Toward improved streamflow forecasts: Value of semidistributed modeling

The focus of this study is to assess the performance improvements of semidi stributed applications of the U.S. National Weather Service Sacramento Soil Moisture Accounting model on a watershed using radar-based remotely sensed . precipitation data. Specifically, performance comparisons are made within an automated multicriteria calibration framework to evaluate the benefit o f "spatial distribution" of the model input (precipitation), structural com ponents (soil moisture and streamflow routing computations), and surface ch aracteristics (parameters). A comparison of these results is made with thos e obtained through manual calibration. Results indicate that for the study watershed, there are performance improvements associated with semidistribut ed model applications when the watershed is partitioned into three subwater sheds; however, no additional benefit is gained from increasing the number of subwatersheds from three to eight. Improvements in model performance are demonstrably related to the spatial distribution of the model input arid s treamflow routing. Surprisingly, there is no improvement associated with th e distribution of the surface characteristics (model parameters).