Colorado River

One of the major rivers of the western United States, the Colorado River flows for some 1,500 mi (2,415 km) from Colorado to northwestern Mexico. Dropping over 2 mi (3.2 km) in elevation over its course, the Colorado emptied into the Gulf of California until human management reduced its water flow. Over millions of years the swift waters of the Colorado have carved some of the world's deepest and most impressive gorges, including the Grand Canyon.

The Colorado River basin supports an unusual ecosystem . Isolated from other drainage systems, the Colorado has produced a unique assemblage of fishes. Of the 32 species of native fishes found in the Colorado drainage, 21–66%, are endemic species—species that arose in the area and are found nowhere else.

Major projects carried out since the 1920s have profoundly altered the Colorado. When seven western states signed the Colorado River Compact in 1922, the Colorado became the first basin in which "multiple use" of water was initiated. Today the river is used to provide hydroelectric power, irrigation , drinking water, and recreation ; over 20 dams have been erected along its length. The river, in fact, no longer drains into the Gulf of Colorado—it simply disappears near the Mexican towns of Tijuana and Mexicali. Hundreds of square miles of land have been submerged by the formation of reservoirs, and the temperature and clarity of the river's water have been profoundly changed by the action of the dams.

Alteration of the Colorado's habitat has threatened many of its fragile fishes, and a number are now listed as endangered species . The Colorado squawfish serves as an example of how river development can affect native wildlife . With the reservoirs formed by the impoundments on the Colorado River also came the introduction of game fishes in the 1940s. One particular species, the Channel catfish, became a prey item for the native squawfish, and many squawfish were found dead, having suffocated due to catfish lodged in their throats with their spines stiffly locked in place. Other portions of the squawfish population have succumbed to diseases introduced by these non-native fishes.

Major projects along the Colorado include the Hoover Dam and its reservoir , Lake Mead, as well as the controversial Glen Canyon Dam at the Arizona-Utah border, which has a reservoir extending into Utah for over 100 mi (161 km).

[Eugene C. Beckham and Jeffrey Muhr ]

RESOURCES

BOOKS

Fradkin, P. L. A River No More: The Colorado River and the West. New York: Knopf, 1981.

Richardson, J. The Colorado: A River At Risk. Englewood, CO: Westcliffe Publishers, 1992.