Simulations were run over historical, mid-century, and end-of-century periods to quantify differences in recharge between rain versus snow recharge events under climate change.
Preliminary results indicate snowmelt historically makes up a significant proportion of groundwater recharge. However, the region experiences recharge events year-round from a combination of snowmelt and rainfall. By the year 2100, the simulated snowpack depth declined 40% on average from historical observations. Additionally, the annual number of days with snow cover reduced to around one third of the historical count. Overall, evolutions in snow cover and melt patterns, as well as soil ice content, shifted recharge dynamics in the watershed. The results illustrate the complex mechanisms controlling groundwater recharge in cold regions and the utility of modelling to understand how decreases in snow and increases in rain will impact groundwater resources.
How to cite: Gillette, J., Strong, R. B., McIsaac, A., Baechler, F., Kurylyk, B., and Somers, L.: Climate Change Impacts on Groundwater Recharge in a Low-Mountain Area, Eskasoni First Nation, Nova Scotia, Canada., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12152, https://doi.org/10.5194/egusphere-egu26-12152, 2026.
Groundwater-level seasonality (regime) is shifting under climate change, with direct implications for drought and flood risks, water supply reliability, agriculture, and ecosystem functioning. These shifts are accentuated in shallow, fast-responding aquifers, particularly in boreal settings where the recharge- and evapotranspiration-constrained freezing winters are changing. To characterize subarctic groundwater regimes and assess their past development, we analyzed 50-year groundwater level records from 53 monitoring stations across Finland (covering >300,000 km²). After method evaluation, we classified regimes using partitioning around medoids (PAM) clustering based on Pearson correlation distances, supported by principal component analysis (PCA) of normalized monthly groundwater levels to summarize seasonal variability.
The clustering identified four groundwater regimes that align primarily with a southwest–northeast gradient of frost-season intensity. Comparing two periods (1975–1999 vs. 2000–2024) revealed the regimes to have migrated northeastward, toward colder regions. This is locally seen as higher winter groundwater levels, lower summer levels, earlier spring recharge peak, and prolonged summer low season. Regime expression also varied with aquifer size: within the 0.01–70 km² range, larger aquifers exhibited lagged seasonal responses, consistent with longer flow paths and greater storage. The results implicate that the selected approach effectively displays the spatially evolving groundwater dynamics, and highlight the importance of long-term environmental monitoring for effective decision-making and preparedness for shortages in water availability in the changing climate.
How to cite: Pöykkö, P., Tammelin, M., Ronkanen, A.-K., Ahopelto, L., and Rossi, P.: Climate change effects on the annual cycle in shallow subarctic groundwater over 50 years, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17148, https://doi.org/10.5194/egusphere-egu26-17148, 2026.
Groundwater flow in hillslopes in permafrost environments is strongly controlled by seasonal freeze-thaw dynamics. The seasonally thawed active layer acts as a transient groundwater system perched above permafrost, where coupled thermal and hydrological processes control subsurface connectivity, solute residence times and export to surface water recipients. Understanding these processes is critical for predicting hydrological responses to climate warming in permafrost regions.
Here we investigate groundwater flow and solute transport in a high-Arctic hillslope setting in Endalen Valley, Svalbard, underlain by continuous permafrost, using a physics-based numerical thermal-hydrological flow model with solute transport. Breakthrough curves are obtained for tracers released at different depths in the subsurface under present-day climatic conditions and under a set of warming scenarios. Results show that solute transport behaves very differently depending on release depth. Solutes originating near the ground surface are transported slowly, reflecting predominantly unsaturated flow conditions with seasonal thaw, producing long residence times. In contrast, solutes released at depth, near the permafrost table, experience rapid lateral groundwater transport following thaw, driven by water saturated conditions and the development of laterally connected subsurface flow paths above the permafrost.
Furthermore, solute mobilisation from newly thawed permafrost under climate warming is highly sensitive to the rate and mode of warming. Gradual warming promotes limited annual mobilisation dominated by vertical transport through percolation and cryosuction, whereas abrupt thaw associated with anomalously warm years leads to more rapid lateral transport comparable to that observed within the active layer.
