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002981 May 5, 1999). Further communication with CWCB concerning the baseline hydrology (Moore, 1999) indicates that this data set (C I Scenario hydrology with RIPRAP flow relat~d projects and without the 60,000 acre-feet or 120,000 acre-feet of future projects) is available for the Phase 2 investigation. This data set also includes the Green Mountain Reservoir HUP's surplus. HUP surplus is that water estimated in late summer to not be needed for replacement purposes and which can be released for authorized purposes. The CWCB through a contractor has extended the hydrologic data set for the Colorado River from 1991 through 1996 and from 1975 back to 1909. Two data sets have been developed: (1) a historic data set based on gauge data with missing data estimated through appropriate statistical procedures; and (2) a baseline data set in which the effects of all projects which had been in existence for all or part of the 1909 through 1996 period were extended so that these project effects will be included for the entire 1909 through 1996 period. These extended data are now available. I j Therefore, the baseline hydrology which will be initially used for analysis purposes in Phase 2 will be the 1975 through 1991 monthly flow data used in the CI Scenario and will include the effects of the RIPRAP projects as listed in the PBO, but will not include the 60,000 acre-feet or 120,000 acre-feet per year of estimated depletions from new projects. The principal reason for not initially including the 60,000 or 120,000 acre-feet per year of possible future depletions is the significant difficulty in developing an acceptable forecast of where and when these future depletions would most likely occur. (U.S. Fish and Wildlife Service, 1999, pg. 11). As further described below, however, sensitivity analysis will be completed to determine possible effects on existing facilities of proposed alternatives and future depletion of 60,000 - 120,000 acre-feet per year. '1 ~ Facilities identified as having sufficient flexibility to contribute water toward the average annual 20,000 acre-feet target will be the subject of sensitivity analyses in Phase 2 to determine facility . flexibility with respect to the 60,000 acre-feet and 120,000 acre-feet of new depletions contemplated by the PBO. This will be developed in conduction with the Executive Committee by making assumptions about where (at what facilities or location) and when new depletion will occur. Analysis of each facility will include analyses to determine loss of flexibility in the future and the expected impacts on that facility's ability to continue contributing in the future toward the 20,000 acre-feet average annual target in those years when the expected peak spring flow is between 12,900 cfs and 26,600 cfs. It is likely that the sensitivity analysis will show that some facilities can contribute water toward the 20,000 acre-feet per year average with little loss in delivery capability, but with growth in future depletions, the facility's costs of continuing to contribute water may rise dramatically. In this case, there would be recognition that these facilities would be allowed to decrease their participation, or compensation for losses in delivery capability would be agreed upon. As indicated above, the extended baseline hydrology is now available; however, initial model investigations of the alternatives will be completed using the 1975-1991 hydrology. The results of these initial model investigations will be used to screen the set of alternatives to produce a p:\data\gen\Ocwcb\18] 33\report\phase-l \chap-2.doc 2-7