A simple, regionally parameterized model for predicting nonpoint source areas in the northeastern US

Study RegionTen watersheds in New York, New Jersey, and Pennsylvania, USA.Study FocusA three parameter model based on variable source areas (VSAs) that does not require calibration within the region, was developed and tested. The model maintains a lumped daily water budget, but distributes runoff spatially using a soil topographic index (STI). We used ten gauged watersheds across the region to establish the model parameters, and compared model predicted VSAs against shallow water table depth and surface soil moisture field measurements in three sites.New Hydrological Insights for the RegionThe model was able to correctly predict VSAs at all three monitoring sites, indicating that saturation-excess runoff is important in these watersheds. The pattern of error in the model suggests that lateral subsurface flow paths could be exerting an influence on overland runoff generation in a way that is not captured by a static STI. The model has potential to be used as part of a strategy to limit nonpoint source pollution from saturation-excess runoff dominated areas in the region, and has been incorporated into an online decision support tool in central NY (www.hsadss.bee.cornell.edu).