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<br />
<br />RIVER OPERA liON
<br />
<br />The Board continually collects basic data
<br />on all items which affect the operation of the
<br />Colorado River. In this section, water supply
<br />and use data are reported on a water year
<br />basis (October I through September 30).
<br />Power generation data is reported on an op-
<br />erating year basis <June I through May 31).
<br />
<br />Welter Supply
<br />The flow of the Colorado River at Lee Fer- '
<br />ry during the 1970-71 water year was 8,574,-
<br />000 acre-feet. If reservoir surface and bank
<br />storage conditions in the Upper Basin had
<br />remained unchanged through the year, flow
<br />at Lee Ferry would have equaled 11,781,000
<br />acre-feet. The Bureau of Reclamation esti.
<br />mates that if there had been no man-made
<br />depletions upstream, the virgin flow of the
<br />Colorado River at Lee Ferry would have
<br />been approximately 14,903,000 acre-feet. For
<br />comparison, the long term annual average
<br />undepleted or virgin flow figures at Lee Fer.
<br />ry for three hydrologic perio~s ar~ as follows:
<br />for the period 1922-71, which Illcludes all
<br />recorded flows since the Lee Ferry gage was
<br />established, 13.8 million acre-feet; the 1896-
<br />1971 period, which is based in part on cor-
<br />related data, 14.8 million acre-feet; and the
<br />1953--64 period, which represents the d~c~de
<br />with the lowest average flow, 11.6 millIon
<br />acre-feet. Plate 3 shows the estimated ann ual
<br />virgin flows at Lee Ferry since 1896.
<br />Table I relates measured flows for the wa-
<br />ter year 1970-71 at various points in the Ba-
<br />sin. Flows at the first three stations listed
<br />represent approximately 95% of the inflow
<br />to Lake Powell. During the year, flows below
<br />Hoover Dam, also shown in Table 1, were
<br />limited to the amounts necessary to meet
<br />consumptive use requirements in the United
<br />States plus the deliveries to Mexico.
<br />
<br />Table 1
<br />MEASURED FLOW IN COLORADO RIVER
<br />BASIN FOR WATER YEAR 1970-71
<br />(Thou,and, of Acre-Feet)
<br />
<br />Station
<br />Upper Basin Aleasured Flow
<br />Green R. at Green River, Utab ...'........, .....0...........0.................. 4,063
<br />Colorado R. near Cisco, Utab ........0.,......,.."...'..........'......" '.... 5,617
<br />San Juan R near Bluff, Utah......,.,.............".....,..........,........, 1,328
<br />Colorado R, at Lee Ferry ,..'..........0.......,..........0.......,.............0.,.' 8,574
<br />Lower Basin-Colorado River
<br />Near Grand Can yon.,..,..."..",..,..,.,.".".,.,.."...".,.,..,.".,....'.'..', ,.,.. 8,829
<br />Below Hoover Dam ..................'...........'........'.....,....,.......,'.',.....0. 8,233
<br />Below Davis Dam '.m.'.'.'""..,....,.',..,.......,.,.,...'..,..".,..',..,.'".,....,., 8,266
<br />Below Parker Dam ..,..'....0............."........,'...................,.'..,..0........ 6,936
<br />Flow into Mexico .,.",.,."......,.,.,.,..',.,.,.,'..,....".".,.",.,...',.,..,...."." 1,561
<br />
<br />Article III (d) of the Colorado River Com-
<br />pact provides that the states of the Upper
<br />Division will not cause the flow of the Colo-
<br />rado River at Lee Ferry to be depleted below
<br />an aggregate of 75,000,000 acre-feet for any
<br />period of ten consecutive years. The lowest
<br />ten consecutive year aggregate flow at Lee
<br />Ferry prior to the closing of Glen Canyon
<br />Dam occurred from 1931-40. In that period,
<br />approximately 118 million acre-feet passed
<br />Lee Ferry.
<br />Since the beginning of storage in Lake
<br />Powell in 1963, the accumulation of storage
<br />in the Colorado River Storage Project reser-
<br />voirs and the generally low runoff, has result-
<br />ed in a total flow at Lee Ferry of only 65,945,-
<br />000 acre-feet. The break-down of this figure
<br />is as follows:
<br />
<br />Water Year
<br />1962-63 .... ,............................................................
<br />1963-64 ...... ,.........................................................
<br />1964-65 ...... ........................, ................................
<br />1965-66 ..... .....................
<br />1966-67 ........................ ..........................................
<br />1967-68 ..... ....................... ....................................
<br />19~-69 ....,..............................
<br />1969-70 .... ..................... .....................................
<br />1970-71 ...... ................. ........................
<br />
<br />Flow at
<br />Lee Ferry
<br />(acre-fer:r)
<br />2.520.000
<br />2,427,000
<br />10,835,000
<br />7,870,000
<br />7,823,000
<br />8,358.000
<br />8,850,000
<br />8,688,000
<br />8,574.000
<br />
<br />Total...,..... ......,,,...'.... ..,...............................,.. 65,945,000
<br />9-year average..,.",... ................,.. ..,'.................. 7,327,000
<br />
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