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<br /> <br />0D2ilG4 <br />Stream-temperature data have been collected by Stearns-Roger, Inc. <br />(written commun., 1976), on the Yampa River upstream from the water intake <br />for the Hayden Powerplant (fig. I). This site is comparable to the U.S. <br />Geological Survey's station 09244410, Yampa River below diversion, near <br />Hayden, Colo. (site Y-47). Harmonic analysis of the data collected by <br />Stearns-Roger, Inc., from March 10 to December 30, 1975, resulted in the <br />coefficients given in table 3. <br /> <br />To assess the effect of measuring stream temperatures at less than daily <br />frequencies on the results of the harmonic analysis, successively smaller <br />subsets of the data shown in the top row of each section of table 3 were <br />selected and analyzed. The results are shown in rows 2 through 7 of each <br />section of table 3; they indicate minimal loss of information in terms of <br />seasonal stream-temperature characterization. This supports a conclusion <br />reached earl ier by Gilroy and Steele (1972) and by Shampine (1977), and shows <br />that relatively few measurements evenly spaced during a year will provide <br />adequate estimates of the annual harmonic-temperature coefficients. <br /> <br />The results of the harmonic analysis applied to intermittent stream- <br />temperature data collected from 1960 through 1975 at 34 U.S. Geological <br />Survey stream-gaging sites are summarized in table 4. The absence of time <br />trends in the stream-temperature characteristics of these sites was assumed, <br />and temperature data for several years were composited for each site. Inter- <br />mittent stream temperatures generally are measured randomly during dayl ight <br />hours and are subject to the same bias indicated for instantaneous daily <br />stream temperatures (p. 10). Harmonic-analysis results for the five sites <br />where intermittent temperature measurements are made by the Colorado Depart- <br />ment of Health (see p. 5) are included in table 4 for comparison. <br /> <br />A general downstream increase in harmonic-mean temperature was noted for <br />both the Yampa River (sites Y-76, Y-64, Y-47, and Y-17, fig. 1 and table 4) <br />and the Little Snake River (sites Y-12, Y-8, Y-2, and Y-1, fig. 1 and <br />table 4). The harmonic-temperature coefficients for the U.S. Geological <br />Survey sites, which provide a general areal characterization of seasonal <br />stream-temperature variations in the basin, were correlated with selected <br />basin characteristics to see if regional 'patterns were discernible. For <br />example, plots of the harmonic-mean temperature, amplitude, and phase angle <br />versus altitude at each site are given on figure 4. The I ines defined by the <br />I inear least-squares regression equations all show a general inverse corre- <br />lation between the variables, the scatter generally being greater at higher <br />altitudes. Harmonic-mean temperature is related to altitude according to the <br />equation: <br /> <br />M=20.8-0.0022. (altitude, in feet). <br /> <br />(2) <br /> <br />Ampl itude and phase angle, on the other hand, can be estimated effectively <br />from average values of amplitude (A) and phase angle (e), as indicated by <br />comparison of the standard error of estimate of the regression line with the <br />standard deviation (fig. 4). <br /> <br />16 <br /> <br />'..;- <br />