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<br />,. <br /> <br />, <br /> <br />develop flood control storage space greater than required by <br />the regulations, and provide for the required flood control <br />storage space by using available space in the different <br />reservoirs, within the constraints set by the flood control <br />regulations, the Operating Criteria, and the remainder of <br />-The Law of the River". <br /> <br />1.4 Recent and Near Future River Operations <br /> <br />From operating Year (Water Year) 1983 through 1986, <br />about 44 million acre-feet (maf) of excess water flowed to <br />Mexico. Table 1 presents a summary of Lower Basin reservior <br />releases and total water arrivals to Mexico during this four- <br />year period, a period when the annual undep1eted river flow <br />exceeded 20 maf for each of these years. Flows to Mexico in <br />excess of the Mexican W~ter Treaty de1iv~ry obligation are <br />likely to occur, at least periodically, through 1992, when <br />the Central Arizona project (CAP) is projected to be fully <br />operational. Recent Colorado River Simulation System (CRSS) <br />studies indicate that on the average, approximately 16.5 maf <br />will flow to Mexico between WY 1988 through 1992, <br />representing a total delivery of 9.0 maf in excess of the <br />minimum treaty delivery obligation. <br /> <br />prior to the occurrence of excess water, and consistent <br />with filling the reservoir system, reservoir releases were <br />governed by downstream water needs and minimum flood control <br />requirements. In general, under full reservoir conditions, a <br />minimum flood control requirement operation forces excess <br />water releases during the winter-to-summer flood routing <br />season and again dur ing the fa11-to-ear1y-winter flood <br />control vacant space-building season. Given the likelihood <br />of full reservoirs and excess water until 1992 and possibly <br />beyond, together with the experience gained in managing <br />excess water since 1983, more flexibility over the timing and <br />magnitude of excess water releases is central to more <br />effective river management. <br /> <br />Operating under full reservoir and mlnlmum flood control <br />requirements greatly reduces operational flexibility and the <br />assurance of effectively handling extreme outlier events <br />similar to the 1983 runoff. Major steps have been <br />implemented to improve river operations and to further ensure <br />public safety since 1983, including improved real time <br />climatologic and hydrologic data networks, increased runoff <br />forecast uncertainty terms, the pending re-estab1ishment of <br />an effective f100dway pursuant to the. Colorado River F100dway <br />protection Act (P.L. 99-450), levee improvements in the lower <br />Colorado River, and improved reservoir spillways at the <br />river's dams. Greater operational flexibility can be <br />created, without adversely altering the priority purposes of <br /> <br />-4- <br />