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Colorado River

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The turbulent Colorado River is one of the most heavily regulated rivers in the world.

Serving as the “lifeline of the Southwest,” the Colorado River provides water to 35 million people and more than 4 million acres of farmland in a region encompassing some 246,000 square miles.

The Colorado falls some 10,000 feet on its way from the Rocky Mountains to the Gulf of California [see Colorado River Facts]. From its headwaters northwest of Denver, the 1,450-mile long river and its tributaries pass through parts of seven states:  Arizona, California, Colorado, New Mexico,  Nevada, Utah and Wyoming  and is also used by the Republic of Mexico.

Along the way, almost every drop of the Colorado River is allocated for use.

The Colorado River Basin is also home to range of habitats and ecosystems from mountain to desert to ocean.


Colorado River Overview

The Colorado River has been tapped for use by humans for almost 1500 years.

Today, more water is exported from the Colorado River Basin than any other river basin in the United States.

Water is diverted over the Continental Divide to supply Denver and other Front Range cities. Water is diverted in Utah to the Salt Lake Valley, in New Mexico to the Rio Grande Basin to serve Albuquerque, in Wyoming to serve Cheyenne and in California to the southern coastal plain of Los Angeles and San Diego.

Seven western states, the federal government, Mexico and 23 American Indian tribes share water rights to the water that flows 1,450 miles from the headwaters of the river in Colorado’s Rocky Mountain National Park to the Gulf of California. (For a more depth look at the various Colorado River stakeholders see the Layperson’s Guide to the Colorado River.)

The states comprise two basins: the Upper Basin consists of Colorado, New Mexico, Utah and Wyoming.  The Lower Basin consists of Arizona, California, and Nevada. (Lee Ferry is the dividing point between the Upper and Lower Basin.)

As part of its diverse environments, the Colorado River boasts more than 30 fish species found nowhere else in the world. However, 50 percent of all native fish and in the Colorado Basin have either gone extinct are or considered vulnerable.  The river itself was originally muddy , brown and seasonally warm (the source of its name Colorado) but is now clear and cold due to dams and reservoirs.

The Colorado River was the last major area of the 48 contiguous states to be explored. In 1869, an expedition led by John Wesley Powell first explored and mapped the Colorado and Green rivers.

Recreation is also a significant part of the Colorado River system. The Colorado River is used by millions of people annually for activities ranging from rafting to snow sports and generates billions of dollars in revenue.


Colorado River Agreements

Colorado River water is shared by states, the federal government, American Indian tribes and Mexico, resulting in many compromises, interstate compacts, a U.S. Supreme Court decree and an international treaty.

In 1905, the Colorado River broke through a series of dikes, flooding an ancient seabed in the Imperial Valley and forming the Salton Sea. Subsequently, in 1922 the Colorado River Compact divided the water among the seven Western states with an allocation formula, apportioning 7.5 million acre-feet to each basin. As part of the agreement, courts established that California could use no more than 4.4 million acre-feet of water per year, plus half of any officially declared surplus.

In 1944, a U.S.-Mexico treaty resulted in an annual 1.5 million acre-feet allocation to Mexico.

The 2003 Quantification Settlement Agreement incorporated an Imperial Valley to San Diego County water transfer.  This was followed by a 2007 agreement among the seven Colorado Basin states  that established  a new water release formula between Powell and Mead lakes to help meet increased demand for water.

More recently, in 2012 the U.S. and Mexico signed Minute 319. Minute 319 establishes new rules for sharing Colorado River water through a five-year pact. Mexico, with limited storage capacity, may now store some of its Colorado River water in Lake Mead. In exchange, should a shortage be declared in the Lower Basin, less water will be sent to Mexico.

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