Validation of a Spatially Distributed Energy Balance Snow Simulation Model

A spatially distributed snow simulation model (ISNOBAL) is used to simulate the development and ablation of the seasonal snowpack for the 1998 water year over the Boise River basin, a large mountainous basin in Idaho. The model accounts for topographic effects on the snowpack energy balance, corrects for forest canopy effects on solar and thermal radiation, and uses spatially distributed precipitation, temperature, and other meteorological inputs. While snow water equivalent measurements at several sites within the basin show good agreement with simulation results, verification in the spatial domain is more difficult. A series of AVHRR-derived snow covered area (SCA) images, corrected for forest canopy effects, are used to show that the simulated SCA over the basin closely matches that derived from the satellite data. Simulated runoff from snowmelt and rain from ISNOBAL are used to drive a spatially distributed watershed hydrology model, the Bochum Water Balance Model developed at the Ruhr University in Germany. Measured streamflow from the basin closely matches simulated streamflow, showing that both the simulated distribution and volume of snowmelt runoff must approximate reality. This effort will help scientists and hydrologists develop water management models that more effectively address the diverse natural resource management issues in mountainous regions.