SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Impact of subwatershed partitioning on modeled source-and transport-limited sediment yields in an agricultural nonpoint source pollution model 
Authors:FitzHugh, T.W. and D.S. Mackay 
Journal:Journal of Soil and Water Conservation 
Volume (Issue):56(2) 
Article ID: 
URL (non-DOI journals):http://www.jswconline.org/content/56/2/137.short 
Broad Application Category:hydrologic and pollutant 
Primary Application Category:HRU, subbasin, grid and/or landscape unit delineation effects 
Secondary Application Category:land use change 
Watershed Description:47.8 km^2 Pheasant Branch, located in south central Wisconsin, U.S. 
Calibration Summary: 
Validation Summary: 
General Comments:Predicted streamflow and sediment levels at the watershed outlet were relatively unaffected by variations in subwatershed and HRU configurations. Hypothetical land use scenarios were performed to depict source- and transport-limited conditions. It was found that that data aggregation, resulting from changes in subwatershed/HRU resolution, resulted in different relationships between predicted sediment at the watershed outlet and subwatershed size depending on whether the watershed was source- or transport-limited. The importance of how channel parameters impact predicted sediment loss at the outlet, as a function of the size or number of subwatersheds, is also reported. 
Abstract:Distributed parameter hydrologic models have a potential use as tools for supporting watershed management policy. However, proper model implementation will require an understanding of how to integrate data collection and models in watersheds that have differing characteristics. This study investigated the behavior of one such model, the Soil and Water Assessment Tool (SWAT), in relation to the level of spatial aggregation of input data and the extent to which the watershed is source- or transport-limited in terms of sediment yield. The approach here was to first test SWAT in an agricultural watershed in Southern Wisconsin. Then, a series of computer model applications were generated with a range of sediment source- and transport-limited conditions. SWAT was run for each watershed condition using eight watershed delineations, each with a different number of subwatersheds. Data aggregation affected model behavior differently depending on whether the watershed was sediment source-limited or transport-limited. This indicates that care is needed in selecting distributed sampling points, characterizing stream channel processes, and improving the selection of subwatershed sizes to match SWAT to watersheds with different characteristics. 
Keywords:Agriculture, geographic information systems, nonpoint sources, mohh, sediment transport, sediment yield