BOARD01355

• Board Meeting Date: 5/19/2003
• Description: WSP Section - Colorado River Basin Issues - Coordinated Facilities Operations Study
• Board Meetings - Doc Type: Memo

.

.

.

Agenda Item 27 - Coordinated Facilities
May 19-20, 2003 Board Meeting
Page 5 of 12

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
results of using a monthly hydrology model called StateMod and the HCl data set as agreed bv the Executive
Committee at the start of the studv process. It i5 was realized that these perspectives and model analysis
might differ from the perspectives and model analysis of some Executive Committee members and the water
conservation districts, water suppliers and water users who may be affected by these alternatives.

In reality, reservoir operators will not preemptively release water from theirreservoir( s) unless one of two
conditions exists: 1) the operator, based upon real time snow pack and runofflmowledge, determines that it is
highly likely the reservoir will fill 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 operatiells 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 Programmatic Biological
Opinion. to list the following study results for documentation purposes:

1.

Supplying the 20,000 acre-feet to the 15-Mile 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 fur 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, However, iIt 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 5affi 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
lmowledge" on when the reservoir would refill-reservoir operators do not Because the model
indicates that not havillg to supplyi.ng the 20,000 acre~feet in dry years is not required. it provides
reservoir operators some comfort that finn yield would might not be impacted.

3. Based on the results of sensitivity analysis, it appears that it should be possible to make the CROP
bypasses and the 20,000 acre-feet release and have only limited effects {on junior water rights}.

4. Results of sensitivity analysis indicate that if an alternative is feasible under the current conditions of
the C 1 Data Set, it is likely to remain feasible under future flow conditions in which there would be
UP to approximately 120.000 119,900 acre-feet of additional depletions,

5.

Sensitivity analysis on eOHcemillg estimated CROP'S bypasses releases, reduced Grand Valley
Project demands, Palisade Pipeline bypasses -flews and the Shoshone Power Plant maintenance
schedule indicates continued feasibility of the alternatives investigated in the Technical Memoranda.
Sensitivity analyses involving these parameters indicates there would be little effect on availability of

Flood Protection. Water Project Planning and Finance. Stream and Lake Protection
Water Supply Protection. Conservation Planning