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<br />. <br /> <br />. <br /> <br />2.3.7 Recreation, Fish and Wildlife Resources <br />Considerations. Less fluctuations in river flows serve to <br />enhance recreational opportunities and fish and wildlife <br />resources. The higher flood control releases and widely <br />fluctuating river flows negate recreational opportunities and <br />destroy fish and wildlife habitats. Mitigating higher spring <br />flood control releases and redistributing excess water <br />releases serves to minimize the impact on fish spawning and <br />wildlife nesting and the loss of habitat, and provides for <br />greater recreational opportunities. Fluctuating river flows <br />may conceal or create natural hazards such as shifting <br />sandbars, gravel bars, unstable river banks, and floating or <br />submerged debris. No studies have been done to relate the <br />loss of fish and wildlife resources or the loss of <br />recreational opportunities and revenues to specific river <br />flows or velocities. <br /> <br />2.4 Mitigation to Preserve Conservation Storage <br /> <br />Excess water, as def ined ear 1 ier, is water that is <br />anticipated to be released at Hoover Dam under the most <br />probable water supply conditions in compliance with the flood <br />control regulations. This water is in excess of reservoir <br />conservation storage and all downstream requirements in both <br />the United States and Mexico. Certain risks are involved <br />with the rescheduling of these excess waters in advance of <br />their mandatory release pursuant to the flood control <br />regulations. Any deviations in the water supply conditions <br />for the year from the most probable condition, assumed in the <br />determination of the excess flows, would result in either <br />over or under release of excess water. Of primary concern to <br />conservation storage is the over release of excess water. <br /> <br />The 24-month river operation studies prepared each month <br />by the Bureau can examine the effect on water conservation <br />under an array of water supply conditions and varying <br />operational assumptions regarding the rescheduling of excess <br />water. These studies, conducted monthly or more frequently <br />as may be required, serve to ensure that a prescribed <br />conservation storage level would be attainable even under <br />adverse water supply conditions for the remainder of the <br />year. Using a process of systematic ongoing evaluations of <br />the risks associated with the rescheduling of an~ anticipated <br />excess water releases, the level of risk to conservation <br />storage can essentially be eliminated or held to an <br />acceptable level as agreed upon among the Basin states. <br /> <br />The level of assurance or level of risk acceptable in a <br />water-short Basin relative to water conservation for the <br />purpose of redistributing excess water release has to be no <br />less than the ability to adjust operations, at any given <br />time, to recover to the reservoir vacant flood control <br /> <br />-20- <br />