Finally, we demonstrate how groundwater saturation and temperature conditions influence in situ solute transformation, showing that rapid transport under highly saturated conditions coincides with low potential mineralisation prior to export. These results highlight the central role of seasonal groundwater flow regimes in controlling subsurface transport in permafrost hillslopes and their response to climate change.
How to cite: Frampton, A., Hamm, A., Schytt Mannerfelt, E., Mohammed, A. A., Painter, S. L., and Coon, E. T.: Groundwater flow and solute transport in a permafrost hillslope under seasonal thaw and climate warming, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15791, https://doi.org/10.5194/egusphere-egu26-15791, 2026.
Subarctic and Arctic regions are experiencing rapid warming that is accelerating permafrost thaw and altering groundwater systems, with implications for the transport of solutes, including contaminants. Simulating these processes requires numerical tools that couple water, energy, and solute transport under dynamic freeze–thaw and variably saturated conditions. We present SUTRA-solice, a new version of the USGS SUTRA code developed to simulate variably saturated groundwater flow, advective–conductive heat transport with phase change, and reactive transport of multiple solute species. SUTRA-solice integrates the multi-species solute transport capabilities of SUTRA-MS with the phase-change energy transport framework of SUTRA 4.0, and adds functionality to represent temperature- and saturation-dependent reaction rates. We illustrate the application of SUTRA-solice by exploring contaminant transport in a continuous permafrost setting under warming conditions. Results show that increased seasonal thaw depth and duration enhance groundwater flow and increase solute mobility and transformation, particularly for weakly sorbing species. These results demonstrate the flexibility of SUTRA-solice for investigating solute dynamics in cryohydrogeologic systems. Continued development and testing of the model against field data will lead to improved understanding of climate-driven feedbacks and inform water management in permafrost environments.
How to cite: McKenzie, J., Basijokaite, R., Mohammed, A., and Stribling, S.: Modeling Solute and Contaminant Transport in Permafrost Regions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15737, https://doi.org/10.5194/egusphere-egu26-15737, 2026.
Groundwater is a resilient resource that is vital for local water supplies and maintaining baseflow in rivers and streams, particularly during low flow periods. Due to global climate change, the occurrence of meteorological drought is increasing in both frequency and severity, causing or amplifying water scarcity events even in areas considered water rich, like Scotland. While groundwater is generally more resilient to drought than surface water sources, the specific impacts on the resilience of the resource is influenced by local hydrogeology, geography, and climate. To evaluate differences in groundwater response between sites and assess vulnerability and resilience at varying timescales, it is important have standardised parameters to evaluate.
The Standardised Groundwater Index (SGI) is a normalisation procedure that can be applied to groundwater level data from observation boreholes to compare drought response more easily between locations. To standardise groundwater data, typical methods use a specific probability distribution which is unlikely to represent variability over large, diverse regions across different seasons or empirical probabilities requiring large sample sizes. Here, in the transformation to standardised units, probability distributions are optimised using Akaike Information Criterion (AIC) to select the most appropriate distribution for each season at each location. Incorporating model fit statistics for each time and site reduces uncertainty in calculations, particularly at the tails of the distribution which is vital for drought studies.
Groundwater storage and memory is evaluated across 33 sites in Scotland through the autocorrelation function of the SGI time series and correlated with Standardised Precipitation Evapotranspiration Index (SPEI) to evaluate the time scale of groundwater drought propagation at each location and better characterise storage properties for aquifers of different lithologies and dominant flow types (e.g. intergranular, fractured). Autocorrelation lengths of less than 5 months are common in the fractured flow systems compared to lag periods of 9 months or greater in more highly transmissive aquifers likely dominated by intergranular flow.
Hierarchical cluster analysis of the SGI time series provides an added line of evidence to the differential response between hydrogeological units and to identify areas where local changes in geology, structure, or surface water connections could be influencing groundwater response. Characterisation of the groundwater drought response can reveal areas of greater groundwater resilience and provide water managers better metrics to assess the spatiotemporal controls of groundwater drought propagation, along with modelling the timing and magnitude of seasonal groundwater minima.
