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Colorado River Basin

Colorado River Basin

Located in the southwestern United States and northwestern Mexico, the Colorado River is a 2,330-kilometer (1,450-mile) river with its headwaters in the Rocky Mountain National Park in north-central Colorado. The river is the primary source of water for a region that receives little annual rainfall.

More than 1,000 years ago, Native Americans irrigated their crops with the waters from the river. Today, the Colorado River is still used for irrigation , but it is also used to generate hydroelectric power and to supply water to distant urban areas.

The Basin

The Colorado River system, including the Colorado River, its tributaries , and the lands that these waters drain, is called the Colorado River basin, or watershed. It drains an area of 637,000 square kilometers (246,000 square miles), including parts of seven western U.S. states (Wyoming, Colorado, Utah, New Mexico, Nevada, Arizona, California) and Mexico. Three-fourths of the Colorado basin is federal land comprised of national forests, national parks, and Indian reservations. The drainage basin's total runoff is about 700 cubic meters (24,700 cubic feet) per second. It is the international boundary for 27 kilometers (17 miles) between Arizona and Mexico.

Water Resources.

The Colorado River Basin offers a major renewable water supply in the southwestern United States. About two-thirds of the water flowing in the Colorado River and its tributaries is used for irrigation, and the other one-third supplies urban areas, evaporates into the atmosphere, or provides water to riparian (streamside) vegetation. Without Colorado River water, the region would support few crops, and major cities such as Las Vegas, Nevada, and Phoenix, Arizona, would not have grown so rapidly.

Today nearly 17 million people depend on the Colorado's waters. The basin population has expanded dramatically in recent years, with most growth occurring in urban areas, where about 80 percent of the region's residents live. Phoenix and Tucson, Arizona, and Las Vegas, Nevada are the largest cities in the basin, and they use the Colorado River and its tributaries as their primary source of water.

Water from the Colorado River is taken from its primary route and transported to locations far from the Colorado River Basin. For example, water is diverted eastward across the Rocky Mountains to Denver and other cities in Colorado. The Colorado River Aqueduct carries water to metropolitan Los Angeles, and the Central Arizona Project supplies the Phoenix and Tucson areas. The All-American Canal provides water for the Imperial Valley of southern California, a productive agricultural region converted from a desert.

Multipurpose Dams.

Numerous dams were built on the Colorado and its tributaries during the twentieth century. The purpose of these dams was primarily to generate electricity, control floods, and provide recreational opportunities. They also store water during wet times for use during the dry months and, in some cases, during dry years.

The basin dams are able to store more than 86 billion cubic meters (3,037 billion cubic feet) of water, which is about four times the Colorado River's average annual runoff. The largest of these facilities, completed in 1936, is Hoover Dam, located on the border between Nevada and Arizona. The second largest dam is Glen Canyon Dam, which is in north-central Arizona and began operating in 1964. These two dams provide about 80 percent of the water-storage capacity in the basin.

The Morelos Diversion Dam, located on the MexicoArizona border, is the southernmost dam on the Colorado River. It sends nearly all of the remaining water to irrigation canals in the Mexicali Valley and to the Mexican towns of Mexicali and Tijuana. As a result, the river rarely reaches the Gulf of California, normally the river's mouth. Consequently, the vast wetlands at the mouth of the Colorado River have been reduced to just a fraction of their former size, affecting vegetation and wildlife. Before the construction of a number of dams along its reach, the Colorado flowed 129 kilometers (80 miles) through Mexico to the Gulf of California.

Hydroelectric generation from water stored at dam sites along the Colorado River totals about 12 billion kilowatt-hours per year, which is roughly equivalent to one-sixth of the electricity consumed in Arizona each year. This power is shared among several western states.

The dams of the Colorado River are used to control flooding and to permit development of flood-prone land along lower reaches. In addition, some of the reservoirs created by dams have been formed into national recreational areas comprising spectacular engineered wonders amidst natural landscapes. For example, Lake Mead National Recreation Area is made up of Lake Mead, formed by Hoover Dam, and Lake Mohave, formed by Davis Dam, while the Glen Canyon National Recreation Area includes Lake Powell.

