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<br />I. <br /> <br />For an annual volume of 16 million <br />acre feet the releases would be; Oct <br />- Dec19,ooocfs, Jan-Mar22,ooocfs, <br />Apr - Jun 29,000 cis, and Jul - Sep <br />19,000 cfs. <br /> <br />Maximum steady releases would <br />be determined by the seasonal <br />volume of water to be released. <br />Adjustments in releases required <br />by forecast changes would be <br />distributed throughout subsequent <br />seasons. Use of the powerplant, <br />outlet works, and spillway may be <br />required during high water years <br />when Lake Powell is full. <br /> <br />The Monthlll Stea411 Flow <br />alternative would provide steady <br />monthly releases with monthly <br />volumes determined from forecasts <br />and current operating objectives. <br />The median monthly volumes <br />ranged from about 550,000 acre-feet <br />in February to about 900,000 <br />acre-feet in August from 1963 to <br />1989. The steady flow rates <br />corresponding to these monthly <br />volumes would be aboutl0,000 and <br />15,000 cis, respectively. Monthly <br />release rates necessary to avoid <br />spills and maintain storage would <br />be scheduled as at present. <br />Maximum steady monthly releases <br />would be determined by the <br />monthly volume to be released. <br />Minimum steady flows would be <br />about 8,000 cfs, based on a <br />minimum monthly volume of <br />about 500,000 acre-feet. <br /> <br />FLUCTUATING FLOWS <br /> <br />The five fluctuating flow <br />alternatives present a broad range <br />of alternatives with varying <br />amounts of flexibility for power <br />operations while providing a range <br />of downstream resource protection <br />measures. Included in this diverse <br />group of alternatives are three <br />alternatives which restrict the daily <br /> <br />fluctuation allowed at Glen <br />Canyon, the No Action alternative, <br />and a Maximum Fluctuation <br />alternative. <br /> <br />The Low Fluctuation, Moderate <br />Fluctuation, and High Fluctuation <br />alternatives reduce the magnitude <br />of daily fluctuations from present <br />operations. Annual and monthly <br />release targets in the annual <br />operating plan will be based on <br />projected runoff using existing <br />practices. Release volumes will <br />continue to be revised monthly to <br />accommodate forecast changes. <br />The alternatives will maintain <br />current operational flexibility <br />necessary to avoid spills and <br />maintain storage. Powerplant <br />capacity would be exceeded only <br />during floods. <br /> <br />From the expected monthly release <br />volume, a mean daily flow would <br />be calculated. The mean daily flow <br />represents a cfs rate which, if <br />released for 24 hours every day for <br />the month, would equal the <br />expected monthly release volume. <br />These three alternatives would <br />allow daily fluctuations about this <br />mean. A compound allowable <br />daily fluctuation restriction is <br />included in each alternative so that <br />the band of fluctuations is limited. <br />This method recognizes the need <br />for higher. releases, with restricted <br />fluctuations, in months with high <br />volume release targets. The <br />allowable fluctuations were based <br />on estimated river elevation <br />changes below the dam. Each <br />alternative also specifies ramping <br />rate restrictions, and minimum <br />release requirements. <br /> <br />Power operations would be <br />influenced by monthly water <br />release volumes. Generally, power <br />operations would optimize the <br /> <br />water allocation to maximize the <br />ability to generate to meet firm load <br />and to allow greater purchases <br />during off-peak periods, given the <br />release restriction. <br /> <br />The I.ow Fluctuation alternative <br />would limit daily fluctuation to j;, 25 <br />percent of the mean daily flow, or <br />7,000 cfs, which ever was less. <br />Ramping rates would be limited to <br />2,500 cfs per hour. Minimum <br />releases would be 8,000 cis from <br />December through February and <br />5,000 cis for the remainder of the <br />year. <br /> <br />It is assumed that the low <br />fluctuating flow alternative would <br />continue to cause some beach <br />erosion, therefore, this alternative <br />includes a sand pumping <br />operation. A multilevel intake <br />structure is also part of the low <br />fluctuation alternative because <br />fluctuating daily flows are believed <br />to prevent sufficient warming of <br />backwaters for native fish. <br /> <br />The Moderate Fluctuation <br />alternative allows a daily <br />fluctuation of .t 45 percent of the <br />mean daily flow, not to exceed <br />12,000 cfs. Ramping rates are <br />limited to 4,000 cfs per hour and <br />minimum releases must be at least <br />5,000 cis year round. <br /> <br />Sand pumping and a multilevel <br />intake structure are also part of this <br />alternative. In addition, beach <br />protection measures are included <br />to slow beach erosion due to <br />fluctuations. <br /> <br />Beach Protection <br /> <br />Small rock jetties or rock lining <br />could be placed to protect existing <br />beaches or to rehabilitate beaches. <br />Jetties are used to divert high <br />velocity flow away from the beach <br />and create a small eddy on the <br /> <br />11 <br />