This session will bring together the scientific community developing hydrology research on mountain regions worldwide to share new findings and perspectives. We invite contributions that address past, present and future conditions, including changes resulting from climate and/or land use change, their impacts on local and downstream areas, and adaptation strategies to ensure the long-term sustainability of mountain ecosystem services, with a special focus on water cycle regulation and water resource generation.
Topics of interest include, but are not limited to
- sources of information for assessing past and present conditions (in either surface and/or groundwater systems);
- methods to disentangle climatic and anthropogenic drivers of hydrological change;
- modelling approaches for assessing and projecting hydrological change;
- evolution, forecasting and impacts of extreme events;
- case studies on adaptation to changes in water resources availability.
In addition, the session will explore recent technological and methodological innovations, such as leveraging the use of low-cost sensor networks (e.g., LiDAR, motion-triggered cameras), stable isotopes, citizen science, indigenous knowledge systems, and other emerging techniques that help overcome observational challenges.
Lake-effect snowfall was largely studied around the North American Great Lakes, yet similar processes arise in other coastal and mountainous regions where cold continental air flows over comparatively warm water. In this study, we investigate lake-effect snow in two seemingly distant but meteorologically comparable settings: the central Apennines in Italy, influenced by the Adriatic Sea, and Japan’s Niigata Prefecture, affected by air masses crossing the Sea of Japan. Despite their geographical distance, both regions share key ingredients: shallow and narrow seas acting as efficient heat and moisture sources, strong cold-air spells, and steep orography that enhances convergence and precipitation. This results in remarkably analogous snowfall extremes, which are both a key water resource and an intense hazard. Using ground-based observations, weather radar data, and future climate projections, we characterized the mechanisms driving these events and assessed their local impacts, including road closures, infrastructure disruptions, and structural failures. Particular attention was given to how warming air masses and concurrently warming sea surfaces may alter the frequency, intensity, and spatial distribution of lake-effect episodes. Our findings indicate that these phenomena represent a significant and often underestimated hazard, and that their sensitivity to climatic shifts exposes both regions to growing vulnerabilities in a warming world.
How to cite: Avanzi, F. and Yamashita, K. and the Appennine-Snow research team: Cold on the water: mechanisms, impacts, and future scenarios of lake-effect snowfall in Italy and Japan, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1710, https://doi.org/10.5194/egusphere-egu26-1710, 2026.
Mountain regions in Europe are experiencing changes in temperature and precipitation patterns, as well as an increasing frequency and intensity of droughts. Periods of low precipitation reduce winter snow accumulation, while anomalous hot periods during spring and summer accelerate snowmelt, altering the water cycle and discharge patterns of mountain systems and their downstream areas. The combination of warmer and drier conditions increases water scarcity, reduces crop yields and decreases hydropower generation, with reductions in streamflow and groundwater recharge. Implementing high-resolution land surface models allow us to predict future conditions by capturing the complex behavior of flow paths and water storage across entire regions. Consequently, these models facilitate the study of future droughts and their impact on hydrological conditions within the catchment.
We identify a number of droughts including snow droughts in the Central Apennines of Italy, and investigate their compounded effects on the hydrosphere, biosphere and pedosphere using a fully distributed, mechanistic land surface model (Tethys-Chloris) over two decades (from 2000 to 2020). Our model configuration resolves energy budgets and mass balances at an hourly timestep and 250 m resolution to simulate processes such as snowmelt, sublimation and plant transpiration. We force the model using a combination of stations and bias-corrected ERA5Land reanalysis data and evaluate it against streamflow measurements, snow depth, soil moisture and remote sensing products of snow-covered area and leaf area index.
We analyze distributed simulations of snow depth, snow water equivalent, soil moisture, lateral subsurface water fluxes and surface temperature to obtain a highly resolved picture of the functioning of the mountain hydrological system. Our analysis shows how droughts produced by a reduction of snow accumulation, precipitation or warm temperatures produce runoff deficits and positive anomalies of evapotranspiration at high elevations. We focus in particular on the effect of evaporative fluxes in reducing water yields. Our findings indicate that warm periods lead to enhanced evapotranspiration at elevations between 1500 and 2500 m a.s.l. We also investigate the contrasting effect of snow on this so-called drought paradox, as snow provides water vital to plant functioning, but limits the growing season length. This phenomenon ultimately reduces downstream water availability in mountain regions, which impacts water security for mountain-dependent communities and ecosystems. As such, our study provides an entirely new understanding of the eco-hydrological functioning of the Central Apennines water system under drought stresses, and establishes a baseline of unprecedented resolution in time and space to predict the ecological and hydrological impacts of future droughts.
How to cite: Rodriguez, M., Ayala, A., McCarthy, M., Fyffe, C., Shaw, T., Jouberton, A., Romano, E., Fatichi, S., and Pellicciotti, F.: Snow droughts and the water cycle of the Central Apennines, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11422, https://doi.org/10.5194/egusphere-egu26-11422, 2026.
High-altitude wetlands are vital for water storage, flow regulation, and biodiversity in mountain regions. Their hydrologic resilience depends on water inputs from precipitation, groundwater, snow, and glacier melt, making them sensitive indicators of climate-induced hydrological change. However, the specific impacts of rapid glacier retreat and shifting precipitation regimes on the spatiotemporal stability of these ecosystems remain poorly quantified, limiting the development of targeted adaptation strategies.
This study investigates the hydrological drivers and spatial dynamics of high-altitude wetlands in two Peruvian Andean catchments: glaciated Cordillera Vilcanota and nearly deglaciated La Raya. Using high-resolution satellite-based wetland mapping (2019-2025), we employ a sub-catchment-based regression analysis to disentangle the role of precipitation and glacier melt in controlling wetland seasonal and interannual variability.
Our results show that seasonal wetland dynamics are primarily driven by precipitation, which explains up to 25% of wetland variability. However, in proximity to glaciers, wetland seasonality is significantly dampened, indicating a stabilizing effect of glacier meltwater inputs. Spatially explicit analysis reveals that this glacier-buffering effect is highly localized: it attenuates sharply with distance from periglacial and becomes statistically undetectable beyond approximately 12 km. This suggests that most high-Andean wetlands are hydrologically decoupled from direct glacier melt influence, and their future vulnerability will be predominantly governed by precipitation changes.
This work provides a novel spatially explicit assessment of glacier–wetland hydrological connectivity, which is a key and understudies component of mountain water cycles. The findings advance the understanding of how different water resources regulate wetland variability and offer a monitoring framework that can support the development of adaptation strategies for sustaining mountain ecosystem services under climate change.
How to cite: Xuan, D., Becker, R., Vargas Valverde, M. C., Davies, B. J., Ely, J. C., King, O., Montoya, N., Onof, C., Ross, A. C., and Buytaert, W.: Localized buffering, widespread decoupling: Glacier meltwater's shrinking influence on high-Andean wetland hydrology, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18345, https://doi.org/10.5194/egusphere-egu26-18345, 2026.
In the mountainous regions of Armenia, the formation of maximum river flow is heavily influenced by seasonal snowmelt processes. For small and medium-sized river basins, which often lack ground-based gauging stations, understanding the timing and duration of snow cover is critical for flood risk assessment and water resource management. This study focuses on monitoring snow cover patterns over the last decade using Sentinel-2 satellite data.
The research utilizes the Normalized Difference Snow Index (NDSI) to accurately identify snow-covered areas across diverse topographic gradients. The primary objective is to establish a 10-year baseline for snow phenology, specifically identifying the "First Snow Day" (onset) and the "Last Snow Day" (melt-off) for several pilot basins in Armenia. By processing multi-temporal image stacks through Google Earth Engine (GEE), the study analyzes the rate of snow depletion during the spring season.
The research aims to quantify the inter-annual variability in snow duration as a function of shifting temperature patterns and elevation gradients. By establishing this 10-year baseline, the study expects to demonstrate that the timing of the final snowmelt can serve as a primary proxy indicator for predicting maximum flows in ungauged catchments. This remote sensing approach intends to provide a robust, cost-effective alternative to traditional monitoring, offering a scalable tool for modeling peak flows in data-scarce environments. Ultimately, the integration of these satellite-derived snow dynamics into hydrological frameworks will enhance the accuracy of flood risk mapping.
How to cite: Khachatryan, S. and Sarukhanyan, A.: Spatiotemporal analysis of snow cover dynamics in small and medium-sized mountainous basins of Armenia using satellite imagery, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18968, https://doi.org/10.5194/egusphere-egu26-18968, 2026.
The seasonal snow accumulation period – approximated as the number of days between the autumn onset and spring end of sub-freezing temperatures – varies across elevation in mountain basins, with colder, higher elevation areas accumulating snow for longer relative to warmer, lower-elevation areas. Climate warming will reduce the sub-freezing duration throughout a year and alter the timing and magnitude of snow accumulation and melt, with profound implications for downstream ecosystems, infrastructure, and societies; however, it is not well known how such changes will vary across elevation gradients in mountain basins.
Here we present a novel idealized conceptual model to analytically explain how and why the annual sub-freezing period responds differently to climate warming across elevation gradients in mountain basins. We use this model to demonstrate theoretically under what climactic conditions the sub-freezing duration is more sensitive to warming at low elevation areas relative to high elevations, and vice-versa. Both the strength (i.e. the magnitude of change of sub-freezing duration) and the shape (i.e. whether high- or low-elevation regions are more sensitive to warming) of this sensitivity vary non-linearly as a function of mean temperature, temperature seasonality, temperature lapse rate, and the basin elevation range.
We then use ERA5-Land climate reanalysis data to apply this novel framework to mountain basins across North America. We find that in basins with warmer climates (i.e. those with mean annual temperatures greater than freezing), the annual number of days below freezing is more sensitive to warming at low elevations. In contrast, in basins with colder climates (i.e. those with mean annual temperatures less than freezing), the annual number of days below freezing are more sensitive to warming at high elevations. We evaluate both the present sensitivity of the sub-freezing duration, as well as observed changes since 1950.
