SWAT Literature Database for Peer-Reviewed Journal Articles

Title:GIS-based hydrologic modeling in the Sandusky watershed using SWAT 
Authors:Qi, C. and S. Grunwald 
Journal:Transactions of the ASAE 
Article ID: 
URL (non-DOI journals):http://soils.ifas.ufl.edu/faculty/grunwald/home/PDFs/TransactionsASAE_48%281%29_pp169_2005.pdf 
Broad Application Category:hydrologic only 
Primary Application Category:hydrologic assessment 
Secondary Application Category:none 
Watershed Description:388.2 km^2 Honey Creek (HC); 90.3 km^2 Rock Creek (RC); 607.4 km^2 Tymochtee (Tym); 223.8 km^2 Bucyrus (Buc) (all subwatersheds in Sandusky River Watershed, Ohio); gauge at 3,240 km^2 Fremont (Fre) assumed to be overall outlet 
Calibration Summary:Monthly 1998-99 surface water/ groundwater/ total flow E values: Fre = .65/.60/.79 Buc = .31/-.24/.31 HC = .64/.15/.66 RC = .54/-9.13/.81 Tym = .43/.48/.64 
Validation Summary:Monthly 2000-01 surface water/ groundwater/ total flow E values: Fre = .23/.01/.58 Buc = -04/-.16/.40 HC = .45/-.33/.65 RC = .75/-.57/.73 Tym = .33/.22/.40 
General Comments:Performed a spatially disributed calibration & validation for surface water, ground water, and total stream flow with SWAT for four subwatersheds and overall watershed. Surface water was more accurately simulated than groundwater across the different subwatersheds. It was concluded that overall water flow simulations were satisfactory, except for winter rainfall-runoff events, and that hydrologic patterns were adequately accounted for using the spatial calibration & validation approach. Graphical comparisons of simulated vs. measured flows are shown; mean error, RMSE, and correlation statistics are also reported. 
Abstract:Typically, simulation output generated by computer simulation models is calibrated and validated at the drainage outlet of a watershed. Shortcomings of such an approach include the validation at only one geographic location without explicitly accounting for variable hydrologic patterns within the watershed. Our objective was to conduct a spatially distributed calibration and validation of water flow using the Soil and Water Assessment Tool (SWAT). We simulated surface, groundwater, and total flow in the Sandusky watershed in Ohio, located in the Lake Erie watershed and the Great Lakes basin. The calibration and validation of simulated water flow was conducted concurrently at four subwatersheds and the drainage outlet of the Sandusky watershed. We used measured streamflow data at five U.S. Geological Survey (USGS) gauge stations from water years 1998 and 1999 for calibration and from water years 2000 and 2001 for validation. The surface water simulations at all monitoring stations were better than the groundwater simulations. The validation of total water flow showed a range in mean error of 0.03 to 4.00 m3 s-1, a root mean square error of 0.06 to 2.56 m3 s-1, correlation coefficients of 0.70 to 0.90, and Nash-Sutcliffe coefficients of 0.40 to 0.73. In conclusion, spatially distributed calibration and validation accounted for hydrologic patterns in the subwatersheds nested within the relatively large Sandusky watershed. Overall, simulations of water flow in the Sandusky watershed and subwatersheds were satisfactory except for winter rainfall-runoff events. This study showed the importance of spatially distributed calibration and validation. 
Keywords:GIS, Hydrology, Modeling, Sandusky watershed, SWAT