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<br />structure six miles upstream, for the purpose of reducing peak discharges
<br />entering the flood"ay. lIydraulic studies of the existing "orks, including
<br />the detention dam, indicate that the flood"ay capacity of 110,000 c.f.s.
<br />is equivalent to a flood of 1.4 times the flood of record. This high.
<br />degree of protection afforded by the large capacity of the existing
<br />f1ood"ay made it unnecessary to store the total volume of the standard
<br />project flood at Pueblo Reservoir.
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<br />40. The June 1921 flood produced a peak of R7,OOO c,f.s. and a
<br />volume of 93,000 acre-fe~t at Pueblo damsite. The volume is equal to
<br />.38 inch of runoff from the 4,670 square miles of drainage area. This
<br />flood "as selected as the basis of design for the flood control storage
<br />at Pueblo Reservoir, The voltune of the flood has a recurrence interval
<br />of about 100 years. _ Flood control storage in Pueblo Reservoir equal
<br />to the volume of the design flood in conjunction "ith the existing
<br />Pueblo F100d"ay "ould provide the city of Pueblo protection against
<br />Arkansas River floods exceeding standard project magnitude.) An opera-
<br />tion hydrograph of the design flood is shmm on plate 4, In addition
<br />to the summer requirement of 93,nOll acre-feet of flood control storage,
<br />there will be a winter requirement of 27,000 acre-feet of flood control
<br />stor,,!,:" that IIill be held inviol:1te for possible ,,:inter floods. The
<br />27,nOll acre-feet of winter storage ,",'as derived from the June 1921 storm.
<br />This corr.putetl "mount of storage ,,'ould have bcen necessary if the storm
<br />had occurred in late March or early April. The total flood rlmoff was
<br />stored without releases during the period of inflm;. The flood control
<br />storage will not be depleted hy sediment during the life of the project.
<br />As._scdiment-accumulates in the reservoir~~ adjustments "ill be made in
<br />the storage allocated to the conservation p_o()j. That "ill assure the
<br />93,000 a~c~re~feet~of {1'ood~ccintrol storage for the life of the project.
<br />Pertinent design data for Pueblo Reservoir are shOlm in table 3.
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<br />_ JAB~E_l, _ -_-_ ~lOF!!.n~_t_ ~e~~g.!l_ Data, Pue!:>~o_ ~~_ and_ Re~e!voir __ _ _ _ _ _ _ _
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<br /> Capad ty_
<br /> Pool Elevation (Acre- (Inches of
<br /> (feet above m,s.l.) feet) runoff)
<br />Top flood control pool 4,898.74 357,000 1.43
<br />Top of "inter joint use pool 4,893.65 '329,000 I. 32
<br />Top conservation pool 4,880,6 264,000 1.06
<br />Top inactive pool 4 , 796 . 7 30,000 0.12
<br />Flood control storage 4,880.6-4,R98.74 93,000 0.38
<br />Conservation storage 4,880.6 234,000 0.94
<br />Inactive storage 4,728.4 -4,796.7 30,000 0.12
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<br />Note. rhe 100-year sedllnent productIon of 103,100 acre-feet ",ll
<br />be deducted from the 234,000 acre-feet conservation pool as it accrues.
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