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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />California, Diversion locations 2 and 3 above represent the flow to California Irrigation Districts <br />on Figure 3. Under the proposed rule an authorized entity would use their existing facilities to <br />deliver water in satisfaction of an interstate agreement. <br /> <br />A more detailed discussion oflower Colorado River operations and maintenance is contained in <br />Reclamation's 1996 Biological Assessment (BA). Figures 4, 5, and 6, display fluctuations in the <br />water level of Lakes Mead, Mohave, and Havasu respectively over a seven year period. <br />Lake Mead is the principal storage reservoir of these three and the source for meeting <br />downstream water use of the Lower Division States, Water levels at any time are a direct result <br />of the relationship of releases from Glen Canyon Dam, tributary inflow below Glen Canyon <br />Dam, and releases from Hoover Dam, The pattern of fluctuation in water elevations on <br />Lake Mead is very minimal on a daily basis because of the capacity of this reservoir. The <br />patterns shown in Figure 4 primarily reflect seasonal drawdown during the spring and summer to <br />meet water orders, equalization with Lake Powell, and variation in water supply. Fluctuations in <br />the water elevations of Lake Mohave (Figure 5), represent operation of Davis Dam to facilitate <br />water deliveries to Mexico and the other downstream water users, and to re-regulate the flows <br />from Hoover Dam, Fluctuations in Lake Mohave are restrained to a maximum drawdown of one <br />foot per week to meet endangered species needs, <br /> <br />Parker Dam was constructed to create a forebay, resulting in Lake Havasu, for the MWD <br />Whitsett pumping facility, Later, the CAP was constructed just downstream on the Arizona side <br />of Lake Havasu and similarly uses the lake as a forebay for pumping water into the CAP <br />aqueduct system. Because of this, Lake Havasu typically fluctuates within an elevation of about <br />four feet during the year (Figure 6) and is relatively stable, <br /> <br />The pattems of historical and projected releases out of Hoover Dam (Figure 7) are very similar, <br />These releases generally reflect the delivery of water for downstream use in Arizona, California, <br />and Mexico. <br /> <br />Preferred Alternative <br /> <br />Under the Preferred A1temative, in a normal year, the basic annual apportionments available for <br />consumptive use to each of the Lower Division States would not change, Arizona would <br />continue to use its entire 2.8 mar annual apportionment. However, the A WBA may forego <br />storage on its own beha!fin order to make some of Arizona's unused entitlement available for <br />storage on behalf of California or Nevada through the interstate component of the A WBA Act. <br />If Arizona makes a portion of its unused entitlement available to California or Nevada for <br />storage off stream, that will not significantly change the distribution or delivery of Colorado <br />River water, The water would continue to be distributed through the normal conveyance system, <br />primarily the CAP facilities. The only differences would be that the storage credits would be for <br />the benefit of another Lower Division State and the pattern of water deliveries through the CAP <br />may require minor adjustments to accommodate the addition of water for California and Nevada, <br /> <br />LC Region DEAll <br /> <br />12 <br /> <br />12/97 <br />