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<br />In the lower basin, the governing principal that appears to dominate the water supply, under <br />fun development conditions, is the recognition that within the lower basin the total of uses <br />and losses exceed the total of the intervening flows plus the 8.23 maf objective minimum <br />release. Rather than restrict the amount of full dependable development, the lower basin <br />relies upon the application of shortage provisions to reduce depletion levels during times of <br />long-term drought. Under full development, the 8.23 maf plus intervening flows is balanced <br />by determining a shortage to CAP and to SNWS as much as about 40 percent of the years. <br /> <br />Reclamation recognized that under fun development, system storage will be commonly drawn <br />into a shortage determination, and that use of the critical period of record is consistent with <br />upper basin methodology. A surplus strategy was developed which determined surplus as <br />storage in excess of that required to annually provide 7.5 maf consumptive use in the Lower <br />Division through the critical period of record. The surplus threshold was set to equal to the <br />critical storage required above the storage level to be protected for determining a shortage. <br /> <br />The Critical Period Strategy is not arbitrary. It is based on technical rationale, unrelated to <br />an analysis of impacts and benefits, which maintains itself regardless of changes in forecasted <br />use or reservoir storage conditions. The critical period approach is the longstanding <br />guideline commonly used in sizing water supply reservoirs and developing shortage criteria <br />and is consistent with the strategy applied in the upper basin. <br /> <br />The analysis assumed shortages would be determined based on an elevation of 1120 feet, in <br />order to protect elevation 1050 feet after the surplus threshold exceeds Lake Mead capacity. <br />Other shortage strategies could be analyzed and considered. The Critical Period Strategy <br />remains intact regardless of the shortage strategy considered. Adopting this strategy provides <br />a technical base case from which other guidelines can be analyzed and addressed. <br /> <br />The Critical Period Strategy would determine surplus conditions for the next several years <br />for any protection level less than or equal to elevation 1050 feet. Reclamation recommends <br />that interim guidelines for determining surplus adopt the Critical Period Strategy, and that <br />shortages be determined based on elevation 1120 feet, until a specific shortage strategy can <br />be adopted. <br /> <br />39 <br /> <br />'Ilia c.~ ":'l <br />