<P> 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 of 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 . </P> <P> The Rio Grande's watershed covers 182,200 square miles (472,000 km). 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 336,000 square miles (870,000 km). </P> <P> 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 . </P> <P> The official river border measurement ranges from 889 miles (1,431 km) to 1,248 miles (2,008 km), depending on how the river is measured . A major tributary, the Rio Conchos, enters at Ojinaga, Chihuahua, below El Paso, and supplies most of the water in the border segment . Other tributaries include the Pecos and the smaller Devils, which join the Rio Grande on the site of Amistad Dam . Despite its name and length, the Rio Grande is not navigable by ocean - going ships, nor do smaller passenger boats or cargo barges use it as a route . It is barely navigable at all, except by small boats in a few places; at its deepest point, the river's depth is 60 feet (18 m). </P>

Where does the rio grande river start in colorado