A Comparison of PRISM and Cfsr Precipitation Data Effects on Calibration and Uncertainty of SWAT Models.

Precipitation is one of the most important drivers in watershed models. Our objective was to compare two sources of interpolated precipitation data in terms of their effect on calibration, validation, and uncertainty of two SWAT models. One model was a suburban watershed in Metropolitan Atlanta, GA. The precipitation sources were Parameter-elevation Relationships on Independent Slopes Model (PRISM) on a 4-km grid and Climate Forecast System Reanalysis (CFSR) data on a 38-km grid. SWAT-CUP SUFI-2 was used for calibration (1/1/2003 to 12/31/2006), validation (1/1/2007 to 12/31/2010), and uncertainty. The PRISM data resulted in a better fit to the calibration data (NS = 0.66, p-factor = 0.72, and r-factor = 0.27) than the CFSR data (NS = 0.45, p-factor = 0.75, and r-factor = 0.52). Validation results were similar. Annual precipitation for the basin was less in the PRISM data compared to the CFSR data in 7 out of 8 years. Sensitive parameters were similar in both the PRISM and CFSR models, but fitted values indicated more rapid groundwater flow to the streams with the PRISM data. To show the general applicability of the PRISM data, the same comparison was made in another watershed located approximately 1000 km away, in central Louisiana. Results were similar indicating that PRISM data may produce better predictions of streamflow because of a more accurate estimate of rainfall within a watershed.