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<br />
<br />WATER SUPPLY AND REQUIREMENTS
<br />
<br />Streamflow and Storage
<br />
<br />The staff continued its collection of basic data
<br />on watcr supply and use, estimates of unmeas-
<br />ured items and projcctions of all items affecting
<br />the water budget of Colorado River. Data in
<br />this section are reported for the water year from
<br />October 1, 1965, through September 30, 1966.
<br />
<br />The flow of Colorado River at Lee Ferrv dur-
<br />ing the water year was 7,8i3,000 acre-feei:. Ad-
<br />justed for changes in surface storage in the
<br />Colorado River Storage Project reservoirs, the
<br />quantity becomes 7,882,000 acre-feet. The Bu-
<br />reau of Reclamation estimates that if there had
<br />been no upstream man-made depletions the flo,,"
<br />at Lee Ferry would have been appro,imatel~"
<br />11,100,000 acre-feet. For comparison thc esti-
<br />mated annual average undepleted flow or virgin
<br />flow was 13,803,000 acre-feet during the 1922-
<br />66 period of record and 14,884,000 acre-feet
<br />during the 1896-1966 period. Plate 3 shows
<br />estimated annual virgin flows at Lee Ferr~' since
<br />1896.
<br />
<br />Climatological data early in the 1965-66
<br />water year gave indications of high runoff of
<br />the Colorado River. However, the prospect of
<br />having two successive years with above average
<br />flows was eliminated by an extremely dry spring
<br />in the major contributing areas of the basin.
<br />The Januar~' 1966 forecast of the Bureau of
<br />Reelamation predicted an April-July inflow to
<br />Lake Powell of 9,300,000 acre-feet, but suc-
<br />ceeding forecasts were drastically reduced, and
<br />
<br />Table 1
<br />
<br />U. S. BUREAU OF RECLAMATION FORECASTS OF
<br />APRIL-JULY RUNOFF INTO LAKE POWELL
<br />
<br />Mtan ForUOJ{'
<br />1966 ForUl1sti as of (aut-futl
<br />
<br />January 1_________ 9.300,CXX>
<br />Februarr L________ 7,900,000
<br />~-farch L __ _ 7,000,000
<br />April 1_ _ _ _ , _ _ _ _ 4,500,000
<br />M.,. L _ __ __ __ __ _ 3.500.000
<br />Jun' L___________ 3.900.000
<br />
<br />"1tall ForUf1-'1
<br />%of .-!tlt'ragd
<br />1906-/965
<br />109
<br />93
<br />82
<br />53
<br />{I
<br />46
<br />
<br />(;o of
<br />,4clual Runoff
<br />201
<br />171
<br />152
<br />97
<br />76
<br />8{
<br />
<br />. Assuming no regu!;l\lon by m~Jor reservoirs up~Heam.
<br />I U.S.B.R, est,m~le of ..'-era,o;e April-July hIstoric inAows to Lake Powell for lhe
<br />]Q06---1965 period i~ 805m.\))) ;tClc-feel.
<br />
<br />20
<br />
<br />the actual runoff during April-July 1966 was
<br />only 4,618,000 acre-feet.
<br />
<br />Table 1 summarizes the Bureau of Reclama-
<br />tion forecasts of the 1966 April-July inflow to
<br />Lake Powell.
<br />
<br />Measured flows at the three upstream stations
<br />which account for approximately 95 percent of
<br />the inflow to Lake Powell were all less than
<br />average. Regulated releases below Hoover Dam
<br />were below average as they were limited to the
<br />amoun ts necessary to meet consumptive use
<br />requirements in the United States and the
<br />obligations to Mexico.
<br />
<br />Flows at key points in the basin for water
<br />~'ear 1965-66 are shown in Table 1
<br />
<br />Table 2
<br />
<br />MEASURED flOW IN COlORADO RIVER
<br />BASIN FOR WATER YEAR 1965-66
<br />
<br />(Thousands 01 Acre.leet)
<br />
<br />Sla/ion
<br />
<br /> M~aJla(d FIO~L'
<br /> .1djuJud for Chang,
<br /> in Surfact Sloragr
<br />MraJurrd ,1dju.Jtrd 1,-=0 of
<br />Flo':{J Flo,:,. .1~,tragtt
<br />3,213 3.186 75
<br />3,{98 3,801 71
<br />1.9B 1,707 9;
<br /> -
<br />8,654 8,694
<br />7,873 7,882. 6(,
<br />8,324- 8,33). 69
<br />7.765 7.'-<,
<br />7.981 82
<br />6,5010 H
<br />1,720 {;
<br />
<br />Uppu BaJlII
<br />Green R. @ Green R. (Utah) _ _ __
<br />Colorado R. @ Cisco (Utah)_
<br />San Juan R. @ Hluff (Utah)_____
<br />
<br />Subt.-,tal__
<br />
<br />La Fary_
<br />
<br />LO~L'U Basin
<br />
<br />:\ear Grand Canyun _ __
<br />Uclaw Hoo\'er Damu______
<br />Rela..... Davis Dam_ ____nuu__
<br />Below Parker Dam_, ___
<br />Flow into f\lexicon__ _ _ __ _ _ __
<br />
<br />. It i. rSlimated In3t about 846,()JO acre-fen "'as absorbed in Lake Powell banI.:
<br />storage dUILn!,: lhe ....ater )'car 1965-66.
<br />t Thcaveragc$ for Ihc5Ulllons upuream from Hoo'cr Dam rcprc;cnt the 1922-66
<br />period which i! the length 01 record at Let' Ferrl'. Th.. avcrage,; lor Hoo"cr Dam
<br />and dowllslro:am stalions represer'lt the 1950-65 period which j~ the length 01
<br />r~cord Oil DOl";! DJIll.
<br />
<br />\Vater releases and losses almost balanced in-
<br />flow with the result that the surface storage in
<br />the Colorado River Basin increased slightlr dur-
<br />ing the 1965-M year as shown in Table 3.
<br />
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