Snow water equivalents modeled at the mesoscale with geographical information systems

Snow water equivalent (SWE) is spatially distributed within the mountainous basins of climates marked by a seasonal snowpack. This distribution is directly linked to mesoscale physiography such as slope, solar aspect, elevation, canopy, wind transport zones and avalanche tracks, and to time. In the Oquirrh Mountains near Salt Lake City, the SWE distribution of seven subbasins has been modeled with GIS technology and a DEM of the area. The purpose of the model is to obtain accurate estimates of SWE for smaller basins. The modeled subbasins are on the order of 1 km2.Individual maps of mesoscale physiography were developed as the controls of SWE distribution. Daily, water year 1997 data from three SnoTel stations was compared with physiographic maps. Using snow accumulation theory and a statistical analysis of ground measured data, individual SWEdistribution models were fit with the mesoscale models of solar aspect, elevation, vegetation and basin area. The SWE distribution models, representing either loss or gain, were then combined in chronological order to model total snow accumulation for a season. Peak SWE was calculated for March 7, 1997 using the mesoscale accumulation model. A total SWE of 1882.74 acre-feet, 35.6% of average Bingham Canyon annual precipitation, was calculated for peak. Modeled site locations had a very good linear correlation (0.97) with measured site data. A ridge line cornice model contributed 51.99 acre-feet SWE, 2.7% of peak. The Snow Estimation and Updating System (SEUS) is implemented by the Colorado Basin River Forecast Center for macroscale SWE calculations. SEUS modeled 3569.35 acre-feet, 190% of the mesoscale model, for the same area and period. This study shows that the scale of the study area determines the influence of the mesoscale distribution on basin wide SWE determination.