General Description

The Gila Project, located in southwestern Arizona, is divided into two divisions. The Wellton- Mohawk Division begins about 12 miles east of the city of Yuma and continues upstream on both sides of the Gila River for about 45 miles, The Yuma Mesa Division is subdivided into three units; the Mesa Unit; located south and southeast of Yuma, and the North and South Gila Valley Units, which lie northeast and east of Yuma,

Upon full development, the project could provide irrigation service to 65,000 acres in the Wellton-Mohawk Division (this acreage was reduced from 75,000 acres by the Colorado River Basin Salinity Control Act of 1974) and to 42,131 acres in the Yuma Mesa Division, which includes 17,131 acres in the North and South Gila Valleys. The project currently provides irrigation service to about 98,000 acres of land in the two divisions. The project authorization permits diversion of Colorado River water to satisfy beneficial consumptive use of 300,000 acre-feet of water in each division.

Project features include the Gila desilting works at Imperial Dam, the Gila Gravity Main Canal, the Mesa Unit Canals and distribution system, the lateral system in the North Gila Valley (originally constructed as part of the Yuma Project), the canal and pipeline distribution in the South Gila Valley, and the Wellton-Mohawk Canal distribution and drainage systems and protective works.

Plan

Imperial Dam, which also serves the All-American Canal System of the Boulder Canyon Project, diverts Colorado River water at its east abutment through the desilting basin into the Gila Gravity Main Canal. From turnouts in this canal, irrigation water is diverted to serve the North and South Gila Valleys and the Wellton-Mohawk area. The canal ends at the Yuma Mesa Pumping Plant, where water is lifted 52 feet to the head of the Yuma Mesa distribution system which conveys irrigation water to the Mesa Unit lands and to the Yuma Auxiliary Project.

Imperial Dam

See All-American Canal System, Boulder Canyon Project

Gila Canal Headworks and Gravity Main Canal

The Gila headworks of Imperial Dam was constructed with three sets of outlet units, each with three radial gates; water discharges through one gate unit into a settling basin. Original plans contemplated diversions to 585,000 acres, but the area of the Gila Project was reduced by the act of July 30, 1947 (61 Stat. 628), to 117,000 acres. The acreage was reduced again to 107,000 acres by the Colorado River Basin Salinity Control Act. One desilting basin, 1,165 feet long including transitions, is located between the Gila headworks of Imperial Dam and the Gila Gravity Main Canal diversion gates. This single basin has sufficient capacity under normal conditions for one year's accumulation of sediment. An annual outage of the canal permits draining the basin for inspection, repair, and sluicing the accumulated sediment to the Colorado River below Imperial Dam.

Water is discharged from the desilting basin into the Gila Gravity Main Canal, which has a capacity of 2,200 cubic feet per second and extends from the desilting works 20.5 miles in a southerly direction to the Yuma Mesa Pumping Plant. The canal consists of two tunnels, one 1,740 feet long and the other 4,125 feet long; the 0.39-mile Gila River Siphon; and about 19 miles of open unlined canal. It has 10 turnouts to divert water to the project area.

North Gila Valley Unit -- Canals and Laterals

This unit receives water from two turnouts in the Gila Gravity Main Canal, one 7 and the other 11 miles from Imperial Dam. They have a capacity of 150 and 50 cubic feet per second, respectively. The unit contains 10.2 miles of canals and about 15 miles of laterals. Drainage is provided by open drains and the adjacent Colorado and Gila Rivers.

South Gila Valley Unit -- Canals and Laterals

Water is diverted to the South Gila Valley Unit from a turnout on the Gila Gravity Main Canal, located just upstream from the Yuma Mesa Pumping Plant, to the 7.7-mile-long South Gila Canal. There are seven additional smaller turnouts from the Main Canal, four of which are equipped with pumps. There is a total of 27 miles of underground pipeline laterals in the unit. Total diversion capacity to the unit is 282 cubic feet per second, which is supplemented by three deep wells There are 24 drainage wells to maintain adequate ground-water levels. Two of these wells can be used to supply additional irrigation water.

Mesa Unit Distribution System

The Yuma Mesa Pumping Plant lifts water about 52 feet from the Gila Gravity Main Canal into the main canal of the Yuma Mesa distribution system, which carries water to about 25,000 acres in the Mesa Unit and to about 3,400 acres in the Yuma Auxiliary Project. The main canal of the distribution system divides into the A and B Canals, which have a total length of 23 miles. There are 43 miles of laterals within the system. The present capacity of the pumping plant is 700 cubic feet per second.

Wellton-Mohawk Canal and Distribution System

The 18.5-mile Wellton-Mohawk Canal diverts from the Gila Gravity Main Canal about 15 miles below Imperial Dam and has a capacity of 1,300 cubic feet per second. Its branches, the Wellton Canal and the Mohawk Canal, are 19.9 and 46.8 miles long respectively. The Wellton Canal has a diversion capacity of 300 cubic feet per second and the Mohawk Canal has a diversion capacity of 900 cubic feet per second. Three large pumping plants along the Wellton-Mohawk Canal lift the water a total of 170 feet. Thirteen small pumping plants are scattered throughout the Wellton-Mohawk Division on 227 laterals. The Texas Hill Canal takes water from the Mohawk Canal north of the Mohawk Mountains and extends 9.8 miles to the east to irrigate lands in the Texas Hill area. It has an initial capacity of 125 cubic feet per second.

