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<br /> <br />~~ <br />~R$' "" '\ <br />WATER , \ <br />CONTAINS . \ <br />SALT : <br /> <br />Soils <br /> <br />In the Imperial Valley, irrigated <br />farmlands flourish on layers of soil <br />deposited over centuries by the Colo- . <br />rado River. The soils are formed in two <br />principle landscapes. One landscape is <br />the lower Colorado River flood plain <br />and the drY lake basin of old Lake <br />.; <br />Cahuilla. The other landscape is the <br />nearly level to gently sloping plain of <br />the Imperial East and \Vest tvlesas <br />which lie above the beachline of the <br />old lake. <br />There is no "top soil" in the <br />usual sense. The Valley is a large bowl <br />filled with a conglomerate of elements <br />transported by Colorado River flood <br />waters. The soils are up to a full mile <br />or more deep. Beneath the soil surface <br />is a maze of passages of aquifers and <br />aquicludes of clay barriers and sand <br />lenses. In general, there is no gravel <br />and sand water-bearing stratum. <br />StratUm of anyone type of soil does <br />not extend oyer a large area, but occurs <br />more as a lens or pocket. <br />Imperial Valley soil is naturally <br />salty. As river floods left alluvial soils, <br />they also left salt. Saline soils are often <br />recognized by a white crust on the <br />surface. <br /> <br />~ <br /> <br />"Water <br /> <br />The Colorado River is highly <br />saline and carries about one ton of salt <br />per acre-foot of water applied to fields, <br />posing problems for growers. Imperial <br />Valley farmers battle salinity by leach- <br />ing salts through the root zone into <br />subsurface tile drainage systems. This <br />saline water is then carried through the <br />District's drainage canals into the <br />Salton Sea. Adequate drainage in the <br />Imperial Valley makes the difference <br />behveen barren land and highly pro- <br />ductive soil. To date, there are 32,227 <br />miles of tile drains and 1,457 miles of <br />drainage ditches in the Imperial Val- <br />ley. <br /> <br />.. <br /> <br />EVAPORAnON AND <br />TRANSPIRAnON <br />REMOVE WATER AND <br />LEAVE SALTS BEHIND <br />-4 <br /> <br />; <br />\ <br />\ <br />\ <br />\ <br /> <br />11 <br />, <br /> <br />11 <br />, <br />, <br />, <br />, <br />, <br />/ 11 <br />, / <br />, / <br />/ <br />/ <br />/ <br />/ <br /> <br /> <br />SUBSURFACE DRAINS REMOVE SALINE WATER. LOWER WATER TABLE. AVERAGE <br />DEPTH EIGHT FEET. WITHOUT DRAINS SALT CONTINUES TO ACCUMULATE. <br /> <br />DRAINS EMPTY INTO A COLLECTOR SYSTEM WHICH TRANSPORTS <br />THE DRAINAGE WATER TO A DISCHARGE POINT. <br /> <br />LEGEND <br />I. '.0 I 'Ne'CATES <br />II .' . . I SALTS <br />_ _ _ _~ ~~:~~ "lC.., <br />