Salinity Problems in the Lower Colorado River Area

Document: State of California, Colorado River Board of California, "Salinity Problems in the Lower Colorado River Area," September, 1962, page 15SALINITY PROBLEMS-LOWER COLORADO RIVER 15 Wellton-Mohawk Irrigation and Drainage District (75,000 acres). This unit of the Gila Project, the largest single irrigation development in the Yuma area, lies along both sides of the Gila River east of Yuma in a relatively narrow strip about 50 miles long with a maximum width of about 6 miles. Irrigation in the Wellton-Mohawk area began before the turn of the 20th century with surface diversions from the Gila River. In the 1920's wells were drilled to supply 9,000 acres with water from underflow of the river. Construction of upstream storage dams and extensive development of the Phoenix area, including massive exploitation of the ground water basins, practically eliminated the Gila River underflow in the Wellton-Mohawk area. By 1946, water from some of the wells carried nearly half as much mineral content as sea water. The overall poor quality of the water brought about abandonment of many farms and reduced the active lands to about 6,000 acres of salt-tolerant crops. In 1952 the Bureau of Reclamation completed the Gila Project works to bring an ample supply of better water from the Colorado River into the area. More than 50,000 acres are now irrigated in the Wellton-Mohawk unit. However, adequate drainage facilities were not provided in the original construction of the project and the water which brought its blessings also brought a curse in the form of a rising ground water table. In 1959 the first of 70 drainage wells were installed in an attempt to alleviate the waterlogging of farmlands. For several months the wells discharged into the nearest points in the bed of the Gila River, but in 1961, a conveyance channel more than 50 miles long and of about 300 cfs capacity was completed to carry the effluent into the Gila River near its confluence with the Colorado River. The photographs on the next page showing flows of about 285 cfs were taken on June 13, 1962. The wells are said to be working effectively, not only to arrest the spread of the damage caused by high water table, but to make possible the reclamation of lands which had gone out of production. Ironically, this curative measure has proved to be a source of distress to others-the City of Yuma and the Mexican users of Colorado River water. City of Yuma The city, which formerly received its water supply from the Colorado below the mouth of the Gila River, was the first major user to be adversely affected by the return flows from Wellton-Mohawk. Degradation of quality was noticeable as early as September 1960. By permission of the Yuma County Water Users Association the Arizona Water Company, which furnishes water to the City of Yuma, began diverting a third of the city's requirements from the Yuma Main Canal which carries water identical in quality to that in the Colorado at Imperial Dam. Since February 1962, the company, under a two-year contract with the Association has pumped its entire supply from the canal. A 1959 contract between the city and the Secretary of Interior provides for delivery of the water immediately below Imperial Dam. This point of delivery is about 18 miles upstream from the mouth of the Gila.Epson Perfection 4870 Photo, 600 dpi, 8 bit, 4,305,893 byte