Importance of groundwater in the water balance of an alpine headwater lake

The response of snow‐ and glacier‐fed mountain streams and lakes to climate warming is of growing concern. A full understanding of these systems must include the role of groundwater, but this is poorly understood, especially for high‐elevation lakes. This study addresses the role of groundwater in an alpine watershed, located at the continental divide of North America, with a focus on quantifying the groundwater exchange with Lake O'Hara in British Columbia, Canada. This is facilitated using a water balance approach and measurements of electrical conductivity in inflowing streams. The water balance indicates that groundwater inflow is substantial, as it was equivalent to at least 30–67% and 35–74% of the total outflow for the 2004 and 2005 field seasons, respectively. Hydrological and chemical data also suggest contributions from both deep and shallow groundwater flow paths.