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<br />t' <br />~ <br />~ <br />0' <br /> <br />EXTENSION OF STREAMFLOW AND DISSOLVED-SOLIDS RECORDS AT SELECTED SITES <br />IN THE COLORADO RIVER BASIN, ARIZONA, CALIFORNIA, COLORADO, NEVADA, <br />NEW MEXICO, UTAH, AND WYOMING, 1940-83 <br /> <br />By David K. Mueller and Timothy D. Liebermann <br /> <br />ABSTRACT <br /> <br />Monthly streamflow and dissolved-solids concentration were estimated for <br />periods prior to the initiation of data collection at selected sites in the <br />Colorado River basin. Techniques used for this record extension included <br />simple and weighted least-squares regression. Streamflow records were ex- <br />tended at 5 sites and dissolved-solids records were extended at 13 sites. <br />Records were extended from October 1940 through the beginning of the period <br />of record at each site to provide a completely concurrent data set for all <br />sites. Standard errors were 5 to 74 percent for monthly streamflow and 3 to <br />27 percent for monthly, flow-weighted dissolved-solids concentration. The <br />extended records at all sites were consistent with records from the historical <br />period. <br /> <br />INTRODUCTION <br /> <br /> <br /> <br />Monthly streamflow and dissolved-solids data for 20 sites in the Colorado <br />River basin (fig. 1) are compiled and published biennially by the U.S. Bureau <br />of Reclamation as part of a report from the Secretary of the Interior to <br />Congress on the quality of water in the basin. These reports are mandated by <br />several Federal laws, including the Colorado River Storage Project Act <br />(PL 84-485) and the Colorado River Salinity Control Act (PL 93-320). Data <br />used to compute the monthly values are obtained from U.S. Geological Survey <br />streamflow-gaging and water-quality sampling stations located at each of the <br />20 sites (table 1). The monthly values in the biennial reports are tabulated .' <br />beginning with January 1941. For the 12th biennial report (U.S. Department of '; <br />the Interior, 1985), monthly values were recomputed for the period of record <br />at each site using a method developed by Liebermann and others (1987). Values <br />could not be computed for all months for 13 of the sites because data col- <br />lection began after 1941. Missing monthly values were replaced by undocu- <br />mented estimates from previous biennial reports. For the 13th biennial <br />report, the U.S. Bureau of Reclamation desired estimates that were derived <br />using standard techniques and were more consistent with values computed for <br />the historical period of record. <br /> <br />1 <br /> <br />