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<br /> <br />DRAINAGE <br /> <br />Although r/:.'CogniU!d from the beginning that drainage facilities of <br />some kind would eventually be requirt-d, the determination was made <br />at the beginning of construction of the irrigation system that the drain- <br />agt- works should be delayed until there was an actual need, since tht' <br />water table at the time was still depressoo from the previous period <br />of irrigation by means of pumping from wells. The rate of rise of the <br />ground water was so much faster than anticipated, primarily because <br />of the application of largt' quantitit's of It'.aching water to reclaim land, <br />that the schedule for construction of drainage facilities did not prevent <br />some areas from becoming waterlogged and again going out of produc- <br />lion. <br /> <br />The Gila River in Wellton-Mohawk is underlain with immense <br />deposiLR of gra\'el. This sen.'es as an undt'rground rt:'f'.t'rvoir which collects <br />percolatt'd irrigation water and allows it to be pumpt'd thereby keeping <br />the groundwater, for the mOMt part, bt>low the root lOne of the crops. <br />Thi~ i!'lone of the- few irrigation districts in the world that can effectively <br />and economically drain itst>lfby pumpinl{. <br /> <br />A very important factor in the U!lt' of water in thf" Colorado River <br />basin is the prffience of Ralt. Not like sea water, which has a MIt content <br />of 33,000 parts per million; but in leAAer, yet highly damaging, conct"ntra_ <br />tion. The !'.SIL.., there are many varit-tit'1l, come from the natural soil <br />and rock, and wash into a stream with t'ach rain or snowmelt. The <br />Colorado River at Glenwood Springs, Colorado has a concentration of <br />approximatE-ly 25() ppm. By the time the river reaches Lake Mead behind <br />Hoover Dam, it i.. 700 ppm. At the present time, this i.. about 50% <br />natural and ahout 50'l man-madt' by irrigation return nows. Any irriga- <br />tion district must have drainagt' to get rid of excl'fl,.~ water that would <br />waterlog the land and also to get rid of the salts if tht're are- any. Salts <br />are- injurious to crops, to SOffit' crops more than othe-rs of course. Salt <br />ca.n he ta.'lted in drinking WaIN of I5l.Kl ppm. <br /> <br />A concrete-lint'd channel Wll~ ronslructoo. into which the- existing <br />drainage pumJl1l, formerly irriJi:ation pumps, and additional new drainage <br />pumr~; could di.'l<'"harge- their now~. The t'nd of tht' We-lIton-Mohawk's <br />main drainage- conveyanl'e- channe-l was just downstream from Ihe- Gila <br />RivN Siphon of the Gila Gravil.... Main Canal Tht' drainage watN was <br />allowoo 10 00..... into Ihl' okl channe-l of the Gila Hiver and the-nre into <br />the Colorado. Tht' first ",rout'nt came out of this channt'l on February <br />10,19*11 and IUPiit llo'en'lhe rept'fl'us...ions Iht'rf'Of. <br /> <br />The salinity of the Colorado river inneast'll below tht' mouth of <br />the Gila such that the Arizona Watt'r Company, which provlded domes_ <br />tic and industrial walt'r for Yuma. had to ehanj::t' its source from the <br />river to tht. Yum;l ~tain Canal which came from tht' AII-Amt'rican Canal <br /> <br /> <br />13 <br />