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F7 Flow variability altered at Flamin Gorge <br />Instantaneous peak flows on the upper Green River at Greendale were <br />reduced on average about 63% after closure of Flaming Gorge in 1962 (Figure <br />9). Interestingly, the only peak flows exceeding the power plant capacity of <br />130 mjs'' (4700 cfs) occurred in 1983, 1984, and 1986, when higher than <br />expected inflows forced spills and the use of jet-tube by-pass. These high flows <br />were not planned releases to benefit endangered fish but were done to draw <br />down the reservoir level. <br />Variability in flow was better maintained downstream at Jensen, Utah <br />by the relatively natural flows of the Yampa and Little Snake Rivers. The <br />Yampa and Little Snake rivers have been depleted in volume by about 10 and <br />11%, respectively, by consumptive water use, but do not have the large power <br />dam development which has a high impact on annual peak flows (Stanford, <br />1993). <br />Flows exceeding bankfull discharge on the middle Green River (580 <br />m3s' (20,500 cfs) daily average at Jensen, Utah) occurred on only two <br />occasions in the 18-year period (1964-1982) after the closure of Flaming Gorge <br />f in 1963. In the pre-dam period of record 1948-1962, flows exceeded bankfull <br />10 of 14 years. Without Flaming Gorge, bankfull discharges would have <br />LJ occurred 13 out of 18 years in the 1964-1982 post-dam period (U.S Bureau of <br />Reclamation and USGS Data). Although peak discharge and variability in peak <br />discharge on the Green River as measured at Greendale have decreased, total <br />volume of water delivered down the Green River has remained close to pre- <br />dam levels (Figure 10). The primary purpose of Flaming Gorge Dam was to <br />' insure more stable delivery of water to downstream users between wet and dry <br />' years. This tends to reduce variability in total volume to some degree when <br />entering wet cycles as low reservoir levels may be filled. <br />21 <br />.y