9549

• UCREFRP Catalog Number: 9549
• Author: Bestgen, K. R., K. A. Zelasko, R. I. Compton and T. Chart.
• Title: Response of the Green River Fish Community to Changes in Flow Temperature Regimes from Flaming Gorge Dam since 1996 based on sampling conducted from 2002 to 2004.
• USFW Year: 2006.
• USFW - Doc Type: 115,
• Copyright Material: NO

average (30 to 70% exceedance), moderately wet (10-30% exceedance), and wet (0-10%
exceedance). Flaming Gorge Dam spring peak release recommendations range from 130 m3/s
(full power-plant capacity) in dry years to > 244 m'/s in wet years. Base flow (August to
February) release recommendations were also scaled to hydrologic conditions and ranged from
23 to 28 m'/s in dry years to 79 to 85 m'/s in wet years. Warmer releases (up to 15°C) and lower
summer base flows were also recommended to improve downstream water temperature
conditions for native fishes in the Green River. Specifically, water temperatures of 18 to 20°C
were targeted for two to five weeks in summer in Lodore Canyon. Another goal of warmer
summer water temperatures was to ensure that the Green River was no more than 5°C cooler
than the Yampa River, to reduce the possibility of cold shock to Colorado pikeminnow
Ptychocheilus lucius larvae as they drift downstream from the Yampa River. The range of flow
and temperature recommendations were expected to benefit all life stages of native, endangered
fishes and further their recovery. Muth et al. (2000) recognized "uncertainties" regarding effects
of recommended flow and temperature regimes. A primary uncertainty was the extent to which
native or endangered fishes might benefit from recommended flow and temperature regimes and
whether negative effects of hypothesized increased distribution and abundance of certain non-
native fishes would offset benefits.
In the years following 1996, some reservoir operations that matched recommendations in
Muth et al. (2000) occurred. For example, flows in excess of 226.6 m'/sec (8,000 cfs) were
released in spring 1997, and flows in excess of 283.3 m'/sec (10,000 cfs) were released in spring
1999. The magnitude of those spring releases, which were not exceeded since 1986, fell within
the 1992 Biological Opinion recommendations, but were rimed to be consistent with the Muth et
al. (2000) recommendations. In addition, low summer base flow releases in 2000 and 2001 were
patterned to follow the hydrologic water year (e.g., Muth et al. 2000). Also consistent with Muth
et al. (2000) recommendations, main channel temperatures in excess of 20°C were maintained in
Lodore Canyon in July and August 2000.
Because portions of the new flow and temperature recommendations occurred since
1996, we thought it timely to reinitiate sampling of the fish community downstream of Flaming
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