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I I I I I I I I I I I I I I I I I I I 93, and 24 cms), respectively. Total volume released from the dam was 1,607,000 acre-feet in water year 1987, and 1,214,000 acre-feet in water year 1988 (USGS 1987, 1988). Releases during Winter 1 were generally higher than in Winter 2 (Figure 2). Average daily releases from Flaming Gorge Dam in Winter 1 ranged from a high of 3,619 cfs (103 cms) in December to a low of 1,285 cfs (36 cms) in March. Average daily releases in Winter 2 ranged from 2,351 cis (67 cms) in January to 1,308 cfs (37 cms) in March. Flows of the Green River near Jensen for 2 years preceding Flaming Gorge Dam (1960-62) and for 2 years of the investigation (1986-88) illustrate seasonal impact of the dam on the hydrograph in habitat occupied by the endangered fish species (Figure 3), located about 174 km downstream of the dam. In preimpoundment years, winter flows from December through March, were characterized as the lowest of the year. These base flows were sometimes interrupted by spikes representing runoff during an early warming period, or a local rain spate--as in February of 1962. In postimpoundment years, winter flows were higher and spikes representing early runoff or rainfall events were rarely evident. A monthly flow exceedance analysis (Bovee 1986) for a 12-year period before (1951- 62) and after (1977-88) impoundment (Figure 4) shows that postimpoundment winter flows (December through March) were higher than preimpoundment flows near Greendale. Average preimpoundment winter flows exceeded 1,000 cfs (28 cms) twice, while flows in postimpoundment years exceeded 1,000 cfs in all years. Also, average monthly preimpound- ment flows did not exceed 2,500 cfs (71 cms), while postimpoundment flows exceeded that level in 33 to 58 percent of the years examined by month. 5