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<br /> <br />~ <br /> <br />I <br /> <br />~i <br /> <br /> <br />(.:;) <br />"J <br />W <br />W <br />...:I <br />...:I <br /> <br />area spows that sufficient water is not pumped during May, June, <br />July, ~nd August to meet full consumptive use for alfalfa. The <br />irriga~ion efficiency of 78 percent is calculated with the crop <br />consumptive use considered to be the gross application amount for <br />May th~ough August. Application efficiency varies from about 50 <br />percent in March to a high near 85 percent during the summer and <br />back down to about 62 percent in October. <br /> <br />Lower Moaoa Vallev <br /> <br />Wells Siding Diversion located in the north end of Lower Moapa <br />Valley is used to divert Muddy River water into a concrete canal <br />system; to irrigate about 2690 acres and also to carry water to <br />Bowman Reservoir. Bowman Reservoir has a storage capacity of <br />4,060 ~cre-feet. During winter and early spring, Muddy River <br />water is diverted and stored in Bowman. Releases from Bowman <br />usually begin during early May and the reservoir is normally <br />empty l:>y mid-August. The off-farm distribution system is 58 <br />miles ~n length and is organized into six delivery canals: Upper <br />Logan,;Lower Logan, Sproul-Everett, Capallappa, Overton, and, <br />Springtown. Ditches average 18 inch bottom width and vary from <br />16 inches to 30 inches in depth. ' <br /> <br />Overall, the distribution system is in poor condition due to <br />canal fining that has deteriorated from sulfate reactions and <br />portio*s of the canal that have been washed out by flood flows <br />from side washes. Portions of the canals now have earth sections <br />which ~ause water loss to seepage. Short segments of corrugated <br />metal pipes have been installed to bridge some of the more active <br />side w4sh areas and some segments of PVC pipeline have been <br />installed in various locations. However, these segments may not <br />be designed as part of a complete off-farm distribution system. <br /> <br />Water quality measurements in the delivery canals show an <br />increa$e in salinity from about 1,100 mg/l at Wells Siding <br />Diversion to about 2,400 mg/l at the Overton Wildlife Management <br />Area's 'delivery point, the last delivery point on the system. <br />These increases are from water coming into contact with saline <br />soils in earthen sections and from saline seeps and return flows <br />reente~ing canals. <br /> <br />Surfac$ methods are used to apply irrigation water in Lower Moapa <br />Valley. Field ditches are concrete-lined and use gated outlets <br />(ports); for irrigation. Set widths are determined by the number <br />of outlets opened and there are no border ridges installed in <br />fields.; Less than 100 acres have been laser leveled. Most of <br />the fi~lds have cross slope. Shallow corrugations in the <br />direction of irrigation are used to guide the irrigation advance <br />and to control the lateral movement. <br /> <br />Water is measured at Wells Siding,Diversion where the flow is <br />split between the east and west side of the valley. About 2/3 of <br />the flow is delivered down the west side main canal and about 1/3 <br />down the east side. Flow on the west side is further split into <br /> <br />29 <br />