Modeling of Snow Water Equivalent Distribution in a Meso-Scale Mountainous Watershed with GIS

In rugged mountainous regions where snow is a major water resource, physical measurements of snow water equivalent (SWE) are necessary to estimate its spatial distribution, which is then used to predict the volume and timing of snow melt. This paper presents a methodology for construction of Iso-Snow-Climate-Polygons (ISCP) - areas where snow properties are relatively homogeneous - in order to establish optimal and efficient physical measurement strategies for SWE. A medium sized watershed, Parrish Creek (about 5.5 km2) in the Wasatch Mountains was used as a study site. The factors that control SWE distribution that are implemented in this process are elevation effect on snow accumulation, ablation due to solar radiation, wind redistribution (curvature, wind aspect), vegetation effect, and slope angle effects on avalanching and snow sloughing. For each effect, separate digital terrain maps are created using topographical variables including elevation, slope angle, aspect, solar angle and curvature, and vegetation. Finally, all maps are combined in an effort to determine that optimal set of ISCPs that cover the watershed. Also the total volume of SWE estimated using ISCPs compares well with that calculated using all the grid sampling points. In order to fully verify accuracy of the GIS based ISCP method, additional SWE field verification studies are needed.