Environmental change further introduces significant non‑stationarity into aquifer systems, reshaping the resilience of groundwater‑dependent ecosystems and the services they provide. Identifying and predicting these dynamics calls for integrating local-scale field observations, long‑term monitoring, spatial mapping of GDEs, geophysical imaging and advanced modelling from plant to regional scales. Emerging hydrogeophysical tools, such as full‑waveform inversion, distributed temperature sensing, or 3D geostatistical characterisation, as well as transient ecohydrogeological modelling, play a growing role in detecting ecosystem-groundwater interactions, quantifying subsurface heterogeneity and flow pathways, and improving process scaling and predictive capacity.
Relative to lowland systems, alpine hydrological systems face more rapid and impactful changes due to climate change. In this context of altered meteorological patterns, including decreased snow cover and greater variations in precipitation timing, groundwater’s hydrological buffering role is becoming increasingly significant. A multi-method research approach applied in the Vallon de Réchy reserve (Valais Alps, Switzerland) has provided us with new insights into groundwater as a key component of alpine hydrological systems.
The Vallon de Réchy (2182-3149 m.a.s.l., 11 km²) is a non-glaciated, nival-regime alpine headwater catchment with strong elevation gradients and highly heterogeneous geology. Much of our detailed process understanding comes from extensive work in a specific zone, the Tsalet subcatchment (2268-2893 m.a.s.l., 1 km²), where intermittent streams, perennial springs, and extensive unconsolidated sediments have made it a natural laboratory for studying alpine groundwater, developing hydrogeophysical methods, and investigating climate-change sensitivity.
Our hydrological, geochemical, and geophysical investigations reveal a highly heterogeneous system in which unconfined aquifers act as hydrological buffers to ensure year-round streamflow. Geochemical and stable isotope analyses provide us with information on the connectivity of different components of the system, as well as variations of end-member contributions to streamflow. By integrating hydrological observations and electrical resistivity tomography (ERT) measurements into numerical models, we have investigated the impacts of climate change on this hydrological system, finding that the currently perennial stream could eventually become intermittent. The site has also played a key role in the development of time-lapse gravimetry (TLG), a non-invasive geophysical method, as a tool for under-monitored hydrogeological systems in mountain regions. TLG has provided unique, quantitative data on seasonal variations in groundwater storage that would be extremely challenging and costly to obtain through traditional methods. While alpine catchments are undoubtedly highly varied, investigations in the Vallon de Réchy integrate novel monitoring approaches that provide evidence for the importance and finite resilience of groundwater as a vital component of alpine headwater catchments.
How to cite: Halloran, L. J. S., Carron, A., Arnoux, M., Mohammadi, N., Berdat, E., Makkinga, N., Magnenat, C., Figueroa, R., and Millwater, J.: The present and future of alpine groundwater dynamics: Lessons from the Vallon de Réchy (Switzerland) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4876, https://doi.org/10.5194/egusphere-egu26-4876, 2026.
Accurate characterization of the critical zone architecture is fundamental to physically based hydrologic modeling, yet resolving the complex geometry of subsurface boundaries remains a significant challenge. Critical zone seismic studies have predominantly used First-Arrival Traveltime (FAT) tomography, yet this method lacks the resolution to characterize heterogeneity at hydrologically relevant scales, leaving a gap in our understanding of how subsurface structure governs flow routing and storage. Full-Waveform Inversion (FWI) overcomes these limitations by utilizing the complete seismic wavefield to resolve fine-scale subsurface architecture. We compare 2D hydrologic modeling informed by subsurface structures from FAT and FWI. The FAT model yields smooth, layered velocity gradients, whereas FWI reveals pronounced heterogeneity, including depth-to-bedrock variations and steep low-velocity anomalies. We integrated both structures into ParFlow-CLM with consistent hydrologic properties and NLDAS meteorological forcing them to isolate the effects of subsurface geometry. Results show that while annual water budgets remain similar, reflecting comparable mean regolith and fractured bedrock depths, internal flow dynamics diverge markedly. The rugged bedrock topography resolved by FWI imposes geometric control on flow routing: infiltrating water fills deep bedrock troughs before lateral flow initiates, producing a "fill-and-spill" mechanism. These deep troughs act as subsurface reservoirs, temporarily storing water and extending drainage timescales. Consequently, the FWI-informed model buffers hydrologic response, generating a smoother hydrograph with attenuated peaks and sustained baseflow, whereas the FAT model exhibits rapid lateral drainage and flashier storm response. These findings demonstrate that smoothing subsurface heterogeneity in hydrologic models may mask critical storage dynamics and bias estimates of catchment response times.
How to cite: Xiong, C., Holbrook, S., Eppinger, B., and Chen, H.: Full-Waveform Inversion–Informed Hydrologic Modeling Reveals Bedrock Heterogeneity Controls Flow Dynamics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6158, https://doi.org/10.5194/egusphere-egu26-6158, 2026.
Quantifying water and heat fluxes at the interface between surface water (SW), groundwater (GW), and the vadose zone (VZ) is critical for sustainable water and energy resource management under global change. Direct field measurements are challenging because SW–GW exchanges depend on initial and boundary conditions and the spatial distribution of hydrofacies, which are often poorly constrained. Usually, these fluxes are estimated by calibrating models using classical data like hydraulic heads and river discharge. But it is well known that these data did not get enough information to constrain these fluxes. To overcome the lack of direct in situ data, de Marsily et al., (2005) and Schilling et al., (2019) suggested to couple the classical observations with unconventional data such as the geophysical surveys, for instance successfully applied in the context of SW-GW exchanges by Dangeard et al., (2021). Binley et al., (2015), in their comprehensive review, highlighted the robustness of geophysical methods for imaging subsurface structures and estimating saturation profiles, reinforcing their role as essential tools for characterizing vadose zone processes.
