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33 percent reduction in the annual salt load delivered to the river, can be achieved at a one-time valley-wide installation cost of $208,000,000. Level Two (Maximum Efficiency) - This represents the maximum level of structural improvement in existing irrigation systems, including the combinin~ of some small fields, The time of set and flow rate per furrow that tend to maximize irrigation efficiency are the primary changes from eKistin~ mana~ement practices. Usin~ twelve-hour and 3 ~allons per minute increments of chan~e the IRMA program derived the time of set and flow rate per furrow needed to apply the recommended net application havin~ the hi~h- est irri~ation efficiency during each irri~ation. Elements of structural improvements for this plan include the combinin~ of small fields where desired, ditch linin~ or pipelines for field supply ditches, ditch lining and ~ated p>pes for field head ditches, constructin~ lined tailwater ditches to control tailwater, land leveling includin~ that needed for the combinin~ of small fields, and closed drains where appli- cab Ie. Level Two can reduce salt loading by 162,000 tons throu~h reduced seepa~e from onfarm ditches, and 57,000 tons from reduced tailwater ditch seepa~e but will increase salt loadin~ from reduced deep percolation by 75,000 tons. The net 144,000 tons, a 33 percent reduction in the salt load delivered to the river, can be achieved at a one-time valley-wide installa- tion cost of $195,000,000. Level Two (Minimum Deep Percolation) , This level also includes the maximum structural improvement in existing irri~ation systems, including the combinin~ of some small fields. The time of set and flow rate that tend to minimize deep percolation are the pr~mary changes from existing management practices. Using twelve-hour and 3 gallons per minute increments of change the IRMA program derived the time of set and flow rate per furrow needed to ('''''1''1 II-ll