Rapid Snowmelt Leads to Greater Streamflow Across the Western United States: Streamflow Sensitivity to Changes in Snowpack Across Trans-Basin Diversions

Snowmelt is the primary source of surface water in the western United States and for approximately one sixth of the global population (Barnett et al., 2005). Climate change is altering the magnitude of the mountain snowpack and the timing and rate of snowmelt (Mote et al., 2005; Clow, 2010; Harpold et al., 2012). These changes could have profound implications for the water resources of the western United States (Milly et al., 2008). We ask how these changes to the mountain snowpack impact how snowmelt is partitioned between evapotranspiration (ET) and streamflow across the western United States. We hypothesize that rapid snowmelt is able to quickly satisfy atmospheric demand for water and bring the soil column to field capacity, inducing infiltration past the root zone and generating streamflow. Regional- or watershed-scale differences in the sensitivity of streamflow to changes in snowmelt could strain existing water transfer agreements, especially across trans-basin diversions.