Rio Grande

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Lore & Background

The Rio Grande rises in the western part of Rio Grande National Forest, in the U.S. state of Colorado, formed by the joining of several streams at the base of Canby Mountain, in the San Juan Mountains, due east of the Continental Divide of the Americas. From the Continental Divide, it flows through the San Luis Valley, then south into New Mexico, passing through the Rio Grande Gorge near Taos, then toward Española, collecting additional waters from the Colorado River basin via the San Juan-Chama Diversion Project and from the Rio Chama. It continues southwards, irrigating farmlands in the Middle Rio Grande Valley through Albuquerque and Las Cruces in New Mexico, to El Paso, Texas and Ciudad Juárez, Chihuahua, in Mexico. South of El Paso, the Rio Grande is the national border between the U.S. and Mexico. The segment of the river that forms the international border ranges from 889 to 1,248 miles (1,431 to 2,008 km), depending on how the river is measured. Major tributaries include the Rio Conchos, with its confluence 310 km (193 straight air miles) southeast of El Paso near Ojinaga, Chihuahua; the Pecos River and Devils River, both entering from the north near Amistad Reservoir in Texas; and the Rio Salado and Rio San Juan, entering from the south in Tamaulipas, Mexico. The river ends in a small, sandy delta at the Gulf of Mexico. During portions of 2001 and 2002, the mouth was blocked by a sandbar; in the fall of 2003, the sandbar was cleared by high river flows around 7,063 cubic feet per second (200 m3/s).

Reader's Guide

Since the mid–twentieth century, only 20 percent of the Rio Grande's water reaches the Gulf of Mexico, because of the voluminous consumption of water required to irrigate farmland (e.g. the Mesilla and Lower Rio Grande Valleys) and to continually hydrate cities (e.g. Albuquerque); such water usages are additional to the reservoirs of water retained with diversion dams. 260 miles (418 km) of the river in New Mexico and Texas are designated as the Rio Grande Wild and Scenic River. The river flows through a valley with diverse animal and plant populations. Although the river's greatest depth is 60 feet (18 m), it generally cannot be navigated by passenger riverboats or by cargo barges; navigation is only possible near the mouth, in rare circumstances up to Laredo, Texas. Navigation was active during much of the 19th century, with over 200 different steamboats operating between the river's mouth close to Brownsville and Rio Grande City, Texas. Many steamboats from the Ohio and Mississippi Rivers were requisitioned by the U.S. government and moved to the Rio Grande during the Mexican–American War in 1846, providing transport for the U.S. Army under General Zachary Taylor to invade Monterrey, Nuevo León, via Camargo Municipality, Tamaulipas. The Brownsville & Matamoros International Bridge, a large swing bridge dating back to 1910, is still in use today by automobiles connecting Brownsville with Matamoros, Tamaulipas; the swing mechanism has not been used since the early 1900s. A new rail bridge (West Rail International Crossing) connecting the U.S. and Mexico was built about 15 miles west of the Brownsville & Matamoros International Bridge and inaugurated in August 2015. At the mouth of the Rio Grande, on the Mexican side, was the large commercial port of Bagdad, Tamaulipas; during the American Civil War, this was the only legitimate port of the Confederacy, with European warships anchoring offshore to maintain the port's neutrality.

Did You Know?

• The Rio Grande is known as the Río Bravo (del Norte) in Mexico and as Tó Ba'áadi in Navajo.
• Only 20 percent of the Rio Grande's water reaches the Gulf of Mexico since the mid–twentieth century due to irrigation and municipal consumption.
• During the American Civil War, the port of Bagdad, Tamaulipas, at the river's mouth, was the only legitimate port of the Confederacy, with European warships maintaining its neutrality.
• The river's greatest depth is 60 feet (18 m), but it generally cannot be navigated by passenger riverboats or cargo barges.
• The ancestral Rio Grande progressively integrated basins to the south over millions of years, finally joining the Pecos River 800,000 years ago to drain into the Gulf of Mexico.