This study develops a transient, process-based hydrogeophysical forward model that integrates hydrological and geophysical processes. The geophysical methods used in this study are electrical resistivity tomography (ERT), seismic methods, and heat tracing, applied as complementary approaches to characterize vadose zone dynamics and link hydrological processes to geophysical data. The hydrological model (Rivière et al., 2020) rigorously solves Richards’ equation coupled with heat transport—simulating variably saturated water and thermal fluxes in porous media under transient conditions—and was validated with experimental and field data to explore the variability of saturated flow and heat fluxes. The seismic model, based on Solazzi et al., (2021) uses the Hertz-Mindlin contact theory combined with the Biot-Gassmann model and simulates the influence of capillary suction with a transient method. The electrical model uses the Waxman-Smits petrophysical law to quantify electrical conductivity of the soil. The outputs of the hydrological model are coupled with geophysical forward models to compute synthetic geophysical models (P and S wave velocity, electrical resistivity) and associated data (more particularly surface wave phase velocity, apparent electrical resistivity); as well as heat tracing signals). The synthetic case considered in this study is a 1D soil column, subjected to seasonal variations in precipitation and temperature, to analyze the resulting dynamics and their geophysical data.
Testing this integrated model under typical spring conditions in the Paris Basin demonstrates:
- The added value of transient modeling for interpreting geophysical data.
- Sensitivity of seismic and electrical responses to soil saturation and pressure changes, even without water table fluctuations.
- The influence of past infiltration events on geophysical survey interpretation.
This approach provides new insights into VZ functioning and strengthens the link between hydrological processes and geophysical signatures, paving the way for improved characterization of subsurface dynamics under global changes.
How to cite: Radic, N., Rivière, A., Bodet, L., Gesret, A., Gautier, M., Pasquet, S., and Martin, R.: Integrating Transient Hydrogeology Models for Enhanced Interpretation of Geophysical Data in the Vadose Zone, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10002, https://doi.org/10.5194/egusphere-egu26-10002, 2026.
Groundwater is irreplaceable in sustaining populations, maintaining agriculture, and supporting socioeconomic development, especially in arid and semi-arid regions where surface water is limited. However, a comprehensive understanding of groundwater table depth (WTD) changes across China remains constrained, especially following large-scale water management. Here, we present a monthly 0.1° resolution WTD dataset for China from 2005 to 2021, built by random forests using 470,967 monthly measurements from 9,011 stations and 25 predictors across topographic, geological, environmental, and anthropogenic categories. Validation results for nine river basins using testing dataset and compared with the published regional GWD data indicated that the constructed models exhibited reasonable performance, with high R2 (0.85 to 0.95, median 0.89) and low RMSE (2.11 to 13.44, median 3.82). Nationally, WTD is generally shallow in the southeastern regions and deep in the northwest, with a non-significant increasing trend of 3.79×10-3 m/year over the study period. Spatially, WTD experienced significant increases in the Huaihe and Yellow River basins, while exhibiting apparent decreases in the Yangtze and Southeast River basins. With the implementation of a series of water management strategies, such as the designation of groundwater extraction prohibited areas, the operation of the South-to-North Water Diversion Project in late 2013, the WTD in North China Plain's cities such as Beijing and Tianjin had decreased significantly, indicating groundwater table recovery. Similarly, through adjustments in planting structure and irrigation practices, cropland WTD in North China Plain decreased significantly from 2014-2021. These findings highlight the positive impact of the enacted series of water management measures on the recovery of WTD in urban and agricultural regions. Our study provides a high spatiotemporal groundwater table depth dataset for China, offering valuable insights for optimizing water management and enhancing groundwater protection strategies.
How to cite: He, X. and He, B.: High-resolution reconstruction of groundwater table depth in China (2005–2021): evidence for recovery under large-scale water management, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8779, https://doi.org/10.5194/egusphere-egu26-8779, 2026.
The Doongmabulla Springs Complex (DSC) in Central Queensland, Australia, consists of over 160 individual springs ranging from vents less than 10 cm across supporting individual tussocks of grass to wetlands over 9 hectares with permanent pools of water. These unique springs are home to a variety of plant species (many endemic) that are specially adapted to the varied physical, chemical and hydraulic conditions of the local environment and the groundwater discharge on which they rely.
We have examined these springs across multiple spatial and temporal scales, using remote and field data acquisition techniques, to develop a detailed understanding of the water, soil and floristic characteristics and dynamics at a selection of these springs, quantifying spring extents and changes over time as well as documenting species zonation and vegetation dynamics related to seasonal and climatic variability and the local physico-chemical conditions. From these targeted studies we can interpolate and extrapolate to the other springs in the complex and identify where additional studies may be required to fill data gaps.
