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

Filial Report

3-30

September 2000

Further attenuation in flow and stage occurs below Jensen, although this attenuation was
not modeled by Yin et al. (1995). Table 3.11 presents available measurements of flow and stage at
Jensen, Ouray, and Green River, Utah, and the release pattern of Flaming Gorge Dam during the
measurement period. Only measurements taken during periods of fluctuating releases from the dam
and during base-flow periods are presented. On the basis of these observations, one can conclude that
significant attenuation occurs between Jensen and Ouray and that any fluctuation effects are
essentially eliminated by Green River, Utah. This result is to be expected because the Green River
near Ouray is wide and unconfined, with a low gradient (0.0004).

3.5 GREEN RIVER WATER TEMPERATURES

Water temperature, particularly as it relates to habitat suitability in the critical summer
nursery period and to ice conditions in the winter, is an extremely important variable relating to
endangered fish populations. The Service began a program of monitoring river temperatures on the
Yampa and Green Rivers in 1987 (Smith 1997). Thermographs were placed at key locations on the
Yampa and Green Rivers (Table 3.12). Data from these thermographs, USGS gage data, and results
from work done by others are the basis for this section's description of the thermal regime of the
Green Ri ver.

Winter snows accumulate in the Green River basin from October through mid-April. When
air temperatures in the basin begin to rise in March and April, snowmelt and runoff begin. As flow
increases, the cold water gets warmer as a result of interactions with the channel bed, the
atmosphere, and direct solar radiation. Figure 3.14 compares water temperature at five locations
downstream from Flaming Gorge Dam along the Green River during June through September 1996.
This figure illustrates the warming that occurs downstream of Flaming Gorge Dam.

Table 3.11.-Measured within-day flow and stage changes for the Green River at USGS
stream gages near Jensen, Ouray, and Green River, Utah, under different Flaming Gorge Dam
operations.

Flaming Gorge Release (m3/s) Stage Change (m)
Date Minimum Maximum Jensen Ouray Green River
Oct 7,1987 23 71 not available 0.11 not available
Nov 11, 1993 23 120 0.38 not available 0.02
Nov 9,1998 52 84 0.13 0.05 0.00
Nov 17, 1998 40 121 0.31 0.12 0.01