Annual Operating Plan for Colorado River Reservoirs 1998

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meters per second (16,700 cfs) on June 13. These high inflows prompted higher than expected releases during the month of June. Releases of 311 cubic meters per second (11,000 cfs) were made during much of June. However, there was no significant flooding in the city of Green River, Wyoming, located 60 river miles below the dam. The flood stage is exceeded when flows at Green River exceed 354 cubic meters per second (12,500 cfs). Because the mean annual inflow of 1,480 MCM (1.229 MAF) far exceeds Fontenelle's storage capacity of 426 MCM (.345 MAF), significant power plant bypasses are expected under the most probable and maximum probable inflow scenarios. Additionally, there is little chance that the reservoir will not fill during water year 1998. In order to minimize spring high releases, and to maximize downstream resources and power production, the reservoir will probably be drawn down to minimum pool elevation, 1970.0 meters (6463 feet) which corresponds to a volume of 115 MCM (0.093 MAF) of live storage. Flaming Gorge Reservoir Like Fontenelle Reservoir, inflows into Flaming Gorge were much above normal during water year 1997. April through July unregulated inflow was 2,044 MCM (1.657 MAF) or 139 percent of normal. In May of 1997, an April though July inflow forecast of 2,220 MCM (1.800 MAF) was issued by the National Weather Service for Flaming Gorge. This high inflow forecast prompted a decision to use the bypass tubes to release water in excess of power plant capacity from Flaming Gorge. Bypass releases began on May 28, with 57 cubic meters per second (2000 cfs) being released through the two bypass tubes in addition to power plant capacity of 130 cubic meters per second (4600 cfs) for a total release of 187 cubic meters per second (6600 cfs). However, the day after the bypass releases began, heavy precipitation occurred in the Yampa River Basin. Following these heavy rains, unusually warm temperatures became manifest in the Yampa River headwaters as well. The combination of these two circumstances caused flows on the Yampa River to increase significantly. Because of concern over flooding on the Green River near Jensen, Ut. (below the confluence of the Yampa River), bypass releases were suspended on May 30. The Yampa River reached a peak flow of 575 cubic meters per second (20,300 cfs) on June 4, 1997. A day later flows on the Green River at Jensen reached 708 cubic meters per second (25,000 cfs). These flows were the highest peak flows recorded since 1984. Bypass releases were reestablished on June 16. The Yampa River had dropped substantially by this time, but inflow forecasts to Flaming Gorge showed that the additional release of water was needed. The bypass release that began on June 16, however, differed from the earlier bypass operation in that the full capacity of the bypass tubes was utilized; the total release was 243 cubic meters per second (8,600 cfs). This bypass operation was scheduled to Oast from June 16 to June 23. On June 21, however, in the late afternoon, a failure occurred in one of the bypass tubes. This caused flooding to occur within the power plant, which then triggered a complete shut -down of the power plant itself. For about six hours crews worked to contain the damage and return stable September 3, 1997 8