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Comparison of unregulated and regulated streamflow for the Yakima River at Union Gap and near Parker, Washington

January 1, 1994

Records of regulated daily mean discharge for 52 water years, 1926-77, at 13 stream gaging stations were adjusted for changes in storage contents in five reservoirs and flows diverted in 58 canals to estimate effects of reservoir storage and canal diversion on streamflow in the Yakima River at Union Gap and near Parker, Washington. Estimated composite error of computed unregulated discharges, based on analyses of several possible sources of error, was 10 percent. Unregulated streamflow at Union Gap and near Parker was shown to be basically equivalent. Regulation reduced unregulated 52-year mean annual discharge from 5,900 cu ft/sec to 3,800 cu ft/sec at Union Gap and 2,300 cu ft/sec near Parker. Losses were due primarily to diversion for agricultural irrigation and to export of water from Upper to Lower Yakima basin. Regulation reduced springtime high flows and increased August-September low flows at Union Gap, but three canals between Union Gap and Parker caused flow in the Yakima River to diminish to very low values. Coefficients of variation and distribution percentiles of mean discharges indicate that the relative variability of regulated means has generally decreased compared with unregulated means at Union Gap and increased compared with unregulated flow near Parker. (USGS)

Citation Information

Publication Year 1986
Title Comparison of unregulated and regulated streamflow for the Yakima River at Union Gap and near Parker, Washington
DOI 10.3133/ofr82646
Authors J. J. Vaccaro
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 82-646
Index ID ofr82646
Record Source USGS Publications Warehouse
USGS Organization