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<br />q;, <br /> <br />, <br /> <br />e..,) <br />o <br />eJ:) <br />N <br /> <br />..H~}.) <br /> <br />SUMMARY <br /> <br />The Fruitland, Hogback, and Cudei Irrigation Districts, located in Reaches 4 and <br /> <br /> <br />5 of the San Juan County Salinity Contro area, have been identified in USGS <br /> <br /> <br />records as the annual source salt to the San Juan River. This <br /> <br />verification study was undertaken etermine whether a significant portion of <br /> <br />this salt loading was attributable to irrigation agriculture on the Navajo Nation <br /> <br /> <br />and, if so, to evaluate the opportunity to reduce the salt loading by reducing <br /> <br /> <br />ditch seepage and onfarm deep percolation of irrigation water. <br /> <br />These studies indicate that nearly 50,000 tons of salt per year may be picked up <br /> <br />by excess irrigation water returning to the San Juan River. Irrigation <br /> <br />evaluations indicate that nearly one-half of the return flow is deep percolation <br /> <br /> <br />through the salt bearing aquifers picking up dissolved salts as it migrates back <br /> <br /> <br />to the river. The remaining salt is picked up by seepage from canals and farm <br /> <br />ditches. <br /> <br />It is estimated that a program of lining and repairing canals and laterals <br /> <br />coupled with an onfarm program to upgrade irrigation systems and institute sound <br /> <br />irrigation water management can reduce the amount of seepage and deep percolation <br /> <br /> <br />by two-thirds. Hence, irrigation system improvements would reduce the amount of <br /> <br />annual salt pick up by 36,000 tons, from 48,000 tons to 12,000 tons. <br /> <br />3 <br />