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<br />seepage and deep percolation and the associated salt load are summarized in Table 11-1 <br /> <br />and form the basis for plan formulation. <br /> <br />TABLE 11-1 <br />SOURCES OF ONFARM SALT LOADING <br />AND PRACTICES FOR ATTAINING SALT LOAD REDUCTION <br />LOWER GUNNISON SALINITY CONTROL STUDY, COLORADO <br /> <br />SOURCES <br /> <br />APPLICABLE PRACTICES <br />MANAGEMENT STRUCTURAL <br /> <br />Seepage: <br />Onfarm Ditches <br /> <br />Adjust the time of set <br />Number and frequency of <br />irrigations. <br /> <br />Tailwater Ditches <br /> <br />Adjust the time of set, <br />the number and frequency <br />of irrigations. <br />Change to more efficient <br />method of irrigation. <br /> <br />Deep Percolation <br />Excessive and non-uniform <br />application of irrigation <br />water <br /> <br />Adjust the number and <br />frequency of irrigations, <br />time of set, and flow <br />rate. <br />Change to more efficient <br />method of irrigation. <br /> <br />Inefficient layout of <br />fields and irrigation <br />systems. <br /> <br />Combine fields or change <br />to more efficient method <br />of irrigation. <br /> <br />Install ditch lining or <br />pipelines and appurtenant <br />structures. <br /> <br />Install lined and unlined <br />tailwater collection <br />ditches. <br /> <br />Install water measuring <br />devices, land leveling, <br />automated timing devices. <br />Change to border, drip or <br />sprinkler methods of <br />irrigation. <br /> <br />Close existing open drains. <br />Relocation of pipelines <br />and ditches. <br /> <br />Computerized Analysis - The analytical procedure on which plan formula- <br /> <br />tion is based was programmed for computer processing. The Soil Conservation <br /> <br />Service developed the Irrigation Methods Analysis (IRMA) program that was <br /> <br />used to analyze data gathered through an onfarm inventory process. The <br /> <br />inventory included 1,020 farms representing 107,000 acres of irrigated crop- <br /> <br />land. Results from the analysis were expanded to be representative of the <br /> <br />approximately 171,000 acres of irrigated land in the Lower Gunnison River <br /> <br />Valley. The inventory revealed items of concern that have a bearing on plan <br /> <br />formulation. Some farmers desire to combine small fields into one larger <br /> <br />~~\20~ <br /> <br />11-6 <br />