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<br />
<br />RIVER OPERA liON
<br />
<br />Wllter Supply
<br />
<br />During the 1971-72 water year (October I
<br />through September 30), 9,149,000 acre-feet
<br />flowed past Lee Ferry, the Colorado River
<br />Compact point. If reservoir storage condi-
<br />tions in the Upper Basin had remained un-
<br />changed throughout the year, flow at Lee
<br />Ferry would have equaled 8,639,000 acre-feet.
<br />The Bureau of Reclamation estimates that if
<br />there had been no man-made depletions up-
<br />stream, the virgin flow of the Colorado River
<br />at Lee Ferry would have been about 11,905,-
<br />000 acre-feet, Plate 3 shows the estimated an-
<br />nual virgin flows at Lee Ferry since 1896.
<br />The 1971-72 water year was the tenth year
<br />since the closing of Glen Canyon Dam. In
<br />those ten years, 75,094,000 acre-feet passed
<br />Lee Ferry. Thus, the obligation of Article
<br />I1l(d) of the Colorado River Compact, i,e.,
<br />that the states ofthe Upper Division shall not
<br />cause the flow of the Colorado River at Lee
<br />Ferry to be depleted below an aggregate of
<br />75,000,000 acre-feet for any period of ten con-
<br />secutive years, was barely met. A year by
<br />year breakdown follows:
<br />
<br />Water Year
<br />
<br />1962-63 ...................... ................
<br />1963-64 ,.,., .......................
<br />1964-<i5 ................., .........................................
<br />1965-66 ..' ................. ....................
<br />1966-<\7 .., , ...............,
<br />1967-<>8 .
<br />1968-69 ,
<br />1969-70 '
<br />1970-71 .................
<br />1971-72
<br />
<br />Total.....
<br />lO-year a...erage......
<br />
<br />now at
<br />~ Ferry
<br />(8crt'.-f~()
<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 />9,149,000
<br />
<br />75,094.000
<br />7,509,000
<br />
<br />Operating statistics of the river for the wa-
<br />ter year 1971-72 are presented in Tables I
<br />through 6. These follow with accompanying
<br />discussions,
<br />
<br />Table 1
<br />MEASURED flOW IN COlOR:'\DO RIVER AND
<br />TRIBUTARIES FOR WATER YEAR 1971-72
<br />(Thousands of Acre-Feet)
<br />
<br />StariOl1
<br />
<br />Uppcr Basin
<br />
<br />Green R. at Green River, Utah
<br />Colorado R. near Cisco, Utah ..
<br />San Juan R. neac Bluff, Ut1.n...
<br />Colorado R. at Lee Ferry....
<br />
<br />Lower Basin-C%rado Riw..r
<br />Near Grand Canyon
<br />Belov.' Davis Dam..
<br />Below Puker Darn
<br />Flow into Mexico ....
<br />
<br />/r.4e8sured Flow
<br />3.911
<br />3,501
<br />9%1
<br />9,149
<br />
<br />.................. 9,486
<br />................, 8.455
<br />6,945
<br />...................... 1,317-
<br />
<br />. Flow into Mexico at Northerly International Boundary. In addi-
<br />tion, 283,000 af was delivered at the Southerly International
<br />Boundary and 1,000 af of Colorado River water was delivered
<br />through facilities in the United States to Tijuana.
<br />
<br />Table I shows the measured flow at key
<br />stations. The first three stations listed in Ta-
<br />ble 1 represent over 90 percent of the flow
<br />into Lake Powell. As has been the case for a
<br />number of years, flows below Davis Dam
<br />were limited to meeting the consumptive use
<br />requirements of United States and the Mexi-
<br />can Water Treaty delivery requirements.
<br />Table 2 shows changes in storage for the
<br />basin reservoirs in water year 1971-72. Over-
<br />aI!, the total storage decreased by 171,000
<br />acre-feet during the year. The water with-
<br />drawn from storage was necessary to meet
<br />current demands in excess of the runoff for
<br />the year, which was approximately 2,9 mil-
<br />lion acre-feet below the long-term average.
<br />
<br />11
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