8028

• UCREFRP Catalog Number: 8028
• Author: Daly, S. F., et al.
• Title: Effect Of Daily Fluctuations From Flaming Gorge Dam On Formation Of Ice Covers On The Green River -Draft.
• USFW Year: 1997.
• USFW - Doc Type: \
• Copyright Material: NO

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River for both these years. Therefore these USGS observations cannot be considered reliable
indicators of the presence of ice in the Green River at the Jensen gage.
BIO/WEST Reports
Ice observations for the Green River are discussed in two reports (Valdez and Masslich,
1989; Valdez and Cowden, 1996) on the winter habitat of native fish species in the Green River.
These observation cover the winters of 1986-87, 1987-88 (Valdez and Masslich, 1989), 1993-94,
and 1994-95 (Valdez and Cowden, 1996). The first ice observed each winter season was frazil
ice, seen at the water surface in the form of slush and floes. In the winter of 1986-87, a relatively
mild winter, frazil ice was only seen to form downstream of Jensen Bridge (RM 302}. In the
winter of 1987-88, a much colder winter, frazil was first observed in the Canyon of the Lodore,
about 50 miles downstream of Flaming Gorge Dam. In both winters the frazil was observed to
be heaviest early in the morning, although in the winter of 1987-88, "during extended periods of
subzero temperatures...frazil ice was present in the channel throughout the day." In 1993-94 and
1994-95, observations of frazil were similar. In February of 1994, frazil ice "was mixed in the
water column" upstream of the study area. In the study area, the frazil was seen in the form of
"large floating mats" which were termed "lily-pad ice,"(undoubtedly pancake ice).
Stationary ice covers were observed in the Green River immediately following the
appearance of frazil ice. The bridging location of the stationary ice cover was not reported, but
the downstream end of the stationary ice was consistently reported as at the Ouray Bridge or
further downstream. The upstream extent and periods of time the stationary ice cover was in
place varied from year to year. In 1986-87 the maximum upstream extent of the stationary ice
was the Jensen Bridge (RM 302), observed on January 28, 1987 (Figure 9}. The next day the ice
cover retreated downstream. The ice cover was observed to stay in place from RM 270
downstream past Ouray Bridge (RM 250) for the next three weeks (Figure 10). The following
year stationary ice was in place from early January through late February of 1988. The upstream
extent of the ice reached Chew Bridge (RM 316) (Figure 11). Short, disconnected areas of
stationary ice were also seen upstream of the study area in Rainbow Park and Echo Park. The
leading edge of the ice cover retreated to Jensen Bridge (RM 302) on February 19, and to
RM 294 by February 27. In the winter of 1993-94, the stationary ice reached Jensen Bridge
(RM 302) on February 2, 1994 and extended upstream of the 3ensen Bridge for an unreported
distance. The stationary ice extent is not reported for the winter of 1994-95, although it is
reported that an "ice jam" occurred below Chew Bridge in the middle of December.
The appearance of the ice cover was described as "smooth" downstream of Bonanza
Bridge (RM 290} and having a "highly fractured and irregular surface" upstream of Bonanza
Bridge. In February of 1988 the ice cover thickness was measured to be 30-50 cm downstream
of Bonanza Bridge with 30 cm of snow cover. In the winter of 1987-88, frazil ice was observed
to be deposited under the ice cover throughout the 11-mile reach, from RM 305 to RM 316. The
layer of frazil ice deposited beneath the cover was measured to be 60 to 90 cm thick in the main
part of the channel. After the ice cover had retreated from this reach, accumulations of frazil ice
were observed along the river banks that were 0.3 to 3 m thick beneath solid ice. At RM 310.3,
45 cm of solid ice was measured. The frazil ice deposits were not observed in this reach during
any other winter.
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