Gravimetry as a groundwater monitoring solution: combining hydrological and gravimetric measurements to understand a pre-alpine alluvial aquifer

Groundwater resources are increasingly affected by climate change, in which rising temperatures and altered precipitation patterns lead to shifts in recharge rates, thereby impacting water availability. Traditional hydrological data such as stream and piezometric levels provide valuable point information, however the spatial extent to which these data are relevant is not generally straightforward to determine. The limits of point measurements are particularly true in alluvial aquifers with pronounced spatial heterogeneity, as well as in mountain groundwater systems that experience significant seasonal variations in water storage. Time-lapse gravimetry (TLG), a spatially integrative hydrogeophysical method, may help to fill data gaps and evaluate spatial and temporal variability in these systems.
This study examines the spatial and temporal variability of water storage changes using time-lapse gravity data (TLG) and traditional hydrological data in the unconfined alluvial aquifer system of the pre-alpine Röthenbach catchment (Bern canton, Switzerland). We compare monthly TLG surveys with complimentary data, including time-series of groundwater head, river discharge, groundwater levels and recharge, in order to: a) test the limits of TLG in resolving groundwater storage changes, b) characterize the spatial variability in the water storage dynamics of the catchment, and c) develop a new conceptual model for this hydro-system. Our approach reveals the relationship between local gravity changes and the hydrological processes within the study catchment and provides valuable insights into the potential of TLG for hydrological and hydrogeological investigations.