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w w uc. McElmo Creek Unit. Colorado :;1 The McElmo Creek Unit is in Montezuma County in southwestern Colorado where McElma Creek originates. McElmo Creek flows into the San Juan River in the southeastern corner of Utah. McElmo carries an annual salt load of 116.000 tons, most of which comes from irrigation return flows and a lesser amount from natural runoff. Conveyance system seepage from the unlined canals picks up salts from the soil and carries them into McElmo Creek and. eventually, the Colorado River. SCS;s conducting an onfarm program for salinity reduction. while Reclamation ;s involved in the off-farm salinity control efforts. The preferred plan outlined in a status report dated July 1981 and sub- sequently refined consists of combining the Rocky Ford Ditch into the Highline Ditch and concrete-lining 28.5 miles of high- and moderate-seepage canals in the remainder of the MVI (Montezuma Valley Irrigation Company) system. The preferred plan would have a cost-effectiveness of $769,000 per mg/l and would reduce salinity concentrations at Imperial Dam by about 2.4 mg/l and reduce salt loading by about 24,000 tons. The planning report/draft environmental statement is scheduled for comple- tion in February 1984. Palo Verde Irrigaticl District Unit, California Palo Verde Irrigation District is located along the Colorado River between Parker Dam and Imperial Dam in southeastern California. The district of 91,400 acres yields about 152,000 tons of salt to the dver each year. A special report was published in July 1981. Studies to date have indicated a potential for a salinity control project on a subarea of the district (10 percent of total) that is underlain by saline ground water. Control measures would consist of onfarm improve- ments to facilitate more efficient irrigation water application, and lining of canals and laterals to reduce seepage loss. However, more detailed studies, including ground-water mOdeling. are required to verify these conclusions and to provide a basis for initiating a Federal expenditure progrcrn. The Palo Verde Irrigation District has also expressed interest in having its entire 295-mile system of canals and laterals lined to reduce opera- tion, maintenance. and replacement costs; conserve water; and eliminate seepage losses. The district would repay all the costs of construction, except for those allocated to salinity control. laVerkin Springs Unit. Utah laVerkin Springs. on the Virgin River in the southwestern corner of Utah, discharges about 109,000 tons of salt annually. Past studies indicated that up to 103.000 tons of this salt could be removed. xvii