WEHY-HCM for Modeling Interactive Atmospheric-Hydrologic Processes at Watershed Scale. II: Model Application to Ungauged and Sparsely Gauged Watersheds

Abstract

The objective of this study is to evaluate the potential of the Watershed Environmental Hydrology Hydro-Climate Model (WEHY-HCM) for modeling runoff at ungauged or sparsely gauged watersheds. The WEHY-HCM employs an atmospheric module (fifth generation mesoscale model, MM5) that is coupled with its process-based watershed environmental hydrology (WEHY) module. In this study the atmospheric component of the WEHY-HCM was utilized for the dynamical downscaling of the coarse U.S. National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) historical global reanalysis atmospheric data over a foothills region in Northern California in order to reconstruct the historical hydro-climate data over four watersheds in the foothills region at 3 km grid scale at hourly intervals. The WEHY-HCM’s atmospheric module performance was evaluated by the comparison of model-reconstructed precipitation and air temperature against ground observations in time and space with satisfactory results. These results lead to the conclusion that WEHY-HCM may be useful at sparsely-gauged or ungauged watersheds for producing nonexistent atmospheric data as input to the modeling of surface and subsurface hydrologic processes at such watersheds. By means of the reconstructed atmospheric data as its input, the WEHY module of WEHY-HCM was then applied to the Sierra foothills region, encompassing Big Chico Creek (