9603

• UCREFRP Catalog Number: 9603
• Author: Clayton, R. and A. Gilmore.
• Title: Flaming Gorge Environmental Impact Statement Hydrologic Modeling Study Report - Results of Action and No Action Alternative Analysis.
• USFW Year: 2001.
• USFW - Doc Type: \
• Copyright Material: NO

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22

Flaming Gorge Spring Bypass Results

Figure 18, like Figure 13, shows the frequency of bypass releases that occurred during the
spring for all three model runs. Figure 18 shows this information in terms of the annual volume
of water that was bypassed under the control of the three rulesets. The difference between each
of these curves can be related to the power generation that was lost as a result of achieving the
objectives of the each of the proposed alternatives.

FIGURE 18 Excecdance Percenta e B asses durin

Flaming Gorge Spill
May - July

800 k

No Action
All - 1
All

600 k

~
.:;:
2
u
-:;.

80%

I 00%

:s.. 400 k
v.l
eo
:::
oc
C.
v.l

200 k

20%

40% 60%
Percentage Exceedance

Reach One August through February Base Flow Release Results

Figure 19 shows the distributions of Reach One flows that occurred during the base flow
period (August though February), when Reach One flows are typically at their lowest. This
analysis shows the frequency and magnitude of the Reach One flows that occurred during the
base flow period under the Action(ALL and ALL-I) and No Action model runs. The most
notable difference between the Action and No Action flows during the base flow period was for
the 0-20% exceedance flow. The No Action ruleset was more flexible during the base flow
period and allowed releases to increase when conditions became wetter in the Upper Green River
Basin. To give some perspective to the results of the three model runs, historic Reach One base
flows from 1971 to 1991 and historic Reach One unregulated base flows from 1971 to 1991 are