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" ~' I ,. . G) Ict<g7 WELLTON-!10HAWK ONFA.Rl1 IRRIGATION IMPROVE~.ENT PROGRAH HISTQRc' The Well ton-Mohawk Irrigation and Drainage District is located i~ Yuma County in southwestern Arizona. The west e~d of the OlS- trict lies about 7 miles east of the confluence of the Gila an2 Colorado Rivers. The district is bordered on the west by the Gila Mountains and extends east 40 miles to the Moha~k Mountains. Irrigation began in the area before the turn of the centu~y with water diverted from the Gila River. As upstream development along the Gila River occurred, flows in the river gradually dimin- ised. In 1915, the farmers started using water from pumped ~ells. The ground water gradually became saline and lands went out Qf production. Facilities for water were included was to serve 75,000 transport and distribution of Colorado in the 1947 Gila Reauthorization Act. acres of land in the district. River The watel:' Colorado River water was first delivered to the district in 1952. As a result of the irrigation project, the water table rose rapidly. Drainage problems developed and drainage wells were in- stalled in 1957. This drainage water was pumped into the Gila River channel. The drainage water was initially quite saline, averaging about 6,000 parts per million (ppm) of total dissolved solids. The concrete-lined Wellton-Mohawk majn conveyance channel was constructed in the early 196005 to carry the ,pumped drainage water to the Colorado River. These flows were d~livered to Mexico at the International Boundary in accordance with the 1944 water treaty. The average annual salinity of the water delivered to Mexico increased from about 800 ppm of total dissolved solids in 1961 to nearly 1,500 ppm in 1962. This increase was due partly to the dis- charge from the We11ton-t1oha'Nk District. In addition, there '....as a marked decrease in other Coloradc Rive~ flows reaching Mexico. Minutes No. 218 and 241 of the Internatior.al Boundary and Water Commission were int€rim solutions that resulted in a reduction of average annu21 salini~y of the Colo~~dG River at Imge~ial D2m to l~:':C; .-::~;:-[ L""! ~~i7~, Cn ';12q:...:::::;: 30: 1372, th~ PresioEnt of the iJ,~it'2d ---, .. - - -,. - -.. - ~- " . - -. - . -' -,~ - -- -.-'.-"--".""'- -,- --. - . --- . . ~ - .- -- _,:.. 2~: ':;;:::'=:-. :::!:-':i:..3.;:;- llshed ~ "p~rrn2n~n~ an~ deiini~ive solution to ~he internatlonal problem .:- ~ ~ ~ ~ " ..... , ... --.. - - '::.~-,:::; ::-:"::'~-:C:lr:.8." -2-