Estimating mean streamflow in the Duchesne River basin, Utah

Abstract

Monthly, annual, and long-term mean streamflow were estimated for streams in the Duchesne River basin by use of the monthly measurement method. Monthly measurements were attempted at 44 sites in the basin during the 1971 and 1972 water years. Some measurements could not be made because some sites were not accessible at all times, some of the streams did not have flow at all times, or some of the streams could not be measured during high flow. For those sites at which measurements could not be made, monthly discharge was determined by an alternative method involving the use of daily hydrographs for nearby gaging-station sites. Four of the monthly measurement sites were at discontinued gaging stations, and two others were located so that their total discharge would be approximately the same as that for another discontinued gaging station. A comparison of long-term mean annual discharge determined by the monthly measurement method versus that determined from gaging station records was as follows: Good at three sites (8 percent or less), fair-to-poor at one site (39 percent), and poor at one site (87 percent). At the three sites that showed good comparisons, there was flow at every monthly visit and the sites were above most diversions. The site where comparison was fair-to-poor is affected by upstream diversion; at the site where the comparison was poor, the stream was dry at the time of many of the monthly visits.