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. '7.') ~- ~ Q) -...I 1,360,000 acre-feet delivered to Mexico upstream of Morelos Dam have an annual average salinity of no more than 115 ppm plus or minus 30 ppm over the annual average salinity of Colorado River waters which arrive at Imperial Dam * * *." The Minute also states that "the provisions which are dependent for their implementation on the Con- struction of works or on other measures which require expenditure of funds by the United States shall become effective upon notifica- tion by the United States to Mexico of the authorization by the United States Congress of said funds, which will be sought promptly." After January I, 1974, or the authorization by the Congress, which- ever comes later, and until the necessary measures under the permanent solution are completed, the United States will have to bypass all of the Well ton-Mohawk drainage (estimated at between 175,000 and 220,000 acre-feet/year) and replace it with water of Imperial Dam quality to maintain the differential specified in Minute No. 24.2. The Well ton-Mohawk Irrigation and Drainage District extends from about 8 miles east of the confluence of the Colorado and Gila Rivers eas,terly along the Gila River Valley and on bordering mesas for approximately 45 miles. The Well ton-Mohawk Division of the Gila Project was authorized for irrigation of 75,000 acres. In 1972, about 62,000 acres were being irrigated. The troubles with the Well ton-Mohawk drainages date back to the early 1900's when irrigation commenced using waters diverted from the Gila River. After upstream developments, Gila River flows diminished and ground water was used. An underground basaltic rock barrier at the Dome Narrows near the west end of the project area effectively prevents underground flow from the area. As irrigation from wells continued, the constant cycling of the water from the ground water reservoir to irrigation and then deep percolation back to the ground water reservoir caused the water to become highly saline. The first project water from the Colorado River was delivered in 1952. The imported water which was not used in evapotranspiration percolated underground and joined the ground water body, resulting in a rising water table. This in turn dictated the construction of a 'pumped drainage system from wells conveyed originally in a concrete' lined channel to the Gila River about 8 miles above its confluence with the Colorado River. Because of the many years of recycling ground water, the drainage was pretty saline, about 6,000 ppm. This has been declining as the aquifer is being refreshened with Colorado River water. In 1962, the Main Outlet Drain was completed, conveying the drainage to the Colorado River. By 1963, the Main Outlet Drain Extension was completed, permitting delivery of water above or below Morelos Dam. 11