ESTIMATING ROCK GLACIER CONTRIBUTIONS TO STREAMFLOW IN LEHMAN CREEK WATERSHED, GREAT BASIN NATIONAL PARK

Lehman Creek is the largest drainage of the South Snake Range in Great Basin National Park and is a major source of water for the park and neighboring communities. The watershed features the Wheeler Peak rock glacier and other smaller buried ice masses, but the degree to which these masses are thawing and their potential contribution to streamflow are poorly known. This uncertainty, along with declining snowpack and earlier spring runoff in recent decades motivate an assessment of the water budget for Lehman Creek watershed and an estimate of the subsurface thaw contribution to streamflow. We applied a snow and energy balance model to the Lehman Creek watershed to estimate runoff based on gridded monthly meteorology. Available runoff and evaporation are inferred from model calculations of monthly snow accumulation and melting throughout the area of the watershed above a single U.S. Geological Survey gauging station. Model experiments show consistency between snowmelt and measured streamflow during winter and spring months, but overestimate summer runoff despite low monthly precipitation and high evapotranspiration rates. Although a complete assessment of evapotranspiration and infiltration of summer snowmelt and precipitation is not yet available, the low summer discharge of Lehman Creek and the potential contributions of ground water suggest that subsurface thaw is not a major contributor to streamflow. Additional modeling of summer water budgets and improved estimates of buried ice volumes are needed to more accurately compute the potential contribution of buried ice and snow to Lehman Creek.