How to cite: Johnson, B., Comte, J.-C., MacDonald, A., Soulsby, C., and Helliwell, R.: Characterising groundwater drought: Using standard indices and cluster analysis to quantify drought response and propagation across aquifer typology and identify areas of resilience, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10286, https://doi.org/10.5194/egusphere-egu26-10286, 2026.
Under escalating impacts of climate change, the frequency and intensity of hydroclimatic extremes, particularly prolonged droughts, pose a severe threat to global groundwater security. As aquifer systems serve as the primary buffer during droughts, accurately quantifying their resilience under unprecedented stress is essential for ensuring sustainable water availability and ecosystem stability. However, existing resilience methodologies are predominantly based on "Engineering Resilience", focusing strictly on the recovery rate of an aquifer after a disturbance. This approach leads to a misleading paradox: fractured, rocky aquifers are often characterised as "highly resilient" simply because they exhibit rapid hydraulic rebound compared to alluvial aquifers, despite their inability to sustain supply during the stress period itself. This recovery-centric view ignores the critical role of "Endurance" (Ecological Resilience), the qualitative capacity of a system to buffer shocks and resist state shifts during active drought events. To bridge this gap, this study proposes the Endurance-Recovery-Resilience (ERR) Framework. Our primary objective is to operationalize "Endurance" as a quantifiable metric alongside recovery, thereby capturing the "True Resilience" or buffer capacity of the aquifer system. The universal applicability of the ERR framework is evaluated through a comparative analysis of heterogeneous aquifer systems across two continental-scale domains: the Ganga River Basin (India) and major US Aquifer Systems. We contrast the drought response of extensive unconsolidated sedimentary basins (Gangetic Plain, High Plains, Central Valley) against fractured crystalline and basaltic aquifers (Bundelkhand/Vindhyan, Columbia Plateau, Piedmont) to test the framework's validity across diverse hydrogeological settings. The results reveal a fundamental divergence in system behavior. While rocky aquifers demonstrate high engineering resilience (rapid recovery), they exhibit critically low endurance, failing rapidly under drought stress. Conversely, alluvial systems demonstrate "True Buffering Capacity" (High Endurance), successfully maintaining hydraulic heads during extreme events, although they are prone to poor recovery trajectories during prolonged droughts. We conclude that resilience cannot be defined by recovery speed alone. By integrating Endurance, the ERR framework corrects the "rocky aquifer paradox," providing a robust tool for decision-makers to identify region-specific vulnerabilities. This highlights that water security strategies must differentiate between protecting the limited buffer of rocky systems and managing long-term depletion in high-endurance alluvial basins.
How to cite: Jnanadevan, A., Bhatnagar, I., and Dhanya, C. T.: Integrating "Endurance" into Groundwater Resilience: Quantifying the True Buffer Capacity of Aquifer Systems During Droughts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-480, https://doi.org/10.5194/egusphere-egu26-480, 2026.
Groundwater resources are under increasing pressure from both human and climatic drivers. Increasing water demands, driven by population growth, urbanisation, and agriculture, are intensifying groundwater abstractions and, at the same time, climate extremes such as prolonged droughts affect groundwater recharge. Given these pressures, it is important to understand if groundwater aquifers are resilient to increasing water demands and whether they can recover from future drought events, or whether they will reach critical tipping points.