We detail two case studies in which we apply our methodology. First, we present how the snow accumulation period may decrease by substantially more in some glacierized areas than others (i.e. Canadian Rocky Mountains vs Coast Mountains). We find that in many glacierized basins, the snow accumulation period is more sensitive to warming in the high-elevation glacierized areas relative to lower-elevation non-glacierized areas. Second, we adapt our methodology to describe the period of the year when heatwaves, defined as persistent periods hotter than the seasonally-varying 90th percentile of temperature, may be warmer than freezing and thus potentially able to modify basin hydrology. We show that the potential for heatwave-driven ablation in mountain basins changes non-linearly across elevation with warming, and that heatwaves may rapidly emerge as a more prominent driver of high-elevation melt. Overall, our study presents a novel modelling framework to assess and project changes to melt-driven hydrological dynamics in mountain basins.
How to cite: Anderson, S., Horton, R., Hale, K., and Chartrand, S.: Elevation-dependent sensitivity of the snow accumulation period to climate warming in mountain basins, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14455, https://doi.org/10.5194/egusphere-egu26-14455, 2026.
Permafrost degradation on the Tibetan Plateau (TP) has profound impacts on hydrological processes, yet the responses of permafrost hydrology to different climate forcings remain unclear. Here we integrate outputs from global climate models with a watershed cryospheric-hydrological model to provide the first quantitative attribution analysis to examine the responses of permafrost hydrology to anthropogenic and natural forcings in the source region of the Yellow River, northeastern TP. Our results confidently attribute frozen ground degradation to anthropogenic greenhouse gases (GHG), leading to permafrost area decline by 3398.4 km²/10a during 1960–2019, while aerosols exhibit a slight mitigating effect. GHG emissions also drive concomitant hydrological changes, including increased subsurface runoff and winter runoff ratio. They also reduce streamflow seasonality, particularly in regions where permafrost degrades severely. Our study provides critical insights for understanding permafrost and hydrological processes under climate change, highlighting the importance of effective emission reduction and adaptive water resources management strategies.
How to cite: Fang, P., Wang, T., and Yang, D.: Permafrost Degradation and Concomitant Hydrological Changes Dominated by Anthropogenic Greenhouse Gas Emissions in the Northeastern Tibetan Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2710, https://doi.org/10.5194/egusphere-egu26-2710, 2026.
The meltwater from snow and glaciers in the data-scarce mountainous regions of the upper Indus Basin (UIB) confronts significant concerns due to climate change, the consequential cryospheric changes in snow cover dynamics and glacier mass balance are altering hydrological regimes through seasonal streamflow shifts. Taking the UIB as a study area, season dynamics and long-term trends in hydro-meteorological time series was analyzed, and a high-quality meteorological forcing dataset was developed for driving a distributed hydrological model (J2000). The Hydrograph Partitioning Curves (HPC) method was used to assist in model calibration and mitigated uncertainty. Water balance and the distributions of different runoff components in the UIB were further quantified. Our analysis indicates that winter and spring runoff in several sub-basins of the UIB exhibits an increasing trend, characterized by earlier snowmelt runoff timing and considerable regional variability. The timing of runoff center advancement is significantly influenced by the snow fraction (SF). When SF is less than 0.8, alterations in the timing of runoff centers are predominantly influenced by precipitation; when SF exceeds 0.8, these changes are principally dictated by the timing of snowmelt. We included environmental factors, including elevation and NDVI, to facilitate regional downscaling of the TRMM grid-based precipitation product, which was subsequently employed to drive a hydrological model for analyzing runoff processes in the typical Gilgit, Shyok, and Kharmong basins of the UIB. Among these three basins, the Gilgit Basin experiences a precipitation of 793 mm and an evapotranspiration of 334 mm, with snowmelt and glacial melt runoff constituting 34% and 28% of the total runoff, respectively. In the Shyok Basin, precipitation measures 539 mm, evapotranspiration is 289 mm, and snowmelt and glacier melt runoff account for 26% and 41% of the total runoff, respectively. The Kharmong Basin experiences the lowest precipitation at 392 mm, with an evapotranspiration rate of 243 mm, while snowmelt and glacier melt runoff contribute 36% and 25%, respectively. This study provides valuable insights into hydrological changes in the UIB, and underlying methodology can be important for other modelling studies in data-scarce basins and in the context of climate change.
How to cite: Shen, Y. and Wang, Y.: Comparative impact assessment and modelling analysis of river basins in the data-scarce upper Indus Basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4675, https://doi.org/10.5194/egusphere-egu26-4675, 2026.
Climate change reduces snow and ice input to mountain meltwaters, which provide as much as 60% of the world’s annual freshwater flow. Water resource models in these environments are often flawed in their implementation of glacier and snowmelt, affecting model outputs and how stakeholders plan water resource management needs. Therefore, addressing these limitations is key to improving water security.
A water resource model is applied to the Rofental catchment in the Austrian Alps using a model-coupling approach to incorporate glacier and snowmelt processes, as well as new routing mechanics to better simulate flow in these catchments. This modelling is supported by new observations of glacial thickness, extent and meltwater runoff, and enhanced with the use of isotope tracers to distinguish dominant flow paths.
Preliminary results point to more conservative water routing and better glacial water representation within the catchment. Ultimately, this approach serves to constrain uncertainty and deliver a clearer picture of the dominant hydrological processes in mountain catchments, and how changes in these may impact mountain water resources in the future.
How to cite: Bernardi, G., Baron, H., and Rickards, N.: Simulating the water resources of an Alpine catchment within a coupled water resource, glacier and snowmelt model framework, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4910, https://doi.org/10.5194/egusphere-egu26-4910, 2026.
Mountain regions function as natural “water towers” by storing water and supplying it to downstream areas. The source regions of the Yellow, Yangtze, and Lancang-Mekong rivers on the eastern Tibetan Plateau are referred to as the “Chinese Water Tower,” providing freshwater to billions of people across downstream China and Southeast Asia. A cryospheric meltwater tracking hydrological model is developed to simulate hydrological changes as well as variations in snow, permafrost, and glaciers, and to quantify the runoff contributions of cryospheric meltwater. The results show that historically (1960–2019), cryospheric meltwater contributed 21–32% of the total runoff. Under three future socio-economic pathways (SSP1-2.6, SSP2-4.5, and SSP5-8.5), runoff in the three headwater basins is projected to increase during 2020–2100. However, due to substantial cryospheric degradation as indicated by diminishing snow cover, a thickening active layer and declining glacier ice storage, the runoff contribution of cryospheric meltwater is unlikely to be sustainable in a warming climate. Overall, the total contribution of cryospheric meltwater is projected to decline in the Chinese Water Tower, indicating a loss of water storage and regulation capacity, reduced drought mitigation capacity, and weakened interannual runoff stability. Moreover, under different scenarios, the mismatch between population growth and water resources may exacerbate water supply–demand imbalances. This study highlights the widespread risks of declining cryospheric meltwater supply both in the Tibetan Plateau and in other cold-region catchments in a warming climate.
How to cite: Cheng, H., Wang, T., and Yang, D.: Climate change affects the water supply of the Chinese Water Tower, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4760, https://doi.org/10.5194/egusphere-egu26-4760, 2026.
Climate change and glacier retreat in the tropical Andes are transforming mountain hydrology and challenging water security for both upstream communities and large downstream cities. Most research and policies have focused on declining glacier contributions during the dry season, as the loss of buffering capacity threatens water supply for drinking, irrigation, and hydropower. However, glacier shrinkage is also reshaping water quality: as ice recedes and exposes sulfide-rich bedrock, oxidation generates acid rock drainage, reducing pH and mobilizing metals. In several basins (e.g. the Santa River Basin - SRB), this has already led to regulatory bans on the use of historically important rivers for drinking water unless costly treatment is installed, constraining water access well before projected declines in water volumes. Beyond physical impacts, glacier loss has profound cultural and social consequences. High-mountain glaciers hold strong spiritual significance for Indigenous communities; their disappearance disrupts rituals, alters pilgrimage routes, and erodes place-based identities, ultimately shaping how communities perceive and respond to water insecurity. Recent work further demonstrates that glacier retreat has measurable economic consequences for water-dependent sectors. For instance, in the SRB, results indicate that glacier retreat alone can account for up an additional 15% of economic losses in the agriculture and hydropower production sectors.
To address these complexities and uncertainties in future water security, our recent work has focused on supporting robust adaptation planning. We apply robust decision-making and exploratory modelling approaches to test portfolios of adaptation measures, across wide ranges of climate and socioeconomic conditions. Rather than targeting a single “most likely” future, we identify combinations of measures that provide sustained performance in uncertain and evolving contexts while reducing the risk of maladaptation. A key insight is the need for stakeholders to explicitly negotiate thresholds of acceptable loss and damage for both water quantity and quality to guide water governance choices. Building on this foundation, we now plan to expand our research to systematically examine how glacier-related hazards propagate through interconnected social-ecological systems. Using conceptual frameworks on cascading and compound risks, we will analyze cross-sectoral impacts on domestic supply, agriculture, hydropower, and cultural values, and assess how responses in one sector may amplify vulnerabilities in others. This work aims to identify leverage points for adaptation that strengthen resilience rather than shifting or creating risks, supporting long-term resilience in the Peruvian Andes and other rapidly changing mountain regions.
How to cite: Muñoz, R.: Cascading risks and robust adaptation in the tropical Andean glacier-fed systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3179, https://doi.org/10.5194/egusphere-egu26-3179, 2026.
