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<br />-. <br /> <br />1930 <br /> <br />(Existing sedimentation problem) <br /> <br />-~- -- <br />----_...- <br /> <br />--~- <br />------- <br /> <br />--------- <br />-. -- <br /> <br />. <br /> <br />-. <br /> <br />impairedo"and-irrigation-systems-cannot-Oe operated-efficiently;--Pro- <br />ductive bottomlands are damaged or destroyed by deposits of infertile <br />sand and sediment. Bank cutting and caving destroys valuable land and <br />adds to the sediment load. Turbid flows adversely affect the quality <br />of municipal and industrial water supplies and damage supplY systems. <br />Aggradation of stream beds creates flood hazards and high-water tables. <br /> <br />Varied and extensive corrective ,and preventive measures will be <br />required to correct the sediment and erosion problems. The most effec- <br />tive solutions, most of which are contained in the project plan, are <br />provision of sediment capacity in multiple-purpose reservoirs, con- <br />trolled and efficient land use and grazing practices, and more wide- <br />spread and improved soil conservation and land treatment programs. <br /> <br />Although in the past a large percentage of the sediment entering <br />the John Martin Reservoir has been carried on through the reservoir, <br />after the dam is completed in 1948 and the reservoir is operated to <br />the fullest extent possible for irrigation, most of the sediment <br />~J~,e..!lhingthat~poin:t;in~the ,ri:v.e,,,,,wil! ..be. ,rata!n~d..by . tQe~re.ser.v:oir.=-..: c._, <br />~ ,~Therefciret=aimosEai'i~ of~the~s edlment~pas s,j.,i)g:the po,ten{f!\l~dems~He e. <br />~""':1n,:-fhe~:GUnnf'sonoiArJ(arisas"ProJect'. area. must~even.t'uaJ.:ly":b'e=d:ep6s1'ted ,- ' <br />'--'either=iIl~'-t he'-Johr;='MiU'i;'i'n~R~'se;V'oif-oi-'C1ip~;; ~Jl).e':'J)..i1. gat'8d=lJl1ld~in- _ ' <br />u.-=-ex1:e}1ng:1:rtigi'ti on-:-l:ateHili~,i:_.~..ane:is';~:Qr-=-,-allei--,te!'~I:Y.oJ'rs~-- 'The_s_a=-, · .;" ~-~ =. <br />- '~irrigatfon=-ca~ills ,~ci-res::eJ-'yo.!-r.s-.ariHjhown on exh,i bit 3..,c...:-Based-:.on-n, , ' <br />sediment studi.es made by the Soil Conservation Service, the <br />Atchison, Topeks, and Santa Fe Railway Company, The Fort Lyon Canal <br />Company, and the Bureau of Reclamation, an estimate has been made of <br />the average annual proportion of sediment which has been deposited <br />at each of these destinations. By applying these proportions to the <br />sediment passing the potential damsites. as determined at the sediment <br />sampling stations, it is pOSSible to find the reduction in sediment <br />deposition on irrigated land and in existing irrigation canale, <br />laterals, and reservoirs Which would result from construction of po- <br />tential reservoirs in the Gunnison..Arkansas Project. The average <br />annual benefit resulting from retaining the sediment in the potential <br />reservoirs, is therefore, the sum of the anr.usI damage from lost <br />reservoir storage space due to sedimentation and the annual cost of <br />removing sediment from canals and laterals. <br /> <br />EXISTIl~G SEDIMENTA'!'ION ABOVE JOHN M.ARTIN rolSERVOIR <br /> <br />Irri2"-ted llUld <br /> <br />An average of approximately 300,000 acres of land have been irri- <br />gated during the past 60 years on the Eastern Slope above John Martin <br />Reservoir. It is estimated that this land has raised an average of 1 <br />__ ___~oot, ~in~e irrig_a~.!o!l_begfUl, due to the depositi.~~ of sediment fr.om <br /> <br />6 <br />