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<br />In <br />-4 <br />'i..'J <br />..-4 <br /> <br />ONFARM PROGRAM FOR SALINITY CONTROL <br />GRAND VALLEY SALINITY STUDY <br /> <br />,.-', <br />........ <br /> <br />elevation will recede by an undetermined amount. Experience has shown that <br /> <br />ditch lining has caused local watertab1e elevations to drop as much as four <br /> <br />feet. Also, it has been reasoned that the effect of new subsurface drains <br /> <br />would be counter to the objective .of salinity contrel by providing an outlet <br /> <br />to the river for salt-laden ground water. <br /> <br />Fourth, drip and sprinkler methods of irrigation, where adaptable, have <br /> <br />proven to be more efficient than furrow and border irrigation. However, <br /> <br />these methods have not yet enjoyed wide acceptance nor are they suitable on <br /> <br />all soils in the valley. Demonstration type projects will be needed to <br /> <br />enhance their use. Once installed they can increase irrigation efficiency <br /> <br />by 15 to 35 percent, with a similar magnitude of reduction in the salt load <br /> <br />pickup. <br /> <br />Fifth, irrigation water must be delivered te each farm at the locatien, <br /> <br />elevation, flow rate, or pressure needed for proper operation of the <br /> <br />improved onfarm syste~ Therefore, a segment of the off-farm lateral must <br /> <br />be designed and built as an integral part of the onfarm improvement program <br /> <br />to assure accrual of onfarm benefits. Improvements in the lateral system to <br /> <br />be implemented through ongeing USDA programs will be carried to the point <br /> <br />needed to assure proper operation of the en farm improvements. Cost share <br /> <br />assistance will not be provided for laterals under the Government Highline <br /> <br />Revised November 1979 <br /> <br />59 <br />