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V. USDA TITLE I ACTIVITIES (Wellton-Mohawk, AZ) , Highly saline'drai~a!e return flo~ from the Wellton-Mohawk trrigation and Drainage Dis,trict (WHIDD) in Yuma Couhty, Arizona, created the d,ownstre!l11l salinity problems for Ilexico in the' 1960's which, resulted' in Miriute 1T0. 242, and 'the passage of Public Law 93-320, the Colorado River Basin'Salinity '" . Control Act of 1974. ' ..,'.i., <:) USDA activities under Title I of the act are primarily related to,imP.roving ~ irrigation efficiencies, reducing deep percolation, and reducing' highly saline irrigation and drainage return flows from the 65,000 acreWHIDD. As farmers over-irrigate, excess and unused irrigation waters percolate ' down through the soil profile creating a high water table enriched with high salinity levels. To overcome the agricultur~ production problems caused by salinity build-up and poor drainage, pump-drainage wells were used to lower, the, lIalin'll high Water tables. This "pumped" drainage water, with salinity concentrat!.ons ranging from 3,000 to 6,000 partll per million (PPM)" was then removed from the Wellton-Mohawk area through drainage canals and ditches, discharging into the Colorado River. Theile highly saline return flows. caused increased salinity concentrations in the ColOrado River waterll delivered to, Mexico. A separate provision in Title I was the construction of a concrete' lined by-pass drain to divert lIaline drainage water to the Santa Clara slough until the desalinization plant would be constructed near Yuma, 'Arizona.. In. conjunction with the BR planning' for the dellalting plant authorized in, Title I of 'the Act, an Advisory Committee on Irrigation Efficiency and a support Technical Field Committee on Irrigation Efficiency were created.. Theile interagency committeell were formed to develop alternatives to improve irrigation efficiencies and to reduce drainage return flows. This,would ultimately reduce the size and costs of building and operating a ,large desalting plant. A 1974 "Special Report: Measures for Reducing Return Flows from the Well ton-Mohawk Irrigation and Drainage District" includes the specific,recommendations for installing onfarm measures.and technical assistance. The "Initial Program," consisting of 23,800 acres of irrigation and salinity control improvements, is complete. A "Program Extension," consisting of 19,000 acres of regularonfarm treatment and 18,950 acres of irrigation water management, should be completed in 1986. In 1984, 59 plans were developed and contracts signed on 8,105 acres. Practices applied included 28.2 miles of ditch lining, 4,623 acres of,laser leveling, and 678 structures for water control and measurement, see Table V-l. -12-