Rio Grande (river) or Rio Bravo, river of North America, rising in the San Juan Mountains, southwestern Colorado and flowing generally southeast for 3034 km (1885 mi). It flows through New Mexico, forms the boundary between Texas and Mexico for about 2092 km (about 1300 mi), and then empties into the Gulf of Mexico at Brownsville, Texas. The Rio Grande is one of the longest rivers in North America but is too shallow for commercial navigation. The Native Americans used it for irrigation before the arrival of the Spanish in 1540; today major irrigation projects are centered at Elephant Butte and Caballo reservoirs in New Mexico. Among the crops raised in the river valley by irrigation are cotton, citrus fruits, and vegetables. In Mexico the river is known as the Rio Bravo.