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<br />The McElmo Creek contributes about 119,000 tons of salt <br />annually to the Colorado River. About 54,000 (present condition) <br />tons are attributed to the onfarm portion of current irrigated <br />agriculture. Additional water from the Dolores Project wi I I <br />increase this salt loading to about 173,700 tons annually of <br />which about 60,000 tons (future without condition) are attributed <br />to onfarm. Most of the sa It is I eached from the so i I and <br />underlying Mancos shale and carried to the river by deep <br />percolation from irrigation and by seepage from unl ined earthen <br />ditches. <br /> <br /> <br />~ <br />'! <br /> <br />Improved management of irrigation water, including devices <br />for measuring water onto the fields and I ining or piping onfarm <br />and off-farm group ditches and/or sprinklers, has the potential <br />for reducing the river's salt load by as much as 38,000 tons and <br />reducing sal inity ~oncentration of the Colorado River at Imperial <br />Dam by 3.5 mi II igrams per I iter. These impacts are based on the <br />assumption that improvements wi I I be made on about 74 percent of <br />the i rr i gated area. <br /> <br />Five alternative plans, as wel I as future without project <br />actions, were studied that address four concepts for reducing the <br />river's salt load. The concepts are: a continuation of ongoing <br />programs (no accelerated action alternative), onfarm irrigation <br />water management (non-structural alternative), ditch and pipe <br />I ining only, and combining onfarm irrigation water management <br />with onfarm and off-farm ditch and pipe I ining (See Table I). <br /> <br />Adverse impacts to wetlands for the five candidate plans <br />ranged from 33 acres for the continuation of ongoing programs <br />(Future Without) to 615 acres under the recommended plan <br /><Table Al-2). <br /> <br />Plan 5, provides for the installation of 19,700 acres of <br />sprinkler irrigation systems and 268 miles of irrigation <br />pipel ine as well as 1,850 acres of improved surface systems, is <br />the recommended plan for implementation. The implementation <br />period should be ten years and program effectiveness should be <br />evaluated at three-year intervals to determine if the program is <br />achieving the expected degree of sal inity reduction. <br /> <br />Plan 5 is recommended because it maximizes net benefits and <br />has the largest sal inity reduction. The other alternative plans <br />are not economically feasible using current cost and benefit <br />values. Also, plans 3 and 6 do not provide enough onfarm <br />incentives to insure local support. <br /> <br />n"t")1~9 <br />';J .... h, IoJ <br /> <br />2 <br />