Critically, local multi-spectral and thermal drone imagery has augmented regional satellite imagery to constrain spatial discharge patterns of springs and provides spatial linkages that complement visual images taken at the same time. On-ground surveys have identified new springs in some areas and loss of others and can be linked to regolith variability and sub-surface source aquifer pressure controls. The thermal imagery provides a platform to observe and quantify spring discharge changes season to season. Spot sampling of surface waters and groundwater highlights inter-seasonal variability in water source chemistry, whilst isotopes highlight the changing importance of groundwater for maintenance of groundwater discharge and consequent support of spring health. Notably, water samples taken for chemical and isotopic analysis included run-of-river Radon-222 analysis that helps highlight the groundwater discharge constrains.
Underpinning the local-scale observations, regional groundwater pressures define the dynamics of the source waters, though spatially disparate bore data must be complemented by modelling interpolations. The multi-dimensional conceptualisation thus informs, and is informed by, a regional numerical groundwater model and links the regional observations with local-scale, spring-specific eco-hydrological modelling, which is described in a companion paper (Gibson, et al. these proceedings).
The DSC conceptualisation must be coherent at all spatial and temporal scales and then it can be used to customise mitigation responses at individual springs based on groundwater impact modelling considering potential changes from climate change and local mining activities.
How to cite: Cresswell, R., Gibson, A., Short, M., Pyrke, S., Bathgate, E., Yeates, M., Lloyd, P., and Stanton, D.: Multiple lines of evidence provide a holistic and testable conceptualisation of complex ecosystem-groundwater dynamics at the Doongmabulla Springs Complex, Queensland, Australia , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15005, https://doi.org/10.5194/egusphere-egu26-15005, 2026.
Groundwater fauna play an important role in subterranean aquatic ecosystems. In urban areas, their habitats are shaped not only by hydrogeological conditions but also by stressors such as elevated groundwater temperatures and oxygen depletion. However, the combined effects of urbanisation and geological factors on groundwater fauna remain poorly understood.
To characterise urban influences and contrast them with hydrogeological controls, abiotic and faunal data were collected from 91 groundwater monitoring wells in Halle (Saale) over the course of one year, comprising five measurement campaigns. Both the urban area and the surrounding rural region were investigated. The hydrogeological setting of the city is highly variable due to diverse near-surface geological formations, resulting in multiple aquifer types across several hydrostratigraphic units.
The urban gradient was characterised by elevated temperatures (>12 °C) in the city centre, while differences in dissolved oxygen (DO) and dissolved organic carbon (DOC) reflected both urban and hydrogeological influences. Spatial patterns were evident in the regional variation of faunal community composition. However, these patterns did not clearly correspond to contrasts between urban and rural areas or to specific aquifer types. Instead, fauna in near-surface aquifers were more strongly influenced by hydraulic conductivity and groundwater depth. Crustaceans were primarily found at wells with groundwater levels shallower than 6 m, whereas worms (Oligochaeta, Polychaeta, Platyhelminthes) dominated at wells with deeper groundwater levels.
The abundance of stygofauna and the number of taxonomic groups showed significant, albeit weak, correlations with redox-relevant parameters (DO, Eh, NH₄⁺, NO₃⁻ and DOC), with higher DO concentrations generally being associated with higher abundance and diversity. We also observed a weak negative correlation with temperature, which was particularly pronounced in combination with low DO concentrations.
These findings demonstrate the necessity for an integrative approach to assessing complex urban groundwater ecosystems, taking into account the interactions between abiotic and biotic factors within the context of the respective hydrogeological setting.
How to cite: Meyer, L., Griebler, C., Herrmann, M., and Bayer, P.: Disentangling urban and hydrogeological influences on groundwater fauna in Halle (Saale) , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9931, https://doi.org/10.5194/egusphere-egu26-9931, 2026.
Accurate representation of evapotranspiration (ET) and plant water stress is essential for understanding ecosystem resilience to hydroclimatic variability. However, most land surface and Earth System Models infer vegetation stress primarily from shallow soil moisture, implicitly assuming that declining surface water availability directly translates into physiological limitation. This assumption fails in ecosystems where vegetation can access deeper stored water, such as groundwater, leading to systematic mischaracterization of water stress and ecosystem functioning during dry periods.
Here we present a physics-based ecohydrology model that represents root water uptake as an emergent process governed by soil–plant–atmosphere water potential gradients, allowing plants to dynamically shift water sources between shallow soil and deeper reservoirs. This framework captures how access to groundwater modifies plant hydraulic status and regulates water stress across seasonal, interannual, and long-term drying. Applied to oak savanna ecosystems, the model reveals distinct uptake regimes in which groundwater increasingly contributes to transpiration as surface soils dry, buffering ET during dry seasons when shallow soil moisture alone would predict strong limitation.
Our results show that groundwater access fundamentally alters ecosystem stress trajectories, delaying the onset of hydraulic limitation and reducing ET sensitivity to surface drying. Water table depth emerges as a key control on the degree of buffering, highlighting feedbacks between rooting strategies, subsurface water availability, and ecosystem resilience. We further demonstrate that stress metrics based solely on shallow soil moisture substantially overestimate drought impacts in systems sustained by deeper water sources.
By providing a reduced-order representation of ET that explicitly accounts for both soil moisture and groundwater availability, this work offers a pathway to improve model representations of plant water stress and evapotranspiration in ecosystems sustained by deep water storage under a changing climate.
How to cite: Cerasoli, S. and Terrer, C.: Groundwater access modulates plant water stress and evapotranspiration in water-limited ecosystems , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12822, https://doi.org/10.5194/egusphere-egu26-12822, 2026.
