9631

• UCREFRP Catalog Number: 9631
• Author: U.S. Bureau of Reclamation.
• Title: Operation of Flaming Gorge Dam Draft Environmental Impact Statement Executive Summary.
• USFW Year: 2004.
• USFW - Doc Type: Salt Lake City, UT.
• Copyright Material: NO

classification than the assigned hydrology classification for the previous month, then the
classification could be shifted by one classification (up or down) to reflect the change in
hydrology. A shift would only be made when the reservoir condition indicated that the
shift would be necessary to achieve the March 1 drawdown level of 6027 feet above sea
level. Otherwise, the hydrologic classification for the current month would remain the
same as for the previous month.
The range of acceptable base flows for Reach 2 would be selected from the 2000 Flow
and Temperature Recommendations for the hydrologic classification set for the current
month. Reclamation would make releases to achieve flows in Reach 2 within the
acceptable range and also ensure that the reservoir elevation on March 1 would be no
higher than 6027 feet above sea level.
The 2000 Flow and Temperature Recommendations during the base flow period do allow
for some flexibility, and the Action Alternative accommodates this flexibility. Under the
Action Alternative, the flows occurring in Reach 2 during the base flow period would be
allowed to vary from the targeted flow by ±40% during the summer to fall period
(August through November) and by ±25% during the winter (December through
February), as long as the day-to-day change is limited to 3% of the average daily flow
and the variation is consistent with all other applicable 2000 Flow and Temperature
Recommendations. Reclamation would utilize the allowed flexibility to the extent
possible, to efficiently manage the authorized resources of Flaming Gorge Dam. Flaming
Gorge Reservoir would be operated through the base flow period so that the water surface
elevation would not be greater than 6027 feet above sea level on March 1.
During the base flow period, hourly release patterns from Flaming Gorge Dam would be
patterned so that they produce no more than a 0.1-meter stage change each day at the
Jensen gauge, except during emergency operations.
S.13.3.4 Operations in March and April (Transition Period)
From March 1 through the initiation of the spring peak release (typically, this occurs in
mid- to late May), there are no specific flow requirements specified in the 2000 Flow and
Temperature Recommendations. For the Action Alternative, releases during this
transition period would be made to manage the reservoir elevation to an appropriate
drawdown level based on the forecasted unregulated inflow. Appropriate drawdown
levels under normal operations during the transition period are those that would allow for
safe operation of the dam through the spring. The upper limit drawdown levels for
varying percentage exceedances are described in table S-5. These drawdown levels apply
for both the Action and the No Action Alternatives.
Table S-5 implies that upstream regulation above Flaming Gorge Reservoir remains
relatively consistent with historic regulation? In the event that less storage space would
be available above Flaming Gorge Reservoir during the spring, these drawdown levels
may have to be lower than those specified in table S-5 for safe operation of Flaming
Gorge Dam. In extreme wet years, the drawdown level for May 1 could potentially be
lower than what is specified to maintain safe operation of the dam.
2 Historically (1988-2003), there generally has been about 200,000 acre-feet of available space at
Fontenelle Reservoir (above Flaming Gorge) on May 1.
Executive Summary r.? S-27