Annual Operating Plan for Colorado River Reservoirs 1998

Home Browse Search

For water year 1998 operations, Blue Mesa Reservoir will be drawn down to at least an elevation of 2283 meters (7490 feet) by December 31, 1997, in order to minimize icing problems in the Gunnison River. Blue Mesa will continue to be drawn down through April 1998 to a level that will accommodate the current most probable inflow scenario and accomplish the release objectives with minimal power plant bypasses at Crystal. The minimum release objective of the Aspinall Unit is to meet the delivery requirements of the Uncompahgre Valley Project and to keep a minimum of 8.5 cros (300 cfs) flowing through the Black Canyon of the Gunnison National Monument and to maintain a minimum of 8.5 cros (300 cfs) below the diversion structure at Redlands (at the confluence of the Gunnison and Colorado Rivers) during the summer months. Under all three inflow scenarios, Blue Mesa is expected to fill in the summer of 1998 and flows through the Black Canyon of the Gunnison National Monument are expected to be above the minimum release objective during the summer months. Filling of the reservoir in water year 1998 will ensure that reasonable specific releases required to study the protection and improvement of habitat for endangered fish can be accommodated. The forecasted runoff for the spring of 1998 will be closely monitored to achieve these objectives. To protect both the blue ribbon trout fishery in the Black Canyon and recreation potential, releases during 1998 will be planned to minimize large fluctuations in the daily and monthly flows in the Gunnison River below the Uncompahgre Tunnel Diversion. Navajo Reservoir The April through July unregulated inflow into Navajo Reservoir in water year 1997 was 1,026 MCM (0.832 MAF) or 123 percent of average. Water year 1997 unregulated inflow was 1,530 MCM (1.240 MAF) 'or 123 percent of average. Navajo Reservoir did not fill in 1997. Section 7 consultation with the Fish and Wildlife Service on the operation of Navajo Dam continued in 1997. Water year 1997 was the seventh year of a seven -year study to evaluate alternative operations of Navajo Reservoir to benefit endangered fish. In an attempt to monitor the aquatic impact of low winter flows on the San Juan River, winter releases were restricted to 250 cfs during the November - February period. During the spring large releases of up to 140 cros (5,000 cfs) were made during June and July to coincide with the peak flows of the Animas River. This resulted in peak flows of 305 cros (10,800 cfs) at Bluff, Utah. After the completion of the large spring releases, releases were gradually reduced to approximately 17 cros (600 cfs) for the remainder of the year. In water year 1998, Navajo Reservoir is expected to nearly fill only under the probable maximum inflow scenario. The reservoir should fill above 80 percent of full under the most probable and probable minimum scenarios. Releases from the reservoir will be held near 17 cros (600 cfs) through the fall and winter months and large releases will likely be made in May and June in order to improve the habitat and provide better spawning conditions for endangered fish in the San Juan River. September= 3, 1997 10