Mountain snow is a globally important source of water for downstream users and ecosystem sustainability, but it is uncertain when and where traditional snow metrics alone provide reliable indicators of water supply. Here, we synthesize large-sample regional analysis with a high-resolution integrated hydrologic model of a headwater basin of the Colorado River (East River, Colorado, 750 km2) to demonstrate the tight coupling between land surface and subsurface process on mountain streamflow generation. Our analysis of nearly 4,700 western US mountain watersheds indicates that streamflow predictability depends not only on snow accumulation magnitude, but on whether snow represents the dominant water reservoir. Snow storage-dominated mountain basins exhibit a tight coupling between peak snow water equivalent and runoff, while mixed storage systems, such as the East River, depend on interactions among snow, rainfall, and groundwater. Recent declines in runoff efficiency and the degradation of low-flow metrics in the East River coincide with persistent subsurface storage deficits due to overlapping climate extremes, signaling a shift toward subsurface storage-limited behavior. Modeled scenarios of persistent and prolonged warming indicate enhanced vegetation water use reduces recharge, drives substantial groundwater storage loss that disproportionately affects dry years and limits recovery even during wet periods, ultimately reducing annual flows and increasing stream intermittency. Sensitivity experiments further show that the depth and porosity of active bedrock circulation strongly modulate drought response. Deeper, higher-porosity groundwater systems are able to buffer low flows during multi-year drought conditions but experience prolonged post-drought recovery. Collectively, these findings highlight the tight coupling among climate, vegetation, snow, and groundwater, and demonstrate that explicit representation of subsurface storage dynamics is essential for forecasting mountain water supply, ecosystem vulnerability, and drought response under future climate conditions.
How to cite: Carroll, R., Gordon, B., Siirila-Woodburn, E., Varadharajan, C., Albano, C., Lundquist, J., and Williams, K.: Shifting Storage Regimes and Declining Streamflow Resilience in Mountain Systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13430, https://doi.org/10.5194/egusphere-egu26-13430, 2026.
Groundwater-fed river systems in mountainous regions are particularly vulnerable to the combined effects of climate variability and groundwater abstraction. Yet, quantitative assessments are often hindered by limited data availability, especially when the water table lies deep below the topographic surface. This study investigates groundwater–surface water interactions in the Northern Etna volcanic aquifer (Sicily, Italy), a UNESCO World Heritage Site that sustains the Alcantara River baseflow and supplies water for civil and agricultural uses.
A regional groundwater flow model was developed using MODFLOW 6, adopting an equivalent porous-medium representation of the fractured basalt aquifer under data-scarce conditions. The model was calibrated using PEST under steady-state conditions, using hydraulic head observations, and validated in transient mode against monthly discharge measurements from a major drainage gallery over the period 2009–2022. Scenario simulations were performed to quantify the effects of current groundwater abstractions and projected climate-driven recharge changes.
Model results show that current groundwater abstractions reduce spring discharge by approximately 23–37% (mean ≈30%). No significant long-term trend in baseflow is observed over the 2009–2022 period, suggesting that historical baseflow variability reflects the integrated aquifer response to recharge, storage and abstraction processes rather than a sustained climatic forcing.
Conversely, simulations driven by EURO-CORDEX climate projections reveal a substantial future decline in groundwater availability. Drainage gallery discharge is projected to decrease up to 23% in the near future (2021–2050) and up to 40% in the far future (2041–2070), depending on the emission scenario. These results highlight increasing stress on groundwater resources and reduced aquifer–river connectivity during prolonged droughts, with potentially severe impacts on groundwater-dependent ecosystems.
Despite inherent limitations related to data scarcity and necessary conceptual assumptions, this study demonstrates that regional numerical modeling can provide robust, management-relevant insights into mountainous aquifer systems. The proposed framework supports adaptive groundwater management strategies aimed at preserving river baseflow and ecosystem services under changing climatic conditions.
How to cite: Bonaccorso, B., Silipigni, M., Di Salvo, C., Borzì, I., and Preziosi, E.: Modeling Climate and Anthropogenic Controls on Groundwater Recharge, Baseflow, and Spring Discharge in a mountainous volcanic Aquifer in the Mediterranean Area (Northern Etna, Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17360, https://doi.org/10.5194/egusphere-egu26-17360, 2026.
Since climate change is challenging every part of the water cycle, not only at the global scale but also regionally and locally, it is increasingly important to understand its impact on both surface and subsurface hydrological processes, with particular interest in groundwater recharge, which is a key component. This is fundamental for many reasons, starting from irrigation and water management strategies. To do so, we apply two different models to estimate historical groundwater recharge in one case study in a mountainous catchment in Northern Italy.
Specifically, we would employ the GEOframe model, developed by the University of Trento, which offers a flexible, component-based framework for process-based simulations of hydrological dynamics, including evapotranspiration, snowmelt, infiltration and groundwater recharge at high spatial-temporal resolution.
The second one is a linear reservoir model developed at the University of Padova, tailored for efficient lumped-parameter estimation of recharge through simplified storage-discharge relationships calibrated against observed hydrographs and soil data.
The input that we will use are the hourly dataset of precipitation and air temperature from the regional network of Veneto region. The final idea is to analyze the current status and trends of groundwater recharge and compare with the dataset from the observations.
How to cite: Falcone, G., Annis, A., Passadore, G., and Marani, M.: Analysis of groundwater recharge in a mountainous basin, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2629, https://doi.org/10.5194/egusphere-egu26-2629, 2026.
Groundwater has a critical role in mountains regulating hydrological buffering by redistributing water both in space and time. Despite their relevance, it is hard to constrain residence times and flowpaths due to data scarcity and numerical complexity of explicit groundwater model. Here, we use a simplified distributed groundwater model to constrain hydrological buffering metrics in a ∼10,000 km2 mountain catchment spanning altitudes from 1,000 to 6,400 m.a.s.l. We calibrate catchment response with hydrometric timeseries and near surface water table pseudo observations derived from landscape proxies including groundwater dependent vegetation and springs. We find that the framework can constrain residence times within some months of variability. The results has implications to provide better estimates of groundwater role in mountain catchments with few data available.
How to cite: Cuadros-Adriazola, J., Mackay, J., Gimeno Jésus, C., and Buytaert, W.: Constraining groundwater buffering role in mountain catchments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14950, https://doi.org/10.5194/egusphere-egu26-14950, 2026.
Flooding in the mountainous catchments remains a major concern due to its steep terrain, intense monsoon rainfall, and rapidly changing climate. The complex hydro-geomorphic setting makes communities, agricultural systems, and critical infrastructure highly vulnerable to flood hazards in the mountainous regions. As climate change accelerates, shifts in precipitation patterns, storm intensity, and temperature regimes are expected to influence the magnitude, duration, and timing of flood events. Despite these emerging risks, the climatic controls on annual flood hydrographs and their future trajectory in the Himalayan mountains of Nepal remain insufficiently understood. A clearer understanding of how flood characteristics are evolving under a warming climate is essential for improving hydrologic design standards, strengthening flood forecasting systems, and guiding risk reduction strategies in this mountainous environment. This study investigates historical (1986–2019) and projected future (2031–2100) changes in annual maximum flood hydrograph properties across the western Nepal mountains. Key attributes, including flood peak, flood volume, flood duration, and timing of occurrence, are evaluated to characterize how flood behavior has responded, and is likely to respond, to changing climatic conditions. Additionally, shifts in flood seasonality and the sensitivity of flood peaks and volumes to variations in precipitation and temperature are examined to identify the dominant climatic drivers shaping future flood regimes. The historical analysis reveals marked interannual variability in flood characteristics, influenced by monsoon dynamics, catchment topography, and antecedent moisture conditions. Future climate projections indicate a pronounced transformation in flood behavior, with flood peaks expected to increase and flood durations to decrease, suggesting a trend toward more intense and short-lived flood events. The timing of annual maximum floods is also projected to shift later into the monsoon season, reflecting changes in seasonal rainfall distribution and catchment wetness. Sensitivity assessments demonstrate that changes in event-scale precipitation exert a stronger influence on flood peaks and volumes than temperature variations, underscoring the critical role of rainfall intensity in steep mountainous catchments. While temperature-driven effects are evident, they remain secondary compared to precipitation-driven changes. Overall, the findings highlight the need to incorporate climate-informed variations in flood hydrograph characteristics into regional water management, hydro-infrastructure planning, and disaster risk reduction frameworks. This study provides valuable insights into evolving flood hazards and supports the development of adaptive and resilient strategies for safeguarding vulnerable communities in the Nepal mountainous region.
How to cite: Kumar, S., Dey, P., and Yadav, B. K.: Climate-Driven Transformations in Flood Hydrograph Characteristics in a Mountainous Catchment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-503, https://doi.org/10.5194/egusphere-egu26-503, 2026.
Mountain regions play a major role in the hydrological cycle and in sustaining downstream water resources. The link between mountain regions and lowland areas, however, is not limited to the supply of seasonal meltwater but expands to atmospheric moisture exchanges that contribute to local precipitation.
While the connection between the Alps and downstream agricultural land has been widely studied from the riverine perspective, studies on the atmospheric interconnection are still few. This study addresses this knowledge gap by investigating the bidirectional moisture exchange between the Alps and the agricultural areas of the Pianura Padana. In doing so we pay particular attention to the geographical distribution of sources and sinks highlighting the locally unbalanced water supply, giving rise to a “moisture-hopping” mechanism and potential pathway for drought propagation.
Moisture fluxes are quantified using the water vapor tracking model UTrack applied to a climatological mean year for the period 2008–2017. Due to the spatial variability and the critical role of local factors in shaping ET within the alpine environment, we coupled UTrack with the high-resolution ERA5-Land dataset. This combined framework allows for a detailed assessment of atmospheric moisture pathways and estimates the hydrological interdependencies between alpine regions and downstream agricultural systems.
How to cite: Chiesa Turiano, N., Tuninetti, M., Laio, F., and Ridolfi, L.: Hydroclimatic interconnection between the Alps and the Italian agriculture, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5336, https://doi.org/10.5194/egusphere-egu26-5336, 2026.
