Scaling up the SWAT model from Goodwater Creek Experimental Watershed to the Long Branch Watershed

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. In this study, the scaling of the SWAT model from a small watershed to a larger watershed was evaluated. The model was first calibrated and evaluated for Goodwater Creek Experimental Watershed (GCEW), a 70 km2 watershed located in north-central Missouri, using SSURGO and STATSGO soil data sets. Then, the performance of the calibrated model in simulating stream flow from Long Branch watershed, a 462 km2 watershed that contains GCEW, was evaluated. Both GCEW and Long Branch watersheds had similar soil, land use, and cropping and management systems. The performance of the model in simulating stream flow from the Long Branch watershed was as good as that from GCEW. For 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, however, did not perform well in simulating daily stream flow. Overall, the model performed quite well in simulating annual and monthly stream flows. Future plans include (1) improving stream flow simulation on a daily basis, (2) improving sediment yield simulation, and (3) calibrating the pesticide component of the model.