SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Effects of distribution-based parameter aggregation on a spatially distributed agricultural nonpoint source pollution model 
Authors:Chen, E. and D.S. Mackay 
Journal:Journal of Hydrology 
Article ID: 
URL (non-DOI journals): 
Broad Application Category:hydrologic & pollutant 
Primary Application Category:HRU and/or subwatershed delineation effects 
Secondary Application Category:pollutant cycling/loss and transport 
Watershed Description:4730 ha Pheasant Branch (south central Wisconsin) 
Calibration Summary:Monthly (Oct. 1977 - Feb. 1982) MCOE statistics are reported and graphical comparisons between measured & simulated streamflow & sediment are shown 
Validation Summary: 
General Comments:16 combinations of subwatersheds (5 -179) and HRUs (5 - 1569) were simulated using SWAT2000. Annual stream flow was essentially not affected by choice of HRU and subwatershed combination. However, sediment yield varied greatly between the different configurations for two selected subwatersheds, but did not vary greatly at the overall outlet. The results reveal that SWAT's structure influences sediment predictions in tandem with spatial data aggregation effects. The authors state that the integration of MUSLE and HRUs is conceptually incompatible, because the HRUs do not function as watersheds. The linear scaling of MUSLE estimates from the HRUs to subwatershed outlets violates MUSLE assumptions of nonlinear runoff energy and sediment generation, resulting in an artificial increase in predicted sediment generation in response to decreases in HRU size. The authors discuss other problems related to using HRUs and advocate using only subwatersheds to delineate a watershed. Extensive discussion is also provided regarding transport- versus source-limited watershed issues. 
Keywords:Aggregation error; Geographic information systems; Hydrologic modeling; Nonpoint source pollution; Sediment transport