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Major Rivers, Colorado River
Central Arizona Project, desert cities, Colorado River water, lower course, river flows
Originating in the Rocky Mountains of Colorado, the Colorado River extends for 2,330 km (1,450 mi) to the Gulf of California in Mexico. The river flows through the extensive, high Colorado Plateau region in the states of Colorado, Utah, and Arizona. For millions of years, the Colorado River and its tributaries have been carving deep canyons, including the scenic Grand Canyon, into the arid Southwestern landscape. Portions of this spectacular feature reach a width of 29 km (18 mi) and a depth of more than 1,500 m (more than 5,000 ft).
As the only major river flowing through the driest portion of the United States, the water of the Colorado is in great demand by several states as well as by Mexico. To meet this demand for water, dams were constructed in the Colorado River drainage basin beginning in the early 1900s. These dams supported large-scale irrigation projects. As the demand for water in the region increased, more dams were constructed to help control water usage and provide electricity to nearby states.
In 1923 the states of the upper basin (Colorado, New Mexico, Utah, and Wyoming) and those of the lower basin (Arizona, Nevada, and California) met to divide usage of the river's water. The upper basin states agreed upon a subdivision of their total allotment, but the lower basin states went to court to set their distribution shares. Those totals have not been revised for three decades while the populations in many of the areas served by these allotments have grown rapidly.
In the 1930s Hoover Dam was built on the border between the states of Arizona and Nevada. It is the largest of four dams built on the lower course of the river and holds back the waters of Lake Mead, one of the world's largest reservoirs. Beginning in 1973, the Central Arizona Project used a variety of canals, tunnels, pumping stations, and pipelines to carry water from the Colorado to desert cities such as Phoenix and Tucson in Arizona. The Colorado River is the chief source of water for the state of Arizona. Today, there is more Colorado River water claimed through various agreements than actually exists.
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