In Mongolia, the traditional pastoral system has changed by the overuse and degradation of water resources. Currently, there is a research gap between the socio-economic transition and ecosystem degradation on the existing knowledge. In the present study, a process-based eco-hydrology model, NICE (National Integrated Catchment-based Eco-hydrology) (Nakayama et al., 2021a, 2021b, 2023), was applied to the total of 29 river basins in the entire country to quantify the heterogeneous distribution of livestock water use and its relation to pasture degradation there (Nakayama, 2025). The authors also evaluated the change of grassland carrying capacity and carrying status index during the last few decades (Yan et al., 2023). The result showed that the livestock water use in entire basins was the same order of magnitude as mining and urban water uses and that the estimated total water use was similar to that on constant assumption in the previous study. In addition, the simulation also clarified heterogeneous distributions of water uses of 5 types of typical livestock and higher water use in the central part of the country. However, the carrying status index showed more serious situation of overgrazing in the transitional zone between grassland and the Gobi desert. This means that the excessive use of water resources is indirectly related to the degradation of natural vegetation in grassland. These results also imply that the excessive use of livestock water intake can lead to groundwater decline, grassland degradation, and ultimately a reduction in the amount of water available to each livestock head. This methodology is effective to evaluate the grassland carrying capacity and its constraint of water resources (Lu et al., 2020), and to propose solutions to unsustainable pastoral land use patterns.
References
Lu, H., et al. 2020. Environmental Science and Pollution Research, 27, 10328-10341, doi:10.1007/s11356-019-07559-9.
Nakayama, T., et al. 2021a. Ecological Modelling, 440, 109404, doi:10.1016/j.ecolmodel.2020.109404.
Nakayama, T., et al. 2021b. Ecohydrology & Hydrobiology, 21(3), 490-500, doi:10.1016/j.ecohyd.2021.07.006.
Nakayama, T., et al. 2023. Ecohydrology & Hydrobiology, 23(4), 542-553, doi:10.1016/j.ecohyd.2023.04.006.
Nakayama, T. 2025. Environmental Science and Pollution Research, 32, 13626-13637, doi:10.1007/s11356-025-36083-2.
Yan, N., et al. 2023. Ecological Indicators, 146, 109868, doi:10.1016/j.ecolind.2023.109868.
How to cite: Nakayama, T., Wang, Q., and Okadera, T.: Evaluation of grassland carrying capacity and its constraint of water resources in Mongolia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15036, https://doi.org/10.5194/egusphere-egu26-15036, 2026.
Groundwater-dependent ecosystems (GDEs) are hotspots of biodiversity and ecosystem functioning, but are increasingly threatened globally from multiple stressors including land conversion, water diversion and climate change. Protecting these valuable and vulnerable ecosystems has been challenging historically because they are difficult to identify and delineate due to their diverse composition and typically small area (e.g., narrow and irregular riparian zones). Recent advances in remote sensing, machine learning and big data statistical methods have greatly improved our ability to detect GDEs, which is a critical step toward protecting and restoring them. In this talk we summarize some emerging approaches, including novel integration of public datasets, phenological image analysis, dendroisotope series, standardized threshold analysis, and cloud computing. These approaches collectively provide a set of tools for mapping GDEs globally and in assessing their impacts from changes in climate and groundwater. We discuss applications of these tools to policy and management challenges, including the Clean Water Act (USA) and the EU Water Framework Directive.
How to cite: Stella, J., Rohde, M., Ruhi, A., Williams, J., McMahon, C., Kibler, C., Mohammadi, R., Zhao, Y., Pentico, R., Lambert, A., Roberts, D., Singer, M., and Caylor, K.: Emerging Tools to Identify and Assess Impacts to Groundwater-Dependent Ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22184, https://doi.org/10.5194/egusphere-egu26-22184, 2026.
Monitoring groundwater-dependent wetlands at a national scale: lessons from England's first strategic network.
1Elena Armenise, 1 * Mario Manganaro, Sharon Thomas
*Corresponding author
1Environment Agency, Horizon House, Deanery Road, Bristol, BS1 5AH, UK
Abstract:
Recognising the critical role of monitoring in preserving groundwater dependent terrestrial ecosystems (GWDTEs) and the ecosystem services they provide, the Environment Agency is establishing the first national monitoring network for GWDTEs in England. This work forms part of the government-led Natural Capital and Ecosystem Assessment (NCEA) programme, which aims to place nature at the core of decision-making by embedding natural capital evidence into policy and investment strategies.
The network was designed using advanced statistical methods to ensure unbiased site selection and provide statistically robust data on the condition of GWDTEs in England. Specifically, we adopted the Generalised Random Tessellation Stratified (GRTS) sampling, a spatially balanced probabilistic design that provides random site selection while ensuring sampling locations are evenly distributed across the study area. This approach minimises clustering of sites and maximises environmental representativeness, making it ideal for large-scale environmental monitoring.
To validate the design, we conducted a simulation based power analysis to determine the survey effort required to detect ecologically meaningful changes. Results show that the current design achieves ≥70% power to detect medium trends (~3.5% annual change) in groundwater level metrics and wetland quality within 13/15 years, confirming its suitability for long term surveillance. Detecting small changes would require more than 60 sites and over 20 years, which is impractical, but the network is well-suited for detecting meaningful trends within realistic timeframes.
