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<br />1 71 ~'RYINGPAN-ARKANSAS PROJECT, COLORADO <br /> <br />7 <br /> <br />create a risk in meeting the Lee FelTY obligation of the Colorado <br />River compact. <br />18. Irrigation.-The main agricultural part of the eastern slope <br />projcet area is in the semiarid zone of 11 to 16 inches of nnnuu] pre- <br />eipitlltion. Seventy to eight,--six percent flllls during the April to <br />Octoher growing senson. Dry farming is and probahly will c-0ntinue <br />to ue pmcticetl extensively. Livestock grazing on the ranges and in <br />the forests is also an extensive enterprise. However, both t.ypes of <br />ngrjeultllrc require large land arens. nnd dr,v farming particularly <br />depends upon l.he vagaries of the wenther. General cultivated agri- <br />culture und specinlty high-y"nlue crops, mnny of ,'.'hich fire required to <br />stabilize tile Ilgl'iculturnl eCOn0l11Y of t.he area, require more water <br />than t..',"pienl dl'ylnnd crops. Irrigat.ion is t,he only means of providing <br />a nopen""hle supply. <br />19. Earl.\T irJ'ignt.ion in t.he Arkallsas Vlllie.v coincided wit.h antilable <br />st.rcnm rUll-off. As read~7 mal'k<,t.s developed: iJ'l'ignt.ion farming Wfi.S <br />expanded find tt cleInllUd dc-\'elopell for ltttc SC'llson \\-'at.er which could <br />not be supplie(\ 'lDY ulll'cgulat,ed strellmflow. Consequent1)'. between <br />1890 and 1910, three reservoirs ill t,he headwaters area and 11 off- <br />st,ream rl-'sen'oirs below Pueblo were constructed. In 1949 the .John <br />ivlartin Reservoir on t.he Arkansas River was completed by t,he Corps <br />of Engineers for conservation st.orngc l1ud flood c-ont.rol. [t nlso has <br />an il'rigut.ion storage space of 420,000 acre-feet.. The three headwaters <br />reservoirs han~ a capaeity of 84,400 acre-feet. The 11 off-st.reltffi <br />reservoirs hun' [t present 'eapacit.y of 300,000 aere-fcet. which repre- <br />sents about 7.) percellt of the originnl capacit,.v ns a consequence of <br />sediment.ation. Eight privat.ely owned tmnsmountain diversion sys- <br />tems import about, 48,000 acre-feet 1lI11lually. <br />20. More than 40 cnnols anel ditches suppl.,- in'iglltion water t.o lands <br />in t.he valley hdween Canon Cit.v find the Colorado-Kansas boundnrv. <br />Sediment, deposit.ion in canals ancl ditches has become a major irrigation <br />problem in t.he Pueblo-Las Animns rCilch. In some inst.ances long <br />rescr\Toir feeder canals have lost !i0 perecnt of their eapllcity because <br />of sedimentat.ion. <br />21. The illUOllnt of irrigntion water available for t.he 322,000 acres <br />of irrigat.ed land in the project. area varies considerably from year to <br />yenr. Seldom is the supply adequate for maximum crop production. <br />Irrigo.tion water shortages as high us 78 percent of crop requirements <br />have occurred. The cst.imltted avel'o.ge cUllnl hcndgate di\.r('["sioll re- <br />quirement. is 3.19 acre-feet an Itcre. Allowing for t.olerable shortages, <br />that. hendgat.e requirement enn be rcduce,d to ;~.IO acre-feet.. The <br />avernge amount of seasonal irrignt.ion water hist.orically avuilable <br />between Pw-:blo and the Kansas State line has ranged fro'm 0.9 acrc- <br />feet an tlere III 1934 t.o 2.7 acre-feet. in 1942. The base flo\\' of every <br />'tr~aIn in the valley is o\"('rapprc~pril1ted. . Enhnncement of the irri- <br />gatIOn wat.er supply depends updh regulatIon of existinD' supplies for <br />more. efficient lI~e, lI..dditional stomge cnpllcit.y for t.he.o consernltion <br />of excess ftooll flows, resenroir space for hol{lover st.orage, and neW <br />\\:nter .sllpplies WI' which the o.nly upp.ar-ent. source is trt1nSmountllin <br />(hVel'SIOIl from In~ Colorado RIyer tim.mage. <br />, 22. POIcer.-Powe.r fll~ilities of t.he illitialdevelopmellt, will he de- <br />SIgned for IntegrutlUIl wHh the power fnellIt.lCs of the Bureau's Colo- <br />rado-Big fhompson project. and with local utilities t.o serve a com- <br />bined pown market area. The combi.rlell urCll, which consist,s of t.he <br />