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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mention of the inactive storage amount below this level. A maximum head of 110 feet
(Elevation 6090 feet) was also assumed. According to Western Engineers, Inc., the
amount of active storage available in the power pool between Elevation 6050 feet and
Elevation 6090 feet was determined to be 163,000 AF. For this study, the approach used
by Western Engineers, Inc. was implemented but a total active storage of 164,690 AF
was used in the WIRSOS modeling. In the modeling, it was assumed the dead and
inactive storage below the 70 foot head level is inviolate with reservoir releases drawn
from only the 164,690 AF of active storage. The inactive storage amount was estimated
at 57,000 acre-feet. An area-capacity curve for Little Snake Reservoir was developed from
mapping obtained from CRWCD (see Appendix C). WIRSOS uses this information to
calculate reservoir evaporation losses.
Project demands to be modeled include direct flow bypasses and storage releases

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through the Powder Wash Power Plant for hydroelectric power generation. Flows in the
Little Snake River are erratic and vary from year to year. Under actual operations, flows
through the turbines would also vary. However, WIRSOS is not capable of modeling
demands that change from year to year. Therefore, the system was modeled, to the
extent that WIRSOS will permit, such that Little Snake Reservoir fills as of June 1
followed by a constant discharge through the turbines such that the reservoir is at
minimum storage as of April 1 of the following year.
The conditional water right amount for the Powder Wash Power Plant provides for
800 cfs to be supplied by the Little Snake River and Little Snake Reservoir storage
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