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<br />001692 <br /> <br />8.5 Shortage Strategy <br /> <br />The shortage strategy is the decisionmaking process within the CRSM by <br />which water delivery to certain demands in the Lower Basin is curtailed <br />in order to conserve water in Lake Mead to assure future supplies for <br />higher priority users, or to maintain sufficient head for power genera- <br />tion. The shortage strategy has its legal foundation in the "Law of the <br />River." Specifically, the Supreme Court Decree in Arizona vs. <br />California and the Colorado River Basin Project Act (Public Law 90-537) <br />address water shortage situations. The shortage strategy is intended to <br />reconcile the difference between average inflow and total demands during <br />drawdown periods in Lake Mead. <br /> <br />A sequence of dry years modeled by the CRSM will cause Lake Mead to be <br />drawn down to satisfy water demands in the Lower Basin States and <br />Mexico. If the Lake Powell annual release equals the objective minimum <br />release of 8.23 million acre-feet per year, Lake Mead will be drawn down <br />approximately 1 million acre-feet per year. Should a series of dry <br />years be long enough, eventually Lake Mead would fall below critical <br />operating levels, or even go dry. Such extreme drawdown could be con- <br />sidered contrary to the Supreme Court Decree and Public Law 90-537 which <br />require that consideration be given to holders of higher priority water <br />rights in the Lower Basin States, at the expense of those with lesser <br />priority (primarily CAP and SNWP). <br /> <br />The elevation of Lake Mead is checked by the CRSM, and levels of short- <br />ages are imposed, if necessary, in January of each year. Any shortages <br />that are imposed remain in effect for 1 year. There are three levels <br />of shortages imposed by the CRSM. Level 1 shortages are triggered by an <br />elevation specified in the CRSM control file and referred to as the <br />shortage flag elevation. The second level of shortages is triggered by <br />an elevation specified in the CRSM control file and referred to as the <br />minimum Mead elevation. The third level of shortages is imposed if the <br />previous level of shortages are not sufficient to keep Lake Mead above <br />the minimum Mead elevation. <br /> <br />Levell shortages consist of shortages to Arizona and Nevada and are <br />borne by CAP and SNWP, respectively. Arizona's shortage is equal to the <br />difference between CAP's normal diversion and the shortage diversion for <br />CAP specified in the input data. In current CRSM runs, the shortage <br />diversion to CAP is normally set to 400,000 acre-feet per year. <br />Nevada's shortage is equal to 4 percent of the shortage imposed on <br />Arizona, which is approximately equal to 4 percent of the total level 1 <br />shortage. <br /> <br />Level 2 shortages are based on a volume of deficiency which is equal to <br />the volume of Lake Mead at the minimum Mead elevation minus the volume <br />Lake Mead will be at after level 1 shortages are imposed for a year. <br />Level 2 shortages consist of further shortages to CAP and SNWP. SNWP's <br />shortage is equal to 4 percent of the deficiency. CAP's shortage is <br />equal to the remaining deficiency, or the amount that sets CAP's diver- <br />sion to zero, whichever is less. <br /> <br />42 <br />