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

EXECUTIVE SUMMARY
The Green River in Utah and Colorado, downstream of Flaming Gorge Dam, offers an
opportunity to evaluate changes in the fish community in relation to several different dam
operation regimes. A primary purpose of this study was to determine the cumulative effect of
flow and temperature regime changes on physical habitat and native and non-native fishes in the
Green River downstream of Flaming Gorge Dam, including Browns Park, Lodore and Whirlpool
canyons, and Island-Rainbow Park. We place emphasis on comparisons between the 1994 to
1996 and 2002 to 2004 periods. To provide a more comprehensive historical context, we also
compare these recent data to findings from the pre-impoundment period (before 1962), and two
other post-impoundment periods, 1963 to 1978, and 1978 to 1992. We also characterize the
distribution of the humpback chub in Whirlpool Canyon. Recommendations for monitoring
effects of Flaming Gorge flow and temperature regimes on the fish community on the study
reach are also provided.
Four major dam-related events affected physical habitat and the fish community of the
upper Green River: dam installation in 1962, penstock modification in 1978, flow re-regulation
beginning in 1992, and higher peak flows, and lower base flows, and drought events since 1997.
The impacts of construction and operation of Flaming Gorge Dam on physical habitat in the
highly regulated reach of the Green River from the dam downstream to the Yampa River and in
Whirlpool Canyon downstream of the Yampa River were partially remediated by thermal
modifications implemented in 1978, discharge re-regulation in 1992, and 2002 to 2004 drought-
period changes to baseflow levels and patterns. High releases in 1997 and 1999 and drought-
induced high water temperatures created conditions that more closely resembled pre-dam
conditions. Peak flows were relatively high in 1997 and 1999; peak flows in most other years
were at the relatively low power plant capacity including those from 2002 to 2004. Flows in the
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