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<br />r-- <br />M <br />~ <br />C\.I <br />C <br /> <br />d. Plate 15 - Area-capacity curves. <br /> <br />:~~". <br /> <br />e. Plate 16 - Outlet-discharge curves. <br /> <br />f. Plate 17 - Spillway-discharge curve - one spillway. <br /> <br />46. Sedimentation surveys. --The original survey of Lake Mead <br />was made by the Division of Cartography, Soil Conservation Service <br />in 1940. A resurvey was conducted by the U. S. Geological Survey, <br />the Bureau of Reclamation, and the Navy Department during the period <br />of March 1948 through March 1949. Another survey was conducted by <br />the Coast and Geodetic Survey in 1963-64, and interpreted by the <br />Bureau of Reclamation. The results of the new survey are used in <br />this report. A comparison of storage values at significant levels <br />as determined from the 1940, the 1948-49, and the 1963-64 surVeye are <br />shown in the follOWing table: <br /> <br />; <br /> <br /> Elevation Gross stora;a in acre-feet <br />Significant level : in feet 19/+0 : 1 -49 : 1963-64 <br /> survey survey survey <br />Top of flood-control <br />pool. : 1,229.00 32,359,000 31,047,000 29,755,000 <br />Top of spillway gates <br />raised. 1,221.40 31,142,000 29,827,000 28,531,000 <br />Flood-control space : <br />of 1.5 M.A.F. : 1,219.60 30,859,000 . . --...; <br />..............'............ <br />Flood-control space . -}~:. <br /> . <br />of 1.5 M.A.F. 1,219.63 :............: 29,547,()()Q :........... <br />Flood-control space <br />of 1.5 M.A.F. : 1,219.61 . . . 28,255,000 <br />........................... <br />Permanent spillway 1,205.40 28,691,000 ~, 316,000 : 26,086,000 <br />crest. : <br />Sill of lowest intake...: 895.00 3,207,000 2,620,000 : 2.318,000 <br /> <br />47. In both the 1948-49 and 1963-64 surveys, silt accumulation <br />in the deep water portions was determined by use of echo-sounding <br />equipment operated from boats. Sounding courses were run parallel <br />to each other with a spacing of 200 to 300 yards. Controls were ob- <br />tained by sextant and transit observations to and from fixed points <br />on shore. The shallow portion of the reservoir, sbove Pierce's Ferry, <br />was surveyed using standard river-survey methods. <br /> <br />16 <br />