ALPINE HYDROGEOLOGY: LINKING FIELD OBSERVATIONS TO BASIN-SCALE HYDROLOGY

River flow in the Rocky Mountains of North America is characterized by a few months of freshet followed by a prolonged period of baseflow, which is critical for freshwater ecosystems and water supply during dry months. Maintenance of baseflow requires a sustained source of water. While meltwater from glacier, buried ice, and late-lying snowpack can sustain some of baseflow during summer months, groundwater discharge is the only year-around source of water. Due to the difficulty of field work, groundwater in alpine environments (i.e. above the tree line) has not been studied extensively. However, over the past decade or so, a number of studies have shown that groundwater is an important component of the alpine hydrologic cycle. Using a case study from the Lake O’Hara watershed in the Canadian Rockies, we will highlight hydrogeological functions of three common landcover units, namely proglacial moraine, talus cone and slope, and alpine meadow in bedrock depression. Using the field-based understanding of hydrogeological processes, we will interpret baseflow hydrographs of a number of rivers draining high-elevation watersheds of the Canadian Rockies and discuss the hydrological responses of these watersheds to expected changes in climatic factors. The key conclusions are that groundwater reservoirs in alpine watersheds may only have secondary influence on the peak flow driven by snowmelt and summer rain, but they have a sufficient capacity to store snowmelt and provide baseflow for the entire year. Baseflow in the Canadian Rockies appears to have little inter-annual and inter-decadal variability, indicating that groundwater reservoirs are filled up to the maximum capacity every year. The magnitude of area-normalized baseflow, expressed in mm/d is expected to be dependent on several geologic, topographic, and climatic factors. We will explore the correlation between baseflow and these factors using the conceptual framework derived from field observations, and suggest opportunities for future research in alpine hydrogeology.