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<br />Grand Valley <br /> <br />,.... <br />Ul <br />o <br />W' <br /> <br />The Grand Valley Unit is located in west-central Colorado along the Colorado <br />River near Grand Junction. The unit was authorized for construction by the <br />Colorado River Basin Salinity Control Act of 1974 (Public Law 93-320). Public <br />Law 98-569, enacted in 1984, amended <br />Title II provisions of that act and <br />authorized the USDA salinity control' <br />program. <br /> <br />The purpose of the Grand Valley Unit <br />is to reduce the estimated 580,000 <br />tons per year of salt added to the <br />Colorado River from the valley as a <br />result of conveyance system seepage <br />and agricultural practices. <br /> <br />Cobado RIvw . <br /> <br />-- <br />'....... <br /> <br />Studies indicate that salt loading to <br />the Colorado River in the Grand <br />Valley occurs when conveyance system <br />seepage and irrigation return flows <br />pass through highly saline soils and' <br />the underlying Mancos Shale <br />Formation. By reducing the amount of <br />ground water percolating through <br />these saline soils, salt loading to <br />the Colorado River would be reduced. <br /> <br /> <br />FIgure 3Schematic of Grand Valley. <br /> <br />Reclamation' is conducting a conveyance systems improvement program as a <br />cost-effective method of reducing off-farm eeepage and salt loading. Qnfarm <br />improvements, including upgrading irrigation systems through cost assistance <br />and improving irrigation management to reduce deep percolation from farm <br />operations, are being implemented by USDA. <br /> <br />Land Retirement <br /> <br />Inefficient irrigation causes problems with salinity when the excess water <br />returns to the river through saline geologic formations. Land retirement <br />could be intergrated into project plans. In the past, land retirement has <br />been eliminated as an alternative due to its relatively poor cost . <br />effectiveness and adverse local impacts. However, if incorporated into a <br />total management plan, land retirement might become an'acceptable component to <br />a project. <br /> <br />Based on overall cost effectiveness, land retirement was not found to be very <br />competitive with water conservation programs. State.and Federal costs were <br />comparable with other alternatives, but local economic and wildlife impacts <br />would be very high, driving the cost effectiveness well over $200 per ton. <br /> <br />Beyond its cost, a serious problem to be overcome with land retirement is that <br />it will not be effective at controlling salinity if the 'saved" water ie used <br />by other farmers (new or existing). Under existing water law, "saved" water <br />returns to the appropriation system and will be used. Water-short water users <br />are likely to take advantage of the "saved" water, reducing or eliminating the <br />effectiveness of the program. <br /> <br />Irrigation also supports an unusual variety of wildlife habitat in areas that are normally extremely dry, <br />making them extremely valuable for wildlife. The acreages can be substantial. For example, about <br />20,000 acres of wildlife habitat is supported by 60,000 acres of irrigation in the Grand Valley. <br /> <br />27 <br />