PROJ00492

• Contract/PO #: C153364
• Contractor Name: Beck, R. W. and Associates
• Water District: 0
• County: Garfield
• Bill Number: SB 81-439
• Loan Projects - Doc Type: Feasibility Study

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Appraisal-level engineering designs and associated cost esti-

mates, including capital, operation, maintenance and replace-

ment costs.

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Preparation of a comprehensive report which summarizes the
work completed during the study.

HYDROLOGY AND RESERVOIR SEDIMENTATION

The estimated average annual runoff at the dam site is 3,600 cfs or
2,600,000 ac-ft per year. The Probable Maximum Flood (PMF) flow for which the
spillway is de'signed is estimated to be 130,000 cfs. This flood peak is com-
posed of the runoff resulting from the Probable Maximum Precipitation (PMP)
plus the maximum historical snowmelt flood. Estimates of the probable rate of
accumulation of sediment in the reservoir indicate that the gross usable ca-
pacity would decrease from its original 196,000 ac-ft to 106,500 ac-ft after
100 years.

WATER RIGHTS AND STORABLE WATER

The Colorado River Water Conservation District holds a conditional
decree for the Una Reservoir Project for 195,983.5 ac-ft of storage and 2,100
cfs of direct flow rights with an appropriation date of March 16, 1965. An
evaluation of the physical and legal availability of Colorado River water for
storage at the, Una Project based on this decree and estimated depletions by
other senior water rights was made.

The transfer of the Placita Reservoir conditional water rights

decree on the Grystal River, with an appropriation date of April 22, 1951, to

Una Reservoir 'NaS also evaluated. This evaluation does not imply an imminent

transfer of this decree, but was done only to investigate the effect of such

an assumed transfer on the yield of Una Reservoir.