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Alternative 1 In Alternative 1 it is assumed farmers would improve onfarm irrigation systems, but use existing canal and lateral systems with minor repairs, This alternative plan requires minimum structural improvements. This alternative plan includes improvement of irrigation efficiency and reduction in salt loading by improved water scheduling and control of water applied to irrigated fields. Changes to the onfarm irrigation systems would be minimal. Seasonal gross application would be smaller, thus reducing runoff and deep percolation. See Table 8, The repair of water delivery systems will reduce canal seepage, The diversion structures and other components of the irrigation system need considerable maintenance, New diversion structures not requiring high maintenance could have annual costs exceeding present maintenance and replacement cost, Repair of the water delivery canal system and improve- ment of onfarm systems and management are considered complementary components of this alternative, and benefits are not separable. Improved water scheduling will require equipment to measure soil moisture, salinity of irrigation water, and quantities of water delivered, Water delivery schedules, on a more flexible basis than the present system, would be developed. Water scheduling is complicated by a lack of storage for irrigation water on the Virgin River. Automation (or semiautomation) of onfarm irrigation systems is needed to control short irrigation set times (length of time water is applied to fields). Additional labor costs would be incurred to manually operate with shorter set times. Onfarm automation reduces labor about 12,500 hours or $50,000 on an average annual basis. Telemetry could monitor automated (and sem1automated) onfarm irrigation systems. Monitor- ing would alert managers of automation failure so that timely repairs could be made. ".:/ , ~~' Irrigators are assumed to obtain comparable levels of water manage- ment, but onfarm irrigation efficiencies would vary depending on soil type, length of run, irrigation head, slope, etc, Irrigation efficiency is expected to average 58 percent, Water management data are summarized in Table 8, ~~ Increased production from this alternative is based on improved water management. The land use on the 3,495 irrigated acres is projected to be 72 percent alfalfa, 2 percent small grain and 26 percent pasture, Urbanization of agricultural land is assumed to be the same as for future without a salinity control program, Onfarm irrigation management described by this alternative would result in about 50 tons of sediment reduction each year, The annual value of downstream economic benefits resulting from a three-ton reduc- tion is salt load due to a reduction in erosion is only $150. The reduc- tion of irrigation induced seepage and deep percolation by 9,350 acre- feet will reduce salt loading 15,100 tons, ('o003'~ 2 43