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<br />2~QQ
<br />
<br />Mead equal to the active storage in Lake Powell,
<br />and shall be such as to avoid anticipated spills
<br />from Lake Powell.
<br />Water releases and losses during water year
<br />1967-68 were less than inflow with the result
<br />that the total surface storage in the Colorado
<br />River Basin increased during the 1967-68 year
<br />as shown in Table 3.
<br />
<br />PLATE 5
<br />
<br />COLORADO RIVER BASIN RESERVOIRS
<br />STORAGE AND CAPACITY
<br />
<br />"
<br />
<br />
<br />on
<br />
<br />"
<br />
<br /><0
<br />
<br />LAME PO....ElL
<br />FL4""'<C GORGE
<br />"AVlUO
<br />BlU[ MESA
<br />rO"H"~LL[
<br />MO"~O'" POlr'll
<br />
<br />"
<br />, ", ACTIVE C.l.PACITY
<br />" I
<br /> ~
<br /> ,
<br />" .
<br />
<br />f
<br />
<br />
<br />'968
<br />
<br />o
<br />19'0
<br />
<br />1940 '9~O
<br />
<br />1960
<br />
<br />WATER YEAR
<br />
<br />.
<br />,",.".'",...<".,"."....".'.."0.....0.
<br />
<br />Plate 5 shows the combined active surface
<br />storage of Lake Mead and the Colorado River
<br />Storage Proj ect reservoirs for the period 1935-
<br />1968. Lake Mohave and Lake Havasu are not
<br />included because they are operated at relatively
<br />constant levels. In addition to surface storage,
<br />water is absorbed in the areas adjacent to the
<br />reservoirs. At Lake Powell, this absorption or
<br />bank storage was estimated to be about 3,900,000
<br />acre-feet as of the end of water year 1968, or
<br />41 percent of the gross surface storage of 9,512,-
<br />000 acre-feet.
<br />Plate 6 shows the changes in contents of the
<br />major mainstream reservoirs during the 1967-68
<br />water year.
<br />Uses and Losses. The major portion of de-
<br />pletions in the Upper Basin are not measured.
<br />
<br />The Bureau of Reclamation computes irrigation
<br />depletions by applying a unit rate to an estimated
<br />acreage. The unit rate is derived for each year
<br />by applying to the estimated long-time average
<br />a factor varying with the annual runoff, indicat-
<br />ing uses greater than average in years of high
<br />runoff and less than average in years of low run-
<br />off. This type of adjustment is questionable for
<br />application to present development because of
<br />the increasing amount of storage regulation avail-
<br />able to supplement low runoff. Including trans-
<br />mountain diversions which are measured, and
<br />evaporation from reservoirs, the preliminary
<br />estimate bv the U. S. Bureau of Reclamation of
<br />total depletions in 1967-68 at Lee Ferrv was
<br />2,957,000 acre-feer, an increase of 477,000 acre-
<br />feet from the estimated 1966-67 depletion.
<br />Diversions minus measured returns to the river
<br />by the major Lower Basin mainstream users in
<br />water year 1967-68 were 5,756,000 acre-feet,
<br />a decrease of 119,000 acre-feet from 1966-67.
<br />California diversions less returns were 4,760,000
<br />acre-feet, a reduction of 151,000 acre-feet from
<br />the previous year.
<br />Quantities for the past five years are shown
<br />in Table 4.
<br />
<br />Tobie 4
<br />
<br />DIVERSIONS MINUS MEASURED RETURNS
<br />LOWER COLORADO RIVER
<br />
<br />(Thousond, 01 Acre.leet)
<br />
<br />Watu Ytar 19M 1965 1966 1967 /968
<br />CalIfornia
<br />Palo Verde lrrig. Dis!.. 4D3 37J 38. 365 386
<br />Metropolitan Water
<br />DisL__ _ _~_ __ h___ ],092 ],]80 1,121 1,]82 ],105
<br />Yuma Project Reserv.
<br />Div.______________ .8 .6 48 51 55
<br />Imperial Irrig. Dis!..__ 2,859 2,756 2,778 2,860 2,745
<br />Coachella Valley Co.
<br />Water DisL_______ 505 526 484 453 469
<br />TotaL_______... 4,907 ,,881 4,815 4,911 ,,760
<br />Arizona
<br />Colorado R. Indian
<br />Reservation__ _ _____ ]89 178 186 200 235
<br />Gila ProjecL._____h_ 642 616 555 566 560
<br />Yuma Proj. Valley
<br />Div_______u______ 176 182 162 171 ]70
<br />TotaL _ ___ __un 1,007 976 903 937 965
<br />N~rJad(1
<br />Pumping from
<br />Lake ]\:lead________ 27 23 25 27 31
<br />Grand TotaL __ n 5,941 5,880 5,743 5,875 5,756
<br /> 25
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