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.,' . '!I '. (u) Power 1s to bE generated at Hoover to the extent that water required to "eet do~nstream uses, as defined in (3) above, will permi t tluch ger.9r:ltion. If such releases do not permit generation 01 firm p01"~r as defined by contract, then Lake Mead storage wo'Jld be drawn upon for firm power, except that when Lake Mead Jtorage js thereby drawn down to 17,000,000 acre-feet (active), <he accwIlLllation of additional storage in Glen Canyon Reservoil' shall be restricted to the extent necessary to permit '~cntinuance of firm power production at Hoover without furth3r demand upon Lake Mead storage. ,later already stored in Gl~n Canyon Reservoir shall not be released, however, for continu3nce of firm generation at Hoover. Application and furthlr'd1scussion of, and the resulting compu.- tations under the foregoing basic premises are contained hereinafter. Assumed Stream Flow Conditions .~ .. "-'I 1:'1 ~ ~d .- An assWllption as to expected stream flows is necessary in aD7 reservoir filling demonstration. The assumption of average stream flow conditions is a reasonable one for this study. Reservoir operation studies presented herein assume average stream flow at Glen Canyon equal to that obtained from the period 19lu-19u5 inclusive, modified to reflect present conditions of development and progressively reduced each year through the operation period consistent with a projected schedule of increasing annual depletions. Of course, stream flow realized at Glen CaIlj'On will depart from the average in any given year, but speculation involving variants in the developing physical situation is premature and would not be useful. , '.- t. ~' :JJ. ,; ~, ~ I Lake Mead storage reached a low OOint i.n1rnediately prior to the 1951 flood season due to a recent drought (1953-56 being the lowest four years in sequence in the history of the Colorado River). The flood run- orf in 1957 was considerably greater than average and Lake Mead active storage content is expected to be 20.0 million acre-feet on April 1, 1958. Therefore the operation studies begin April 1, 1958, with Lake Mead act1'Y. storage content of 20.0 million acre-feet. 'I'; .1 Historically, the annual flow at the Glen Canyon Dam site averaged 13.8 million acre-feet during the 32-year period 1914 to 1945, inclusive. When modified to reflect present conditions of development in the Upper Basin, the average annual flow is about 13.1 million acre- feet. Further developments in the Uooer Basin, such as construction of water-consuming projects and storage reservoirs, will require further adjustment in the eJP ected flow. T..ble I is a tabulation of the flows to be e:xpected in the near future at Glen Canyon Dam assuming average stream flow COnditions. 2