Effects of Radar-Rainfall Products on Distributed Streamflow Prediction

The authors describe results of comprehensive sensitivity studies of the performance of a physically-based distributed hydrologic model used for streamflow forecasting in real time. The Hillslope-Link Model uses landscape decomposition into hillslopes and links that for a stream and river network. The main model input is high-resolution radar rainfall and evapotranspiration estimated using output from the numerical weather prediction and operational satellites. The investigated effects include the spatial resolution of the Digital Elevation Model used to extract the drainage network, the parameterization of the water velocity in the hydrologic routing component and the vertical structure of hillslope storage components, as well as the spatial and temporal resolution of the radar-rainfall and estimation algorithms. The studies were conducted over basins in Iowa and the results include state-wide evaluations as well as results for selected watersheds. The results show definite skill of the model but they also demonstrate high range of variability in all the studied factors. This implies that even resorting to standard calibration procedures is unlikely to yield highly accurate results.