8188

• UCREFRP Catalog Number: 8188
• Author: Muth, R. T., et al.
• Title: Flow and Temperature Recommendations for Endangered Fishes in the Green River Downstream of Flaming Forge Dam.
• USFW Year: 2000.
• USFW - Doc Type: \
• Copyright Material: NO

Final Report

1-9

September 2000

1.3 1992 BIOLOGICAL OPINION ON OPERATION OF FLAMING GORGE DAM

In 1980, Reclamation entered into Section 7 consultation with the Service on operation of
Flaming Gorge Dam. Studies on the biology and hydrology of the Green River conducted during
1978-1989 (Table 1.1) culminated in preparation of the Biological Opinion (USFWS 1992), which
concluded that historic operations of Flaming Gorge Dam (i.e., dam operations prior to 1992)
jeopardized the continued existence of endangered fishes in the Green River. The reasonable and
prudent alternative of the Biological Opinion included the following five elements.

1. Refinement of the operation of Flaming Gorge Dam so that flow and temperature
regimes of the Green River will more closely resemble historic conditions. Under this
element, seasonal flow and summer temperature recommendations were established to
enhance the status of endangered and other native fishes in the Green River system
downstream of Flaming Gorge Dam. Recommendations for spring, summer/autumn,
and winter periods were based on information presented in consolidated biology (Tyus
and Karp 1991) and hydrology (Smith and Green 1991) reports. However,
recommendations for each season were supported by differing levels of biological and
physical data, with the most comprehensive data set covering summer through autumn.

2. Conduct a 5-year research program, including implementation of winter and spring
research flows beginning in 1992, to allow for potential refinement offlowsfor these
seasons. Except for specific winter and spring research flows during the research
program, Green River flows were to resemble the historic natural hydrograph to the
extent possible. This element was included so that biological and physical responses
of the Green River ecosystem to the recommended flows and temperatures could be
evaluated. Additionally, because winter and spring flow recommendations were based
on limited information, more research was needed to refine flow recommendations for
those seasons.

3. Determine the feasibility and effects of releasing warmer water during the late
spring/summer period and investigate the feasibility of retrofitting river bypass tubes
to include power generation, thereby facilitating higher spring releases. A multilevel
intake structure was installed at Flaming Gorge Dam in 1978 that allowed selective
release of warmer water during most seasons of the year. However, water temperatures
in the Green River between Flaming Gorge Dam and the confluence with the Yampa
River in Echo Park often remain below those deemed suitable for reproduction and
growth of the endangered fish species from spring through autumn. Consequently, this
element required examination of the feasibility of further narrowing the temperature
differential between warmer water entering the Green River from the Yampa River and
cooler water in the Green River upstream of the confluence with the Yampa River
during the spring and summer.