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<br /> <br />0020rJ9 <br /> <br />Simi lar regional stream-temperature analyses have been reported for. <br />other areas of the United States .(Steele and Dyar, 1974; Shampine, 1977; <br />Lowham, 1978; Clement, 1978; Limerinos, 1978). Lowham's regression equation <br />for estimating stream temperatures in the Green River basin, southwestern <br /> <br />Wyoming, M=19.5-0.0019 . (altitude, in feet), (3) <br /> <br />is similar to that used for the Yampa River basin (equation 2). <br /> <br />Regional analysis of stream temperatures may be used for detecting <br />changes resulting from man's activities, even though predevelopment infor- <br />mation may be sparse or lacking. For example, to assess potential effects of <br />a coal-strip mine on stream temperatures in the Yampa River basin, several <br />years of intermittent stream-temperature measurements downstream from the <br />mine would be needed. Harmonic-temperature coeffic:ients calculated from <br />equation 1 (p. 10) could then be compared to predevelopment coefficients <br />estimated from the altitude of the site using the information given on <br />figure 4. This has not been done in the present study because of a lack of <br />time to collect suff-icient stream-temperature data downstream from existing <br />coal mines. <br /> <br />Because mountain streams typically undergo a diel variation in tempera- <br />ture during the summer (fig. 3), and because the sItes visited during August- <br />September 1975 were sampled randomly during dayl ight hours, it is very diffi- <br />cult to determine any conclusions regarding stream temperatures measured .as <br />part of the basinwide reconnaissance. One approach, however, is to compare <br />measured temperatures to appl icable water-qual ity standards.. <br /> <br />Water-qual ity standards app) icable to Colorado streams and . lakes (Colo- <br />rado Department of Health, 1977b) are presented in table 5. Throughout this <br />report, values of water-quality variables are compared only to Colorado <br />standards. This was done, in part, to avoid confusion, as a number of <br />differences exist between the Wyoming (Wyoming Department of Environmental <br />Qual ity, 1978) and proposed Colorado standards. Also, in both the basinwide <br />reconnaissance and the quarterly sampling program, relatively few stream <br />sites were located in Wyoming (table 1). <br /> <br />cold-water biota i.n <br />(11 percent) made <br />The total range of <br />was 9.0 to 25.50C; <br />streams supporting <br /> <br />The upper temperature I im;it for streams supporting <br />Colorado is 200C (Celsius). Nine of the 82 measurements <br />during the basinwide reconnaissance exceeded this limit. <br />stream temperatures observed during the reconnaissance <br />thus, none was greater than the upper I imit of 300C for <br />warm-water biota (table 5). <br /> <br />During the quarterly sampling program from December 1975 through August- <br />September 1976, only 7 of 163 temperature measurements (4 percent) exceeded <br />the 200C I imit. Three of these occurred in June 1976, and four occurred dur- <br />ing August-September 1976. Again, no recorded temperature was greater than <br />30oC, as the range of stream temperature for the quarterly sampling program <br />was 0 to 26.50C. All temperatures that exceeded the 200C I imit during both <br />the basinwide reconnaissance and the quarterly sampl ing program appear to be <br />due to natural causes. <br /> <br />21 <br />