8119

• UCREFRP Catalog Number: 8119
• Author: Valdez, R. A. and B. R. Cowdell.
• Title: Effects of Flow Regulation and Ice Formation on Overwinter Nursery Habitat and Survival of Age-0 Colorado Squawfish in the Green River Below Flaming Gorge Dam - Draft.
• USFW Year: 1996.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

Table 8. Average surface ice thickness, free water depth, temperature, and dissolved
oxygen for 9 backwaters sampled during Trip I (January 6 - 8, 1995) and Trip /I
(February 6 - 7, 1995) of winter, 1994-95. CH = chute, SC = scour, ER = eddy
return.
Average Average Free Average Average D.O.
5ite 5urface 1 Ice Water Depth (ft) Temperature (0C) (mgll)
(River Thickness (ft)
Mile) Tripi Trip II Tripi Trip II Trip I Trip II Trip I Trip II
..
1-CH 0.1 0 1.4 1.2 3.10 2.73 5.1 9.6
(331.6)
2-CH 0.7 1.4 1.95 5.3
(327.6)
3-5C 0.5 0.3 1.0 1.6 1.38 4.78 16.3 10.9
(318.0)
4-ER
(316.2)
5-5C 0.1 0.3 1.1 0.7 0.17 1.21 10.8 11.5
(289.4)
6-CH 1.3 0.6 1.2 0.7 0.16 2.43 10.7 10.0
(288.8)
7-5C 1.1 0.8 2.0 1.0 0.10 2.42 10.4 10.2
(260.2)
8-CH 1.1 1.1 32 2.4 0.14 2.95 10.5 9.7
(257.1)
9-5C 0.4 0.2 2.0 0.8 0.18 1.78 10.9 10.7
(251.9)
'Includes both solid surface ice and frazil ice.

channel in this reach was free of ice all winter except for short periods of frazil ice formation or
during infrequent ice jams.

In reach 2 (Split Mountain to Bonanza Bridge), multiple ice lenses were common on shorelines and
backwaters as a result of daily fluctuations in water levels and diel air temperatures. Ice lenses usually
formed during cold nights along quiet shorelines and calm backwaters. Fluctuating water levels and
alternating relatively warm and cold diel air temperatures caused'these lenses to collapse on each
other, occupying space in backwaters with tilted and fractured pieces of ice. This phenomenon of
ice lensing did not occur in reach 1 because the relatively warm water temperature and the absence
of extremely cold air temperatures precluded diel formation of ice.

Ice development on backwaters in reach 3 was greater than in the two upstream reaches because of
a lack of daily flow fluctuation and more constant cold water temperatures. Surface ice tended to be

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