Hydrogravimetry Enables Quantification of Alpine Groundwater Dynamics

Abstract Groundwater plays a critical role in the functioning of alpine hydrological systems, and its importance is expected to increase under climate change. However, quantification of groundwater processes in these systems remains highly uncertain. Terrestrial time‐lapse gravimetry (TLG) is a geophysical and geodetic technique whose measured variable () varies directly with groundwater storage changes (GWSC). TLG is thus well suited to applications in alpine environments, which often lack subsurface monitoring infrastructure. Here, we use TLG to measure GWSC in an alpine headwater catchment over snow‐free and snow accumulation/melt periods. We compare absolute‐referenced measurements with locally referenced (relative) ones and investigate the advantages of mobile surveys using the most recent generation of relative gravimeters. The results reveal a spatially variable, dynamic system with greater GWSC magnitudes in higher‐elevation regions and demonstrate the untapped utility of TLG for alpine groundwater investigations.