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<br />(:;) <br />C:) <br />C-, <br />l~ <br />Q:l <br />l..:l <br /> <br />t':,\-. \-'-'6 <br /> <br />SECTION 9 (Preliminary Draft) <br />CONCLUSIONS <br /> <br />The flow recommendations are made in two parts. The first part consists of recommended <br />operating rules for Navajo Dam. By recommending operating rules, natural variability in the <br />hydrograph is maintained and annual decision making for releases is simplified. The second <br />part contains the conditions of the hydrograph required for endangered fish recovery. These <br />flow/duration/frequency recommendations will result from applying the operating rules <br />recommended, but will impact the level of future water development. These recommendations <br />are based on the best available information at this time, given the present status of the two <br />endangered fish species. Since there are still life stages of the two species that have not been <br />studied in the San Juan River due to low numbers offish, these recommendations should not be <br />considered final. As populations of fish increase, refinement of these recommendations can be <br />made. <br /> <br />Reservoir Operating Rules <br /> <br />Mimicry of a natural hydrograph requires maintenance of variability in the hydro graph while <br />maintaining the recommended flows in the San Juan River below Navajo dam. The following <br />operating rules allow for these conditions to be met. They are based on numerous model runs <br />for water development conditions ranging from 585,000 acre feet of depletion (approximate <br />current level of development) to 986,000 acre feet of depletion (baseline + 278,000 acre feet). <br />Each oftbe parameters has been tested for a range of values and the conditions recommended <br />are those that provide the closest match to the desired hydrograph conditions over the range of <br />development. <br /> <br />. Minimum peak release consists of I week ramp to 5,000 cfs, 1 week at 5,000 and one <br />week ramp down. Volume is 140,000 af <br /> <br />. Primary peak release hydrograph consists of 4 week ramp to 5,000 cfs, 3 weeks at 5,000 <br />cfs and 2 week ramp down. Volume is 420,000 af <br /> <br />. Median Peak on Animas is May 30. No correlation between volume or magnitude of <br />runoff and date of peak exists. Fix the center of5,000 cfs release at May 30 every year. <br /> <br />. Use the attached decision tree to determine magnitude ofrelease. Available water on the <br />chart is defined as: predicted inflow less base release plus available storage, where <br />available storage is reduced from full storage by the amount of carry over storage <br />necessary to prevent shortages in future years. "Release last 3 years> 420,000 af," <br />means that a release of at least 420,000 af occurred during at least one year out of the last <br />3. Table 7-1 lists the model calibrated values for carryover storage to be used in this <br />calculation for a range of development. When new development is proposed., the model <br />should be operated to verify the value to be used. <br />