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<br />. <br /> <br />primarily for the purpose of water mana.gement to provide the moisture <br /> <br />. <br /> <br />environment for optimum crop prodliction and to control the salinity <br /> <br />1./::0. <br />o <br />c..n <br />o <br /> <br />level in the soil to insure its perpetual use for agriculture.. The tech- <br /> <br />nologies were not specifically developed or designed as pollution or <br /> <br />. <br /> <br />salinity control measures applicable under the provisions of PL 92-500. <br /> <br />However, depending on the particular circumstances, they may be use- <br /> <br />ful, and in that sense could be the best available technology at the pre- <br /> <br />. <br /> <br />sent time. These technologies fall into the broad categories of water <br /> <br />application (irrigation methods), wa.ter removal (drainage methods), <br /> <br />. <br /> <br />soil salinity control (leaching), and. erosion control. Rather than re- <br /> <br />turn flow salinity control, the basic purposes behind the development <br /> <br />of these technologies have been the efficient utilization of the water <br /> <br />. <br /> <br />resource, maintaining and ,improvi~g the soil resource, and preventing <br /> <br />erosion, salinization and water-logging of the soil. The following is a <br /> <br />. <br /> <br />brief summary of the various aapects of irrigation technology. <br /> <br />Water Delivery Technology. The design of canals for the efficient <br /> <br />delivery of water to the irrigated lands has long been a subject of en- <br /> <br />. <br /> <br />gineering concern, the delivery efficiency usually being considered as <br /> <br />the ratio of the water delivered to the water diverted. Efforts to in- <br /> <br />crease the amount of water delivered have resulted in the development <br /> <br />. <br /> <br />of large numbers of canal lining materials including concrete, masonry, <br /> <br />wood, stell, membranes of rubber, and platic, and improved earth <br /> <br />. <br /> <br />linings, along with pipelines, flumes, ,and control structures to prevent <br /> <br />seepage and other losses from the system. <br /> <br />l4 <br /> <br />. <br />