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.' Draft San Juan Operating Model Consideration for Operating Rules February 24, 1998 ~chrn "-n f- L " o o \", ~l u; o Note: Considerations here are considered preliminary. Conditions finally recommended are subject to Ihe resullS of the Biology Committee integral ion process to determine the biological and geomorphic requirements for the fish and Iheir habitat. These values and rules have been used in model runs presently being analyzed and are being studied for adequacy and appropriateness. . Minimum peak release consists of I week ramp to S,OOO cfs, I week at 5,000 and one week ramp down. Volume is 140,000 af . Primary peak release hydrograph consists of 4 week ramp to 5,000 cfs, 2 weeks at 5,000 cfs and 4 week ramp down. Volume is 420,000 af. . Median Peak on Animas is May 30. No correlation between volume or magnitude of runoff and date of peak exists. Fix center of 5,000 efs release at May 30 every year. . Use attached decision tree to determine magnitude of release. Available water on the chart is defined as: predicted inflow less base release plus available storage, where available storage is reduced from fun storage hy the amount of carry over storage necessary to prevent shortages in future years. "Release last 3 years> 420,000 af." means that a release of at least 420,000 af occurred during at least one year out of the last 3. Iterations of model runs will be required to set minimum allowable storage. . In years when spill is predicted to be greater than 420,000 af, adjust the hydrograph by first adding a nose of2,000 cfs and extending to as early as March I. Increase nose by 500 cfs and increment calculation of duration until time extension is March I if necessary. Ramp up on beginning of nose from base flow cannot exceed 1,000 cfs per day. . In years when the release will be greater than 140,000, but less that 420,000 af, use the following adjustment rules in this order of preference: 1. Decrease time of decending limb by as much as 3 weeks to achieve necessary reduction (105,000 afreduction possible - 315,000 afrelease) 2. Decrease time of ascending limb by as much as 3 weeks to achieve necessary reduction(105,000 af reduction possible - 210,000 af release) 3. Reduce duration of peak by as much as I week (70,000 afreduction possible- 140,000 af release) . Minimum base flow following spring peak is 500 cfs at Farmington, Shiprock, Four Corners and Bluff gages (average of any two gages). Minimum release - 250 cfs. . Flood control releases to be handled as a spike flow (high magnitude, short duration), released when flood control rules require, except that the release shall not occur earlier than September 1. If an earlier release is required, extend descending limb of hydro graph. /:;