Physical Geography & Course

The Rio Grande takes its source in the western reaches of Rio Grande National Forest in south-central Colorado, where several streams converge at the foot of Canby Mountain in the San Juan Mountains, just east of the Continental Divide. From this high-altitude origin, the river carves southward through the San Luis Valley before entering New Mexico, threading through the Rio Grande Gorge near Taos and continuing toward Española. Along this stretch it gathers additional volume from the Colorado River basin via the San Juan-Chama Diversion Project and from the Rio Chama. The river then irrigates the Middle Rio Grande Valley past the desert cities of Albuquerque and Las Cruces before reaching El Paso, Texas, and Ciudad Juárez, Chihuahua. At Albuquerque the valley floor sits at 5,312 feet above sea level, dropping to 3,762 feet at El Paso. In New Mexico the river traverses the Rio Grande rift, cutting canyons between sediment-filled basins while sustaining a delicate bosque ecosystem on its floodplain. The journey concludes in a small, sandy delta where the water meets the Gulf of Mexico. At 1,896 miles, the river ranks as the fourth-longest main-stem waterway in the United States and North America, with a drainage basin spanning 182,200 square miles.

Water, Irrigation & Consumption

The Rio Grande serves as a critical water source for seven states across the United States and Mexico, flowing predominantly through arid and semi-arid terrain where every drop carries enormous weight. Since the mid-twentieth century, the demands of agriculture and urban life have transformed the river's downstream flow dramatically: only about 20 percent of its water now reaches the Gulf of Mexico. The remainder is consumed by irrigation of farmland in regions such as the Mesilla and Lower Rio Grande Valleys, by the continuous hydration of cities like Albuquerque, and by water retained behind diversion dams. Irrigated agriculture is particularly extensive in the subtropical Lower Rio Grande Valley, where the river's waters sustain crops in an otherwise desert landscape. Major tributaries feed the system, including the Rio Conchos, whose confluence lies roughly 310 kilometers southeast of El Paso near Ojinaga, Chihuahua. Downstream, the Pecos River and Devils River enter from the north near Amistad Reservoir in Texas, while the Rio Salado and Rio San Juan join from the south in Tamaulipas, Mexico. Together these tributaries and the main stem form a watershed of 182,200 square miles, expanding to 336,000 square miles when adjacent endorheic basins are included.

Navigation & River Commerce

Despite a maximum depth of 60 feet, the Rio Grande has generally resisted sustained commercial navigation by passenger boats or cargo barges. Practical navigation has been limited to the river's mouth and, in rare circumstances, as far north as Laredo, Texas. Yet during much of the nineteenth century the lower river bustled with activity: more than 200 steamboats operated between the mouth near Brownsville and Rio Grande City. During the Mexican-American War of 1846, the U.S. government requisitioned many of these vessels from the Ohio and Mississippi Rivers, using them to transport General Zachary Taylor's army toward Monterrey, Nuevo León, via Camargo in Tamaulipas. Army engineers at the time recommended that modest improvements would make the river navigable all the way to El Paso, but those proposals were never implemented. The Brownsville & Matamoros International Bridge, a large swing bridge completed in 1910, still carries automobile traffic between the two cities today, though its swing mechanism has been dormant since the last big steamboats departed in the early 1900s. In August 2015, the West Rail International Crossing opened about 15 miles west of the swing bridge, marking the first new international rail crossing between the United States and Mexico in over a century.

Border, Identity & Conservation

After traversing the full length of New Mexico, the Rio Grande assumes its most politically significant role: forming the international boundary between the United States and Mexico. This border segment stretches between 889 and 1,248 miles, depending on the measurement method used, separating Texas from the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas. A shorter stretch also serves as a partial state line between New Mexico and Texas. The river carries different names reflecting its cultural layers: Río Bravo del Norte in Spanish, Tó Ba'áadi in Navajo, and simply the Rio Grande in English. In the Albuquerque metropolitan area, the river flows past historic Pueblo villages including Sandia Pueblo and Isleta Pueblo, linking modern urban life to centuries-old communities. The valley it carves supports diverse animal and plant populations, and conservation of both the river and its surrounding ecosystem remains a persistent concern for residents of the region. Two hundred sixty miles of the river in New Mexico and Texas hold the designation of Wild and Scenic River, a recognition of the natural character that so much of the surrounding landscape has lost to development and water diversion.

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