Runoff response to spatial variability in precipitation: an analysis of observed data

We examine the hypothesis that basins characterized by (1) marked spatial variability in precipitation, and (2) less of a filtering effect of the input rainfall signal will show improved outlet simulations from distributed versus lumped models. Basin outflow response to observed spatial variability of rainfall is examined for several basins in the Distributed Model Intercomparison Project. The study basins are located in the Southern Great Plains and range in size from 795 to 1645 km2. We test our hypothesis by studying indices of rainfall spatial variability and basin filtering. Spatial variability of rainfall is measured using two indices for specific events: a general variability index and a locational index. The variability of basin response to rainfall event is measured in terms of a dampening ratio reflecting the amount of filtering performed on the input rainfall signal to produce the observed basin outflow signal. Analysis of the observed rainfall and streamflow data indicates that all basins perform a range of dampening of the input rainfall signal. All basins except one had a very limited range of rainfall location index. Concurrent time series of observed radar rainfall estimates and observed streamflow are analyzed to avoid model-specific conclusions. The results indicate that one basin contains complexities that suggest the use of distributed modeling approach. Furthermore, the analyses of observed data support the calibrated results from a distributed model