The 13-mile Dome Canal branches off the Wellton-Mohawk Canal about 10 miles from its beginning and serves the western end of the division. Its diversion capacity is about 220 cubic feet per second. It has 7.5 miles of laterals.

Power for pumping is furnished through the Department of Energy's Parker-Davis transmission system.

Operating Agencies

The Imperial Irrigation District currently operates and maintains Imperial Dam, the All American Canal and the Gila Diversion works.  Operation and maintenance of the Gila Gravity Main Canal has been transferred to the districts obtaining water from this canal.  The distribution system in the North Gila Valley Unit is owned and operated by the North Gila Valley Irrigation District.  The Yuma Mesa Irrigation and Drainage District operates the Yuma Mesa Pumping Plant and the distribution system downstream from the pumping plant.  The Wellton-Mohawk Irrigation and Drainage District operates the irrigation facilities in the Wellton-Mohawk Division.

Development

Spain dominated the Arizona desert for nearly 300 years after its discovery. The United States acquired the territory north of the Gila River in 1848 and, in 1856, took formal possession of the lands south of the Gila.

Early history of agricultural development in the Wellton-Mohawk area dates back to 1538 when the Pima Indians irrigated some of the bottom land adjacent to the Gila River. Early pioneer settlement started with the establishment of the Butterfield Stage Line in 1857. The Southern Pacific Railroad began serving the area on February 1, 1879. In the late 1800's, the Mohawk Canal was constructed with diversion headworks on the Gila River at Texas Hill and the Antelope Canal was constructed to serve the Wellton area. However, calamitous floods that washed out crops and destroyed diversion works, alternating with long periods of drought, continuously plagued the early settlers. These conditions resulted in the settlers turning to the use of the abundant ground water in the area for irrigation and other purposes.

In 1906, the Antelope Irrigation District was formed and a wood-burning steam generating plant was built near Wellton to provide energy for pumping. In 1921, the Gila Valley Power District was organized to develop and supply electric power for pumping irrigation water and for municipal and industrial uses. The settlers continued to drill wells but, by 1934, Wellton-Mohawk farms were facing another hazard. Excessive salt appeared in many wells and the water table had declined alarmingly.

One after another, farms were abandoned as water and soil became too saline for successful farming. Spring floods in 1941 and cloudbursts in 1951 furnished short reprieves, but these served to emphasize the fact that permanent relief would come only with the importation of Colorado River water. To that end, the Gila Project was completed in 1957 by the Bureau of Reclamation.

Irrigation with water from the Colorado River caused the water table to rise and threatened crops with drowning.

Drainage wells were constructed to remove the excess ground water. The drainage water was highly saline, initially averaging about 6,000 parts per million. This drainage water was discharged into the Gila River.

Late in 1961, the Wellton-Mohawk Main Conveyance Channel was constructed for the entire length of the Wellton-Mohawk Division to carry drainage water from about 67 wells. Additional wells were installed in 1963 to allow for selective pumping to reduce the salinity of the effluent during the winter months and to provide drainage to other areas with high ground water.

Investigations

In 1934, the Bureau of Reclamation submitted a favorable report based on an investigation of Gila Project potentialities. The investigations were authorized by the Boulder Canyon Project Act of 1928.

Authorization

The project was originally authorized for construction under a finding of feasibility approved by the President on June 21, 1937, pursuant to section 4 of the act of June 25, 1910 (36 Stat. 836), and subsection B of section 4 of the act of December 5, 1924 (43 Stat. 701). It was reauthorized and reduced in area to 117,000 acres by the act of July 30, 1947 (61 Stat. 628). Further reduction in irrigable acreage of the Wellton-Mohawk Division was authorized by the Colorado River Basin Salinity Control Act of June 24, 1974 (88 Stat. 266).

Construction

Project construction was begun in 1936, and the first water was available for irrigation from the Gila Gravity Main Canal on November 4, 1943. Construction was postponed during World War II. Canal and lateral construction was resumed as soon as hostilities ended.

Construction of the Wellton-Mohawk Division features was started in August 1949. On May 1, 1952, water from the Colorado River was turned onto the Wellton-Mohawk fields for the first time. The project was essentially complete by June 30, 1957.

Benefits

The Yuma Mesa Unit grows citrus, alfalfa hay and seed, peanuts, cotton, and grains. Alfalfa, cotton, melons, citrus, winter vegetables, small grains, and Bermuda grass seed are grown in the North and South Gila Units and the Wellton-Mohawk Division. Sheep are brought from summer ranges into the area and are wintered on irrigated pastures of the project before being shipped to feed lots and markets. Cattle feed lots of various sizes operate in the area.

Dams | Projects | Powerplants | Contact Us | Maps | Glossary | FAQ´s | Links