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<br />'. I' <br /> <br />PROVISIONS BASED ON ASSURANCE OF AVOIDANCE OF EXCESS RELEASE <br /> <br />Model runs were also designed to provide a comparison of the alternate Lake Mead threshold <br />elevation provisions with surplus provisions based on the Assurance of A voidance of flood <br />control releases which had been used in previous modeling exercises. These runs included: <br /> <br />10. 70A: 70 Percent Assurance of Avoidance. This run utilized a surplus <br />strategy commonly used in which surplus conditions are made to provide <br />assurance of avoidance of a flood control mandated release. It is based <br />on the depletions that year and about 17 maf of runoff. Later analysis <br />found the surplus threshold elevation generated under the 70 Percent <br />Assurance Strategy to vary from 92 percent to 96 percent capacity as use <br />increases. <br /> <br />11. 90A: 90 Percent Assurance of Avoidance. This run utilized a surplus <br />strategy in which surplus releases are made to provide assurance of <br />avoidance of a flood control mandated release. It is based on depletions <br />of that year and about 21 maf of runoff. The surplus threshold elevation <br />generated under a 90 Percent Assurance Strategy was found to vary from <br />86 percent to 90 percent of capacity as use increases. <br /> <br />SHORTAGE THRESHOLD ELEVATION RESET BACK TO ELEVATION lUO <br /> <br />The model runs shown above assumed a shortage threshold elevation of 910 feet, allowing <br />the full capacity of Lake Mead to be drawn down before triggering a shortage with reduced <br />CAP and SNWS diversions. Additional model runs were designed to evaluate the effect of <br />combining a more conservative shortage strategy with the alternate Lake Mead surplus <br />strategies. These runs were made to determine a shortage threshold that would protect the <br />minimum objective Lake Mead elevation of 1050 feet. <br /> <br />Three runs were made which compared the surplus strategies 6OCI&OC(2001), &OC and 70A, <br />when using a shortage threshold elevation of 1120 feet. Elevation 1050 feet was monitored <br />as it represents the intake to SNWS. All three runs also assumed that should a flood control <br />release occur, surplus conditions would be triggered. The three runs included: <br /> <br />12. 60C/80C (2001) + lUO SHORT: Surplus threshold set at 60 percent capacity <br />of Lake Mead during years 1993 to 2000. Surplus threshold changed to <br />80 percent capacity of Lake Mead for years 200 1 to 2050. Shortage threshold <br />elevation set at elevation 1120 feet. <br /> <br />13. 80C + lUO SHORT: Surplus releases are determined when capacity of Lake <br />Mead reached 80 percent. Shortage threshold set at elevation 1120 feet. <br /> <br />14. 70A + lUO SHORT: Surplus releases made to provide a 70 percent assurance <br /> <br />17 <br />