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<br />PLAN SELECTION <br /> <br />landowner participation is the key for achieving results indicated for <br />each plan displayed in this report. The most effective plan is not <br />necessarily the one with the highest potential reduction, but the one <br />having the greatest likelihood of attaining its potential. Therefore, <br />, to reach its potential the selected plan must have farmer acceptance and <br />offer incentive that will attract voluntary participation. <br /> <br />/ <br /> <br />Analysis shows irrigation practices managed for minimum deep percolation <br />yield greater potential salt load reduction than managing for maximum <br />efficiency. Therefore, in addition to efficiency other considerations <br />are needed in selecting the plan to achieve maximum potential reduction <br />in salt loading. The potential reduction relies almost as much on <br />improved management as on structural measures. Figure 1 shows potential <br />reduction for each plan as influenced by irrigation management practices <br />and physical improvements displayed by attainable irrigation efficiency. <br />For this display it was assumed that physical improvements primarily are <br />reflected in ditch lining, and that water management practices strongly <br />influence deep percolation. That assumption is not correct because <br />field runoff, influenced by water management practices, affects salt <br />loading through seepage from tailwater ditches; and the degree of <br />leveling in a field affects salt loading through deep percolation. <br />However, Figure I is sufficiently accurate to show potential salt load <br />reductions as a function of physical improvements and improved manage- <br />ment practices. <br /> <br />The likelihood of achieving potential salt load reduction attributed to <br />improved management practices became a criterion for plan selection. To <br />be successful, the implementation program must provide incentive for <br />improving management practices as well as installing improvements in the <br />conveyance system. The degree of improved management practices achieved <br />through voluntary participation in the implementation program will be <br />directly proportional to the incentive offered. <br /> <br />Physical improvements offered by Plan One consist of ditch lining and <br />land leveling with land leveling limited to about 3 percent of the <br />irrigated area. These improvements offer little incentive for achieving <br />improved management practices on a large majority of the irrigated area; <br />yet a high level of participation is needed to achieve the 80,000 tons <br />reduction in salt loading attainable through improved management practices. <br /> <br />The volume of improvements offered in Plan Two can be implemented with <br />the least unit cost; and the scope of improvement offers incentive to <br />all farm operators in the valley. With this incentive there is more <br />certainty that the 60,000 tons reduction in salt loading attainable <br />through improved management would be achieved. The weakness of Plan Two <br />is that it does not incorporate new technology in the form of today's <br />improved methods of irrigation. <br /> <br />Plan Three includes new technology in its scope of physical improvements <br />and reflects the higher cost of the new technology. Participation in <br /> <br />S4 <br />