While the role of High Mountain Asia (HMA) as water tower is well established, the evaporative loss component of the high-altitude water balance remains poorly constrained. Quantifying evapotranspiration (ET) in these environments is complicated by extreme topographic relief and the severe scarcity of in-situ observations. Consequently, the interplay between atmospheric demand, soil moisture, and alpine vegetation remains a significant source of uncertainty in assessing current and future mountain water resources. In this study, we characterize the temporal variability and controlling mechanisms of ET in the Nepal Himalayas using data from a unique high-altitude hydrometeorological observational setup. In addition to measurements of temperature, precipitation, relative humidity and soil moisture, we continuously monitored turbulent fluxes using an eddy covariance system installed at 4214 m a.s.l. in the Langtang Valley in Nepal for a full year (November 2023 – October 2024), providing an exceptionally detailed dataset for understanding temporal ET dynamics and model evaluation. We observed high ET rates in the pre-monsoon season, driven by vegetation transpiration when there is sufficient soil moisture in a water-limited regime. With the increased precipitation during the monsoon season, the system shifts to a largely energy-limited regime. ET is suppressed during precipitation, but rebounds rapidly during multi-day dry spells. In the post-monsoon season, when precipitation is mostly absent, evapotranspiration is dominated by receding soil moisture and exceeds the precipitation input. Over the entire year, ET returned 44% of the precipitation input to the atmosphere. This substantial fraction indicates that these high-altitude headwaters are not merely passive runoff generators but active ecohydrological systems that contribute substantially in regulating catchment yield. To support robust climate adaptation strategies, future hydrological projections in HMA should therefore explicitly account for vegetation dynamics and soil moisture coupling to avoid significant misinterpretations of the water balance under global change.
How to cite: Kraaijenbrink, P., van den Berg, A., Stigter, E., and Immerzeel, W.: Drivers and magnitude of evapotranspiration in a high-altitude Himalayan catchment: insights from eddy covariance observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5930, https://doi.org/10.5194/egusphere-egu26-5930, 2026.
Wildfires can alter hydrology and stream temperature (Ts) in headwater catchments, yet their effects in humid forests remain poorly understood. In the Western U.S., warming and declining snowpacks are increasing fire frequency and severity, threatening small streams that provide critical aquatic habitat. We examined how catchment storage mediates hydrologic response—both summer flows and Ts—following wildfire in the H.J. Andrews Experimental Forest (Oregon, USA), an old-growth conifer system. We leveraged long-term hydrometric records for watersheds that burned in 2020 Holiday Farm Fire and using 75 sensors, we monitored Ts in six headwater streams before, during, and after the 2023 Lookout Fire. While low flows appear to be increasing post-fire given reductions in evapotranspiration, effects of the fire on high flows are not evident. Pre-fire Ts ranged from 7–14 °C, driven by solar radiation and subsurface storage. Post-fire, burned streams warmed by 0.5–3 °C, with the largest increases in low-storage catchments. Diel amplitudes also rose more in these systems. Spatial models linked burn severity and storage to both thermal and flow shifts, offering predictive insight into future fire impacts. Our findings underscore the buffering role of subsurface storage and the interaction between fire severity and storage in shaping stream resilience. This research advances understanding of wildfire impacts on thermal regimes and hydrology in humid forests and informs management of fire-affected headwater ecosystems under a warming, fire-prone climate.
How to cite: Segura, C., Perry, Z., Duffy, S., and Sullivan, P.: Wildfire Effects on Stream Temperature and Flow in Humid Mountain Forests: Insights from the H.J. Andrews Experimental Forest, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5195, https://doi.org/10.5194/egusphere-egu26-5195, 2026.
Knowledge of the flow regime of streams and rivers is fundamental for assessing their ecological resilience and impacts from human activities and climate change. However, for many streams, especially those in remote mountain areas, streamflow data are lacking. For ungauged catchments, citizen science and participatory action research methodologies can be used to generate the needed streamflow data. The CrowdWater (www.crowdwater.ch) app can, for example, be used to record observations for different hydrological variables. Repeated observations of the relative stream water level or the presence of water and flow in intermittent streams can provide data for otherwise ungauged catchments. To demonstrate the usefulness of the CrowdWater app for collecting data on streamflow in a marginalized mountainous community setting, this presentation will highlight a case study in the Queuco catchment in Chile. The catchment is located in the indigenous Mapuche-Pehuenche territory. Due to threats related to water rights, it became urgent for the local communities to obtain reliable hydrological data. Therefore, the communities observed stream water-levels using the CrowdWater app. The community co-designed the research objectives and selected the monitoring sites, while the researchers organized the initial training workshop and provided ongoing support. The data were used in a lumped hydrological model (HBV) to obtain estimates of the streamflow, which were then compared to historic monthly data (1938 – 1970). The model results suggest that even though there are no dams or water abstractions yet, the natural flow regime has already changed, with reduced flow throughout the year, and especially in October and November, likely due to declines in snowmelt. Overall, this case study highlights the usefulness of a citizen science app in participatory action research to collect data on the natural flow regime, which can be used in other (mountain) catchments with pressing issues related to water availability and security as well.
How to cite: van Meerveld, I., Bañales-Seguel, C., Vis, M., and Seibert, J.: From ungauged to informed: combining community observations, a citizen science app, and hydrological modeling to estimate mountain streamflow, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14567, https://doi.org/10.5194/egusphere-egu26-14567, 2026.
High-altitude tropical ecosystems, such as the Andean Páramo, play a fundamental role in regional hydrological regulation and the provision of essential ecosystem services.Traditionally, the characterization of these rainfall-runoff systems has focused on terrestrial catchment controls—including vegetation-soil complexes, topographic gradients, and hydrogeological baseflow—to understand water movement within the Area of Interest (AOI). However, the corresponding 'precipitation watershed' (the atmospheric moisture source) remains largely uncharacterized in terms of its own hydrological drivers. While terrestrial basins characterize their hydrological response through discharge dynamics and evapotranspiration fluxes, the precipitation watershed is effectively probed through a stable isotope approach to decouple its governing controls—such as precipitation amount, temperature, and altitude—encoded within the meteoric isotopic signature.
Addressing this gap, this investigation utilizes the WAM-2Layers Eulerian moisture tracking model to characterize the hydrological drivers and transport pathways for the Chingaza Páramo 'precipitationshed'. This integrated tracking approach provides the essential provenance context required to interpret isotopic data from both geographic and hydrological perspectives, allowing for a comprehensive evaluation of how moisture origin and transport history are manifested within the environmental signature of meteoric waters. To ensure model consistency, isotopic data were collected at dual daily and monthly frequencies, purposefully aligned with the temporal timestamps and 'sink' settings of the WAM-2Layers model.
By leveraging this spatio-temporal alignment, the study analyzed isotopic compositions concurrently with the precipitation, elevation, and temperature history along the moisture trajectories en route to the Chingaza Páramo. The integration of these variables into novel hydrological driver archetypes enabled a detailed characterization of the atmospheric environmental signature. Preliminary results demonstrate the robustness of this classification framework when mapped against the Global Meteoric Water Line (GMWL). For the monitored period, the daily sampling characterization identified a dominance of warm-source trajectories (63%), followed by mixed (19%) and cold-source (16%) archetypes, with moisture provenance primarily originating from the Atlantic Ocean. The distribution of these samples within the stable isotope biplot (d18O vs. d2H) effectively illustrates the transition between enrichment and depletion phenomena, underscoring the potential of this approach to quantify the influence of atmospheric drivers on Andean meteoric water behavior.
How to cite: Piña, A. and Romero, P.: Characterizing Hydrological Drivers of the Andean Precipitationshed: Integrating Moisture Tracking and Stable Isotopes to Disentangle Precipitation Amount, Altitude, and Temperature Effects., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20483, https://doi.org/10.5194/egusphere-egu26-20483, 2026.
Freshwater springs are the primary source of drinking water for people residing in remote and inaccessible mountainous terrains. Additionally, springs play a crucial role in maintaining the base flow of Himalayan rivers during the lean season. However, half of the Himalayan springs are experiencing a noticeable decline in discharge and are drying up due to current climate change and anthropogenic influences. The rejuvenation and restoration of freshwater springs have long been a challenging task due to the presence of complex geological terrain, along with fractured aquifers that connect across multiple watersheds. Previous studies have focused more on the watershed approach, lacking aquifer-targeted springshed management. This study integrates isotopic (δ18O, δ2H and 3H) and field-based hydrogeological and geophysical resistivity surveys to uncover multifaceted hydrogeological elements, including recharge sources, recharge altitudes, surface and subsurface conduits, and hydrological processes controlling spring flow for springshed management.
In the present study, 240 samples were collected from 120 springs for pre-monsoon and post-monsoon seasons, and 66 samples of precipitation were collected on an event basis throughout the year. The Local Meteoric Water Line (LMWL) for the study region has been developed as δ2H = 8.02*δ18O + 11.79 and found equivalent to GMWL. The isotopic values of the springs (δ18O ranges from -10.6‰ to -5.2‰ and δ2H ranges from -68.0‰ to -35.9‰) coincide with seasonal precipitation signatures (δ18O ranges from -16.23‰ to +2.82‰, δ2H= -125.0‰ to 20.5‰), indicating that the springs are recharging from the Indian Summer Monsoon. The precipitation exhibited an isotopic lapse rate of -0.4‰ and -4.1‰ for δ18O and δ2H, respectively, for a 100m increase in altitude. The recharge elevation of all springs, calculated from the isotopic lapse rate, lies within the altitude range of 1386 to 2194 m in the study area. These locations can be utilised for artificial recharge interventions, such as the construction of check dams, ponds, and trenches, as per the suitability.