This presentation will outline the GWDTE monitoring network design principles and implementation challenges. We will cover how operational constraints required pragmatic adjustments to maintain spatial coverage while preserving representativeness. The network will provide a foundation for long-term surveillance of wetland condition in England delivering meaningful data to support future national policy. All monitoring data will made openly available in December 2026, supporting research and policy applications.
How to cite: Manganaro, M., Armenise, E., and Thomas, S.: Monitoring groundwater-dependent wetlands at a national scale: lessons from England's first strategic network., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21899, https://doi.org/10.5194/egusphere-egu26-21899, 2026.
Aquifers and karst springs are among the most studied and challenging topics of hydrogeology in recent years. They are difficult to model due to the aquifer's heterogeneity and anisotropy, as well as the difficulties of conventional monitoring. However, they are among the most important groundwater resources, accounting for a significant portion of freshwater intended for human consumption, especially in the EU.
The study area is located in the Umbria Region in central Italy and is characterised by an elongated carbonate ridge formed by a multilayered karstified carbonate succession, locally separated by marly interbeds. Groundwater circulation is controlled by Apennine tectonics, with faults either enhancing or limiting hydraulic connectivity between hydrogeological units. Recharge occurs predominantly through diffuse but also local infiltration over carbonate outcrops and high plains.
This study contributes to the understanding of hydrogeological functioning by integrating long-term monitoring data (more than 20 years) of discharge and rainfall with numerical modelling.
The data reveal that the karst system exhibits highly complex hydrological behaviour, and the distinctive hydrograph shapes observed for certain springs are attributed to direct surface water inputs entering the system through local sinkholes. Modkarst Model that was applied to six major karst springs, allowed the quantification of surface water contribution.
This work highlights that effective management of karst aquifers under increasing climate change effects that usually requires integrated approaches combining geological understanding, continuous monitoring, and modelling.
How to cite: Katsanou, K., De Filippi, F., Maramathas, A., Sappa, G., and Lambrakis, N.: Identifying the recharge processes of karst aquifer in Umbria (Central Italy) using long-term monitoring data and Modkarst Model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22234, https://doi.org/10.5194/egusphere-egu26-22234, 2026.
The Wüstebach stream is a headwater stream with a 38.5 ha catchment located in the Eifel National Park, Germany, and is part of the TERENO Eifel Lower Rhine Valley Observatory.
Surface water temperature was measured since October 2023 along a 293 m reach of the Wüstebach Stream with a spatial resolution of 25 cm and at 15 min intervals using a Fibre Optic Distributed Temperature Sensing (FO-DTS) connected to a Silixa XT-DTS. In April 2024, the length of the FO was extended to 440 m. The presence of a series of monitoring devices and sharp elevation changes in the stream bed led to the partial exposure of the FO cable to the atmosphere in specific locations. Moreover, the fluctuations of the water level caused intermittent exposure of the cable in a series of locations, which vary in time and space. Atmosphere-exposed sections produce erroneous temperature data, which must be carefully filtered out from the dataset to capture the actual spatial and temporal variability of stream temperature. Moreover, radiative effects from cable sections exposed to the atmosphere can also affect temperature measurements in adjacent points. Manually filtering such a large dataset is not feasible and requires an automated approach.
This work presents a methodology for filtering FO-DTS data in space and time that uses the median daily temperature range as a core metric to identify areas of the FO exposed to the atmosphere. Additionally, screening methodologies such as spectral analysis for the identification of changes in temperature fluctuation due to groundwater contribution are applied and discussed.
How to cite: Cattapan, A., Vis, G., Katsanou, K., Venneker, R., Bol, R., and Wenninger, J.: Filtering and Analysing Distributed Temperature Sensing Data: lessons learnt from the Wüstebach headwater stream, Germany, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22249, https://doi.org/10.5194/egusphere-egu26-22249, 2026.
An increasing number of critical zone models are seeking to capture hydrological dynamics in an integrative fashion, reconciling water dynamics at multiple scales, and capture reciprocal linkage with plant dynamics. EcH2O-iso (Kuppel et al., 2018) is such a numerical tool, where a process based, fully distributed formulation has been balanced with computational efficiency using a simplified formulation of subsurface water dynamics: three layers where top-layer infiltration is described using the Green-Ampt approach, while vertical water travel to deeper layers is gravity-driven, all using a saturation dependent hydraulic conductivity. This approach is sequential within grid cells and along the lateral drainage network, providing a fast, robust, and stable water budget. While this formulation has been successful in capturing ecohydrological dynamics (including that of isotopes tracers) in a variety of critical zone settings, gravity-driven percolation has failed to reproduce finer dynamics in some critical zone observatories displaying arid conditions and thick vadose zone (several tens of meters).
In this work, we add the possibility of considering a vertical dynamical water fluxes exchange between the layers using the Richards equation. The simulations are performed on a single pixel in order to focus on the importance of the subsurface water flux dynamics on the vertical axis only. The implementation of the Richards equation is based on the numerical resolution of Ross (2003). The resolution makes use of the Kirchhoff transform to increase the speed and the stability of the solution. The Brooks and Corey retention curve parameters are used for the resolution as it is in the original EcH2O-iso model. The resolution of Ross (2003) is also usable for heterogeneous soils and provides a solution for the advection-dispersion equation for solute transport. The latter features paves the way for future work, including the tracer module implemented isotopy tracking in EcH2O-iso. The fact that both the original (sequential) and current (dynamical) vertical routines are available as options in the same critical model allows for a direct benchmarking of performances and computing in a flexible comparison of the consequences of such different approaches of the subsurface flux modelling. We first validated the implementation of unsaturated zone representation thanks to standard 1D benchmarks. The impact of the new vertical routing scheme in EcH2O-iso is then evaluated in a deeply weathered profile in a dry tropical forest where a calibration of hydrodynamic parameters had been previously carried out with the sequential routing version of the model. Finally, at the same site, the newly-implement dynamical approach is used to perform a sensitivity analysis and a calibration of the parameters over a large number of simulations, and compared again to the performances of the sequential-base model.
