WSP07520 - Laserfiche WebLink

Home Browse Search

I \ , I; The No Action operational pattern would continue existing water release practices. Annual releases presently are a function of inflow and space available in Lake Powell. From 1966 to 1989, releases ranged from the minimum of 8.23 million acre-feet to 20.4 million acre-feet (1984). Monthly and annual releases are scheduled to avoid spills, to maintain storage, to meet power system conditions and electrical energy loads, and to balance storage between Lake Powell and Lake Mead. Median monthly releases have ranged from about 550,000 acre-feet in February to about 900,000 acre-feet in August. Each month releases for the remainder of the year are recomputed based on updated streamflow forecast information. With existing operations, peak discharges are limited to 31,500 ds, although full powerplant capacity is 33,200 ds. These limits are exceeded only during floods. Minimum flows are 1,000 ds from Labor Day until Easter and 3,000 cfs during the remainder of the year. From 1980 to 1989, ramping rates were less than 8,000 cfs per hour 99 percent of the time and less than 5,000 cfs 95 percent of the time. A typical ramping rate is about 4,000 cfs per hour. Present Glen Canyon power generation is used to meet firm and non-firm loads, and to allow off-peak purchases when possible. The Maximum Fluctuations alternative would have releases from Glen Canyon Dam similar to the No Action except that maximum releases would be increased to powerplant capacity of r:" 33,2000 cfs, and minimum releases would be 1,000 cfs year round. The powerplant capacity would be exceeded only during floods. Daily flows would be allowed to fluctuate between the two extremes. Annual and monthly release volumes would be based on existing practices. Releases for the remainder of a given year would be recomputed monthly based on updated forecast information. Ramping rates, as in the No Action alternative would be limited by the mechanical and electrical constraints of the powerplant, and the rates would not be expected to be any more extreme than those currently experienced. The Maximum Fluctuations alternative would include pumping river bottom sand and a reregulation dam as described for the High Fluctuations alternative. A summary of the key descriptive information for each of the alternatives is shown in Figure 6. There appears to be no single solution to the diverse concernS for operation of Glen Canyon Dam and powerplant and the physical and biological resources downstream. Both the assumptions and logic, and, therefore, the alternatives are subject to refinements as new information becomes available. Other Actions to Be Considered Other actions will be considered that are not initially included in the alternatives. These actions may be added to the alternatives, as the EIS analysis proceeds. These include changes in flood prevention procedures, the potential for controlled high water spikes to transport sediment, power system adjustments, management changes in recreation and fishing activities, and similar administrative considerations. The need for and description of such actions can be better defined during the impact analysis phase; rather than specified up front in each alternative. A brief general overview of potential power system adjustments is presented in a separate newsletter article; however, details must await the analysis and quantification of impacts. A later edition of this newsletter will present more information on these actions. The public will have the opportunity to review adjustments made to the alternatives during the draft EIS review. Research and Monitoring A long-term monitoring and research plan will be prepared as part of each alternative. This will reflect EIS scoping comments that suggested" adaptive" alternatives. Continuing research during the EIS process and long-term monitoring after implementation of an alternative may confirm future operations or may indicate the need for future adjustments. 13