river in Sonora state, northwestern Mexico. Formed in the Sierra Madre Occidental by the junction of the Bavispe and Papigochi rivers near the U.S. border, the Yaqui flows generally southward and westward through Sonora for approximately 200 miles (320 km), crossing the coastal plain to empty into the Gulf of California 28 miles (45 km) southeast of Guaymas. The Yaqui is Sonora's largest river system. Retained by the Álvaro Obregón Dam above Ciudad Obregón and by the Novillo Dam above Soyopa, the river is used extensively for irrigation. Wheat, corn (maize), rice, and fruits are the principal crops cultivated along its lower course. The Yaqui is not navigable.