7813

• UCREFRP Catalog Number: 7813
• Author: Vanicek, C. D., R. H. Kramer and D. R. Franklin
• Title: Distribution of Green River Fishes in Utah and Colorado Following Closure of Flaming Gorge Dam
• USFW Year: 1970
• USFW - Doc Type: The Southwestern Naturalist
• Copyright Material: YES

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TABLE 2

Monthly mean Green River water temperatures (F), before and after impoundment,
Greendale and Jensen, Utah (compiled from USGS data)

Greendale Jensen
Before After impoundment Before After im~ent
impoundment (calendar year) impoundment (calen year)
Month 1957-1959 1963 1964- 1965 1966 1957-59, 1962 1963 1964- 1965 1966
January 33 36 41 41 45 33 32 32 32
February 33 35 37 38 41 33 33 32 36
March 36 36 38 39 39 36 43 35 39
April 45 36 40 40 39 <W3 49 48 45 49
May 52 39 41 42 39 56 59 56 54 58
June 60 41 42 45 40 64 66 61 60 62
July 70 43 45 49 41 72 72 66 67 68
" August 68 44 47 50 43 70 72 64 66 64
. September 60 42 48 51 64 66 59 57 58
44-
October 50 43 54- 53 50 53 54
November 35 58 53 53 38 42 47
. -. December 33 <W3 46 49 34 32 37

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water releases have been dependent upon power demands and down-
stream water needs. Flows are now less stable on a daily basis but more
stable on an annual basis than before impoundment.
Below the mouth of the YampaRiver, the flow of the Green River
has been altered less because the Yampa waters modify the dam's im-
pact. The seasonal flow pattern at Jensen, about 25 miles below the
Yampa's mouth, resembles that of pre-impoundment years. Peak
spring-ron-off generally occurs in May under present conditions rather
than in June as it did before impoundment and it has not reached the
mean pre-impoundment peak run-off in the four years since closure of
the dam (Table 1). Mean monthly Dows in late fall and winter have
, been higher than before impoundment.
Water Temperature,-Before impoundment, annual water-temper-
ature patterns were similar at Greendale and Jensen (Table 2). Tem-
peratures began rising in March from winter lows of 330F and reached
a mean of about 720F in July. In late August, temperatures began a
steady decline to lows in December.
Since closure of the dam, water temperatures at Greendale have
fluctuated little seasonally and have remained in the 35-55 F range
because water is discharged from the reservoir's hypolimnion. The
rise in temperature to the mid-50 F range observed at Greendale in
October or November since impoundment occurred at the time of fall
overturn in the reservoir (Eiserm~ et aI, 1967). At Jensen, the post-

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