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

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Modeled project demands included storage water diversions for industrial uses by
P&M. P&M holds no direct flow diversion rights under this project. It was assumed
that the industrial water is diverted directly from the reservoir area and 100 percent
consumed with no return flows. Anticipated industrial demands upon the Three Forks
storage water is unknown at this time. To quantify realistic industrial demands that the
reservoir could meet on a year to year basis, WWC performed a firm yield evaluation
using the WIRSOS model. An initial constant industrial demand of 90,000 AF/year was
used in the firm yield investigation. In a previous study, WWC calculated a firm yield of
about 90,000 AF/year (123 cfs) for a 160,000 AF reservoir (SWEC, November 1984).
However, in that study no other projects, such as Pot Hook Reservoir, were operated
simultaneously with the Three Forks Reservoir. Additional WIRSOS runs were performed
to determine the actual firm yield demand to be used in evaluating downstream flow
impacts.
Bypass flow requirements for instream flow considerations were included in the
WIRSOS modeling. An instream flow requirement of 100 cfs has been suggested for the
Little Snake River below Savery Creek by the Wyoming Game and Fish Department. Of
this 100 cfs, it was assumed that 24 cfs would come from Savery Creek and Sandstone
Reservoir storage releases as modeled in the Sandstone Depletion Study (SWEC, 1987),
24 cfs from Slater Creek and Pot Hook Reservoir, and 24 cfs from the Little Snake River
and Three Forks Reservoir. The remaining 28 cfs was assumed to come from Battle
Creek and other ungaged inflows. If the model estimates that the 28 cfs is not available,
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