The hydrogeological survey reveals that freshwater spring discharge is influenced by gravity flow along local-scale geological discontinuities, including fracture zones, joint networks, and minor fault and fracture interactions that have developed within the rock mass. In contrast, geothermal springs are channelised across major regional geological discontinuities, such as the MCT. The geophysical resistivity survey in the springshed of the different springs is capable of mapping the subsurface conduits and pathways in the fracture-dominant lithology. These results provide site-specific guided intervention, along with validation of the isotopic results. The proposed methodological integration of stable isotopes and field-based hydrogeological and geophysical surveys can successfully aid in the investigation of complex mountain hydrology. The study can help policymakers, the government, and other stakeholders in the successful implementation of targeted recharge interventions for springshed management.
How to cite: Kumar, P., Krishan, G., and Chattopadhyay, P. B.: Novel Application of Isotopic and field-based survey for uncovering spring hydrogeology for sustainable management, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-957, https://doi.org/10.5194/egusphere-egu26-957, 2026.
High-mountain wetlands have the potential to store and release large volumes of water, providing crucial supplies to highland communities and receiving lowlands, especially in seasonally dry climates due to their flow regulation capacity and extended residence times. Despite their significance to mountain hydrology and water resources, gaps remain in understanding the connection between wetlands and streams. This study uses a combination of fluorescent tracing and high frequency monitoring of rainfall-runoff and wetland water levels to assess the movement and timing of flow through wetlands. The experiments were conducted during the wet or dry season in 5 representative study catchments (0.38 km2 – 12.58 km2) with varying wetland coverage, from Northern Ecuador to Southern Peru. Fluorescein was introduced into wetlands and monitored downstream with activated carbon samplers for 5-12 months. Our results suggest transit times from less than 1 week to upwards of 3 ½ months, with one experiment seeing little to no response. Results indicate that wetlands are likely far more hydrologically connected to streams in the wet season than in the dry season, where in some cases they may not be connected at all. Several peaks in fluorescein concentration during the wet season may suggest that the wetlands contribute to streamflow via multiple pathways. The potential lack of fluorescein response at one site could indicate a very high transit time or that the wetlands did not feed the stream at the monitored locations during the monitoring period. The results demonstrate a complex connection between wetlands and streams depending on location and season, amongst other factors. However, persistent contributions from wetlands to streams observed several months after dye introduction support their significance to downstream, year-round water supply. We discuss potential hypotheses for divergent wetland behaviours and provide a baseline for further investigation.
How to cite: Ross, A. C., Howard, B. C., Lahuatte, B., Fuentes, P., De Bievre, B., Jerves, M., Crespo, P., Montoya, N., Oshun, J., and Buytaert, W.: Transit times and governing processes in high-mountain wetlands, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19626, https://doi.org/10.5194/egusphere-egu26-19626, 2026.
Climate change is exacerbating spring water scarcity in the trans-Himalayan region of Ladakh, India, owing to increased uncertainty in winter snowfall. Amidst this growing concern, artificial ice reservoirs emerged as a climate adaptation technique and have gone through several engineering iterations since the late 1980s. These gravity-based systems capture winter streamflow in the form of ice and release meltwater during the crucial spring agricultural season. Despite their rapid implementation across the region, data integration into their construction process and quantitative monitoring of their water systems and volumetrics remain limited.
This study demonstrates the application of a lightweight, consumer-grade unmanned aerial vehicle (UAV) for photogrammetry-based volumetric analysis of ice reservoirs. A DJI Mini 3 was used to conduct 20 repeat surveys during the winter–spring 2024–2025 season on ice reservoirs constructed by a Ladakh-based startup, Acres of Ice, in two villages: Igoo and Sakti. Oblique imagery was captured at a 65° camera angle with 80% overlap to constrain ice reservoir geometries. Photogrammetric data processing was used to generate high-resolution digital elevation models (DEMs), which were coregistered using ground control points surveyed in situ with a Trimble RS2 GNSS with real-time kinematics (RTK). Finally, on-site weather station and pipeline-based sensor inputs provided water and air temperatures, as well as discharge data, to further contextualise the construction process.
Preliminary results reveal a maximum ice volume of approximately 4,116 m³ at the Igoo site, with mean discharge rates of ~3.5 L s⁻¹ and a low water-to-ice efficiency of 13% between November and April. During this period, water temperature averaged 4 °C and mean air temperatures averaged −8 °C. At the Sakti site, ice volumes reached ~1,814 m³, with average discharge rates of ~5 L s⁻¹, indicating a lower water-to-ice efficiency of 6% between December and April. During this period, water temperatures averaged ~2 °C, while air temperatures averaged −10 °C. These results indicate a need to optimise design parameters for water management and better integrate microclimate data into ice reservoir construction.
This research offers the first comprehensive, data-driven approach to volumetric measurements of ice reservoirs, laying the groundwork for future studies on groundwater hydrology, watershed management, and socio-ecological impacts, and contributing to a holistic, scalable approach to adaptive climate strategies in high-altitude villages in Ladakh.
How to cite: Sah, K. M. and Balasubramanian, S.: UAV-Derived Volumetric Monitoring of Artificial Ice Reservoirs for Climate Adaptation in Ladakh, India, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15370, https://doi.org/10.5194/egusphere-egu26-15370, 2026.
The Himalayas represent one of the world’s major water towers, sustaining downstream populations across Asia. However, hydrological processes in this region remain poorly constrained due to extreme topography, limited accessibility, and sparse in situ observations. Consequently, most existing studies rely on modeling and remote sensing, with a strong emphasis on glacier melt. Yet water-budget estimates suggest that up to two-thirds of discharge originates from groundwater, underscoring the need to better understand subsurface water dynamics.
To anticipate future water availability in a progressively glacier-free Himalaya, ground-based observations are required. Here, we exploit the dense Hi-CLIMB seismic array to investigate hydrological variability along a Trans-Himalayan transect. The array spans ~250 km from the Terai plains to the Tibetan Plateau, with an average station spacing of ~5 km. Most stations operated between late 2022 and 2024, capturing at least one full monsoon cycle.
We derive temporal seismic velocity changes from ambient noise interferometry as a proxy for groundwater storage variations, and analyze seismic noise amplitudes as an indicator of river activity. These seismic observations are compared with climatological datasets, regional geology, glacier cover from the Randolph Glacier Inventory, and geomorphic features extracted from GIS analysis. Our results reveal strong spatial contrasts in monsoon-driven hydrological responses and identify distinct zones and phases contributing to runoff along the transect, highlighting the potential of seismic monitoring for resolving groundwater dynamics in high-mountain environments.
How to cite: Illien, L., Makus, P., Andermann, C., and Hovius, N.: Groundwater monitoring along a Trans-Himalayan transect using seismic velocity changes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13449, https://doi.org/10.5194/egusphere-egu26-13449, 2026.
High mountain environments provide a critical store of water in the form of winter snow that is released as liquid water in the summer months. Globally, one sixth of the human population is dependent on this meltwater as it moves down the mountains into more heavily populated regions. The rapid warming of our planet threatens the security of this resource, with winter snow becoming less predictable and glaciers shrinking at an accelerating rate. In this context, understanding the storage and release of water from the high alpine environment is an urgent research need.
The Big Thaw project aims to fill four observational gaps to improve intelligence relating to mountain water resource availability, with runoff being a key element. To supplement and inform modelling, a series of very low-cost wildlife cameras was installed in the Rofental region of the Austrian Alps, and programmed to obtain short videos of meltwater-fed rivers between three and four times a day. The videos were analysed and processed to provide a time series of streamflow using a Space Time Imaging Velocimetry (STIV) technique.
This presentation describes the success of this approach, as well as challenges relating environmental conditions, morphological change and the practicalities of operating low-cost sensors for long periods in harsh environments.
How to cite: Everard, N., Rickards, N., Islam, N., Barr, A., and Pritchard, H.: Trailcam Hydrology – Can very low-cost wildlife cameras be used to monitor streamflow in an Alpine environment?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18420, https://doi.org/10.5194/egusphere-egu26-18420, 2026.
Stationary precipitation measurements are frequently affected by undercatch errors, which are particularly pronounced in cold and alpine regions with strong winds. Since gridded precipitation products used in land surface modelling are often derived from spatial interpolation of meteorological station data, these measurement errors propagate directly into gridded datasets. Hydrological models provide a powerful tool for validating precipitation products through their integration of multiple water balance components. In this study, we develop a monthly undercatch correction product for Austria using Generalized Additive Models (GAMs) trained on station observations with geographical exposure and terrain elevation as predictors (R² > 0.76 in cross-validation), and apply these corrections to existing gridded precipitation datasets.
We validate the undercatch correction using the conceptual rainfall-runoff model COSERO across Austria and in two high-alpine reservoir catchments (Kölnbrein and Schlegeis). Austrian-wide simulations demonstrate elevation-dependent improvements, with reduced runoff biases particularly in catchments above 1500-2000 m elevation. In the alpine case study regions, the corrected precipitation closes the long-term water balance where uncorrected data showed deficits exceeding 20 %. The physically-based snowpack model Alpine3D, validated against stereo-satellite observations, shows substantial improvements in snow depth simulations with median biases decreasing from -0.87 m to +0.15 m. Additionally, the correction improves representation of snow melt-out behaviour during the ablation season and enables more realistic simulation of long-term glacier volume changes. These results highlight the importance of accounting for undercatch errors in high-alpine terrain and demonstrate the value of comprehensive hydrological validation for precipitation products.
Acknowledgements: We thank the Austrian Climate Research Programme (ACRP), and the Verbund Energy4Business GmbH for funding, fruitful discussions and providing us with data.
How to cite: Ehrendorfer, C., Maier, P., Lücking, S., Pulka, T., Lehner, F., Herrnegger, M., Formayer, H., and Koch, F.: Snow-hydrological validation of undercatch corrected precipitation across alpine regions in Austria, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18858, https://doi.org/10.5194/egusphere-egu26-18858, 2026.
