ARS | Publication request: Scaling up the SWAT model from Goodwater Creek Experimental Watershed to the Long Branch Watershed

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings/Symposium
Publication Acceptance Date: May 17, 2007
Publication Date: June 17, 2007
Citation: Ghidey, F., Sadler, E.J., Lerch, R.N., Baffaut, C. Scaling up the SWAT model from Goodwater Creek Experimental Watershed to the Long Branch Watershed. ASABE Paper No. 072043, ASABE, St. Joseph, MI, 2007.

Interpretive Summary: The primary objective of the Conservation Effects Assessment Project - Watershed Assessment study (CEAP-WAS) is to quantify the benefits of conservation programs and their many practices on water quality at the watershed scale. The Salt River Basin (~6500 km2), located in north-central Missouri, is one of the USDA-ARS watersheds selected for CEAP-WAS. A comprehensive water quantity and quality model capable of simulating the impact of weather, land use, land management, and Best Management Practices (BMPs) on water quality will be an important tool for CEAP-WAS. The Soil and Water Assessment Tool (SWAT) model developed by USDA-ARS was selected for this study. The SWAT model was calibrated and validated for the Goodwater Creek Experimental Watershed (GCEW), a 70 km2 watershed within the Salt River Basin, using the State Soil Geographic (STATSGO) and Soil Survey Geographic (SSURGO) data sets. The study showed that stream flow simulation of the SWAT model using the STATSGO soil data set was as good as the results obtained running the model using the SSURGO soil data set. This indicates that, for our soil condition, using the SSURGO soil data set, which has higher resolution than the STATSGO soil data set, did not improve stream flow simulation of the model. The model performed well in simulating stream flow and sediment yield from GCEW on an annual and monthly basis. The performance of the calibrated model using the STATSGO data set was evaluated for its ability to simulate flow for the Long Branch watershed, a 462 km2 watershed containing the GCEW and draining into Mark Twain Lake within the Salt River Basin. The model also performed well in simulating annual and monthly stream flows from Long Branch watershed. Overall, the performance of the SWAT model using the parameters obtained from GCEW was satisfactory in simulating stream flow from a watershed approximately 7 times larger in area (Long Branch watershed). Once the model is further calibrated for stream flow, sediment yield, and nutrient and herbicide losses, it will be a useful tool to farmers, extension/education personnel, and regional and state agencies by providing relevant information on the effects of various land use management systems on surface water quantity and quality.

Technical Abstract: The primary model selected for use in the Conservation Effects Assessment Project-Watershed Assessment Study (CEAP-WAS) was the Soil and Water Assessment Tool (SWAT) model. The first objective of the study was to calibrate and validate the SWAT model to simulating stream flow and sediment yield for the Goodwater Creek Experimental Watershed (GCEW), a 70 km2 watershed located in north-central Missouri, using the SSURGO and the STATSGO soil data sets. The model performed well in simulating stream flow, particularly on an annual and monthly basis. The study showed that the performance of the model in simulating stream flow using the STATSGO soil data was as good as that using the much more complex SSURGO soil data. The second objective of the study was to evaluate the performance of the model calibrated for GCEW using the STATSGO data set in simulating stream flow for the Long Branch watershed, a 462 km2 watershed containing the GCEW and draining into Mark Twain Lake within the Salt River Basin. The performance of the model in simulating stream flow from the Long Branch watershed was as good as that from GCEW. For the Long Branch watershed, the 9-yr (1995-2003) average simulated annual stream flow was less than 4% higher than that measured, and the ENS and r2 values were 0.97 and 0.94 for annual stream flow and 0.79 and 0.77 for monthly stream flow, respectively. The model did not perform as well in simulating stream flow on a daily basis but its performance was similar in the GCEW and Long Branch watersheds. Future plans include: (1) to evaluate the parameters that influence the flow component of the model to determine if daily stream flow simulation could be improved, (2) to calibrate the pesticide component of the model, and (3) to perform further calibration of the sediment yield component of the model, once the sediment load computation process from GCEW is completed. When these steps are completed, simulation for 12 other watersheds on the Salt River Basin will be done.