Rio Grande  The Rio Grande ( or ; , or simply Río Bravo) is one of the principal rivers (along with the Colorado River) in the southwest United States and northern Mexico. The Rio Grande begins in south-central Colorado in the United States and flows to the Gulf of Mexico. After passing through the length of New Mexico along the way, it forms part of the Mexico–United States border. According to the International Boundary and Water Commission, its total length was in the late 1980s, though course shifts occasionally result in length changes. Depending on how it is measured, the Rio Grande is either the fourth- or fifth-longest river system in North America. The river serves as part of the natural border between the U.S. state of Texas and the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas. A very short stretch of the river serves as part of the boundary between the U.S. states of Texas and New Mexico. Since the mid–20th century, heavy water consumption by farms and cities along with many large diversion dams on the river has left only 20% of its natural discharge to flow to the Gulf. Near the river's mouth, the heavily irrigated lower Rio Grande Valley is an important agricultural region. The Rio Grande's watershed covers . Many endorheic basins are situated within, or adjacent to, the Rio Grande's basin, and these are sometimes included in the river basin's total area, increasing its size to about . The Rio Grande rises in the western part of the Rio Grande National Forest in the U.S. state of Colorado. The river is formed by the joining of several streams at the base of Canby Mountain in the San Juan Mountains, just east of the Continental Divide. From there, it flows through the San Luis Valley, then south into the Middle Rio Grande Valley in New Mexico, passing through the Rio Grande Gorge near Taos, then toward Española, and picking up additional water from the San Juan-Chama Diversion Project from the Rio Chama. It then continues on a southerly route through the desert cities of Albuquerque and Las Cruces to El Paso, Texas, and Ciudad Juárez, Chihuahua. In the Albuquerque area, the river flows past a number of historic Pueblo villages, including Sandia Pueblo and Isleta Pueblo. Below El Paso, it serves as part of the border between the United States and Mexico.