WSPP283

• File Number: 8240.200.39.C
• Description: Colorado River Threatened-Endangered - RIPRAP - CFOPS - Water Availability
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 9/1/2003
• Author: Brown and Caldwell
• Title: Phase 2 Coordinated Facilities Water Availability Study for the Endangered Fishes of the Upper Colorado River - Final Report - 09-01-03
• Water Supply Pro - Doc Type: Report/Study

000771

FEASIBILITY OF NEW TRIBUTARY STORAGE PROJECTS BELOW SHOSHONE

The alternatives for building new tributary storage (Alternatives 4f, 4g, 4k, 4n and 40) are all costly,
due primarily to the limited physical supplies of water available from the \tributaries and the need to
depend on pumping from the mainstem Colorado River to supply water to most of these proposed
reservoirs. However these new reservoir sites should be considered further. if the reliability and
frequency to provide the 20,000 acre-feet of water from existing reservoirs is not sufficient to meet the
Programs needs. This alternative should also be considered in coordination with other possible
reservoir storage projects that water users need to provide the 10,825 acre-feet oElate summer and fall
base flow releases for the Program. The economy of scale of building a new reservoir to provide both
the 10,825 acre-feet and the 20,000 acre-feet could make a new tributary reservoir more attractive.

FEASIBILITY OF NEW MAIN STEM STORAGE PROJECT

An additional engineering and economic feasibility investigation of the mains tern Webster Hill site was
completed in Technical Memorandum No. 4a (See Appendix E). The cost of reservoir storage at this
site for making the 20,000 acre-feet release to the 15-Mile Reach would be partially offset by the
generation of hydropower. Net capital costs per acre-foot of yield from the Webster Hill Reservoir
would range from $29 to $134/ acre- foot of yield per year depending on the assumed value of
hydropower produced at the site. Results from this additional investigation further indicate that this
site would likely be feasible if: (1) the necessary right-of-way can be obtained at reasonable cost and
(2) the U.S. Fish and Wildlife Service (Service) would approve construction of a reservoir at the
Webster Hill site, which would be located in the upper end of the currently designated critical habitat.

The Webster Hill Reservoir would produce a firm yield of 20,000 to 40,000 acre-feet per year. It is
important to emphasize that the 20,000 acre-feet release would be available from Webster Hill
Reservoir even in dry years when this release would not be required. Therefore, the Webster Hill
Reservoir alternative would produce yield with a greater reliability than is required. It makes sense as
a next step to analyze the economy of scale of building Webster Hill Reservoir to provide both the
10,825 acre-feet committed by the water users and the 20,000 acre-feet that is the subject of this
study.

FEASIBILITY OF POWER PLANT OPERATIONS AND SCHEDULING
ALTERNATIVES

Ii

Alternative 5a, East Slope Power Operations and Scheduling, was investigated as one component of
Alternative 1d, CBT West Slope Facilities Operations. This alternative primarily consisted of:
(1) delaying winter deliveries through the Adams Tunnel, (2) using these delayed winter deliveries to
replace the release/bypass of the 20,000 acre-feet from Granby Reservoir to the 15-Mile Reach and
(3), replacing the delayed deliveries to east slope reservoirs by diversions to storage in these reservoirs
under the east slope priorities.

Alternative 5a was not modeled because:

.

This alternative cannot be fully investigated using StateMod and the C1 Data Set.
StateMod and the C1 Data Set only cover the Colorado River basin in Colorado and

P: \Data \ GEN\CWCB\ 19665\Repon Phase 2\FinalRepon9.03\Final_ CFOPS_Repon(9-03).doc

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