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<br />t <br /> <br />In addition to institutional constraints, economics also constrain the use of <br />the jet-tubes and spillway. Any water that bypasses the generators represents <br />a significant loss of revenue, likewise with the spillway. Use of the <br />spillway also has a further disadvantage in that physical damage to the <br />spillway and downstream access roads are incurred and must be repaired. These <br />again are economic costs which can be valued and assigned to different <br />operational objectives. <br /> <br />3.5.4 Environmental Constraints <br /> <br />Environmental constraints are those which in some way restrict the operation <br />of the dam to limit adverse impacts to the natural resources of the Green <br />River. Examples of current constraints are the minimum flow for the trout <br />fishery, moderate power plant ramping rates, the installation of the multi- <br />level intake structure to increase the temperature of the releases, and the <br />avoidance of spills to limit the erosion and danger of extreme releases. <br />Environmental constraints are closely linked to economic constraints, since in <br />most cases maximizing one reduces the other. <br /> <br />3.6 Flaming Gorge Construction and Hydrology <br /> <br />Advanced planning for Flaming Gorge Reservoir began in the early 1950's, and a <br />gage was installed at the present dam site in 1951 and hydrological data <br />collection continues to the present. Dam construction began in 1956 and was <br />completed in 1964. Filling of the reservoir initiated in 1962 and continuing <br />through 1966. Full operation of the facility began in 1967 and has continued <br />under a number of different operational criteria. <br /> <br />The average unregulated inflow to Flaming Gorge Dam is about 1.7 MAF which <br />represents 45 percent of the storage capacity. The great majority of this <br />inflow comes in the April-July period in the form of snowmelt runoff from the <br />Wind River Mountains and the Uinta Mountains. The reservoir formed by the dam <br />has a surface area of 42,000 acres and is 91 miles long, extending to within 5 <br />miles of Green River, Wyoming. The reservoir live storage capacity is 3.75 <br />MAF, 12 percent of the total CRSP live storage of 31.4 MAF. To accommodate <br />inflow, Flaming Gorge Reservoir is annually drawn down about 800,000 acre-feet <br />to elevation 6,020 feet. Winter and spring releases are adjusted according to <br />the forecasted spring inflow to fill the reservoir during the latter part of <br />the spring runoff. The minimum reservoir level occurs in March while the <br />maximum level usually occurs in July. During the remainder of the year, <br />releases are patterned, when possible, ~o match monthly electrical energy <br />demand. <br /> <br />Historically, Flaming Gorge has been maintained as full as possible to ensure <br />that compact requirements can be met. Within this constraint, Flaming Gorge <br />is primarily operated for power generation, but as the Upper Basin States <br />develop their compact entitlement scheduled monthly releases could become more <br />important. Currently no firm schedule of monthly releases from Flaming Gorge <br />exists, principally due to the lack of water development along the Green River <br />below the dam. Flaming Gorge storage has remained "on call" from Lake Powell, <br />eventually supplying water to be delivered to the lower Basin. Throughout <br />Flaming Gorges operating history the Upper Colorado Basin States have <br />indicated a desire to keep the reservoirs full. After major flood events in <br />1983 and 1984 this objective was currently tempered by spill avoidance <br />criteria designed to avoid power plant bypasses (spills) which not only forgo <br />power revenue but also can produce great environmental damage downstream of <br />the dams. <br /> <br />3-6 <br />