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29 Reclamation also stated that it was willing to consider a reasonable and prudent alternative that would be limited to construction of Ridges Basin Reservoir, Durango Pumping Plant, and inlet pipeline. Approximately 80,000 acre-feet of water for municipal and industrial purposes would be developed with a net depletion of 50,000 acre-feet (subsequently corrected to 57,100 acre-feet). Process Set Forth in Reclamation's SeDtember 28 Memorandum In its September 28, 1990, memorandum, Reclamation identified a process by which Reclamation, States, tribes, environmental interests, and water users would work together regarding the feasibility of developing a reasonable and prudent alternative that would be both hydrologically and biologically supportable. The Service provided biological and hydrological assistance to that process. As a result of Reclamation's proposal, a meeting was held in Salt Lake City on October 9, 1990, with all interests represented. At that meeting three committees (Biology, Hydrology, and Legal) were established to collect additional information from experts in the areas of biology, hydrology, and law relating to the Project. A fourth group, the Management Task Force, was established to oversee the entire process and track progress. During the ensuing months, numerous technical committee meetings were held while discussions between the Service and Reclamation continued. Products from these committees were used to provide Reclamation with additional data and opinions regarding the development of a proposed reasonable and prudent alternative to the Project. This phase ended with Reclamation's March 4, 1991, letter (Appendix D) to the Service with its proposed reasonable and prudent alternative. A summary of the pertinent hydrological and biological information that formulated the basis for Reclamation's, and subsequently the Service's, reasonable and prudent alternative follows. The Biology Committee held three meetings between October 22 and December 7, 1990. One of the first priorities of the group was to develop a list of major assumptions/hypotheses that apply to the San Juan River. The hydrological analysis contained in Appendix B was provided to and considered by the Biology Committee. , !~ !~ -~ .~ 1 w ~~ Appendix B compares historic (pre- and post-Navajo Dam) hydrographs and flows to existing capabilities through operation of the Navajo Dam (assuming current levels of depletion) for representative average, wet, and dry years at Bluff, Utah. The predeve10pment mean annual flow of the San Juan River is approximately 1.95 MAF. The current level of development on the San Juan River accounts for consumptive uses of about 0.566 HAF, reducing the mean annual flow to approximately 1.38 HAF. The Navajo Dam currently redistributes this remaining water as shown in Figure I, Appendix B. As can be seen from the figure, spring peaks are severely reduced while flows throughout the remainder of the year are elevated above historic levels. Figure 2, Appendix B, illustrates pre-Navajo Dam hydrographs for average (1945), wet (1949), and dry (1951) years, which demonstrates the natural variability of the San Juan River depending on the hydrological cycle. It is important to note that in each case (average, wet, or dry) the overall shape of the hydrograph remains the same (i.e., spring peaks, gradually descending limb, and low stable flows) the remainder of the year.