Precipitation data sets representing four spatial resolutions were used to evaluate the performance of the Soil and Water Assessment Tool (SWAT) on the basis of reproducing measured streamflow, and to show differences in model parameters when different precipitation data sets are used to calibrate the model. The experiment was conducted on the 786 km2 Ft. Cobb Reservoir experimental watershed (FCREW) in southwestern Oklahoma. Precipitation data sets included the National Weather Service (NWS) cooperative weather network (Co-op), NWS next-generation radar precipitation estimates (NEXRAD), the University of Oklahoma and Oklahoma State University's joint state-wide weather station network (Mesonet), and the USDA-ARS weather station network (Micronet) deployed in the FCREW. The FCREW was divided into three main subwatersheds (Cobb, Lake, and Willow Creeks), with SWAT calibrated for each subwatershed using each precipitation data set. Model simulations were generally good to very good at both the daily and monthly time steps for all precipitation data sets, except in the Willow Creek subwatershed, which scored satisfactory at the monthly time step and unsatisfactory at the daily time step when the Co-op data were used. Calibrated parameter values within the Cobb Creek subwatershed changed little across precipitation data sets. In the Lake Creek and Willow Creek subwatersheds, the deep recharge calibration parameter values varied greatly with respect to precipitation data source. Such variation could inappropriately affect, for example, model assessments of conservation practices designed to ameliorate the movement of agro-chemicals from the surface to lower positions in the soil profile and eventually into the groundwater.
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Starks et al. (2009) studied this question.