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<br />A, 3,145
<br /> 2 POINTS FROM ANALYSIS OF 35
<br /> 3,140 1914 PHOTOGRAPHS B
<br /> )1 ::: EST-FIT LI EAR REG ESSION
<br /> :: ::;, /
<br />f-- ' , , 30
<br /> . . '.' (f)
<br />w 3,135 . , '.'
<br />~ --1
<br />W )>
<br />LL :: :, --- ~:
<br />;;;: " --. @~ 25 Gl
<br />3,130 m
<br />-.i ' 83' )>
<br />w . : : 20 --1
<br />> 3,125 r
<br />w . m
<br />-' l: m
<br /><( 15 (f)
<br />w 3,120 "
<br />(f) m
<br />w W JJ
<br /> > 10 JJ
<br />> 3,115 0 -<
<br />0 0
<br />ro : W -' I Gl
<br /><( :<9 0: 00 5 )>
<br />z 3,110 '0: W W 0: Gl
<br />:<9 -' >: '"
<br />0 ,<9 W 0
<br />~ :" '0: <9 z -' 0
<br />3,105 :0: w<9 0:0: 0: 0: Z
<br />: W <9>- ..J' W<9 I 0: "
<br /> , CO 0:0: -' >:LL W 0
<br />W W:;, <90: WI OLL X W m
<br />-' ~:o 0: I -5 m
<br />w 3,100 ~w 00 -'0: ~ --1
<br /><9", o:LL >-z c-
<br /> oo
<br /> w: Woo -'0: 0
<br /> -', COw ~o: -10
<br /> 3,095 co: :;'W 0
<br /> 0:: :0-' -'
<br /> ~: z
<br /> 3,090 -15
<br /> -1,0 -0,5 0.0 0.5 1,0 1,5 2,0 2.5 3.0
<br /> STREAMWISE DISTANCE FROM LEES FERRY GAGE, IN MILES
<br /> EXPLANATION
<br /> WATER-SURFACE PROFILES
<br /> __ AT 5,000 CUBIC FEET PER SECOND
<br /> -0-- AT 60,000 CUBIC FEET PER SECOND
<br /> ____ AT 90,000 CUBIC FEET PER SECOND
<br /> ---0--- AT 120,000 CUBIC FEET PER SECOND
<br /> -0- AT PEAK OF 1921 FLOOD
<br />
<br />
<br />. WATER-SURFACE ELEVATION AT PEAK OF 1884 FLOOD
<br />83 TERRACE ELEVATIONS DOWNSTREAM FROM LOWER STAFF GAGE
<br />. ELEVATIONS OF "Gl" DEPOSIT
<br />
<br />Figure 4. Flattening water-surface profiles with increasing stage and the reversal in curvature of the 8tag8-
<br />discharge rating curve. (A) Water-surface profiles in the Lees Forry reach at 5,000 cubic feel per second, 60,000,
<br />90,000, 120,000 cubic feet por socond, and during the peak olthe 1921 flood, Shown are locations olthe gages
<br />and tho Lonely Dell Ranch where stages were measured. Stag8s at the Cable and Number 4 Gages during the
<br />1 921 flood were determined by analysis olthe September-October 1921 and May 1924 photographs in
<br />Appendix B, Points between the gages on the 5,000 cubic feet per second profile were obtained from 1 :2.400
<br />scale topographic maps (Bureau of Reclamation, 1990). Elevations of terraces capped by the G1 deposit of
<br />O'Connor and others (1994) in the reach below the Lower Staff Gage were determined using airborne L10AR
<br />datd collected by the Grand Canyon Monitoring and Research Centor in Marcil 2000.
<br />
<br />The reversal in the curvature of the stage-discharge
<br />rating curve was tirst recognized by the USGS in 1923,
<br />but was not accounted for in estimatcs of peak nows until
<br />1927, Becansc the USGS did not account for this reversal
<br />in curvature, slightly morc water was computcd passing
<br />the Lccs Ferry Gage during high-discharge months than
<br />was computed passing the Grand Canyon gaging station
<br />prior to 1927. This problem motivated IS. Gatewood and
<br />
<br />l
<br />I
<br />1
<br />I
<br />
<br />H,S. Hunter in 1938 (in an unpublished USGS report) to
<br />recompute thc dischargcs during watcr years 1921
<br />through 1926 by titting a mean stage-dischargc rating
<br />curve to thc data from this period. They thcn used the now
<br />standard shitting-control method (Kenncdy, 1984, p. 25)
<br />to bring their dischargcs computcd on thc basis of this
<br />mcan curve into beller agreement with the measured
<br />discharges, The shi fting-control mcthod had not been
<br />
<br />12 Computation and Analysis of the Instantaneolls~Discharge Record for the Colorado River at Lees Ferry, Arizona-May 8, 1921, through September 3D, 2000
<br />
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