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Methods for estimating monthly and annual streamflow statistics at ungaged sites in Utah

January 23, 2009

The monthly 80-, 50-, and 20-percent exceedance streamflows were calculated for 266 streamflow-gaging stations in Utah and the surrounding states. Using geographic information systems software, 24 physiographic and climatic basin characteristics were computed for each gaging station location. Using these data, regional regression equations were created to predict monthly 80-, 50-, and 20-percent streamflow and annual mean streamflow at ungaged sites in Utah. The state of Utah was divided into seven distinct geohydrologic regions on the basis of a variety of physiographic, climatic, and hydrologic characteristics. Separate regression equations were developed for each region except region 3, which was combined with region 5 because of the small number of gaging stations in region 3. Root mean square error percent for the equations ranged from 34 to 379 percent. The equations are more reliable for predicting high-streamflow statistics (20-percent exceedance) than for predicting the low-streamflow statistics (80-percent exceedance). In general, the mean annual streamflow equations had smaller errors than the monthly predicting equations. The developed equations documented in this report will be implemented in StreamStats, a USGS Web-based tool that allows users to obtain a variety of streamflow statistics and basin characteristics by selecting a location on a map interface.

Citation Information

Publication Year 2008
Title Methods for estimating monthly and annual streamflow statistics at ungaged sites in Utah
DOI 10.3133/sir20085230
Authors Chris D. Wilkowske, Terry A. Kenney, Shane J. Wright
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Scientific Investigations Report
Series Number 2008-5230
Index ID sir20085230
Record Source USGS Publications Warehouse
USGS Organization Utah Water Science Center

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