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<br />2312 <br /> <br />\later Supply <br /> <br />.. <br /> <br />At the Narrows site, the lower of the two alternatives, the average <br />annual r\Uloff 'Qll be somellhat ereater. On the basis of preliminary <br />data the annual r\Uloff will range from 0 to 60,000 acre-feet greater <br />at the Narrows site. The average annual difference for the 1942-58 <br />:period was approximately 24,000 acre-feet. This sectional gain can <br />be attributed to nat\U"al s\U"face and subs\U"face return flows which <br />are not rediverted within the intervening reach of the river. <br /> <br />There are approximately 60,000 irrigated acres physically located <br />between the two sites. Construction of the upJ?t!r site would permit <br />direct deli very of supplemental ;rater to most of these lands, <br /> <br />Flood Control <br /> <br />The follwing flood peaks and volumes have been used for tentative <br />studies of the two sites: <br /> <br />Table 1 <br /> <br />Desip;n Floods <br /> <br />'. <br /> <br />Item <br /> <br />Narrows Site <br /> <br />Weld County <br />Site <br /> <br />r~ " <br /> <br />Drainage area in sq. miles <br />Inflo;r design flood pealt in cfs <br />Inflow design flood volume in ac.-ft. <br /> <br />14,900 <br />301,000 <br />1,321,000 <br /> <br />11,400 <br />437,700 <br />1,363,000 <br /> <br />The 1nflmT design flood :peak and volUD1e are greater at the upper <br />site because of channel losses occurring between the two sites, <br />The Kiowa and Lost Creek tributaries would remain uncontrolled by <br />construction at the upper site. <br /> <br />Sediment Control <br /> <br />A comparison of the tentative sediment inflow to the two sites is <br />shown belo'T: <br /> <br />Table 2 -- Sediment Deposition <br /> <br />Item <br /> <br />Narrows Site <br /> <br />Weld County <br />Site <br /> <br />Unit weight of sediment (lbs. per cu. ft.) <br />Possible loo-year sediL~nt deposition <br />(ac.-ft) <br /> <br />70 <br />176,00OY <br /> <br />70 <br />60 ,000 <br /> <br />y Includes 90,000 acre-feet from Bijou Creel(. <br /> <br />4 <br />