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<br />IV LO"R GL,SISON SECTIOS <br /> <br />w <br />.... <br />o <br />"=' <br /> <br />A. Introduction <br /> <br />ThIS portion of the supplement to the Colorado River water Quality <br />Improvement ProRram EIS covers the cumulative effects of implementing the <br />anfacm irrigation water management and land treatment measures for the Lower <br />Gunnison Basin Unit in Colorado. Environmental impacts of individual conserva- <br />lion practice ~ill be evaluated for each specific practice as it is planned <br />and implemented. <br /> <br />B. Alternative Plans Evaluated <br /> <br />Introduction <br /> <br />This section discusses eight alternative plans that address fOur <br />levels of resource development for reducing the river's salt load. These <br />levels are: continuatIon of the ongoing USDA program (the no accelerated' <br />action), improved onfarm irrigation water management (the nonstructural alterna- <br />tive). improved onfarm ditch lining, and combining onfarm irrigation ...'ater <br />manag~ment ~ith oofarm ditch lining with two options of onfarm system improve- <br />ments. One option requires manual labor, ~hile the second option is adapted <br />to semi automated time- controls for operation. Lining portions of the off-farm <br />delivery systems is displayed as a supplemental action for six of the alterna- <br />tives. The eight alternative plans ar~ summarized in Table IV-I. <br /> <br />Plan Formulation <br /> <br />Thf' three basic solution alternatives were scoped in plan formulation, <br />Under the first solution the effect of onfarm management of irrigation water <br />was examined. Effeclive dnd efficient irrigation requires uniform distribution <br />of waler across the field while applying the needed amount of water. Land <br />leveling e-nhances opportunity for unlform distribution of water. Measuring <br />devices are needed to measure the rate at WhlCh water is delivered to the <br />field. The duratlon of flow must be carefully timed to assure application of <br />the proper amount of water. Thus, the management only solution requires control- <br />ling the time of each irrigation set supplemented by land leveling and installing <br />water measuring devices. This solution assumes that, using manual labor, <br />irrigalors ~dll irrigate to the recommended time of set thus reducing the <br />volume of deep percolation and volume of runoff from each field. The recommended <br />time of set, calculated for each field and crop, will be a part of the landowner's <br />conservation plan. <br /> <br />The second solution considers onfarm ditch linIng ~here existing earth ditches <br />would be placed in pipelines, or replaced by gated pipe or impervious lining <br />to reduce seepage. A significant share of the salt load pickup is attributed <br />to seepage from earth ditches. Reorganization of onfarm systems ~ill require <br />that ~ater be delivered to the farm at the proper location, elevation, quantity, <br />and pressure suited to onfarm improvements. Therefore, the onfarm ditch lining <br />concept examined the cost and the effect of implementing a program for lining <br />existing onfarm ditches or installing pipelines. Ditch lining under the maximum <br />level of implementation includes improving a sufficient reach of the off-farm <br />~ater delivery system to assure proper operdtion of the onfarm improvements. <br /> <br />11'-1 <br /> <br />J <br />