Using the global groundwater model GLOBGM1,2, a physically based groundwater model with a 1km spatial resolution, we assess the spatial pattern of global groundwater drought recovery and its potential drivers. We defined drought periods over the entire simulation period 1960-2019 and gathered additional drought characteristics, including the rate of drought development and recovery, drought duration, and drought intensity. Using these characteristics, we assessed spatial groundwater drought recovery patterns worldwide, finding that the average drought recovery rate is highly variable, not only between regions but also within them. Globally, we have identified four groundwater drought recovery regimes: resilient, stable, vulnerable, or unstable. These regimes are then linked to climatological, societal and geophysical drivers that describe the spatial recovery pattern. We observe that, as expected, climatology plays a key role, however on the local scale geophysical parameters are linked to local recovery patterns and highlight differences in recovery behaviour. Locations in the unstable recovery regime (approximately 26%) show a higher number of drought events, where pre- and post- conditions play a strong role relative to the other regimes. Locations within the vulnerable regime (approximately 15%) differ in terms of geophysical parameters, such as topography and groundwater storage characteristics. Furthermore, strong climate signals in these regions affect drought characteristics, including lower drought frequency and longer duration. High numbers of events, combined with faster development and post conditions, as well as higher groundwater conductivities, are standing out for locations within the resilient regime (approximately 57%).
Using this new recovery regime classification and information on drought recovery drivers can help society to potentially improve groundwater resilience to future droughts, as well as identify regions where tipping points are either exceeded or close.
1) Verkaik, J., Sutanudjaja, E. H., Oude Essink, G. H. P., Lin, H. X., and Bierkens, M. F. P. (2024) : GLOBGM v1.0: a parallel implementation of a 30 arcsec PCR-GLOBWB-MODFLOW global-scale groundwater model, Geosci. Model Dev., 17, 275–300, https://doi.org/10.5194/gmd-17-275-2024
2) van Jaarsveld, B., Wanders, N., Otoo, N.G., Sutanudjaja, E.H., Verkaik, J. Zamrsky, D. and Bierkens, M.F.P: Global hyper-resolution groundwater dataset for assessing historical and future groundwater dynamics. Submitted, Preprint, https://doi.org/10.31223/X5QX7W
How to cite: Hauswirth, S. M. and Wanders, N.: Patterns and drivers of global groundwater drought recovery based on recovery regime classifications, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6978, https://doi.org/10.5194/egusphere-egu26-6978, 2026.
Given the changes in precipitation and evaporation over the past 60 years and the expectation that the climate will continue to change, it is to be expected that groundwater heads will change in such a way that land use, infrastructure, ecology and water availability will be strongly impacted if the current water management is continued.
In order to assess the impact, the response of the groundwater system to precipitation and evaporation needs to be determined. Challenges are the inclusion of slow responses and capturing extremes. Responses in the order of decades often are not considered in groundwater modelling due to calibration periods shorter than 10 years and the time scale of impacts to be simulated. Capturing the level of high extremes is important for e.g. groundwater flooding. Capturing the level and duration of low extremes is needed for water availability and subsidence.
A case study from the Netherlands will be presented in which predictions until 2100 are made based on the climate scenarios from the Royal Dutch Meteorological Institute (KNMI) in combination with weather data and measured groundwater heads from a polder area in Friesland.
How to cite: Zaadnoordijk, W.: Long term time series modelling of groundwater heads for assessment of climate change impact, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1737, https://doi.org/10.5194/egusphere-egu26-1737, 2026.
Soil salinity distribution in cold regions is often affected by freeze-thaw processes, yet the influence of surface topography on salt transport dynamics remains poorly understood. Based on a validated numerical model, we investigate the effects of topography on salinity distribution under freeze-thaw conditions. Results show that freeze-thaw processes on a flat surface induce unstable convective fingering. In contrast, ridge-furrow topography promotes the development of stable salt plumes that preferentially form beneath surface depressions. Compared to the flat surface, ridge-furrow topography significantly accelerates downward salt transport following the thawing phase. Further quantitative analysis reveals that increasing ridge height promotes deeper vertical descent of high-salinity plumes and enhances the downward migration of the centroid of salt mass. These findings provide critical insights for understanding subsurface salinity dynamics and optimizing soil management in cold regions.
How to cite: Li, Y. and Yu, X.: Effects of topography on soil salinity distribution under freeze-thaw processes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9106, https://doi.org/10.5194/egusphere-egu26-9106, 2026.
