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Off-Farm - In the Littlefield area, the off-farm distribution systems were considered and improvements are recommended as part of the onfarm program. A larger sand trap or desilting basin is needed in the Mesquite Canal. The existing trap does not function properly, Improvements for the Mesquite Irrigation Company system include replacing about 300 feet of concrete lining, repairing the overshot structure 0,4 miles west of the Mesquite-Bunkerville division box, and replaCing the 48 inch CMP flume (45 feet long) at Abbott Wash, The major distribution system improvement needed is the lining of approximately 13,850 feet of the Bunkerville Canal, This would reduce seepage by about 885 acre-feet per year, Nineteen turnouts would need to be reinstalled when the ditch is lined, A sand trap located near the river diversion structure is needed, River channel stabilization measures are needed to improve the diversion site, Repair of about 50 feet of existing concrete ditch and two overshots are oeeded for the Bunkerville Irrigation Company system, A permanent diversion structure is needed at Riverside, Nevada., The present canal system needs to be maintained for the Riverside area. The diversion canal system requires a large stilling basin, turnout structures, and streambank protection to prevent river overflow damage to the main ditch, Lining the 9,240 foot main ditch would reduce seepage an estimated 570 acre-feet annually, An alternative is installation of a pumping plant in lieu of a diversion structure. This would eliminate 7,000 feet of the main canal. However, additional energy costs for a pumping plant is an adverse effect to be considered. Annual repair of the present Riverside Irrigation Group system in- cludes rebuilding the diversion structure, and removal of sediments from the main canal, and replacing washed out sections after minor flood flows. Problems and Needs Associated With Erosion and Sedimentation Average annual sheet, rill and gully erosion varies from less than one to greater than ten tons-per-acre-per-year, (See Figure 14 - Erosion Areas). Teo percent of the stream channel has erosion io excess of 1,000 tons per mile. Sheet and rill erosion account for 20 to 30 per cent of the sediment yield. Erosion of gullies, washes, streambanks and channel bottoms account for the other 70 to 80 percent of sediment yield. Sediment yield from Virgin River drainage above Littlefield averages three million tons annually based on 20 years of gage data, The estimated salt loading resulting from erosion in this reach is based on an analysis of surface water data, Annual suspended sediment, indicated by the gage at Littlefield, Arizona, has varied from less than one million to over seven millions tons, A flood event on December 6 and 7, 1966 produced 3.1 million tons of sediment and 110,000 tons of salt by erosion in the watershed above the gaging station, ~~~ ;, i I ~. ,., (l ,) ,,'JI.. c.v4 34