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<br />SUMMARY
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<br />The Colorado River Basin Salinity Control Act, Public Law 93-320, pro-
<br />C) vides authority for USDA to participate in salinity control investigations
<br />in the Colorado River System. Title II, .Section 203, of the Act defines
<br />USDA responsibilities for investigating irrigation and diffuse source units
<br />where salinity problems have been'identified. This designation includes
<br />the Virgin River Unit.
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<br />The Virgin River Unit comprises about 19,550 square miles in southern
<br />Nevada, southwestern Utah, and northwestern Arizona. The Unit is a direct
<br />hydrologic tributary to Lake Mead and the Lower Colorado River. About
<br />70,000 acres of land are irrigated.
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<br />The Unit is estimated to contribute about 760,000 tons of salt annually
<br />to the Colorado System from surface and underground sources. Included with~
<br />in this amount is about 336,000 tons from point sources at LaVerkin Springs,
<br />Littlefield Springs and Las Vegas Wash. The remaining amount is from water-
<br />shed areas and irrigation return flows. Additionally, the Virgin River
<br />Unit produces in excess of 10 million tons of sediment annually, of which
<br />about 1 million tons or 10 percent is delivered to Lake Mead.
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<br />It is estimated that USDA irrigation improvement programs could reduce
<br />seepage and deep percolation 30-40 percent resulting in a 65,000-75,000 ton
<br />reduction in salt loading to the Colorado River. Watershed treat~ent pro-
<br />grams are estimated to reduce sediment delivered to Lake Mead about 20 per-
<br />cent with an associated 10-15 percent (15,000-25,000 tons) reduction in ~lt
<br />loading to the river system. The Virgin River Salinity Control Study will
<br />be carried under the leadership of the Soil Conservation Service in Nevada,
<br />with significant inputs provided by SCS in Utah and Arizona. The study is
<br />scheduled to start in FY77 and end in FY79, with a total estimated cost of
<br />$223,855.
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<br />The total includes $13,224 for input from the Forest Service, in line
<br />with the following tabulation:
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<br /> State Fiscal
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<br />Fiscal Year Nevada Utah Arizona Year Totals
<br />1977 Man Days 0 0 5 5
<br /> Funds 0 0 580 580
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<br />1978 -t'.an Days 32 37 25 94
<br /> Funds 3,712 4,292 2,900 10,904
<br />1979 Man Days 5 5 5 15
<br /> Funds 580 580 580 1,740
<br />rotal Man Days 37 42 35 114
<br />~otal Funds 4,292 4,872 4,060 13,224
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