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

percent of the time, therefore the firm yield of Three Forks Reservoir for this study is
approximately 80 c.£s (58,000 acre-feet per year). The reasons for the difference between
this firm yield of 58,000 acre-feet per year and the 90,000 acre-feet per year calculated in
a 1984 study could be: 1) the use of different models, i.e. the 1984 study used the
OPSTUDY model and this study used WIRSOS, and 2) Scenario No. 2 modeled the Little
Snake River Basin with the Three Forks, Pot Hook and Sandstone Projects, and the 1984
study considered only Three Forks.
Scenario No. 2 flows at Lily for the 80 c.f.s. demand WIRSOS run are presented
in Table D.9. The average annual flow at Lily for the 80 c.f.s. demand was calculated
to be 210,406 acre-feet. A comparison between Scenario No. 2 flows and Scenario No.
1 flows is presented in Table D.10. Average annual flows at Lily for Scenario No. 2 (80
c.f.s. demand) are 61,080 acre-feet lower than the Scenario No. 1 Lily flows. As shown
on Table D-11, the average annual reduction in flow for Scenario No. 2 from the WDB
is 95,762 acre-feet. These reductions are also shown in hydrograph format on Figure D-
16 through D-20.
4.3 SCENARIO NO. 3 IMPACTS
Scenario No. 3 was the same as Scenario No. 2 with the addition of the Powder
Wash Project to the system. All reservoirs were modeled assuming one-fill operations.
The main modeling assumptions used for the Powder Wash Project are discussed in
Section 3.2.2 of this report.
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