8270

• UCREFRP Catalog Number: 8270
• Author: Hayse, J. W., S. F. Daly, A. Tuthill, R. A. Valdez, B. Cowdell and G. Burton.
• Title: Effect of Daily Fluctuations from Flaming Gorge Dam on Ice Processes in the Green River.
• USFW Year: 2000.
• USFW - Doc Type: ANL/EA/RP-102041,
• Copyright Material: NO

I INTRODUCTION
The Green River originates in western Wyoming, flows south through Wyoming, Utah,
and Colorado and merges with the Colorado River in southeastern Utah (Figure 1). The Green
River provides habitat for the Federally endangered Colorado pikeminnow (Ptychocheilus
lucius), razorback sucker (Xyrauchen texanus), humpback chub (Gila cypha), and bonytail (Gila
elegans). Since October of 1962, flows in the portion of the Green River in Utah and Colorado
have been regulated by Flaming Gorge Dam, located near the border of Utah and Wyoming
(Figure 1). Construction and operation of the dam has affected the downstream portions of the
river by altering the seasonal pattern of flows and water temperatures, increasing daily
fluctuations in flow and river stage, and reducing sediment loads. Because of these and other
changes, there are concerns pertaining to the effects of the dam on the viability of the populations
of endangered fishes in the downstream portions of the river.
While there have been numerous studies conducted to examine the effects that flows from
Flaming Gorge Dam have on endangered fish populations and habitats during spring, summer,
and fall periods of the year, there have been relatively few investigations conducted during
winter months. Fluctuations in flow during winter have been observed to increase the activity of
some Green River endangered fishes especially during ice breakup and formation of ice jams
(Valdez and Masslich 1989; Valdez 1994). Shoreline scouring that can result from ice breakup
and movement may also adversely affect overwintering endangered fish (USFWS 1992),
although effects from scouring have not been documented. Although the degree to which
fluctuating flows in winter, ice breakup, and shoreline scouring may affect endangered fish is not
well understood, it would be prudent to avoid repeatedly or prematurely breaking up ice covers
that form on the river in areas used by overwintering endangered fish. In order to more
accurately evaluate potential effects on endangered fish, quantitative information about the
effects of fluctuating flows due to hydropower or maintenance operations at Flaming Gorge Dam
on ice processes in the Green River is needed. A need for additional information about the
effects of winter flows on conditions in overwintering areas for endangered fishes was also
identified in the Biological Opinion on the Operation of Flaming Gorge Dam (USFWS 1992).
This report presents the results of an investigation of ice processes in the main channel of
a section of the Green River extending from Split Mountain Canyon (about 90 miles downstream
of Flaming Gorge Dam) to the Ouray, Utah Bridge (about 161 miles downstream of the dam),
where overwintering razorback suckers and Colorado pikeminnow adults have been observed in
the past (Valdez and Masslich 1989). Specifically, the objective of the study was to examine the
influence of daily fluctuations in water releases from Flaming Gorge Dam on the formation,
breakup, and movement of river ice in the main channel of this reach of the river. In order to
better understand ice processes in the Green River, historical records of winter water
temperature, flow, and ice conditions were reviewed and analyzed. In addition, a field study was
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