Globally, at least one in four people are directly dependent on water originating from mountain catchments. Reliance on water from these alpine and sub-alpine regions is rapidly increasing while climate change is severely impacting them. Recent studies have highlighted the complex buffering role of hydrogeological processes in mountain catchments. Accurate measurements of groundwater storage changes on the sub-catchment scale are critical for understanding subsurface flow processes including inter-catchment groundwater export. These measurements are currently lacking and thus there is a severe gap in knowledge about the annual dynamics of mountain groundwater resources and their future role in maintaining perennial water resources down-gradient. It is striking that mountain catchments are the most strongly affected by climate change, yet remain very poorly understood and insufficiently monitored. Where monitoring wells exist in these catchments, their information value is minimal due to the pronounced heterogeneity and dynamics that characterise mountain hydrogeology. While catchment-scale groundwater storage changes can be estimated via water balance methods, uncertainties are large, often greater than the estimated inter-catchment groundwater export, and this provides no spatial information. There is thus an acute need for innovative methods that provide quantitative and spatially-resolved information on groundwater storage changes in mountain catchments. Time-lapse gravimetry (TLG) is a highly promising method that could provide a solution to these needs; however, its full potential in constraining groundwater storage changes, particularly in mountainous areas, remains unexplored.

RADMOGG will employ innovative numerical and field-based methods to characterise, in a quantitative and spatially-resolved way, hydrogeological processes in mountain catchments and to evaluate the extent to which TLG can be used to respond to the critical mountain hydrogeology information deficit. To meet these goals, we will combine numerical methods with regular TLG surveys and continuous "ground truth" hydrological measurements. We focus on the sub-alpine Röthenbach (alluvial aquifer) and the alpine Tsalet (moraine & talus aquifers) catchments, selected due to the global ubiquity of these types of hydrological contexts. RADMOGG is led by Dr. Landon Halloran together with partners at UNINE, CREALP, and METAS.