RIVER FLOW RESPONSE TO PRECIPITATION AND SNOW BUDGET IN CALIFORNIA DURING THE 1994 95 WINTER/

A numerical study of precipitation and river flow from November 1994 t o May 1995 at two California basins is presented. The Hopland watershe d of the Russian River in the northern California Coastal Range and th e headwater of the North Fork American River in the northern Sierra Ne vada were selected to investigate the hydroclimate, snow budget, and s treamflow at different elevations. Simulated precipitation and streamf low at the Hopland basin closely approximated observed values. An inte rcomparison between the semidistributed TOPMODEL and two versions of t he lumped Sacramento model for the severe storm event of January 1995 indicates that both types of models predicted a similar response of ri ver outflows from this basin, with the exception that TOPMODEL predict ed a faster recession of river flow with less base flow after precipit ation ended. Precipitation in this low-elevation watershed was predomi nantly in the form of rain, causing a fast streamflow response. The hi gh-elevation Sierra Nevada watershed received most of its precipitatio n as snowfall. As a result, the frozen water held in surface storage d elayed runoff and streamflow. Application of a simple elevation-depend ent snowfall and rainfall partitioning scheme showed the significance of finescale terrain variation in the surface hydrology at high-elevat ion watersheds.