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

conditions indicated that bypasses or spills would be necessary for safe operations of the
dam. Bypasses or spills would be timed to occur when the Yampa River peak flows and
immediate post peak flows occur.
Reclamation would establish a range of spring operational scenarios, through
consultation with the U.S. Fish and Wildlife Service and Western. These scenarios
would achieve the objectives of the Reasonable and Prudent Alternative of the
1992 Biological Opinion on the Operation of Flaming Gorge Dam under one of three
hydrologic conditions (dry, average, or wet). The range of scenarios would provide
flexibility in operations to adjust to changing hydrologic conditions and would be based
on the probable minimum and probable maximum inflow forecasts issued in April by the
River Forecast Center. Timing of the spring peak release under the range of possible
operational scenarios would occur with the peak flows and immediate post peak flows on
the Yampa River.
When the hydrologic condition is determined to be dry, the spring peak duration would
be 1 to 2 weeks. Most likely, the magnitude of the release during the spring peak in dry
years would be limited to powerplant capacity and could be limited to 4,000 cfs to
conserve reservoir storage. In dry years, the spring peak release would be completed no
later than June 20.
When the hydrologic condition is determined to be average, the spring peak duration
would be 2 to 5 weeks. The magnitude of the release during the spring peak most likely
would be limited to powerplant capacity (about 4,600 cfs). The spring peak release in
average years would be completed by July 10.
Wet hydrologic conditions would establish a spring peak duration of 5 weeks or greater.
Peak releases in wet years could include bypass releases and possibly spillway releases,
depending on conditions at Flaming Gorge Reservoir. The use of bypass tubes or the
spillway would be based on the safe operating criteria for the dam. The magnitude of
peak releases in wet years would be at least powerplant capacity (about 4,600 cfs) and the
spring peak release in wet years would be completed by July 20.
S.13.2.2 Use of Bypass Tubes and Spillway at Flaming Gorge Dam
Under the No Action Alternative, the use of the bypass tubes or the spillway would occur
only when hydrologically necessary to maintain safe operations of Flaming Gorge Dam,
during emergency operations, or when the full release capacity of the powerplant is
unavailable. For the No Action Alternative, under normal operations, the magnitude of
peak releases for endangered fish would be limited to powerplant capacity (about
4,600 cfs). However, if Reclamation determines that bypass releases would be likely for
hydrologic reasons, Reclamation would attempt to schedule these bypass releases to
occur with the peak flows and immediate post peak flows of the Yampa River.
S.13.2.3 Summer and Fall Operations (Early Base Flow Period)
Under the No Action Alternative, after the spring peak release is completed, releases
from Flaming Gorge Dam would be reduced so that flows of the Green River, measured
at Jensen, Utah, would achieve a target flow ranging from 1,100 to 1,800 cfs. Daily
average flows would be maintained as close to this target as possible until September 15.
Executive Summary :• S-21