Temporal and Spatial SWE Predictions for Hydrologic Model Input

A multiple regression equation was developed to describe temporal and spatial variability of daily snow water equivalent (SWE) in Lake Tahoe's Incline Basin. SWE maps of the basin are needed for the parameterization of the physically-based Alpine Hydrochemical Model (AHM) to simulate basin hydrology and solute transport. SWE data collected during 2002's peak snow accumulation were used in conjunction with data from three local SNOTEL stations to calibrate the regression equation. Calibration was conducted during a dry and average water year using the sum of least squares. The multiple-regression was dependent on elevation, aspect, slope, vegetation density and solar radiation and was normalized by the average SWE measured at the three SNOTEL sites. Basin-wide computations were done at 30 m resolution in ArcView to generate daily SWE maps. Verification was performed at the three SNOTEL sites for a wet year and another average year. While errors in prediction were relatively low (approximately 0.3%), the regression over predicted peak accumulations for upper elevations, under predicted SWE at lower elevations and allowed greater attenuation of SWE into the summer months for lower elevations. In contrast, the mid-elevations were extremely well predicted in both timing of peak accumulation and overall SWE volume.