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<br />, <br />i,i <br />~. <br />~ <br /> <br />31 <br /> <br />, <br /> <br />In addition to these 11 major assumptions/hypotheses, the Biology Committee also <br />agreed to three "critical assumptions," which included: <br /> <br />1. The San Juan River population of Colorado squawfish, while representing a <br />reproducing population, is in danger of becoming extirpated. However, <br />with appropriate management, the status of the populations might be <br />enhanced. <br /> <br />2. The present conditions of the San Juan River have been significantly <br />altered or impacted by the operation of the Navajo Dam and other man- <br />caused impacts along the river. <br /> <br />3. There is an urgent need to collect indepth biological, physical, and <br />chemical information on the fish and their habitat and to assimilate and <br />assess all other existing information. <br /> <br />The next major issue that the Biology Committee investigated was the <br />hydrological basis for operating the Navajo Dam to improve river conditions for <br />the endangered fish (Appendix E, Figures 1-6). The hydrological analysis went <br />through several iterations and concluded that the Navajo Dam can best be <br />operated to provide approximately 300,000 acre-feet of water for a large spring <br />peak release to provide a gradually ascending limb followed by a gradually <br />descending recession limb lasting into early summer, while maintaining a minimum <br />release of 300 cfs during all other periods of the year. This flow scenario <br />would be available in 96 percent of the years under present conditions <br />(Section 7 baseline). It also would be available 96 percent of the time with <br />the Project (depletion of 57,100 acre-feet). The purpose of the operations of <br />the Navajo Dam would be to mimic a historical hydrograph, thus returning the San <br />Juan River to a more natural state, similar to that under which the endangered <br />fish evolved. It is very important that the water management decisions <br />underlying the reasonable and prudent alternative be described accurately and <br />completely, because they have a direct, major effect on the magnitude and timing <br />of the flows that are available to provide habitat in the San Juan River for <br />endangered fish. These key elements were presented to the Biology Committee as <br />an explanation of the hydrological basis underlying the proposed reasonable and <br />prudent alternative and are presented in Appendix E. <br /> <br />Reclamation asked the members of the Biology Committee if, in their professional <br />judgment, the operation of the Navajo Dam could form the beginning of a <br />biologically supportable reasonable and prudent alternative that would allow for <br />survival of the endangered fish and development of the Project. After <br />considering all the assumptions it had previously agreed to, the Biology <br />Committee concluded that returning the San Juan River to more natural <br />conditions, with the reduced depletions by the Project, was biologically <br />supportable as long as additional protective provisions similar to those <br />included in Reclamation's September 28, 1990, memorandum were included and <br />guaranteed. The members of the Biology Committee believed that additional <br />research on the San Juan River and its tributaries is needed to quantify and <br />refine specific flow/habitat requirements, test hypotheses, and identify other <br /> <br />~;'fr <br /> <br />:';;~ <br /> <br />.,., <br />"0 <br /> <br />~ ~ <br /> <br />