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<br />reconnaissance study, described later, discharge measurements were made at 85 <br />locations In the basin. <br /> <br />Within the basin there is a large variation of yearly precipltation--from <br />more than 50 inches (1,270 mm) In some of the higher mountain areas to 9 inches <br />(230 mm) or less in much of the plains area. Yearly runoff varies greatly with <br />64 percent of the annual streamflow occurring during the months of May and <br />June In the Yampa River near Maybell. Surfa'ce water is diverted at numero'us <br />points, principally for agricultural use. Available water for irrigation is <br />not sufficient during the entire growing season and water shortages occur for <br />about 50 percent of the presently delineated irrigated land. <br /> <br />Under a present agreement (Upper Colorado River Basin Compact of 1948), <br />streamflow of 5 million acre-feet (6,165 million m3) for the Yampa River near <br />Maybell must be maintained over any 10-consecutive-year period. Flow condi- <br />tions at this location from past data average 1.062 mill ion acre-feet (1,309 <br />mi 11 ion m3) per year, and downstream at the Colorado-Utah State I ine the aver- <br />age annual flow is 1.468 mi 11 ion acre-feet (1,810 mill ion m3) (Colorado Water <br />Conservation Board and U.S. Department of Agriculture, 1969). <br /> <br />Available data will be used in Phase I for a preliminary analysis of the <br />surface-water avai labi I ity for various water uses--both current and planned. <br />These data subsequently can be used to compute natural flow characteristics, <br />flow characteristics without man-made effects, and seasonal flows with both <br />present and expected water use in the basin. <br /> <br />Stream Temperature <br /> <br />Daily records of stream temperature are available at two National Stream <br />Quality Accounting Network (NASQAN) sites, U.S. Geological Survey station num- <br />bers 09251000 and 09260000. Periodic data for approximately 34 surface-water <br />gaging stations are also available. These data will be analyzed using a <br />harmonic-analysis technique documented by Steele (1974). The method will be <br />used to characterize seasonal patterns affecting surface-water temperature. <br />Supplemental stream-temperature data from the reconnaissance survey (p. 9) <br />will be used to test the regional relationships developed from the harmonic. <br />analysis technique. <br /> <br />Major Inorganic Ions <br /> <br />Long-term data on major inorganic constituents have been collected at <br />two sites in the Yampa River and Little Snake River subbasins (NASQAN stations <br />09251000 and 09260000). As part of a comprehensive study of water resources <br />in the Upper Colorado River Basin, lorns a~d others (1964) collected and ana- <br />lyzed 101 samples, primarily for major inorganic constituents and for dissolved <br />solids, at 34 stations in the Yampa ll.iver basin. These data ultimately will be <br />evaluated with regard to possible bivariate regression relationships and sea- <br />sonal changes. As part of the regression technique, it is hoped to develop <br />relationships between individual concentrations of major inorganic constitu. <br />ents and;specific conductance. The long-term records from stations 09251000 <br />and 09260000 will be evaluated for significant changes in annual time trends <br />(see, for example, Steele and others, 1974). <br /> <br />8 <br />