8119 - Laserfiche WebLink

Home Browse Search

I I I I I I I I I I I I I I I I I I I of dissolved oxygen available for fish. No information on dissolved oxygen tolerance limits for Colorado squawfish was found, so general limits reported for Ictalurids (catfishes) and Centrarchidids (sunfishes) were used. Culture guidelines for Centrarchids suggest maintaining oxygen concentrations above 5 mg/L with concentrations near 1.0 mg/L being avoided and potentially fatal (Whitmore et aI. 1960; Moss and Scott '1961; Bonn et aI. 1976; Piper et aI. 1982; and Stickney 1986). Oxygen tolerance of catfish is similar with minimum concentrations of 5.0 mg/L (Tucker 1985) and lethal levels near 1.0 mg/L (Moss and Scott 1961). For this study dissolved oxygen concentrations below 5.0 mg/L were considered unsuitable habitat for age-O Colorado squawfish. 4.0 RIVER HYDROLOGY The Green River is regulated year around by Flaming Gorge Dam for water delivery, flood control, and power generation. At an elevation of 1,708 m, the dam is located in northeastern Utah, about 660 km upstream of the confluence with the Colorado River (Figure 1). Flaming Gorge Dam was authorized by the Colorado River Storage Project Act of 1956 (43 U. S. C. 620). Construction began in 1956 and was completed in 1964. The reservoir began filling in November, 1962, and continued through 1966, with full operation in 1967. Flaming Gorge Reservoir impounds water for about 145 Ian upstream to Green River, WY, with a total surface area of about 17,000 ha and a live storage capacity of about 3.75 million acre feet. Releases from Flaming Gorge Dam vary during a 24-h period, primarily because of hydropower generation. Releases vary seasonally primarily because of spring runoff or downstream water demands. Minimum releases of 800 Cfs (23 cms) have been established by UDWR to provide necessary flows for the tailwater trout fishery, and maximum releases of 4,700 cfs (133 cms) are constrained by power plant capacity and reservoir elevation. In addition to the power plant capacity, releases of 4,000 cfs (113 ems) can be made through two river outlets Get tubes), and 28,800 cfs (816 ems) can be released through the spillway. Flow regulation is ameliorated with distance downstream from the dam and by inflow from several major tributaries, including the Yampa, White, Duchesne, San Rafael, and Price rivers. The presence of the dam has had a significant effect on the yearly hydrograph by reducing spring peaks and increasing fall and winter flows. Flow data are provided for the Green River at Greendale, Utah and at Jensen, Utah, in order to show releases from the dam and the effect of downstream amelioration and tributary inflow. The Greendale gage is located 0.5 miles downstream of the dam and the Jensen gage is located 108 miles downstream of the dam and below the inflow of the several tributaries, including the Yampa River. 4.1 Flows During Winter of 1993-94 Releases from Flaming Gorge Dam in winter of 1993-94 (November-March) were of a higher volume with greater daily fluctuations than in winter of 1994-95. In 1993-94, mean daily flows of the Green River at Greendale varied from a high of2,584 cfs in December to 1,125 cfs in March, and monthly volume released varied from 158,900 acre-feet in December to 69,160 acre-feet in March (Table 3). Hourly releases varied from about 1,000 cfs to nearly 4,000 cfs during the months of December through February (Figure 2). On a daily basis, lowest releases usually occurred between 0100 hrs and 0500 hrs, and highest releases usually occurred between 1900 hrs and 2200 hrs (Figure 3). 7