References
Kuppel, S. et al : EcH2O-iso 1.0: water isotopes and age tracking in a process-based, distributed ecohydrological model, Geosci. Model Dev., 2018.
Ross, P. J.: Modeling soil water and solute transport - Fast, simplified numerical solutions, Agronomy Journal, 2003.
How to cite: Fuseau, D., Kuppel, S., Riviere, A., Weill, S., Marcais, J., and Braud, I.: Impact of the representation of water transfer in the unsaturated zone on water flux in a ecohydrological critical zone model., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14308, https://doi.org/10.5194/egusphere-egu26-14308, 2026.
Hillslope groundwater in the critical zone (CZ) links subsurface water storage, hydrologic connectivity, and chemical export, yet its concentration–discharge (C–Q) relationships remain poorly constrained because internal discharge and chemistry are rarely observed simultaneously. The Poshan drainage tunnel system in Hong Kong consists of two sub-tunnels intersected by dense sub-vertical drains (SVDs), providing a valuable groundwater observation platform for investigating how hydrologic processes control solute concentrations within the volcanic rock hillslope. From April 2023 to April 2025, groundwater was sampled biweekly to monthly at the two tunnel outlets, the high tunnel weir (HTW) and low tunnel weir (LTW), and at four representative SVDs distributed along the tunnels across position and elevation. Concentrations of major ions, dissolved Si, and ²²²Rn were measured, and discharge at each location was monitored or calculated. Power law fitting, hysteresis index, and reactive transport model inversion were used to analyze C–Q relationships and to identify controls on solute export and transport. Hydrologic deconvolution was applied to time series of rainfall, groundwater levels from 9 piezometers, and discharge at the two weirs (HTW and LTW) to obtain residence time distributions, thereby constraining groundwater discharge and hydrologic connectivity. Across the hillslope, C–Q relationships showed strong solute-specific and spatial variability. At the weir scale, upslope groundwater more commonly exhibited enriching or diluting C–Q behaviors, whereas downslope groundwater more often showed chemostatic C–Q relationships. At the SVD scale, an upslope SVD showed significant dilution of Cl⁻ but strong enrichment of ²²²Rn with discharge, whereas a downslope SVD showed dilution of Na⁺, Cl⁻, and NO₃⁻ together with enrichment of K⁺, SO₄²⁻, and Si with discharge. The C–Q relationships of different solutes showed distinct behaviors: Na⁺, Cl⁻, and NO₃⁻ generally showed dilution or near chemostasis. In contrast, K⁺, Mg²⁺, and SO₄²⁻ more frequently enriched at high discharge, consistent with seasonal accumulation in shallow reservoirs followed by storm-driven flushing. Si displayed intermediate behavior, tending toward dilution or weak enrichment depending on location. ²²²Rn showed strong enrichment at specific sites, which may indicate rapid activation of short flow paths and groundwater mobilization. Hysteresis loop direction also varied by solute and location, with more counter-clockwise loops in the upslope area where solute signals lagged behind discharge and followed a seasonal cycle. More clockwise loops were observed for K⁺, Mg²⁺, and SO₄²⁻ in the downslope area, suggesting relatively abundant source reservoirs. Hydrologic deconvolution further indicated shorter mean residence times downslope than upslope, while groundwater near the tunnel could be discharged rapidly. Overall, the spatial and solute-specific C–Q variability within the volcanic CZ reflects the spatial distribution of solute storage and the interplay of thermodynamic limits, reaction kinetics, and residence time, and apparent chemostasis at larger scales may be due to mixing-driven signal averaging along heterogeneous flow paths.
How to cite: Yang, T., Jiao, J. J., and Mao, R.: Solute-specific and spatially variable concentration–discharge relationships in hillslope critical zone groundwater, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8609, https://doi.org/10.5194/egusphere-egu26-8609, 2026.
Groundwater fluxes and interacting zones between groundwater and surface water are crucial for understanding the water dynamics of the critical zone. Groundwater within the critical zone plays a significant role in the ecosystem, biodiversity, and water supply. However, estimating these fluxes remains a key challenge because they are not directly measured in the field. Model calibration involves adjusting key parameters—such as saturated hydraulic conductivity and soil-water retention properties—using observed data like hydraulic head and river discharge, while initial and boundary conditions are prescribed to define the model l setup. That calibration is often done by comparing simulated soil water saturation and water table level to piezometers. Nevertheless, real flows occur in 3D in a complex medium containing heterogeneities with various lithologies, with different hydraulic parameters such as hydraulic conductivity and porosities.
