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the historic flow regime (pre-Navajo Dam), the current or baseline flow, and the flow with the full Animas-La Plata Project for a series of wet, average, and dry years. The analysis of Stage A will consider the historic flow regime, and the baseline flow with Navajo Reservoir operated to mimic the natural hydrograph (Figures 1-18). Stage A development allows the project to deliver M&I benefits if the total depletion of the project is limited to an average annual depletion of 57,100 AF. Key water management options underlying the reasonable and prudent alternative remain the same as under the 1991 reasonable and prudent alternative and need to be described accurately and completely. These options have a direct, major effect on the magnitude and timing of the flows that are available to provide habitat in the San Juan River for the endangered Colorado squawfish and razorback sucker. These options are described below and form the basis for the development of the reasonable and prudent alternative. A. Regulation of Releases for Trout During"the initial filling period of Navajo Dam (1962-1965), there were periods when the releases from Navajo Dam were below 500 cfs. Since 1965 releases of less than 500 cfs from Navajo Dam have occurred only on a very infrequent basis. With the establishment of an excellent trout fishery in the tailwater, Reclamation has attempted to maintain releases of at least 500 cfs. No formal minimum flow exists. Fishery biologists do not have sufficient data to define a minimum flow regime below the dam, but have estimated, based upon their knowledge and judgement, that a minimum flow of 300 cfs should be adequate. Maintaining a flow of 500 cfs can require up to 360,000 AF per year, depending upon spills and required releases. At the present level of depletions, and including a depletion of 57,100 AF for the Animas-la Plata Project, providing a 500 cfs flow for trout does not affect the number of years that a high spring release can be made for the endangered fish. However, spring spills in advance of the peak provide a more "natural" flow pattern; these spills are reduced if 500 cfs is provided year-around for the trout. The graphs presented in this report represent Reclamation's ability to operate Navajo Reservoir to mimic the natural hydrograph over the life of the Project while providing for a minimum trout flow of 300 cfs. The reasonable and prudent alternative proposed by the Service finds it appropriate to provide winter test flows of 250-300 cfs during the research period. B. Release of Water for Colorado Squawfish and Razorback Sucker The primary feature of the reasonable and prudent alternative proposed by the Service and concurred by Reclamation is the operation of Navajo Reservoir to release water during the spring peak runoff to reproduce, as closely as possible, the natural flow pattern that existed prior to the 4