Climate change poses a major threat to vulnerable regions, necessitating the development of adaptive strategies to ensure a sustainable future. To achieve sustainability, a deeper understanding of ecosystems and their nexus with climate is needed. Moreover, the interconnection between mountains and valleys demonstrate the synergies of water services in these two zones. Mountain regions, which function as critical water sources for downstream users, are particularly vulnerable and should be prioritized in adaptation strategies. These areas play a central role in water production, storage, and distribution, rendering their resilience essential for regional sustainable water management. Remote sensing products, such as MODIS and GMET, provide valuable tools for monitoring ecosystem dynamics and their interconnection with climatic variables. Precipitation emerges as the key driver influencing ecosystem responses. Our analysis reveals that vegetation indicators, NDVI and EVI, exhibit a lag by approximately one month in response to changes in precipitation. Seasonal-Trend decomposition (STL) confirms a strong correlation in the trend component: wet events typically trigger ecosystem responses after about one month. Furthermore, both wet and dry extreme events, significantly influence ecosystem development and their capacity to deliver services. Climate change scenarios indicate that future extremes will predominantly be wet rather than dry. This suggests an increase in the frequency and intensity of precipitation events by 2050, raising the risk of flooding and associated socio-ecological challenges. Such extremes can disrupt vegetation dynamics in EVI and NDVI indicators which may reflect a reduction in plant productivity and altering the dynamics of ecosystem services. Understanding these dynamics is crucial for designing resilient integrated water and ecosystem management strategies that safeguard both human and environmental well-being in the Inter - Andean region of Bolivia.
How to cite: Chavez Flores, I. A., Mendoza Paz, S., Gonzales Amaya, A. S., Villazon Gomez, M. F., Nuñez Mejia, S., Willems, P., and Gobin, A.: Understanding the water-ecosystem nexus in the Inter-Andean region of Bolivia – a synergistic, historical and complex connection, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13176, https://doi.org/10.5194/egusphere-egu26-13176, 2026.
The Andes support critical mountain ecosystems and water resources that are highly sensitive to climate variability. Spanning multiple climate zones and steep topographies, Andean ecosystems exhibit distinct ecohydrological responses to changes in climate and land use across elevational gradients. However, interactions between vegetation dynamics and hydrological processes remain poorly understood at the scale of the Andean domain. This key knowledge gap is partly driven by local data scarcity and the limited representation of strong spatial heterogeneity. In this study, we investigate the spatial patterns of ecohydrological dynamics in the Andes using a hyper-resolution, physics-based ecohydrological modelling framework. Specifically, we develop a catchment selection scheme to identify representative catchments of all major climates and biomes across the entire mountain range of the Andes, quantify their hydrological and vegetation dynamics across elevational and latitudinal ranges. More specifically, we applied K-means clustering to all non-Amazon Andean catchments using key hydroclimatic, topographic, and soil variables. Four primary clusters were identified to represent the regional diversity: the North Tropical Andes, South Tropical Dry Andes, Central Dry Andes, and Extratropical Wet Andes. The North Tropical Andes cluster is located in Peru, while the remaining three clusters consist of Chilean catchments. Within each cluster, we analyse (1) vegetation dynamics and water balance components across elevation bands, (2) elevation-dependent plant water limitations and their variability among catchments, and (3) the relative importance of key drivers including precipitation, vapor pressure deficit, and air temperature in controlling evapotranspiration, gross primary productivity, and discharge, and how these relationships are modulated by topography. Through this integrated analysis, we aim to provide new insights into how climate, vegetation and hydrology vary systematically across the Andes.
How to cite: Gu, R., Becker, R., Buytaert, W., and Paschalis, A.: Ecohydrological Controls Across Elevation and Climate Gradients in the Andes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12094, https://doi.org/10.5194/egusphere-egu26-12094, 2026.
Mountains, often called the world’s "water towers" due to their important role in global hydrology and water resources including supply for human uses and ecological processes, are interconnected with lowlands in a system that encompasses both natural resources and society. Climate change in mountain regions affects the amount, timing and quality of mountain runoff, with important consequences downstream. While mountain streamflow and associated climate change impacts always travel downstream, these impacts can cascade not only spatially and temporally but also causally across a wide range of social-ecological systems. Additionally, upstream-downstream teleconnections can have important impacts that shape upstream water tower systems, for example, through infrastructure development based on priorities for downstream users.
We synthesize key water cycle changes in mountain regions worldwide and examine their consequences downstream, such as shifts in surface and groundwater availability, disaster risks, water quality, human water use, sediment transport, aquatic ecosystems, and sea-level rise. We link these dynamics to social processes, including culture, economy, and well-being in local and transboundary contexts. Furthermore, we highlight feedback mechanisms where downstream activities shape upstream water dynamics, including infrastructure development (e.g., hydropower), land and water use (roads, mining, tourism), and conservation (glacier protection, low-impact recreation). Our analysis underscores the importance of an integrated framework for advancing the understanding of interconnected mountain-lowland systems to inform sustainable water management and policy development in rapidly changing mountain regions and beyond.
How to cite: Viviroli, D., Drenkhan, F., Scott, C. A., Somers, L., and van Tiel, M.: Cascading downstream impacts of climate change in the world’s water towers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1691, https://doi.org/10.5194/egusphere-egu26-1691, 2026.
Deglaciation alters hydrological processes in mountain catchments by modifying runoff regimes, impacting water quality, availability, and storage, with widespread consequences for downstream water security. While the timing and rate of glacier loss are increasingly well constrained, how glacier retreat translates into spatially heterogeneous water security risk remains poorly understood. In water-scarce catchments, small reductions in glacier melt may have severe impacts, whereas in water-abundant systems, large losses may be inconsequential. Risks can also differ substantially between upstream and downstream regions due to spatial heterogeneities in hazards, and the exposure and vulnerabilities of social-ecological systems.
To address this gap, we present a conceptual and quantitative framework to assess deglaciation-driven water security risk in Andean catchments, grounded in a comprehensive risk assessment approach (risk = hazard × exposure × vulnerability). First results quantify the effects of glacier retreat on the hazard and exposure components using high-resolution hydrological simulations from the JULES land surface model. The analysis spans ten glaciated river basins across the Andes, covering a broad climatic gradient from hyper-arid to humid conditions. A key novelty is our spatially explicit approach, accounting for upstream-downstream heterogeneities in hazard and exposure quantifications.
Our framework moves beyond glacier-centric assessments by explicitly linking cryospheric change to downstream water security risk across diverse hydro-climatic settings. By providing a transferable but region-specific method, our approach offers a foundation for identifying hotspots of emerging water security risk under continued glacier retreat.
How to cite: Becker, R., Castro, S., Drenkhan, F., Montoya, N., Davies, B., Ely, J., and Buytaert, W.: Spatial patterns of water security risks in the deglaciating Andes , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13406, https://doi.org/10.5194/egusphere-egu26-13406, 2026.
High-elevation regions are increasingly exposed to intensifying droughts, challenging the role of mountains as reliable water towers. Glacierized catchments represent particularly complex systems, where atmospheric forcing, snow and glacier dynamics, and hydrological processes interact across multiple timescales to shape drought impacts.
Despite this complexity, drought processes in glacierized alpine basins remain only partially explored. Here we focus on glacierized catchments across the Italian Alps, including basins in north-western and north-eastern Italy (Piedmont, Aosta Valley, and Trentino), a climatic transition zone between Mediterranean and continental alpine regimes where drought responses may differ from those observed in other alpine regions, while downstream water availability supports hydropower production, irrigation, drinking water supply, and alpine ecosystems.
This study investigates how droughts have manifested and evolved in Italian glacierized catchments over the period 2000–2024, analyzing their spatial and temporal variability and their propagation across meteorological, snow, glacier, and hydrological compartments. Meteorological droughts are characterized using precipitation and temperature anomalies derived from the BigBang dataset, while snow droughts and glacier melt contributions are assessed using snow water equivalent and melt simulations from the S3M Italy model. Hydrological drought conditions are further investigated using streamflow observations provided by regional monitoring agencies. The analysis aims to examine how meteorological variability, hydrological mechanisms, and glacier melt influence drought duration and intensity, and how these relationships have evolved over the last two decades, particularly at high elevations.
By providing an integrated assessment of drought mechanisms in southern alpine glacierized basins, this work addresses a key knowledge gap in mountain hydroclimatology. The results will improve understanding of how glacierized catchments respond to drought under ongoing climate change, offering a basis for future investigations of high-elevation drought signals and their implications for alpine water resources, as well as for assessing drought impacts across different environmental compartments in mountain regions.
How to cite: Leone, M., Avanzi, F., Gabellani, S., Isabellon, M., Manganaro, C., Ayala, A., and Fyffe, C.: Droughts in glacierized catchments of the Italian Alps: evolution and emerging high-elevation variabilities (2000–2024), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12537, https://doi.org/10.5194/egusphere-egu26-12537, 2026.
Temporary storage of precipitation in mountainous regions as snow is crucial for downstream water users, including agriculture and hydroelectric power generation. However, the amount and duration of this storage are changing over time. We used snow water equivalent (SWE) data from the pre-alpine Wägital in Switzerland, one of the longest datasets of SWE globally, to analyze trends in SWE. Measurements have been made annually on April 1st at multiple locations in the Wägital catchment since 1943. To overcome the limitations of relying solely on April 1st SWE measurements, we applied a degree-day model to reconstruct daily SWE values, and identified the annual maximum SWE (maxSWE) and duration of snow cover. Here, we present trends in meteorological parameters, April 1st SWE, maxSWE, and the duration of snow cover. In addition, we describe the spatial variation in maxSWE with respect to elevation, aspect, and slope.