Geophysical methods such as electrical resistivity tomography (ERT), seismic refraction tomography (SRT), and multichannel analysis of surface wave (MASW), which are sensitive to lithology, content, and nature of fluid, represent helpful tools for hydrogeological modelling, both in terms of model parameterization and physical property characterization. ERT, which is particularly sensitive to lithology, allows us to identify and delineate heterogeneities, while seismic methods, which are sensitive to mechanical properties, will enable us to infer the water saturation and the piezometric surface in the near surface through the P-wave and S-wave velocities ratio (Poisson’s ratio, e.g. ) (Dangeard et al., 2021).
We propose a workflow combining geophysics and geostatistics to reconstruct the heterogeneities and the piezometric surface in an alluvial plain context. We implemented the workflow in a 30 x 30 m area at the Avenelles site of the Orgeval Critical Zone Observatory (CZO), which is part of the French network of CZOs OZCAR. ERT, SRT, and MASW surveys were carried out along 7 profiles to obtain 2D sections of electrical resistivity, P and S wave velocities (6 profiles of 72 electrodes/geophones and one profile of 48 electrodes/geophones, with 0.40 m spacing leading to 12,708 apparent resistivity data, 33,888 first wave arrival picks, and 277 dispersion curves). Geophysics allows us to pass from punctual piezometer data to 2D vertical sections. However, carrying out 3D geophysical acquisition is cumbersome. To overcome these limitations, we then use geostatistics to get a distribution of our geophysical parameters in the 3D volume delineated by the geophysical survey. Once the 3D interpolation is done by kriging methods, we can retrieve a view of the heterogeneities distribution in the near surface as well as the water table position to inform hydrogeological inversion. Furthermore, with the addition of petrophysical relationships, it is possible to estimate saturation and porosity distribution for a future 3D hydrogeological physics-based model run to better characterise groundwater fluxes. Finally, all these workflows, including complementary methods, could be performed on different dates for time-lapse monitoring of the water table.
How to cite: Gautier, M., Pasquet, S., Radic, N., Renard, D., Martin, R., Gesret, A., Nespoulet, R., Loget, N., Bodet, L., and Rivière, A.: 3D near-surface geophysics and geostatistics for heterogeneities characterization and water table monitoring on the Orgeval critical zone observatory, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9657, https://doi.org/10.5194/egusphere-egu26-9657, 2026.
The August 2023 Lahaina wildfire caused extensive environmental impacts, including the release of untreated wastewater and combustion-derived contaminants such as nutrients and polycyclic aromatic hydrocarbons (PAHs). This study examines seasonal groundwater flow and solute transport dynamics within a post-wildfire beach aquifer. Using field observations and a two-dimensional, density-dependent, variably saturated groundwater model calibrated with year-long data, we simulated groundwater flow and salinity patterns and applied Lagrangian particle tracking to evaluate solute pathways and transit times. Summer conditions are characterized by elevated inland groundwater levels and predominantly seaward flow, resulting in rapid solute discharge to the shoreline. In contrast, enhanced tidal and wave forcing in winter drives greater seawater infiltration, deeper recirculation, and net landward solute transport with longer residence times. Our results highlight the importance of seasonal and tidal variability in controlling post-wildfire contaminant fate and provide insights for time-sensitive coastal management and ecosystem protection.
How to cite: Geng, X., Lopez, E., Kanoa, H., Zhang, H., Haroon, A., Dulai, H., and Yan, T.: Seasonal Coastal Groundwater Dynamics at Lahaina Beaches, Hawaiʻi, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2635, https://doi.org/10.5194/egusphere-egu26-2635, 2026.
The Doongmabulla Springs Complex (DSC) is a cluster of groundwater-dependent wetlands located in central Queensland, Australia. The DSC has over 160 individual springs ranging from over 9 ha, with pools of water, down to vents less than 10 cm across, supporting individual grasses. The springs are home to a variety of plant species (many endemic) that are adapted to the unique physico-chemical parameters of the groundwater discharge on which they rely. Wetlands and scalds of the DSC support a listed Threatened Ecological Community of species dependent on this natural discharge of groundwater from underlying artesian aquifers of the Galilee Basin. The springs are protected under Australia’s State and Commonwealth Environmental legislation.
Aquifer depressurisation due to mine dewatering occurring to the east of the springs has the potential to threaten spring biodiversity in future by reducing groundwater discharge and consequent wetland persistence. Assessing the likelihood and possible magnitude of these threats requires a multi-disciplinary modelling approach to address complex groundwater – surface water – ecosystem interactions: 1) define groundwater pressure change probabilities; 2) simulate likely wetland response; and 3) evaluate potential ecological impacts. Once such a modelling chain is in place, impact mitigation may be assessed, considering the effect of interventions at each stage of the chain.
To support the numerical modelling, extensive hydrological, ecological and physio-chemical data collection and analysis was undertaken to understand spring wetland area and species microhabitats and distributions over multiple scales and time frames, including seasonal and inter-annual variability. Generation of realistic and defensible conceptualisations for the springs is critical and is described in a companion paper (Cresswell, et al., these proceedings).
Regional numerical groundwater modelling (MODFLOW) generated potential groundwater pressure change responses relevant to the DSC source aquifers. Potential groundwater depressurisation over time at the individual spring locations was utilised in a wetland water balance model (GoldSim) to describe wetland persistence, size and seasonality. Water balance outputs were translated into spatial representations of predicted spring hydrology (TUFLOW), generating area and shape configurations that could be compared to historical wetland persistence data and then utilised to predict potential effects on suitable habitat for key flora species under a range of scenarios including mining-related groundwater drawdown and climate change using maximum entropy species distribution modelling (MaxEnt). This latter process relates known species’ occurrences to measurable variables that describe the environment (such as soil moisture, soil salinity and pH) to predict the presence or absence of a species at unsampled locations and under future groundwater drawdown scenarios.
