Defining flow and recharge to an alpine karst aquifer in the Canadian Rockies through hydrogeochemical characterization

ABSTRACT: vegetative cover and higher hydraulic gradients. Rapid recharge from snowmelt and precipitation, and high flow velocities lead to marked spring responses. Global air temperature is gradually rising, resulting in less snow accumulation and shorter periods snow storage. A shifting climate may have significant impacts on karst groundwater availability, but little research has focused on alpine karst in the Canadian Rockies owing to a lack of data from these rugged landscapes. The Watridge Karst Spring in Kananaskis, Alberta is a perennial spring at 1870m elevation that flows at up to 3.9 m3/s. For decades, the source of the aquifer has been contemplated by local hydrogeologists. The volume of water that discharges at the spring is disproportionately large when compared to the topographical watershed area. A conduit-flow regime, characterized by a diurnal discharge fluctuations and diluted chemical signature, is initiated during snowmelt periods. Conversely, baseflow recession through fractures yields estimated groundwater response times on the order of dozens of days. The aquifer is hosted by a massive micritic Devonian limestone unit, underlain by an argillaceous, silty aquitard. The geological package is folded in a 2-3 km wide regional syncline that is thought to laterally constrain the aquifer. Annual water budget estimates suggest that the recharge area is up to 35 km2. Considering the elongated shape of the aquifer, the greater recharge zone likely spans across five or more alpine watersheds. This study demonstrates the value of a high-resolution multi-year hydrogeochemical database for the study of alpine karst aquifers. Hydrologically relevant metrics are used describe the parameters that control the recharge and transmission of water from sources to spring. This conceptual understanding can improve hydrological models of snowmelt-dominated alpine karst in response to a warming climate.