The model results revealed that April 1st measurements often fail to capture maxSWE, highlighting the importance of using maxSWE for trend analyses. There was a general decline in maxSWE across the catchment during the study period and maxSWE now occurs earlier than in the past. Positive trends for maxSWE dominated from the 1940s to the 1980s, followed by stronger negative trends from the 1980s onward. The strength of these negative trends depended strongly on the chosen start year. Similar patterns were observed for the duration of snow cover. Not surprisingly, "cold and wet" years resulted in the most snow, whereas "warm and dry" years resulted in the lowest maxSWE. The variability in maxSWE was larger for higher elevations sites. Spatially, maxSWE increased with elevation, was lowest on south-facing slopes and highest on west-facing locations, and was lower for steeper than flat slopes. While uncertainties in input data and modeling limitations exist, this study underscores the value of long-term datasets like those from the Wägital monitoring program for understanding trends in snow cover and storage, and anticipating future challenges related to a reduced snow cover due to climate change.
How to cite: van Meerveld, I., Sigrist, F., Rohrer, M., and Seibert, J.: Snow in transition: 80 Years of SWE data for the Wägital, Switzerland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14652, https://doi.org/10.5194/egusphere-egu26-14652, 2026.
A significant hydrological feature of the cryosphere is that water bodies exist in multiphase forms. Abrupt shifts in multiphase water indicate a break in the stability of the hydrological cycle and may threaten sustainable water resources supply. However, the phenomenon of abrupt shifts in alpine regions and their underlying driving mechanisms remain poorly understood. This study investigated the spatiotemporal patterns, gradual accumulation–abrupt characteristics, and driving mechanisms of multiphase water in the Three-River-Source Region (TRSR). The results revealed that solid water decreased, while liquid and gaseous water increased from 2002 to 2022. A total of 32.25% of the TRSR experienced abrupt shifts, primarily in the Yangtze and Yellow River source regions. The critical thresholds for solid, liquid, and gaseous water were identified as 2.54×104 m3，1.60×107 m3, and 3.21×105 m3, respectively. Abrupt shifts were most likely to occur when the volumes of solid, liquid, and gaseous water reached their respective thresholds. Climate was the primary driver of gradual and abrupt changes, while vegetation significantly moderated solid water ablation and enhanced liquid water accumulation in regions with abrupt shifts. Specific environmental conditions, such as leaf area index (0.11–1.00), annual rainfall (199.26–649.76 mm), and the maximum temperature (0.83–9.80℃), were found to increase the likelihood of triggering abrupt shifts. This study proposed a more accurate method to depict the shift regime of multiphase water, providing critical insights for water resources management and risk governance in alpine regions.
How to cite: Lu, M.: Shift regime of multiphase water in the Three-River-Source Region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3660, https://doi.org/10.5194/egusphere-egu26-3660, 2026.
Alpine areas play a major role in the water supply of downstream valleys by releasing water, and especially during dry periods. The response of catchment discharge to climate change can be significantly influenced by groundwater processes. However, these processes are still poorly understood in Alpine areas.
In this study, we use isotopic monitoring of a small alpine catchment to investigate the evolution of snowpack isotopic composition and its implications for groundwater recharge assessment. The results highlight the dominant contribution of snowmelt to recharge processes in the studied alpine catchment located in the Swiss Alps. This finding is critical for improving the evaluation of alpine hydrological responses under future climate change.
Then, we apply an integrated surface–subsurface hydrological model to assess the role of groundwater in buffering future summer low flows and to provide new insights into the influence of geological controls on discharge dynamics. The spatially explicit modelling framework enables the quantification of groundwater storage and its variability across different geological units within an alpine catchment under both present and future climate conditions. In parallel, conceptual hydrological models are used to assess future changes in spring discharge in different alpine settings, these resources being particularly relevant for drinking water supplies. The used climate scenarios were CH2018 RCP 8.5 and 4.5.
The results suggest that under future extreme climate change conditions: the average groundwater storage in quaternary deposits at the catchment scale increases in winter and decreases in summer as well as spring and catchment discharges. Annual groundwater storage for the entire catchment decreases due to a reduction in mean annual groundwater recharge, and total catchment discharge also decreases. In relative terms, the modelled decrease in groundwater storage was less severe than the simulated decrease in discharge in the analysed climate change scenarios. This study demonstrates that both quaternary deposits (especially moraine and talus units) and bedrock play an important role in sustaining discharge during low-flow periods.
How to cite: Arnoux, M., Carron, A., Halloran, L. J. S., Carlier, C., Cochand, F., Brunner, P., Schaeffli, B., Brauchli, T., Winstral, A., and Hunkeler, D.: Groundwater storage in alpine catchments and response to climate change: the importance of geology and snow cover, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20444, https://doi.org/10.5194/egusphere-egu26-20444, 2026.
Mountain regions, characterized by glacial and periglacial features, constitute a major global freshwater resource, yet climate-driven changes in the magnitude and timing of groundwater discharge threaten large-scale water resource sustainability. Though the widespread retreat of mountain glaciers and degradation of permafrost are well-documented, their individual and combined influences on groundwater systems remains poorly understood. Quantifying the temporal and spatial relationship between glacial melt, permafrost extent, groundwater discharge, and streamflow is necessary to assess the sustainability of streamflow under changing climate conditions. We present a two-dimensional coupled groundwater flow and heat transport model with seasonal freeze-thaw capability using the United States Geological Survey SUTRA 4.0 modeling software to investigate how warming air temperatures influence groundwater discharge patterns from a permafrost-affected aquifer recharged by glacial meltwater. The model represents a hillslope-valley cross-section adjacent to a small alpine glacier in the Rocky Mountains of Colorado, USA. The model is forced with baseline and observed warming air temperature scenarios and explicitly resolves the relative importance of permafrost thaw, seasonally-variable recharge, and changes in glacial meltwater contribution to groundwater discharge patterns to an alpine lake. Results suggest that interactions between a saturated glacial meltwater recharge zone and the adjacent permafrost hillslope may drive groundwater discharge seasonality and contribute to talik development beneath the hillslope. Simulations assess sensitivity to warming rate, permafrost thickness and continuity, and the timing and magnitude of glacial meltwater recharge.
This research provides process-based insight into mountain groundwater flow dynamics in areas of degrading permafrost and glacial features, and helps clarify the role of glacial meltwater recharge in sustaining mountain-derived streamflow under elevation-dependent warming. Results will inform predictions of hydrologic resilience and water resource sustainability in alpine watersheds, which are experiencing rapid environmental change.
How to cite: Celupica-Liu, C., McKenzie, J., and Ge, S.: Assessing the sustainability of mountain groundwater resources under conditions of permafrost degradation and glacial recession , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7946, https://doi.org/10.5194/egusphere-egu26-7946, 2026.
Evapotranspiration (ET) is an important process in the water-balance of alpine catchments but usually superimposed by snow and glacial processes. Due to complex topography, vegetation segmentation and scarcity of observation data, large uncertainty exists in the description and modelling of ET processes in alpine terrain. This is especially the case when looking at detailed process functioning on the distributed sub-kilometer scale. To address this knowledge gap and better quantify the spatial distribution and temporal dynamics of ET rates in alpine areas, we are combining detailed field monitoring and distributed, physically based modelling in the 12 km² sized Fundusbach catchment (Tyrol, Austria). The monitoring network includes four water level and water temperature loggers along the longitudinal river profile (since 2022), two meteorological stations (Temperature and Precipitation since 2022), three Bowen-Ratio Stations coupled with soil moisture sensors and placed at locations with different elevation and vegetation cover (since 2024), as well as one CNRS-probe (since 2025) to quantify distributed soil moisture. All sensors operate at hourly or 15-minute intervals. To bridge the gap between the point- and catchment scale, we use a high-resolution water balance model (WaSiM, 25 m, 1 h). Based on the temporal resolution of the observations and the model, we are able to include both seasonal as well as diel cycles of the water balance.
In a two-step approach we first use the measurements and model to investigate integrated process functioning within the last decade. While changes in the diel streamflow cycles along the longitudinal river profile helped disentangling the contradictory signals of melt and ET, they were not sufficient to investigate spatial patterns of process behaviour. Bowen-Ratio measurements add some spatial information, but observations are still sparse with reference to the complex micrometeorological conditions and topography. However, all observations proved crucial for the calibration and validation of the model, particularly given the goal of capturing process interactions and quantifying ET volumes.
In a second step, we apply an ensemble of six EURO-CORDEX climate projections to investigate how process dominance might change until the end of the century. Furthermore, we investigate the key role of vegetation distribution on spatial process behaviour. In this regard, we combine the climate projections with different land use scenarios. We hypothesize that especially the distribution of shrubs will have major influence on the partitioning of water within the catchment, potentially limiting water availability for lower elevation forested areas.
How to cite: Herzog, A., Francke, T., and Vormoor, K.: Between scales and complexity: Integrated process functioning of evapotranspiration in alpine catchments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16807, https://doi.org/10.5194/egusphere-egu26-16807, 2026.