The results of the application of this novel chain of models have informed a revised impact assessment for the potential impacts of mine dewatering on the unique vegetation communities at the Doongmabulla Springs Complex and enables development of targeted mitigation approaches for individual wetlands and species.
How to cite: Gibson, A., Cresswell, R., Muller, J., Capon, S., Grieger, R., Lloyd, P., Stanton, D., and Yeates, M.: Using a novel chain of models to mimic source aquifer depressurisation impacts across the Doongmabulla Springs Complex , Queensland, Australia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8457, https://doi.org/10.5194/egusphere-egu26-8457, 2026.
Karst aquifers play a fundamental role in sustaining groundwater-dependent ecosystems (GDEs) through their capacity to deliver large flows and highly buffered thermal regimes via springs. In Mediterranean environments, where hydrological variability and climate-driven extremes are intensifying, these groundwater contributions act as ecological stabilizers that support biodiversity and enhance ecosystem resilience. Drawing on two complementary case studies, this contribution examines how karst groundwater controls thermal and ecological dynamics in surface ecosystems: (i) the Argens River at Châteauvert (France), monitored within the ESTHER project, where the Bouillidoux spring system generates persistent cold-water refuges during summer low flows; and (ii) the Lez karst spring system near Montpellier (France), investigated under the SentinelSprings project initiative as a representative “sentinel” of long-term environmental trends, where the abstraction of water for drinking water supply competes with the river baseflow necessary to sustain aquatic ecosystems.
In both the Argens and Lez study sites, high-frequency monitoring networks were installed, including continuous temperature, electrical conductivity, and dissolved oxygen probes deployed in springs and river reaches. These datasets enable detailed thermal budgets to be established, revealing the mechanisms by which groundwater inflows generate thermal refuges and regulate stream metabolic conditions. The combined analysis of hydrological and thermal signals also supports the development of refined conceptual models that can be used to simulate groundwater–surface water interactions and quantify the potential impacts of climate change on spring-fed thermal regimes and river corridor resilience. These groundwater inputs sustain critical habitats, modulate the sensitivity of river corridors to warming, and provide natural buffering capacities that constitute important nature-based solutions for climate-change adaptation. By linking high-resolution monitoring with hydrogeological conceptualisation, our study advances the understanding of feedback processes between karst groundwater and surface ecosystems, highlighting springs as essential indicators and protectors of ecological stability. This work contributes to improving the identification, assessment and long-term management of GDEs.
How to cite: Selles, A., Marechal, J.-C., Caballero, Y., and Bronnec Castanet Desages, E.: Where springs save rivers: Karst springs as sentinels and refuges in a warming world, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12304, https://doi.org/10.5194/egusphere-egu26-12304, 2026.
Current challenges in the assessment of groundwater characteristics in karst areas result from the difficulties to effectively identify episodes of high water discharge and flow paths rates. The characteristics of karst aquifers formed by interconnected network of pores, fissures, fractures and conduits, with an alternation of high and low permeability zones and distinct water residence time, makes contamination difficult to be detected and monitored over underground flow paths. Groundwater’s have a high variability in recharge and flow rates, influenced by weather and climate patterns. At high flow, resulting from intense precipitations and/or significant snowmelt, karst groundwater’s moves rapidly through the rock, carrying effectively pollutants in and through the host rock. In contrast, during periods of drought and/or reduced surface inflow, groundwater moves slowly and diffuses more effectively within the primary/secondary pores of the rocks. In karst, the base flow is associated with long-term storage of the groundwater that creates a relatively stable environment for strictly subterranean dwellers organisms. Stable conditions in groundwater creates biodiversity hotspots where temperature, chemical composition highly influenced by lithology and potential contaminants acts together to ensure healthy habitats that supports a suite of associations of organisms indicative for the overall groundwater health. In contrast, a high discharge and a rapid flow path are associated with disturbances of groundwater habitats, associated with a shift in community patterns structure and dynamics. In this presentation, we combine water chemistry monitoring, stable isotope analyses (indicators of water source, recharge patterns and timing), identification of microbial communities (i.e., E. coli, enterococci, enterobacteria) and of groundwater fauna monitoring (indicative of both contamination and as biomarkers for groundwater flowpath) to identify episodes of high and base flow in a karst aquifer in the Padis karst area in NW Romania. We assume that a fine tune evaluation of groundwater communities (microbes and meiofauna biodiversity) can be used to: 1) understand the pattern of water flow variation across seasons, acting as disturbances for groundwater communities; and 2) detect the contaminated groundwater spots and potential degraded habitats. From this perspective, we used the microbes and groundwater fauna as biomarkers models to describe the potential causal linkages among groundwater karst flow and flow-path variation, groundwater habitat diversity/stability and quality, and groundwater community diversity in disturbed/undisturbed habitats.
How to cite: Iepure, S., Sambor, O., Cociuba, D., Persoiu, A., Marin, C., Tudorache, A., Coada, D. I., Denes, A., Denes, A. L., Bucur, R., and Scrob, N.: A comprehensive bioassessment of karst aquifer flow paths , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22055, https://doi.org/10.5194/egusphere-egu26-22055, 2026.
