Snowmelt-induced subsurface and overland flows in a hillslope in Noname Watershed, Laramie River Basin, Wyoming

Abstract:

Only few field observations have been implemented using surface and sub-surface trenches to investigate snowmelt-induced hillslope runoffs in mountainous regions. Hillslope trenches may be one of the most direct ways to measure subsurface and overland flow during winter and spring seasons. In July 2014, a 10 meter long trench was constructed with hand tools through glacial till on a south facing hillslope in the Noname Watershed, Medicine Bow National Forest, Wyoming, where heavy equipment and motorized vehicles were restricted. This trench measures subsurface and overland flow for a 610 square meters catchment which has an average slope of 25 degrees. This water-collecting trench is equipped with 4 soil-moisture and temperature sensors to detect the presence of unsaturated flow. Field observations from the trench showed that diurnal oscillation of snowmelt seemed to control the overland flow between the snow and soil surface. The water inputs to the hillslope, including rainfall, evaporation, and snowmelt rates, were estimated from the energy balance computations using the observed meteorological data at the site. Using the water input data, the lateral flow component through the deeper soil or weathered bedrock layer was also quantified by the mass balance in the catchment. This study provides one of key field activities for Wyoming Center for Environmental Hydrology and Geophysics (WyCEHG) project.