EFFECTS OF IMPROVED PRECIPITATION ESTIMATES ON AUTOMATED RUNOFF MAPPING - EASTERN UNITED-STATES

We evaluated maps of runoff created by means of two automated procedur es. We implemented each procedure using precipitation estimates of bot h 5-km and 10-km resolution from PRISM (Parameter-elevation Regression s on Independent Slopes Model). Our goal was to determine if using the 5-km PRISM estimates would improve map accuracy. Visual inspection sh owed good general agreement among our runoff maps, as well as between our maps and one produced using a manual method. A quantitative uncert ainty analysis comparing runoff interpolated from our maps with gage d ata that had been withheld showed slightly smaller actual and percenta ge interpolation errors for the 5-km PRISM-based maps. Our analyses su ggest a modest region-wide improvement in runoff map accuracy with the use of PRISM-based precipitation estimates of 5-km (compared to 10-km ) resolution.