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~. ~ s' I '"~ ,! >, ~~ f, 84 and turbid, but the volume sometimes changed drastically and suddenly Table during flash floods. For example, before Flaming Gorge Dam was com- pleted in 1963, tbe Green River characteristically had high spring flows Month and low winter flows (Vanicek, Kramer, and Franklin, 1970). These flows have been replaced by relatively stabilized flows. However, monthly Janua Febn and daily flows have varied as a result of water releases at the dam, Maret which depend on power and downstream water demands. Apri! Impoundments have changed the natural warm, turbid river into cold, May clear tailwaters with a controlled flow. Below Flaming Gorge Dam, in- June troduced rainbow trout (Salmo aairdneri) have replaced the endemic ape- July cies. Between 1962 and 1966-67, while the impoundment was filling, the Augu tailwater fishery for rainbow trout was excellent. Since 1967, however, Sept water has been drawn from the hypolimnion of the reservoir, resulting Octo in reduced water temperature. (table 1). which. in turn. have reduced Nove trout production and the potential for recreational fishing. The Upper DecE Colorado Region of the U.S. Bureau of Reclamation (BR). in cooperation Anm with the state agencies of Colorado, Utah, and Wyoming. has proposed modifications of the penstock intake at Flaming Gorge Dam to increase Assl Lak. the water temperature in the tailwater (U.S. Department of the Interior. Bureau of Reclamation. 1975b). This modification is expected to result in temperatures between 500 to 550, for about five months, based on a BR Cen mathematical model of river temperature, These temperatures are within the range required for good trout growth. These temperatures are also within the range for good growth and production of various trout food organisms such as caddis flies (Tricoptera) and stoneflies (Plecoptera) (U.S. Department of the Interior, Bureau of Reclamation, 1975b). The endemic fish that virtually disappeared from the Green River between , :;:-:'1,,,<<'/-,\ "-"" .;