As global extreme climates intensify, freeze-thaw dynamics in cold-region agricultural farmland have become increasingly complex, directly regulating soil water-heat-salt migration and salinization. While previous studies focused on 1-D vertical dynamics, 2-D processes remain unclear. Freezing induces water-salt movement from ditches to farmland, and the downward migration of meltwater elevates the groundwater table, thereby inducing drainage from farmland to ditches. Such asymmetric water-salt exchange, characterized by delayed responses to surface temperature, affects salt exclusion efficiency.This study used the SUTRA-MS-FT model to simulate freeze-thaw-affected farmland-ditch systems in salinized areas, exploring 2-D dynamics. Different desalination measures (varying salinity irrigation leaching and subsurface pipe drainage) were tested to analyze their sensitivity. The findings provide scientific support for water-salt regulation in cold-region farmlands.
How to cite: Tian, H.: Freeze-thaw processes influence soil water and salt migration in farmlands, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9278, https://doi.org/10.5194/egusphere-egu26-9278, 2026.
Recent years have highlighted Europe’s increasing vulnerability to climate change through the rising frequency and severity of extreme hydrological events, such as droughts and floods. In addition, winter warming and gradual decline in snow cover depth and duration have occurred in northern Europe since the middle of the 20th century. These changes not only affect surface waters directly but also alter groundwater recharge patterns and disrupt the balance between surface and subsurface hydrological systems.
To support effective water resource management under future climate conditions, it is essential to understand how projected climatic changes will influence surface–groundwater interactions. However, predictions of future dynamics are not possible without first analysing how past and ongoing climate changes have already affected key components of the hydrological regime, including groundwater recharge, runoff generation, and their relative contributions to total flow.
In Estonia, this need is being addressed through the development of coupled surface–groundwater models in five pilot areas across the country, as part of the LIFE-SIP AdaptEST project. The overarching goal is to increase the readiness and adaptive capacity of regional and local authorities in Estonia to respond to the impacts of climate change.
The objective of this study was to assess the impact of climate change during the 20th century on surface–groundwater interactions in Southern Estonia. A hydrological model, PRMS (Precipitation-Runoff Modeling System), was applied to a small pilot catchment in Southern Estonia characterized by a high baseflow component and pronounced surface–groundwater interaction. The model was calibrated and validated for the period 1952–2017 using measured hydro-meteorological data. Model performance, evaluated using the Kling–Gupta efficiency, ranged between 0.56 and 0.77, indicating a satisfactory representation of hydrological processes and surface–groundwater interactions. The interpretation of the model results shows how changes in climatic parameters (air temperature, precipitation amounts) in the past have brought about parallel changes in river runoff regime (e.g. timing of low-flow and high-flow periods) as well as in baseflow and groundwater recharge. The results indicate that the applied surface water modelling approach provides a suitable basis for coupling with groundwater models and for future climate change impact assessments in Estonia.
This study has been funded by the project LIFE21-IPC-EE-LIFE-SIP AdaptEST/101069566 "Implementation of national climate change adaptation activities in Estonia”.
How to cite: Eensoo, A., Hunt, M., and Pärn, J.: Assessing 20th Century Climate Change Impacts on Surface–Groundwater Interactions in Southern Estonia, Northeastern Europe, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11050, https://doi.org/10.5194/egusphere-egu26-11050, 2026.
