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<br />RIVER OPERATION
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<br />The Board continually collects basic data
<br />on water supplies and uses, power genera-
<br />tion, and all items which affect operations on
<br />the Colorado River. Water supply and use
<br />data are reported on a water year basis, Octo-
<br />ber 1 through September 30; power genera-
<br />tion data is reported on an operating year
<br />basis, June 1 through May 31.
<br />
<br />Water Supply
<br />The flow of Colorado River at Lee Ferry
<br />during 1969-70 was 8,621,000 acre-feet. Ad-
<br />j ustments to this flow for changes in surface
<br />storage and estimated bank storage in up-
<br />stream reservoirs, makes the flow 12,301,000
<br />acre-feet. The Bureau of Reclamation esti-
<br />mates that if there had been no upstream
<br />man-made depletions, the virgin flow of the
<br />Colorado River at Lee Ferry would have
<br />been approximately 15,319,000 acre-feet. For
<br />comparison, the estimated annual average
<br />undepleted or virgin flow was 13.8 million
<br />acre-feet during the 1922-70 period of meas-
<br />urements at Lee Ferry and 14.8 million acre-
<br />feet during the 1896-1970 period. Plate 3
<br />shows estimated annual virgin flows at Lee
<br />Ferry since 1896.
<br />
<br />Table 1
<br />MEASURED FLOW IN COLORADO RIVER
<br />BASIN FOR WATER YEAR 1969-70
<br />(Thausands af Acre.Feet)
<br />
<br />Sr:uion
<br />Vp~r Bllsin A-/~~surro Flow
<br />Green R. at Green River, Utah. ............................. 4,288
<br />Colorado R. near Cisco, Utah .. ...................... ...................... 5,903
<br />San Juan R. near Bluff, Utah...... .................. 1,531
<br />Colorado R. at Lee Ferry............. ................... .................. 8,620
<br />
<br />Lowu B:uin-Colorado Riyt:r
<br />Near Grand Canyon.................
<br />Below Hoover Dam ............... .................. ...................
<br />Below Davis Dam. ................. ..................
<br />Below Parker Dam .................
<br />Flow inro Mexico ........................... ........................................... .
<br />
<br />9,120
<br />7.895
<br />8,089
<br />6,543
<br />1,566
<br />
<br />The 1969-70 measured flows at the three
<br />upstream stations that account for approxi-
<br />mately 95 percent of the inflow to Lake Po-
<br />well are shown in Table 1. Regulated releases
<br />
<br />below Hoover Dam, which are limited to the
<br />amounts necessary to meet consumptive use
<br />requirements in the United States and the
<br />obligations to Mexico, are also shown in Ta-
<br />ble 1.
<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 often consecutive years. Since the be-
<br />ginning of storage in Lake Powell in 1963,
<br />the accumulation of storage in the Colorado
<br />River Storage Project reservoirs coupled
<br />with the generally low runoff has resulted in
<br />a total flow at Lee Ferry of only 57,317,000
<br />acre-feet as shown below:
<br />
<br />H'.lIlU }-'e.ar
<br />1962"';;3 .......
<br />1963-64 ......
<br />1964-65 ........
<br />1965"';;6 ..... .........................
<br />1966--67 ...........................
<br />1967...;;8 ........
<br />196~9
<br />19{fJ-70 ,......................
<br />
<br />Flow III
<br />Let: Fury
<br />(Acre--Fet:r)
<br />2,520,000
<br />2,427,000
<br />10.835,000
<br />7.870,000
<br />7.824,000
<br />8.358,000
<br />8,863.000
<br />8,620,000
<br />
<br />'l'otal ..................
<br />8.Year Average....
<br />
<br />57.317,000
<br />7.165,000
<br />
<br />During 1971 and 1972, the Secretary of the
<br />Interior will be required to release 17,683,000
<br />acre-feet at Lee Ferry, or an average of 8,841,-
<br />000 acre-feet a year, to meet the Colorado
<br />River Compact lll(d) obligation of 75,000,-
<br />000 acre-feet for the ten-year period 1963-72.
<br />Since water releases and losses during 1969
<br />-70 from the major Colorado River Basin
<br />reservoirs were less than inflow, the total
<br />surface storage in these reservoirs increased
<br />by 3,104,000 acre-feet during the year, as
<br />shown in Table 2. The previous year was also
<br />one of substantial surface storage gain, with
<br />an increase of 3,223,000 acre-feet, or a total of
<br />6,327,000 acre-feet increase for the two years.
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<br />11
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