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<br />,~ <br />C1j <br />Cl:) <br />N <br />C <br /> <br />~ ~-. <br />"" :.- ~ , <br />....~~~~ <br /> <br />Date Forecast method <br /> <br />l-in-10 error <br /> <br />: <br /> <br />1 ApriL.....: Water equivalent of snow, plus accumu-: <br />lated precipitation, plus antecedent : <br />runoff. <br /> <br />Million acre-feet <br />2.5 <br /> <br />1 l4e.y........:... .do.................................: 1.5 <br />1 J\1Ile.......:... .do.. ............. ..................: 1.0 <br />1 July.......: 30 June mean daily flow...............: .3 <br /> <br />30. 1 August to 1 November releases. --Whenever appreciable runoff <br />from rainstorms occurs during the period 1 August to 1 November, mini..... <br />releases from I4ke Mead are deterlll1ned daily from table 7 of Appendix A. <br />for various conditions of available flood-control storage space in I4ke <br />Mead, inflow to Lake Mead, and releases from Glen Canyon Dam. <br /> <br />31. Minimum releases from Lake Mead as given in table 7 of Appendix <br />A, if 40,000 cubic feet per second or less, are not redooed when once ini- <br />tiated, UIltll thelll1n1mum storage space specified under preceding heading, <br />"Current operation plan," becomes available. If greater than 40,000 cubic <br />feet per second, they are not reduced, when once initiated, until the reser- <br />voir vater surface has receded to elevation 1,221.4 (top of spillway gates <br />in raised position). Releases may then be gradually reduced to 40,000 cubic <br />feet per second and l18intained at not less than that rate until the IIl1n1Jllum <br />storage space becomes available. <br /> <br />32. Table 7 of Appendix A was derived from routing studies to determine <br />the space required in Lake Mead to control a maximWD probable and a standard <br />project rain flood. These floods were developed for the tributary area above <br />and below Glen Canyon Dam and include the appropriate outflows from the dam. <br />AssWD1ng Lake Mead full to the top of the spillway gates in the raised <br />position, the maximum probable rain flood can be controlled to a Hoover <br />Dam release of 86,500 cubic feet per second and the standard project rain <br />flood to a release of 40,000 cubic feet per second. <br /> <br />3i. 1 NoveDlber to 1 Januaryreleases.--For the period 1 November to <br />1 January, IIl1n:llllWD releases frem Hoover Dam are those necessary to make <br />available the storage space specified under preceding heading "Current oper- <br />ation plan." <br /> <br />34. RoutinP; of l884 spring snowmelt flood. --The 1884 spring snow- <br />melt flood vas routed through Lake Mead by the Bureau of Reclamation as <br />shown on plate 4, using the current operation plan. Because precipitation <br />records from which a forecast could be made are not available, it was <br />assllllll!d that the maximWD inflow forecast at the first da,. of each month <br />was the same 88 the actual inflow that was est1J2ted to have occurred. It <br />vas :rurther assllllll!d that the IIl1nimWD necessary flood-control storage space <br />below elevation 1,229 ot 1,500,000 acre-feet in Lake Mead, and that a total <br />ot 5,350,000 acre-teet, including storage at upstream daIIs, vas available <br /> <br />12 <br />