SNOTEL Representativeness in the Rio Grande Headwaters using Remotely Sensed Snow Covered Area Data and Energy Balance Modeling

Snowpack telemetry (SNOTEL) sites in and around the Rio Grande headwaters basin are located at the middle elevations of the watershed, in relatively dense vegetation, and toward the western boundary of the watershed. Based on 8 years of Advanced Very High Resolution Radiometer data (1995 - 2002), the snow cover persistence index value at the six SNOTEL sites ranged from 3.9 to 4.4 with an average 12% greater than the mean persistence of the watershed. Therefore, information from the sites does not capture the variability in snowpack accumulation and ablation processes across the watershed. Using elevation, western barrier distance, and vegetation density, a 32-node binary regression tree model explained 75% of the variability in average snow-cover persistence. Terrain classes encompassing the Lily Pond, Middle Creek, and Slumgullion SNOTEL sites represented 4.1, 6.4, and 4.0% of the watershed area, respectively. SNOTEL stations do not exist in the spatially extensive (e.g. 11% of the watershed) terrain classes located in the upper elevations above timberline. The results and techniques presented here will be useful for spatially distributed hydrologic analyses in that we have identified the physiographic conditions currently represented by SNOTEL stations (i.e. the snowpack regimes at which SWE estimation uncertainty can be determined).