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Last modified
1/26/2010 12:46:38 PM
Creation date
10/11/2006 11:19:08 PM
Metadata
Fields
Template:
Water Supply Protection
File Number
8276.852
Description
Moapa Valley Unit - Colorado River Salinity Control Program
State
NV
Basin
Colorado Mainstem
Date
2/1/1981
Title
Salinity Control and Environmental Assessment
Water Supply Pro - Doc Type
EIS
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<br />SUMMARY <br /> <br />Moapa Valley Subevaluation Unit, Nevada, is the first part of a study <br />of Virgin River Unit in Arizona, Nevada and Utah. See Figure 1, The study <br />identifies alternative solutions for reducing salt loading of Colorado River <br />from irrigation and other diffuse salt sources. <br /> <br />Muddy River flows through Moapa Valley into Lake Mead. Moapa Valley is <br />divided by the "Narrows" downstream of Glendale. Upstream of the Narrows the <br />area is cOlllllOnly known as "Upper Moapa Valley", and downstream the valley is <br />known as "Lower Moapa Valley." The amount of 1 and i rri gated vari es from year <br />to year. The irrigated acreage is 4,982 with 2,060 acres in Upper Valley and <br />2,922 acres in Lower Valley. <br /> <br />The existing condition was evaluated and three levels of salt reduction <br />were analyzed: Future Without Program, Alternative 1, and Alternative 2. <br />The benefits and costs associated with these proposals are summarized in <br />Table 2, page vi. <br /> <br />Muddy River is estimated to contribute an average of 73,400 tons of <br />salt and 385,000 tons of sediment to Lake Mead each ~ear. A future reduction <br />of 19,500 tons of salt could be accomplished by: (1) improving the irrigation <br />delivery system to reduce canal seepage (1,835 tons), (2) improving water <br />management b~ increasing onfarm irrigation efficiency from 45 to 61 percent <br />(17,390 tons), and (3) reducing erosion by shaping and seeding channel banks <br />with protective measures at road crossings (270 tons) and irrigation manage- <br />ment with return flow structures (5 tons). Installation of the erosion con- <br />trol measures is estimated to reduce the annual sediment yield by 5,000 tons. <br />These components are explained in Alternative 2, the recommended plan. <br /> <br />Implementation of the recommended plan, Alternative 2 would requie semi- <br />automated onfarm irrigation systems with a cost of $2,064,600. The present <br />annual operation and maintenance cost would increase from $5,000 to $22,000 <br />because of operation and additional maintenance (and replacement) cost needed <br />for the automated systems. These increased costs would be offset by increased <br />efficiency of crop production. <br /> <br />The existing canal and lateral systems in Upper Moapa Valley need <br />improvement. The improvement of distribution systems in Upper Moapa Valley <br />is needed to obtain onfarm improvements. A pipeline distribution system in <br />Lower Moapa Valley is recommended for the automated onfarm irrigation systems. <br />The cost of the off-farm distribution system is estimated to be $3,596,400. <br />Presently, about $12,000 is spent annually for operation and maintenance. This <br />cost does not include replacement commensurate with needs of the existing <br />distribution system. Operation, maintenance and replacement cost of the recom- <br />mended off-farm distribution system would be $30,300 annually. <br /> <br />Erosion control improvements are estimated to cost $112,100. Operation <br />and maintenance cost is estimated to be $3,000 annually. <br /> <br />002675 <br /> <br />ii <br />
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