7748

• UCREFRP Catalog Number: 7748
• Author: Western Water Consultants, I.
• Title: Final Report on Little Snake River Depletions by Pot Hook, Three Fork and Powder Wash Rights.
• USFW Year: 1990.
• USFW - Doc Type: Laramie, WY.
• Copyright Material: NO

[I

The conditional water right amount for the Powder Wash Power Plant call for 800
c.f.s. to be supplied by the Little Snake River and Little Snake Reservoir storage releases.
However, a constant demand of 800 c.f.s. could be met only part of the time during the
1930-82 period as Little Snake Reservoir inflows average only 430 c.f.s. As with the Three
Forks project, a firm yield study of the Little Snake Reservoir was performed. For the
initial Scenario No. 3 run, a constant power release demand of 225 c.f.s was evaluated.
The initial run with a 225 c.f.s. demand showed this demand was not met about 16
percent of the time. Therefore, additional runs were performed with lower demands until
these demands were met. The last WIRSOS run made utilized a demand of 150 c.f.s.
This power release demand was met about 99 percent of the time. The results of this run
were used to determine the incremental impact of Powder Wash Project upon the flows
at Lily, Colorado.
The Scenario No. 3 flows at Lily are presented in Table D.12. Average annual
flows at Lily for Scenario No. 3 were calculated to be 203,099 acre-feet. A comparison
between Scenario No. 3 flows and Scenario No. 2 flows is presented in Table D.13.
Scenario No. 2 flows. The primary reason for this reduction is the increased evaporation
Average annual flows at Lily for Scenario No. 3 are 7,307 acre-feet lower than the
from the reservoir water surface. However, it is important to note that flows at Lily would
be higher during the winter and late summer than WDB flows with the Powder Wash
Project in operation. These comparisons are shown on Figures D-21 through D-25.
Comparisons of Scenario No. 3 with the WDB are shown on Table D-14.
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