Rio Grande, CO

The Rio Grande (known in Mexico as the Río Bravo del Norte, or simply Río Bravo) is a river that forms part of the border between the United States and Mexico. At 1,885 miles (3,034 km) long, it is the fourth-longest river system in the United States.

The Rio Grande rises in the eastern part of the Rio Grande National Forest in the American state of Colorado. This river is formed by the joining of several streams at the base of Canby Mountain, just east of the Continental Divide. From there, it flows through the San Luis Valley, then south into the state of New Mexico and passes through Espanola, Albuquerque and Las Cruces to El Paso, Texas, where it begins to form the natural border between the United States and Mexico. A major tributary, the Río Conchos, enters at Ojinaga, Chihuahua, below El Paso, and supplies most of the water in the 1,254 miles (2,018 km) Texas border segment. Other well-known 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. In fact it is barely navigable at all, except by small fishing boats. The natural flow of the Rio Grande is only 1/4 the volume of that of the Colorado River, and less than 1/50 that of the Mississippi River.

The Rio Grande rises in high mountains and flows for much of its length at high elevation; El Paso is 3,762 feet (1,147 m) above sea level. In New Mexico, the river flows through the Rio Grande Rift from one sediment-filled basin to another, cutting canyons between the basins and supporting a fragile bosque ecosystem in its floodplain. From El Paso eastward, the river flows through desert. Only in the sub-tropical lower Rio Grande Valley is there extensive irrigated agriculture. The river ends in a small sandy delta at the Gulf of Mexico. During portions of 2001 and 2002 the mouth of the Rio Grande was blocked by a sandbar. In the fall of 2003 the sandbar was cleared by high river flows of about 7,063 cubic feet per second (200 m3/s).