Snowpack variability on western rangelands

Snow accumulations vary greatly on large tracts of western rangelands due to wind patterns, topography, and storm characteristics. These variations complicate water supply and flood forecasting techniques. Most hydrologic models assume snow accumulation and melt to be unifom over relatively large areas or elevation zones. Detailed measurements of snow depth and density, precipitation, snowmelt, and streamflow on a 26 hectare watershed in southwestern Idaho were used to assess the magnitude of the variations and to assist in understanding the processes involved. Samples taken 30 meters apart varied in depth from zero to 5 meters, and snow density determined from the same samples varied from less than 15 to over 50. The relationship between accumulated snow and accumulated precipitation was different for each field and exposure. Streamflow responded to overland flow from early snowmelt and subsurface flow from later melt of isolated drifts.