Scientific Investigations Report 2008-5230
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.
First posted January 15, 2009
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Wilkowske, C.D., Kenney, T.A., and Wright, S.J., 2008, Methods for estimating monthly and annual streamflow statistics at ungaged sites in Utah: U.S. Geological Survey Scientific Investigations Report 2008-5230, 63 p.
Streamstats Web-Based Application
Purpose and Scope
Hydrologic and Physiographic Description of Utah
Regional Regression Methods for Estimating Streamflow Statistics at Ungaged Sites
Geohydrologic Regionalization of Utah
Basin and Climate Characteristics
Regional Regression Analysis
Regional Regression Results
Limitations of Regional Regression Equations