9612

• UCREFRP Catalog Number: 9612
• Author: N.A.
• Title: Flaming Gorge Flow Recommendation Investigation FG-1 Technical Integration and Final Report - Hydrology and Physical Science Chapter - Draft.
• USFW Year: 1998.
• USFW - Doc Type: \
• Copyright Material: NO

•
DRAFT February 25, 1998
Estimated Natural Flows - Green River
Ll
Historic streamflow records for the gauges along the Green River were adjusted to reflect
regulated (as of 1957) conditions in the basin for the 1914 - 1957 period by Iorns, Hembree, and
Oakland (1965). The flow-duration data from this reference describing existing conditions prior
to Flaming Gorge Dam are compared to estimated unregulated ("natural") flow conditions for the
Green River computed by Reclamation in 1996 (personal communication, Tom Ryan, U. S.
Bureau of Reclamation, 1996) in Table 1.
Table 1. Flow -duration for Green River gauges for estimated regulated conditions and estimated "natural flow" oonditions fitalics).

L Mean daily discharge, f /s, that was equaled or exceeded for indicated percentage of time
au record used) 1 5 10 25 50 75 90 95 99
Greendale (1914 -57) 13,390 8,600 6,375 2,845 1,150 610 426 365 300
Greendale (1950-83)

:

• h x.,r}':•n.

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........ t•.2. x,
NEWS.

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{:...h.......n...a... ..;•v.::'%?f.??:•ji:::ii$i?{:: v::.a. 15,949

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..............::.:..:: 7,130

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......7x::::::: x::v- 3,274

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Green River (1914-57) 38,970 23,970 18,050 7,440 2,966 1,940 1,424 1,125 650

Some of the observed variability in these data is due to the different time periods available for use
in computing natural flows from the gauged data. Yet, this comparison suggests that regulated
flow conditions (as of 1957) at Greendale and Jensen were roughly similar to estimated "natural"
flow conditions. Further downstream, flow conditions at Green River, Utah were slightly
modified under regulated conditions relative to "natural" flow conditions prior to closure of
Flaming Gorge.
Flow Duration - Green River
Flow duration curves for the Jensen and Green River, Utah gauges pre- and post- 1963 were
prepared (Figs. 2 and 3) by FLO Engineering, Inc. (1996). These curves describe the average
duration of a given mean daily discharge on an annual basis.
These flow duration curves show the shift in flow duration resulting from the operation of
Flaming Gorge Dam. This shift occurs at 4,500 ft3/s at the Jensen gauge and 5,300 ft3/s
at the Green River gauge. Prior to 1963 at Jensen, the mean annual peak discharge of roughly
24,000 fl /s was equaled or exceeded about 5 days per year. - After 1963, the 24,000 ft3/s was
equaled or exceeded about 1 day per year. The post-1963 mean annual discharge of 17,400 ft3/s
i
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