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<br />- <br /> <br />Projec.\:, I.J3.nd.o <br /> <br />Irrigable lands having moderately saline soils make up alJout <br />30 percent of the total irrigable area.. They occur mainly in ",he <br />bottomlands, but small tracts are located also on the high terrace <br />and the upland positions. The soluble salts, concentrated within <br />the 0.02 to 0.05 percent range, are confined to the subsoils. This <br />condition, although prohibiting the attainment of maximum yields, <br />will not limit productivity below the class 2 ra.nge. These <br />moderately saline soils in nearly all instances are associated with <br />restricted subsurface drainage which results in temporary high water <br />tables. In many areas the subsurface drainage is restricted by <br />fine-textured soils ~nd substrata, while others are affected by <br />excessive amounts of water from caQals and farm losses. <br /> <br />Since the moderately saline soils have been irrigated for <br />many years, a balance has apparently been reached between the <br />accwuulated salts and the water supply. With the project in operation, <br />this balance is expected to be ~intained. Therefore, under the same <br />drainage conditions productivity within the class 2 range can be <br />obtained under sustained irrigation, <br /> <br />Some of the nonirrigable lands have saline or saline-alkaline <br />soils. The salinization and alkalization process has advanced to <br />the point that in tbe worst areaS no vegetation exists and in other <br />areas plant growth is limited to highly salt tolerant species. The <br />lands classed as nonirrigable because of saline or saline-alkaline <br />soils are located primarily in the southeastern part of the Model <br />tract. However, small isolated areas occur in other parts of the <br />service area, ,Inade~uate drainage is responsible for the <br />salinization and alkalization of the soils. <br /> <br />DRAINAGE <br /> <br />The land classification survey included studies of the drainage <br />conditions in the service area, These studies assisted in evaluating <br />the irrigability of the lands, and they also furnished information <br />as to the ade~uacy of drainage under existing conditions. <br /> <br />Surface Drainage <br /> <br />Surface waters to be disposed of will originate mainly from <br />storm and irri~tion runoff from within the service area. In <br /> <br /> <br />31 <br /> <br />.".. <br /> <br /> <br /> <br />'. <br /> <br />-"". <br /> <br />?-'. <br /> <br />- <br />