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<br />002843 <br /> <br />, <br /> <br />fig. 1). Although the average annual suspended-sediment concentration in the <br />Little Snake River subbasin is an order of magnitude greater than in the <br />Yampa River subbasin, total sediment load is only 3 to 4 times greater in the <br />Little Snake River subbasin due to lower streamflows. This compares favor- <br />ably to the estimate of 3~ times reported previously (Iorns and others, 1965). <br />Moreover, Iorns, Hembree, and Oakland (1965, p. 35, table 16) estimated that <br />the Yampa River basin contributed about one-eighth the total streamflow of <br />the upper Colorado River basin, but that the suspended-sediment discharge <br />contribution was less than 1.5 percent. <br /> <br />MAJOR INORGANIC CONSTITUENTS <br /> <br />;; <br /> <br />Concentrations of major inorganic constituents frequently are correlated <br />with specific conductance to such a degree that specific-conductance measure- <br />ments can be used to estimate chemical composition (Steele and Matalas, 1974; <br />Singh and Kalra, 1975). In this study, historic regression functions were <br />developed using regional data collected by Iorns, Hembree, Phoenix, and Oak- <br />land (1964) during 1944-58 for 34 sites in the basin. Regression functions <br />also were developed from site-specific data for the Yampa River near Maybell, <br />Colo., and from site-specific data for a combination of the Little Snake <br />River above Lily, Colo., and the Little Snake River near Lily, Colo. (fig. 1). <br />This latter combination is necessary because of a change in location of the <br />water-quality sampling site at the end of the 1969 water year; hereafter, this <br />combination will be referred to as the Little Snake River near Lily. Two <br />different time periods were used for the site-specific regressions. One en- <br />compassed the entire period of record at the time of the analysis (1951-75 <br />water years); whereas, the other (1966-72 water years) was that used by <br />Steele, Gilroy, and Hawkinson (1974) in a nationwide study for the Council on <br />Environmental Quality (1973, p. 283-284; 1975, p. 362, table 20). The latter <br />period of record was chosen to minimize the effect of possible time trends on <br />water quality. The resultant regression functions are given in the expanded <br />technical report. <br /> <br />. <br /> <br />The regression functions were applied to daily specific conductance rec- <br />ords available for the Yampa River near Maybell and Little Snake River near <br />Lily. Using a computer program documented by Steele (1973), annual mean <br />discharge-weighted chemical loads and concentrations were determined. <br /> <br />. <br /> <br />Annual concentrations of dissolved solids at the Yampa River near May- <br />bell estimated from the regression analyses were almost identical using the <br />three equations (regional and site-specific for 1966-72 and 1951-75) appli- <br />cable to this site (fig. 5A). Moreover, comparisons of these estimates with <br />annual values obtained from the actual data (fig. 5B) are quite good up <br />through 1970. Larger deviations since 1970 are attributed largely to chang- <br />ing from composited to monthly grab samples for determining the actual annual <br />mean concentrations. Agreement among the three applicable equations and the <br />fit to the actual data may not be as good for individual constituents. For <br />example, figure 6 shows graphically the three regression functions for esti- <br />mating calcium concentrations at the Little Snake River near Lily. The diver- <br />gences of the functions will result in widely different calcium concentrations <br />estimated for extreme values of specific conductance. <br /> <br />9 <br /> <br />,1, <br />