Coastal aquifers are hydraulically connected to the sea, making them highly sensitive to storm-induced disturbances; however, the impacts of tropical cyclones on surface water-groundwater (SW–GW) interactions remain poorly understood. This study has investigated the impact of short-term climate extremes specifically cyclone-induced storm surges on coastal aquifer systems along India’s eastern coastal regions in Nizampatnam Andhra Pradesh (Tropical cyclone Dana, May 2024) and in Sundarbans of Ganges delta front (Tropical cyclone Bulbul, November 2019) adjoining to Bay of Bengal. The study has incorporated a field-laboratory, isotopic, and multivariate statistical observations-based approaches to assess and compare the influence of storm-driven impacts on groundwater level (GWL) and displacement of toxic solutes in porewater which eventually hampered the SW-GW interaction processes across the regions. Results revealed a positive relationship between cyclonic translation speed, rainfall intensity, and GWL response, especially in lithologically conductive aquifers. In Sundarbans, the storm surge was associated with increased GWL, enhanced salinity, and the downward transport of surface-derived contaminants into groundwater. In addition, wave surges produced instantaneous, rapid, and synchronous GWL fluctuations across all aquifer depths in Sundarbans. Whereas in Nizampatnam, cyclone-induced atmospheric pressure decline and storm surge caused transient offshore displacement of the SW–GW interface, enhancing fresh groundwater discharge, as indicated by depleted δ¹⁸O elevated ²²²Rn, and reduced salinity. The duration of SW–GW system re-stabilization varies widely from weeks to several years and is strongly controlled by local hydrogeological conditions and storm intensity. Therefore, the findings highlight the growing vulnerability of coastal groundwater resources under increasing storm frequency and intensity, emphasizing the need for proactive management strategies to ensure freshwater sustainability to achieve SDG-6 in a changing climate.
Keywords: Coastal aquifer; Groundwater Level; Porewater; Tropical Cyclone; SW-GW Interaction; SDG-6
How to cite: Das, K.: Influence of Short-Term Climate Extremes on Surface Water-Groundwater Interaction: A Regional Perspective on Drinking Water Vulnerability, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16368, https://doi.org/10.5194/egusphere-egu26-16368, 2026.
Shallow groundwater levels in lowland catchments are highly sensitive to geological heterogeneity, climate variability and human activities. The town of Bylderup-Bov (southern Jutland, Denmark) is characterized by persistently high groundwater tables, especially in winter months, resulting in recurrent basement inundation and excessive inflow of groundwater into the wastewater system. After a major renovation of the sewer system in 2014-2016, groundwater intrusion into the sewer system remains substantial, leading to wastewater volumes up to five times higher than expected.
This study investigates the controls on shallow groundwater dynamics in and around Bylderup-Bov using a catchment scale hydrological modelling approach evaluating the effects of different hydrogeological and anthropogenic factors. To do this, a suite of scenario simulations was used to quantify the effects of (i) local stream geometry, levels and resistance, (ii) drainage efficiency and depth, (iii) changes in groundwater recharge related to urban development, (iv) groundwater abstraction, (v) restoration of surrounding lowland peat areas, and (vi) projected climate change.
Model results show that drainage depth and drainage efficiency are the most influential parameters controlling groundwater levels within the urban area of Bylderup-Bov, lowering the groundwater table by up to 50 to 75 cm during critical winter periods. Stream depths affect groundwater levels by lowering levels up to 10 to -30 cm over large parts of the town, indicating strong lateral groundwater surface–water connectivity controlled by geological layering. In contrast, climate change scenarios based on three regional climate models indicate only modest increase in mean groundwater levels (+0 to +10 cm by 2071–2100), suggesting that recent groundwater rise is unlikely to be primarily climate-driven. Scenarios introducing enhanced groundwater recharge through local infiltration measures further exacerbate high groundwater conditions during already critical wet winter periods.
The findings demonstrate that shallow groundwater dynamics in the study area, are governed primarily by anthropogenic drainage and subsurface connectivity rather than climate change alone. Detailed urban hydrological modelling provides valuable insights for identifying effective mitigation strategies, avoid maladaptation, and supporting groundwater management under future climatic and land-use change.
How to cite: Gulfeldt, J., Kidmose, J., and Sonnenborg, T.: Identifying controls on shallow groundwater levels in a lowland urban catchment: a scenario-based approach, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10590, https://doi.org/10.5194/egusphere-egu26-10590, 2026.
The Ningnan region, located in the Jinsha River hot-dry valley of southwest China, faces severe groundwater scarcity and declining water levels, threatening local production and daily life. This study investigates the drought characteristics and mechanisms of groundwater resources under the combined impacts of climate change and tunnel construction, addressing the limitation of traditional single-factor assessments.
