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

3.1.3 Ice Formation on the Green River
3.1.3.1 USGS Observations
The USGS ice observations were made in conjunction with retrieval of discharge
measurements from the Jensen gage. The observations are summarized in Figure 29 (personal
communication, Bryan Cowdell; based upon unpublished data obtained by Dr. Jack Schmidt,
Utah State University, 1992) for the years 1946 through 1992. Shown are the first and last dates
ice was reported for the years of record at the Jensen gage. The most striking feature of these
data is the apparent decline of observed ice in the years following the closure of Flaming Gorge
Dam in November 1962. The creation of the reservoir upstream of Flaming Gorge undoubtedly
altered the temperature regime of the river between the dam and Jensen. One of the results of
this alteration was to increase winter water temperatures and reduce ice production downstream
of Flaming Gorge for some distance. Unfortunately, it is very difficult to use these data to draw
any quantitative conclusions about the formation of ice in the study reach because the data were
collected irregularly. For example, in 11 of the 30 years following 1962, only one visit to the
gage was made during the winter (These years are marked with a question mark in Figure 29.).
Dates of observations reflect the USGS schedule of discharge measurement retrieval as much as,
if not more than, the actual appearance of ice in the Green River at Jensen. For example, there
was no ice observed in the winters of 1986-1987 and 1987-1988 even though the reports of
Valdez and Masslich (1989), discussed below, documented extensive ice formation in the Green
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.
3.1.3.2 BIO/WEST Reports
Ice observations for the Green River are discussed in two reports (Valdez and
Masslich 1989; Valdez and Cowdell 1999) on the winter habitat of native fish species in the
Green River. These observations occurred during the winters of 1986-1987, 1987-1988 (Valdez
and Masslich 1989), 1993-1994, and 1994-1995 (Valdez and Cowdell 1999). The first ice
observed during these studies was frazil ice, seen at the water surface in the form of slush and
floes. In the winter of 1986-1987, a relatively mild winter (see Figure 20), 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 Lodore Canyon, about 50 miles downstream of Flaming
Gorge Dam. In both winters, frazil was heaviest early in the morning, although for the winter of
1987-1988 Valdez and Masslich (1989) observed that "during extended periods of subzero
temperatures ... frazil ice was present in the channel throughout the day." During the winters of
1993-1994 and 1994-1995, observations of frazil were similar (Valdez and Cowdell 1999). In
February of 1994, frazil ice was reported to be mixed in the water column upstream of the study
area. Within the study area, frazil was seen in the form of "large floating mats" which were
termed "lily-pad ice" (undoubtedly pancake ice).
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