The Hydrogeology of a Rock Glacier and Its Effect on Stream Temperature

Abstract

Rock glaciers can be important aquifers that supply streamflow during dry periods and provide cold-water refuges in mountain streams. This study investigated the hydrogeological and thermal processes within an inactive talus rock glacier, and the effects of its groundwater discharge on stream temperature. Permafrost in the rock glacier is associated with the presence of large coarse blocky surficial materials, and appears to have minimal effect on groundwater flowpaths and sources. The primary control on groundwater flow and storage in the rock glacier is the hydrostratigraphy at the rock glacier base, where water inputs displace long-term groundwater storage. Either a basal low-conductivity layer (‘transmissivity feedback’ mechanism) or depressions in fractured bedrock (‘fill-spill-drain’ mechanism) are postulated to represent this control. The cold groundwater discharged from the rock glacier strongly cools the adjacent creek, providing a cold-water refuge that may be resilient to climatic warming.