Hydrological modelling in snow-dominated high-alpine karstified catchments remains challenging due to complex snow processes and their influence on runoff generation. This study investigates the impact of snow model complexity on discharge simulations in the Zugspitze region, at the border of Germany and Austria, in the European Alps across two neighbouring catchments. Both catchments are located in the same mountain range, are heavily karstified, share similar geological structures, and have practically no surface runoff. However, some catchment characteristics differ, which we will investigate in this modelling study. The Partnach spring catchment (15.4 km², 1430-2962 m a.s.l., W-E orientation) comprises steep rocky terrain in the upper and lower part in the south-, west- and north-facing terrain with dominant a high-altitude plateau in the middle part, and overall limited vegetation. In contrast, Hammersbach (17.8 km², 768-2951 m a.s.l., N-S orientation) shows stronger elevation gradients and is predominantly covered by forests in the lower third of the catchment. Steep north-facing rock walls reach down to ~1000 m and lead to a longer lasting snow cover in the upper and middle part of the catchment due to terrain shading. We examine for these two catchments how a physically-based snow representation (Alpine3D) compares to a degree-day approach (CemaNeige) regarding its impact on snowpack evolution and runoff generation when coupled with an identical lumped conceptual GR4H hourly routing scheme and meteorological forcing. Alpine3D explicitly simulates boundary layer fluxes and energy balance processes, while CemaNeige relies on the upper GR4H storage to represent evapotranspiration and interception. The GR4H routing parameters are calibrated using a 5-year moving window approach across hydrological years 2014-2025 for both catchments, which face characteristic high-alpine measurement challenges such as winter data gaps, avalanche events, and sediment transport. Multicriteria validation incorporates SWE measurements, Sentinel-2 snow-covered area information, and discharge observations. Results show on the one hand, that both modelling approaches achieve comparable annual discharge performance, while Alpine3D consistently provides a more realistic representation of spatiotemporal snow distribution. On the other hand, the comparative analyses of the adjacent catchments present model behaviour under different snow, terrain and land-cover conditions. This study provides insights into the conditions under which increased physical realism improves runoff simulations and for which situations conceptual approaches are a good choice, supporting informed model selection for snow-dominated and ungauged alpine regions.
How to cite: Bögl, E., Facchinetti, R., Schattan, P., Wetzel, K.-F., Knieß, J., Schulz, K., and Koch, F.: Coupled Snow-Runoff Modelling in Alpine Karst: Comparing physics-based vs. conceptual snow model representation in neighbouring catchments with different characteristics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17778, https://doi.org/10.5194/egusphere-egu26-17778, 2026.
During rain-free periods, and in catchments without considerable human intervention, diel streamflow cycles are characterized by distinctive patterns of rising and falling streamflow over the course of day. This dynamic is mainly driven by variations in solar radiation leading to an impact of snow and glacier melt, and evapotranspiration (ET) on diel streamflow cycles in alpine catchments. However, there are also other processes such as thermal expansion of water and streamflow-groundwater exchange that can lead to variations in diel streamflow patterns.
In this study, we investigate diel streamflow cycles in the 12 km² sized Fundusbach headwater catchment of the Ötztaler Ache in the Eastern European Alps. Based on observation data from three water level loggers along the longitudinal river profile (installed in 2022), we aim to identify the relative role of meltwater, ET, and water temperature on diel streamflow cycles along the river profile to better understand the interaction of these ecohydrological processes both spatially and seasonally. Results reveal that throughout the year without snowfall, diel streamflow cycles are mainly driven by meltwater dynamics. However, isolating the meltwater impulse from the uppermost part of the catchment from the water level loggers further downstream, diel streamflow cycles highlight the potential influence of ET. In the next step, we aim to correlate these streamflow variations with water temperature to quantify the effects of thermal expansion and the potential impact of water exchange between streamflow and soil- and groundwater.
How to cite: Vormoor, K., Anna, H., Till, F., and Axel, B.: Exploring diel streamflow variations in an alpine headwater catchment, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19972, https://doi.org/10.5194/egusphere-egu26-19972, 2026.
The European high-alpine landscapes are particularly sensitive to climate change, with accelerating glacier retreat, reduced snow cover, and altered precipitation patterns. Glacier and snowmelt play a crucial role in determining the water availability in such environments. Quantifying long-term historic streamflow variations under the impact of climate change in high-alpine landscapes has, however, rarely been studied due to limited long-term hydroclimatic observations, complex topography, and modeling challenges. Here, we develop a cascading hydroclimatic coupling framework (Reanalysis-WRF-WaSiM) to simulate streamflow changes in three high-alpine catchments (55-77 km2) with varying glacier coverages (3% to 31%) in the central European Alps from 1850 to 2015 in an hourly time step and a spatial resolution of 25m × 25m. We first build a physics-based and fully-distributed hydrological model, WaSiM, for each site, and the model performances of the snow, glacier, and river discharge modules are evaluated in detail. The models are then forced with the dynamically downscaled and bias-corrected reanalysis climate data from the Weather Research and Forecasting Model (WRF). By performing such detailed long-term hydrological simulations with high temporal and spatial resolutions for the first time, our study provides new insights into the evolution of extreme hydrological events and changes in water availability via internal flux partitioning in high-alpine environments with accelerating glacier retreats under climate change.
How to cite: Fan, X., Hofmeister, F., Schaefli, B., and Chiogna, G.: Physics-based simulation of long-term hydrological changes in the high-alpine environments in central Europe , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2820, https://doi.org/10.5194/egusphere-egu26-2820, 2026.
Mountain regions are major recharge areas that sustain downstream groundwater and river systems, yet they are among the least observed parts of catchments. In dual-monsoon climates, the proportion of precipitation falling as pre-monsoon snow and monsoon rain varies greatly between regions. However, harsh environmental conditions and limited accessibility have restricted observations in mountain areas. As a result, it remains unclear how much different types of precipitation, such as snow and rain, contribute to groundwater recharge and which controlling factors, such as geology and slope, regulate these contributions.
Stable water isotopes and d-excess are powerful tracers of the seasonality of recharge precipitation and subsurface groundwater mixing processes. For example, Nakamura (2017) clarified seasonal local meteoric water lines (LMWLs) in the Kofu Basin of central Japan and demonstrated that groundwater in the alluvial fan is strongly dominated by pre-monsoon (snow-season) precipitation, even though pre-monsoon precipitation accounts for only about 25% of the annual precipitation in the lowlands. This apparent paradox has been explained by recharge from snowmelt originating in the surrounding mountains. However, due to limited accessibility, precipitation and river water have not been sufficiently observed in mountain regions, and large-scale, observation-based verification from the mountain side remains limited.
In central Japan, mountain ranges with elevations of approximately 3,000 m extend across the main island of Honshu from the Sea of Japan to the Pacific Ocean. These ranges are collectively referred to as the Japanese Alps and are subdivided into the Northern, Central, and Southern Alps. Several alluvial fans have developed along their foothills, forming important recharge areas for downstream water resources.
In this study, we focused on the Japanese Southern Alps, located on the Pacific side of the Japanese Alps. The Japanese Southern Alps are characterized by steep topography, multiple geological units, and a dual-monsoon climate. River water was sampled at 48 sites across an elevation range of 392–1,556 m (the elevation of the downstream urban area of Kofu City is approximately 200 m).
River water samples were collected during both the pre-monsoon and monsoon seasons, and δ¹⁸O, δD, and d-excess were analyzed. In both seasons, river water d-excess values were close to those of pre-monsoon precipitation, indicating that winter-origin water dominates streamflow even during the monsoon period. Mass-balance analysis further confirmed that pre-monsoon precipitation makes a dominant contribution to river water in both seasons.
Furthermore, significant differences in d-excess were observed among geological units. These differences followed a consistent ranking, with higher d-excess associated with higher hydraulic conductivity. This suggests that, in steep and geologically complex mountain regions under a dual-monsoon climate, permeability contrasts among geological units regulate the infiltration of pre-monsoon precipitation and thereby influence the relative contributions of pre-monsoon and monsoon precipitation to river water.
These results demonstrate that differences in geological structure within mountain blocks influence the d-excess values of downstream alluvial-fan groundwater and river water. This finding has important implications for identifying recharge areas and for understanding mountain–lowland hydrological connectivity in dual-monsoon regions.
How to cite: Kimura, T., Sakakibara, K., and Nakamura, T.: Influences of a dual monsoon system on River Water Recharge in the Japanese Southern Alps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16038, https://doi.org/10.5194/egusphere-egu26-16038, 2026.
Posters virtual: Wed, 6 May, 14:00–18:00 | vPoster spot A
EGU26-4141 | ECS | Posters virtual | VPS9
Geostatistical Interpolation Approach for Improving Flood Simulation Within a Data- Scarce Region in the Tibetan PlateauWed, 06 May, 15:21–15:24 (CEST) vPoster spot A
The complex orography of the Tibetan plateau (TP) and the scarcity and uneven spatial distribution of meteorological stations
present significant challenges in accurately estimating meteorological variables for hydrological simulations. This study aims
to enhance the accuracy of daily precipitation and temperature interpolation for hydrological simulations in the Lhasa River
Basin (LRB), particularly during flood events. We evaluate and compare the performance of deterministic Inverse Distance
Weighting—IDW and geostatistical (Ordinary Kriging—OK and Kriging with External Drift—KED) interpolation methods for
estimating precipitation and temperature patterns. Subsequently, we investigate the influence of different interpolation meth
ods on hydrological simulations by using the interpolated meteorological data as input for the Water Balance Simulation Model
(WaSiM) to simulate daily discharge in the LRB. Our results revealed that geostatistical methods, specifically OK and KED, are
more effective in capturing the spatial variability and anisotropy inherent in precipitation patterns influenced by the Indian
summer monsoons. In addition, the KED method effectively captured the daily variation of the temperature lapse rate, indicating
the inadequacy of using a constant lapse rate for hydrological modelling in high- elevation regions like the TP. The geostatistical
technique outperformed the Deterministic method, with KED realising the best temperature and precipitation interpolation
performance based on cross- validation results. However, although KED provides superior results based on cross- validation per
formance, applying its precipitation interpolation as input into WaSiM led to the poorest discharge simulation. The combination
of OK for precipitation and KED for temperature produced the most accurate discharge simulations in the LRB, highlighting
the importance of not solely relying on cross- validation results but also considering the practical implications of interpolation
methods on hydrological model outputs. Our study offers a robust framework for improving flood simulations and water resource
management in a data- scarce, high- elevation region like the TP.
How to cite: guede, K. G., Yu, Z., and Hofmeister, F.: Geostatistical Interpolation Approach for Improving Flood Simulation Within a Data- Scarce Region in the Tibetan Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4141, https://doi.org/10.5194/egusphere-egu26-4141, 2026.
