9600

• UCREFRP Catalog Number: 9600
• Author: Brown and Caldwell.
• Title: Phase 2 Coordinated Facilities Water Availability Study for the Endangered Fishes of the Upper Colorado River - Final Report.
• USFW Year: 2003.
• USFW - Doc Type: \
• Copyright Material: NO

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5. Other Alternatives
Alternative 6a: Insurance Pool.
The methodology used in the analyses, together with the results and conclusions from this
investigation are summarized in this report. Detailed analysis methodology, results and conclusions
are presented in a series of eleven Technical Memoranda that are included in the Appendices.
GENERAL RESULTS, CONCLUSIONS AND RECOMMENDATIONS
' The findings, conclusions and recommendations listed below concerning feasibility of the alternatives
are the result of using a monthly hydrology model called StateMod and the C1 Data Set as agreed to by
the Executive Committee at the start of the study process. It was realized that perspectives and model
' analysis might differ from the perspectives and model analysis of some Executive Committee
members and the water conservancy districts, water suppliers and water users who may be affected by
these alternatives.
r In reality, reservoir operators will not preemptively release water from their reservoir(s) unless one of
two conditions exists: 1) the operator, based upon real time snow pack and runoff knowledge,
' determines that it is highly likely the reservoir will fill and spill or 2) the operator has access to an
"insurance pool" of water in case a preemptive release results in the loss of water to the reservoir. The
first condition is basically what occurs in the CROPS and cannot be counted as a new alternative. The
' second condition is the most promising alternative for meeting the 20,000 acre-foot goal through use
of existing reservoirs. While these conclusions are somewhat different than a reader might deduct by
solely reading the study, the study participants agreed that it was important, in furtherance of the
' commitments in the PBO, to list the following study results for documentation purposes:
1. Supplying 20,000 acre-feet to the 15-1\ile Reach was not required every year. It was
necessary to supply the 20,000 acre-feet in only six years (1975, 1978, 1979, 1980,
1985 and 1986) and possibly 1982 and 1991 for a total of eight years out of the 17
years during the 1975-91 study period.
' 2. Supplying the 20,000 acre-feet was not required during the very dry years of the
study period. For example, releases were not required in 1977 or 1981. Further
analysis indicates that supplying the 20,000 acre-feet would not have been required in
2001 and 2002. It is also important to recognize that there is a fundamental
difference between what a monthly hydrology model calculates is possible and what
' reservoir operators will actually agree to do after dry years. For example, no
reservoir operator would allow non-required reservoir releases in years following dry
years - like 1978 or 1982 - until it was demonstrated that the reservoir would fill,
regardless of the fact that the model indicates this type of release could be
accomplished. The difference in the projected availability of releases and the reality
of available releases is because the model has "perfect knowledge" on when the
reservoir would refill - reservoir operators do not. Because the model indicates that
supplying the 20,000 acre-feet in dry years is not required, it provides reservoir
operators some comfort that firm yield would not be impacted.
' PAData\GEN\CWCB\19665\Report Phase 2\FinalReport9.03\Final_CFOPS_Report(9-03).doc 2