Field surveys, remote sensing interpretation, hydrochemical and isotopic analyses were conducted to clarify groundwater occurrence, recharge-discharge processes, and karst development. Climate data statistics, NDVI-based vegetation coverage analysis, and analytical calculations were used to quantify the impacts of these factors. A 3D "climate-groundwater-tunnel" coupled seepage model (Visual MODFLOW) was established to simulate the evolution of the seepage field.
Key findings: (1) Groundwater is dominated by carbonate karst water, with atmospheric precipitation as the primary recharge source. (2) Annual precipitation decreased by 46.17% from 2020 to 2023, while vegetation coverage (exceeding 50%) dropped by 16.47% from 2019 to 2024. (3) Water inflow of the tunnel group ranged from 4537.47 to 63051.93 m³/d, with a maximum impact radius of up to 8806.98 m. (4) Numerical simulation showed that natural groundwater levels declined by 0.5–7.5 m due to drought; tunnel construction caused maximum drawdowns of 130 m (Ningnan Tunnel) and 200 m (Ningqiao Tunnel). (5) A survey of 47 typical points indicated that 66% experienced moderate to severe drought, 71.4% of which were jointly affected by tunnel drainage and reduced precipitation.
Conclusion: Groundwater drought within tunnel impact zones results from the combined effects of climate change and human activities, while areas outside the zones are mainly affected by climate change. This study provides a theoretical basis for groundwater protection and restoration in the Ningnan region.
How to cite: Zhang, Q., Wang, W., and Sun, J.: Drought Analysis of Groundwater Resources in the Ningnan Region Under the Combined Effects of Climate Change and Human Activities, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7632, https://doi.org/10.5194/egusphere-egu26-7632, 2026.
Extreme hydroclimatic events are increasingly challenging groundwater security, especially in intensively exploited regions; yet, the recovery dynamics of aquifer systems after prolonged drought events remain poorly quantified. This study investigates the response and recovery times of the multi-layered aquifer system in Emilia-Romagna region (north-eastern Italy), one of the country’s most populated and productive areas. We analyze how climatic stressors and anthropogenic pressures shape groundwater head decline and post-drought rebound, comparing the results provided by a numerical groundwater flow model implemented in MODFLOW 6, and by a random forest algorithm.
Both models are calibrated over the years 2010-2018 to reproduce the historical evolution of groundwater heads across the regional aquifer system. A scenario analysis is then carried out from 2019 to 2050, imposing a set of drought conditions characterized by reductions in precipitation and varied groundwater abstractions. These scenarios represent short- and long- duration low-recharge periods with different levels of stress intensity, enabling a systematic exploration of aquifer system’s behaviour under combined climatic and anthropogenic forcing.
Groundwater recovery is assessed through the analysis of groundwater heads simulated by both modeling approaches. This study provides quantitative insights into the resilience of the regional multi-layered aquifer system to extreme hydroclimatic events and aims at clarifying the respective roles of climate variability and groundwater exploitation in shaping future groundwater security. In particular, the goals are to quantify (i) the mean recovery time following each drought scenario as a function of its duration and intensity, (ii) the relative contribution of abstraction changes to driving groundwater decline and delaying recovery, and (iii) the sensitivity of recovery times to different input variables. Finally, we aim to assess the extent to which the random forest algorithm can replicate the physics-based model under unseen future scenarios, identifying conditions in which data-driven approaches may complement or, in specific context, substitute numerical groundwater models.
Results show that recovery times are strongly dependent on the imposed precipitation reduction and are often markedly influenced by pumping regimes, which can exert a dominant control on the system. The random forest model accurately reproduces system dynamics under conditions similar to the calibration period but shows reduced reliability under extreme scenarios. Overall, the results highlight the need to carefully account for both climatic variability and human-driven pressures when evaluating future groundwater resilience, and underscore the value of integrating complementary modeling approaches to improve groundwater management strategies under increasing hydroclimatic uncertainty.
How to cite: Delfini, I., Zamrsky, D., and Montanari, A.: Quantifying groundwater recovery after drought: a comparative modelling study in the Emilia-Romagna multi-layered aquifer system, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1171, https://doi.org/10.5194/egusphere-egu26-1171, 2026.
