9602 ‎(2)‎

• UCREFRP Catalog Number: 9602
• Author: Clayton, R. and A. Gilmore.
• Title: Flaming Gorge Draft Environmental Impact Statement Hydrologic Modeling Report.
• USFW Year: 2002.
• USFW - Doc Type: \
• Copyright Material: NO

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7
control the reservoir elevation. Figures showing the reservoir elevations and release hydrographs
for two, three, five and seven year duration wet and dry cycles are located in the Appendix.
Reservoir Water Surface Elevation Percentile Results
For each month of the model run, from .f anuary 2002 through December 2040, there are 65
potential reservoir elevations that make up the model results for reservoir elevation for that
particular month. Each set of potential elevations was ranked from lowest to highest to determine
the probabilities associated with specific reservoir elevations. Figures S, 6 and 7 show the
potential reservoir elevations associated with three levels of probability. Figure 5 shows the 90`~
percentile reservoir elevations during the first 10 years of the model run. These reservoir
elevations were exceeded by only 10% of the 65 potential elevations that occurred in the model
results for that month and that year. Reservoir elevations are typically at their lowest level in early
spring when the Action and No Action alternatives attempt to achieve a drawdown target. During
the late summer, reservoir elevations are typically at their highest level of the year as a result of
storing a portion of the spring runoff. The No Action alternative typically allows the reservoir
elevation to rise significantly higher in the spring than the Action alternative, as evident in Figure
5. Summer reservoir elevations are typically five to seven feet higher for the No Action alternative
than those for the Action alternative.
Figure 5 90"' Percentile Reservoir Elevations from January ZUUL to December Lutz
Flaming Gorge Elevation
Percentiles
6040
60 3 i
6030
602 i -- --- -
6020
601 i
y
'i 6010
- NoAct90~~:ile
600 ~ Action 90~7cile
600( )
5~)~)5 --- ----- -- - -- --- --- -_ -
i~)9O -- -- - -- -- ----- ----- - - ---- -
01 -'O(Y? U I -300-~ Ol - 200(1 O l-'0(18 01-2010 U l -2012
l"car
Figure 6 SOt~' Percentile Reservoir Elevations from January 2002 to December 2012