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

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Table 5.

Mean daily flows (cfs) and volumes (acre-feet) of the Green River for November,
1994 through March, 1995, as measured at Greendale, UT (USGS gage
09234500).

MONTH MINIMUM MAXIMUM MEAN VOLUME
(acre-ft)
November 1994 820 1180 909 549,070
December 1994 1290 1320 1305 80,250
January 1995 1280 1310 1294 79,540
February 1995 818 1310 1088 60,440
March 1995 818 836 828 50,920

Flow of the Green River at Jensen was supplemented by inflow of several tributaries, including the
Yampa River. Mean daily flows at Jensen varied from a high of 1,993 cfs in March to 1,319 cfs in
November (Table 6). The higher flows in March were the result of early spring runoff from the
Yampa River.

Table 6.

Mean daily flows (cfs) and volumes (acre-feet) of the Green River for November,
1994 through March, 1995, as measured at Jensen, UT (USGS gage 09261000).

MONTH MINIMUM MAXIMUM MEAN VOLUME
(acre-ft)
November 1994 1180 1630 1319 78,510
December 1994 1580 1850 1688 103,800
January 1995 1530 1790 1675 103,000
February 1995 1460 2440 1934 107,400
March 1995 1460 2970 1993 122,500

5.0 RIVER ICE CONDITIONS

Historically, an ice cap usually formed on the Green River in winter. For 18 years of record prior to
Flaming Gorge Dam, surface ice was reported on the river at Jensen during 1 to 5 months of each
year (Figure 4; U.S. Geological Survey Field Notebook, Data Courtesy of J. Schmidt, Utah State
University). Following completion of the dam in 1964, surface ice was reported during 1 to 4 months
in only 15 of 29 years. It appears that fluctuating releases of relatively warm hypolimnetic water in
winter have reduced the incidence of surface ice formation and increased the occurrence of jam and
frazil ice. These conditions may reduce the availability of backwater habitat in downstream nursery
areas of age-O Colorado squawfish.

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