Physics-based simulation of hydrological processes in a high-elevation glaciated environment focusing on groundwater

Understanding the role of groundwater is crucial to improving the quantification of the hydrological response to climate change in high-elevation glaciated environments. However, few studies have been conducted due to the lack of in-situ hydroclimatic observations, the complex topography, and the difficulty of characterizing surface-subsurface water exchange processes in these terrains. In this study, we adopt a fully-distributed, physics-based hydrological model, WaSiM, with an integrated 2-dimensional groundwater module to quantify the observed streamflow variations and their interactions with groundwater in a high-elevation glaciated catchment (Martell Valley) in the central European Alps since the 2000s. Extensive field observations (meteorology, vegetation, glacier mass balance, soil properties, groundwater levels, river discharge) are collected to analyze hydrological processes and to constrain the model parameters. We observe that shallow alpine groundwater levels respond nearly as quickly as streamflow to snowmelt and heavy rainfall inputs, as their measured hydrographs show. Because hydrological models rarely simulate this quick groundwater response, this highlights the need for improved subsurface parametrization in hydrological modeling. Surprisingly, subsurface lateral flow plays a minor role in river discharge generation at the study site, providing new insights into the hydrological processes in such an environment. Lastly, our results underline the challenges of integrating point-scale groundwater observations into a distributed hydrological model, with important implications for future piezometer installation in the field. This study sheds new light on surface-subsurface hydrological processes in high-elevation glaciated environments. It highlights the importance of improving subsurface representation in hydrological modeling.