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<br />.. <br /> <br />~ <br /> <br />construction of additional water storage facilities to <br />replace the amount of conservation storage that would be <br />dedicated to flood control space. However, the <br />redistribution of excess water releases under full reservoir <br />conditions could reduce the magnitude of flood control <br />releases that would otherwise have to be made, thus providing <br />for greater flood protection without necessarily sacrificing <br />water conservation. <br /> <br />2.3.2 Lower River Regulation perspective. Redistributing <br />excess water serves to enhance river regulation by <br />controlling the extreme fluctuations of river flows that <br />occur when moving from a downstream water requirements <br />operation to a typical mandatory flood control release <br />operation. The magnitude of release impacts directly upon <br />river operation and maintenance (O&M) costs incurred by the <br />federal government and water users. The river mechanics of <br />the colorado River generally show that river characteristics <br />pertinent to river O&M, such as scour, sediment transport, <br />and bank erosion, vary in proportion to the square of the <br />discharge. In a study prepared by the River Regulation <br />Branch, Lower Colorado Region, Bureau of Reclamation, a <br />relationship was established between total river O&M costs <br />for the federal government from below Davis Dam to the <br />Northerly International Boundary (NIB) and the discharge from <br />Davis Dam. Table 2 shows the relationship between sustained <br />monthly flows from Davis Dam and monthly O&M costs. A <br />sustained monthly flow of 28,000 cfs increases the river O&M <br />costs for that month by $474,000 over normal O&M costs; a <br />flow of 35,000 cfs produces an additional $793,000 cost; and <br />a 40,000 cfs release escalates the monthly costs to <br />$1,081,000 over normal costs. A reduction in the probability <br />of making large magnitude flood control releases (in excess <br />of 19,000 cfs) would yield substantial benefits in terms of <br />reduced river O&M costs. <br /> <br />TABLE 2 <br /> <br />MONTHLY RIVER O&M COSTS AS A FUNCTION <br />OF DISCHARGE AT DAVIS DAM <br /> <br />Release y O&M Costs/Month Increase <br />(cfs) ($1,000) ($1,000) <br />12,000 107 Y 0 <br />19,000 269 162 <br />28,000 581 474 <br />35,000 900 793 <br />40,000 1,188 1,081 <br /> <br />1/ <br />~/ <br /> <br />Sustained release for one month. <br />Represents normal level of operation <br />maintenance costs. <br /> <br />and <br /> <br />-11- <br />