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. DRAFT 4.0 DESCRIPTlOO OF WINTER RIVERINE (DIDITlOOS . The operation of Flaming Gorge dam during the winter months is primarily determined by power demands. Water storage and flood control may also influence discharges as high elevation snow pack is evaluated in anticipation of spring runoff. Daily discharges from Flaming Gorge dam are controlled largely by power demands which result in constantly fluctuating flows. . The influence of discharge from Flaming Gorge Dam on the stage of the river was apparent throughout this study. Generally, the water level in the river was in a constant state of flux, either rising or falling. Stable water levels were rarely seen, except for a few short periods of time. Rates of fluctuation and differences in stage were most dramatic in the upper region of the study area, becoming more attenuated downstream. Generalized operational patterns for the 1986-87 and 1987-89 winters, presented as mean daily releases from Flaming Gorge Dam, are illustrated in Figure 2 (not available). . . Water temperature data were collected concurrently with fish observations. Main channel water temperature data presented below represent means and ranges of reading taken at various times during the day at various locations within the study area. Air temperature data represent readings taken at the National Atmospheric and Oceanic Administration weather station located in Jensen, Utah. 4.1 THE WINTER OF 1986-87 4.1.1 River Flow . . Flow regimes during the first winter of the study were generally higher and more consistent than flowS during the second winter (Figure 2). Average daily releases ranged from a high of 4140 cfs in January to a low of 890 cfs in March. Consistent high releases during December and the first half of January were followed by a period of variable releases through February. Relatively lower, but variable releases were observed in March. 4.1.2 Air and Water Temperature . Water temperatures observed during the 1986-87 winter are presented in Table 2. Higher water temperatures during the 1986-87 winter were related to above normal ambient temperatures present on the study area throughout the winter (Table 2). Monthly means as well as minimum and maximum air temperatures for December through March were substantially above normal. Additionally, higher releases from Flaming Gorge dam may have moderated water temperatures to a small extent. Diurnal flucuations in water temperature ranged from 0 to 4 degrees celcius depending on weather and time of year. . . 13 .