Environmental isotopes as indicators for groundwater recharge conditions below glaciated areas in crystalline rocks of the entral Swiss Alps

摘要

Groundwater recharge conditions in a high alpine catchment are a crucial factor for understanding the groundwater flow regime. Stable isotopes (~2H, ~(18)O) and tritium analysis of groundwater samples support the finding from hydrological modeling in a high alpine research area, that a substantial contribution of glacial meltwater and snowmelt enter the groundwater flow system. This influence is documented in anomalous low temperatures and depleted delta~(18)O values in groundeater samples taken in a gallery passing beneath glaciated areas. Low tritium concentrations in these waters show the imprint of meltwater from old submodern glacial ice. Lumped-parameter modeling, applied to the delta~(18)O signal yields mean residence times of approx 2-4.5 years for the encountered waters.