GROUNDWATER FLOW SYSTEMS OF A MORAINE-TALUS FEATURE IN AN ALPINE WATERSHED

Recent studies suggest that overburden features such as talus slopes and moraines play an important role in groundwater flow and storage in alpine watersheds, though the nature of these processes is not well understood. One likely reason for this is the difficulty in installing wells in these types of environments. However, we can gain insight into the groundwater regime by monitoring springs. Thus, in this study we investigated a large groundwater spring that discharges to a small stream from an interconnected proglacial moraine-talus field, in the Lake O'Hara watershed in the Canadian Rockies. The spring showed substantial spatial variability in electrical conductivity (25 °C), increasing from <50 to >250 μS cm^-1 over a 20-m section. A qualitative end-member mixing analysis based on major ion data suggests the spring area is a mixing zone for potentially three groundwater end members and that their relative contributions vary temporally. Geochemistry and hydrograph analyses suggest the dominant end-member is associated with nearby Opabin Lake. The hydrograph response to rain events indicates another end-member may be shallow subsurface flows from a distinct area on the moraine-talus field. The final, high-sulphate end-member may be associated with deeper flow paths through fractured bedrock or with freeze-thaw cycles involving buried ice. The study results indicate that these overburden features can possess multiple, and possibly disconnected, groundwater flow systems and cannot necessarily be treated as a single, homogeneous groundwater component when modeling the hydrology of alpine watersheds.