Groundwater response to extreme weather events in various hydrogeological regimes across Southern British Columbia

Across the Pacific Northwest, drought and precipitation extremes are becoming stronger and more frequent. Few studies have explored groundwater responses to extremes in mountainous regions. Here, well and catchment scale approaches are used to determine the responses across different hydroclimatological and hydrogeological contexts by: (1) analyzing groundwater levels in observation wells on the South Coast of British Columbia (BC), and (2) analyzing catchment responses in three integrated hydrological models. Across the South Coast, two distinct styles of groundwater responses are identified, as a function of hydraulic connectivity to the Fraser River, with aquifers hydraulically connected to the Fraser River likely being more drought resilient during summer due to the influence of the river's freshet. Model results show that catchment aquifers are sensitive to extreme events; greater consecutive dry days deplete aquifers while atmospheric rivers provide substantial recharge. Catchment boundary conditions and hydrogeological characteristics ultimately determine aquifer response to extremes.