Geography of the Colorado River

A Large, Important River in the U.S. Southwest

The Horseshoe bend in the Colorado river
Daniel Viñé Garcia/Moment/Getty Images

The Colorado River (map) is a very large river located in the southwestern United States and northwestern Mexico. The states it runs through include Colorado, Utah, Arizona, Nevada, California, Baja California and Sonora. It is approximately 1,450 miles (2,334 km) in length and it drains an area of about 246,000 square miles (637,000 sq km). The Colorado River is important historically and it is also a major source of water and electrical power for millions of people in the areas in which it drains.

  • Source: La Poudre Pass Lake, Rocky Mountain National Park, Colorado
  • Source Elevation: 10,175 feet (3,101 m)
  • Mouth: Gulf of California, Mexico
  • Length: 1,450 miles (2,334 km)
  • River Basin Area: 246,000 square miles (637,000 sq km)

Course of the Colorado River

The headwaters of the Colorado River begin at La Poudre Pass Lake in Rocky Mountain National Park in Colorado. The elevation of this lake is approximately 9,000 feet (2,750 m). This is a significant point in the geography of the United States because it is where the Continental Divide meets the Colorado River drainage basin.

As the Colorado River begins to descend in elevation and flow to the west, it flows into Grand Lake in Colorado. After descending further, the river then enters several reservoirs and finally flows out to where it parallels U.S. Highway 40, joins several of its tributaries and then parallels U.S. Interstate 70 for a short time.

Once the Colorado River meets the U.S. southwest, it begins to meet several more dams and reservoirs- the first of which is the Glen Canyon Dam which forms Lake Powell in Arizona. From there, the Colorado River begins to flow through massive canyons which it helped carve millions of years ago. Among these is the 217 mile (349 km) long Grand Canyon. After flowing through the Grand Canyon, the Colorado River meets the Virgin River (one of its tributaries) in Nevada and flows into Lake Mead after being blocked by the Hoover Dam at the Nevada/Arizona border.

After flowing through the Hoover Dam, the Colorado River continues its course toward the Pacific through several more dams, including the Davis, Parker and Palo Verde Dams. It then flows into the Coachella and Imperial Valleys in California and finally into its delta in Mexico. It should be noted, however, that the Colorado River delta, while once rich marshland, is today mainly dry aside from exceptionally wet years due to the removal of water upstream for irrigation and city uses.

Human History of the Colorado River

Humans have inhabited the Colorado River basin for thousands of years. Early nomadic hunters and Native Americans have left artifacts throughout the area. For example, the Anasazi began living in Chaco Canyon at around 200 B.C.E. Native American civilizations grew to their peak from 600 to 900 C.E. but they began to decline after that, likely due to drought.

The Colorado River was first noted in historic documents in 1539 when Francisco de Ulloa sailed upstream from the Gulf of California. Shortly thereafter, several attempts were made by various explorers to sail farther upstream. Throughout the 17th, 18th and 19th centuries, a variety of maps showing the river were drawn but they all had different names and courses for it. The first map using the name Colorado appeared in 1743.

Throughout the late 1800s and into the 1900s, several expeditions to explore and accurately map the Colorado River took place. In addition from 1836 to 1921, the Colorado River was called the Grand River from its source in Rocky Mountain National Park to its confluence with the Green River in Utah. In 1859 a U.S. Army topographic expedition led by John Macomb occurred, during which he precisely located the confluence of the Green and Grand Rivers and declared it the source of the Colorado River.

In 1921, the Grand River was renamed the Colorado River and since then the river has included all of its present-day area.

Dams of the Colorado River

The modern history of the Colorado River consists mainly of managing its water for municipal uses and to prevent flooding. This came as a result of a flood in 1904. In that year, the river's water broke through a diversion canal near Yuma, Arizona. This created the New and Alamo Rivers and eventually flooded the Salton Sink, forming the Coachella Valley's Salton Sea. In 1907 however, a dam was built to return the river to its natural course.

Since 1907, several more dams have been constructed along the Colorado River and it has grown into a major source of water for irrigation and municipal uses. In 1922, the states in the Colorado River basin signed the Colorado River Compact which governed each state's rights to the river's water and set specific annual allotments of what could be taken.

Shortly after the signing of the Colorado River Compact, the Hoover Dam was constructed to provide water for irrigation, manage flooding and generate electricity. Other large dams along the Colorado River include the Glen Canyon Dam as well as the Parker, Davis, Palo Verde and Imperial Dams.

In addition to these large dams, some cities have aqueducts running to the Colorado River to further aid in maintaining their water supplies. These cities include Phoenix and Tucson, Arizona, Las Vegas, Nevada, and Los Angeles, San Bernardino and San Diego California.

To learn more about the Colorado River, visit and the Lower Colorado River Authority.​

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Briney, Amanda. "Geography of the Colorado River." ThoughtCo, Oct. 29, 2020, Briney, Amanda. (2020, October 29). Geography of the Colorado River. Retrieved from Briney, Amanda. "Geography of the Colorado River." ThoughtCo. (accessed June 6, 2023).