Management Efforts

The Colorado Basin states were anxious about their shares of the Colorado River as early as the 1900s. Then as now, growth within the state of California was viewed with concern, as burgeoning expansion meant increased water demands. The signing of the Colorado River Compact in 1922 was an important milestone in the management of the Colorado River and became the foundation for the law of the river. This compact included the seven Colorado River Basin states, and apportioned water from the Colorado River between the Upper and Lower Basin states. The parties to the Colorado River compact were not unduly concerned with Indian water rights, nor did the Compact include provisions to protect the environment.

In 1963, a U.S. Supreme Court decision stated the amount of water to be apportioned among the lower-basin states, as well as the amounts that had been historically reserved for Indian tribes and federal public lands. Because of this landmark case, tribes are now considered to have the best water rights along the Lower Colorado River. The competition for water in the Colorado River Basin continues to be severe, as is shown by the increasing numbers of lawsuits that are within the court system. Water projects must now thoroughly research various environmental-impact studies in accordance with federal environmental protection legislation.

The apportionment of the waters of Colorado River has been cause for a great deal of controversy. The impact of dams and canals along the Colorado has spawned widespread debate on river development and the ecological role of instream flows. Given projected growth in its region, these controversies and debates will continue for some time.

Salinity.

A water quality problem that has grown in importance within the Colorado River is salinity, or the amount of solids (mostly salt) in the water. A variety of sources bring such dissolved salts into the river. The majority of salts run naturally off of soils and rocks. When river water is used for irrigation, some salts evaporate, and become concentrated in the remaining water that returns to the river. The salt problem is also caused by evaporation from reservoir surfaces and water use by plants along the river. The concentration of salt in the water of the lower river valley is so high that it cannot be used for human consumption without treatment. As a result, a desalinization plant near the border with Mexico removes salt from the river and allows the United States to provide Mexico with usable water.

Significant water quality problems occur in the Colorado River Basin, primarily because the river carries an estimated 9 million tons of salts annually. This amount is expected to increase in the future because of increased human use. Even worse, the lower Colorado River contains about 2,000 pounds of salts per acre-foot. Salinity increases downstream primarily owing to agriculture, evaporation, and the leaching of salts from soils. High salinity levels also originate in several tributaries, especially the Virgin River that flows through Arizona into Nevada. Environmental groups study the high salinity in the Colorado River and regularly meet to address this issue and other related water quality problems.

see also Dams; Desalinization; Hoover Dam; Instream Water Issues; Planning and Management, Water Resources; Powell, John Wesley; Prior Appropriation; Reservoirs, Multipurpose; Rights, Public Water; River Basin Planning; Supply Development.

William Arthur Atkins

Bibliography

Graf, William L. The Colorado River: Instability and Basin Management. Washington D.C.: Association of American Geographers, 1985.

Waters, Frank. The Colorado. New York: Rinehart, 1946.

Internet Resources

Colorado River Basin Salinity Control Program. Bureau of Reclamation, U.S. Department of the Interior. <http://www.uc.usbr.gov/progact/salinity/>.

Colorado River Water Dispute (COLORADO Case). American University, Washington, D.C. <http://www.american.edu/ted/COLORADO.HTM>.

Gillon, Kara (Defenders of Wildlife). The Lower Colorado River Basin: Challenges of Transboundary Ecosystem Management. Border Information and Outreach Service (BIOS), Interhemispheric Resource Center (IRC). <http://www.us-mex.org/borderlines/2000/bl68/bl68rivbasin.html>.

The Colorado River: Lifeline of the Southwest. DesertUSA.com, Digital West Media, Inc. <http://www.desertusa.com/colorado/coloriv/du_coloriv.html>.

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Colorado River Explorations

COLORADO RIVER EXPLORATIONS

COLORADO RIVER EXPLORATIONS. The Spanish explorer Francisco de Ulloa unwittingly reached the mouth of the Colorado River, in the Gulf of California, in 1539, but it was not until the following year that Hernando de Alarcón braved the fierce tidal bore of the river's mouth and proceeded upstream in boats drawn by tow ropes. Though Alarcón did not meet with Francisco Vásquez de Coronado's overland expedition, two of Coronado's officers, Melchior Díaz and García Lopéz de Cárdenas, did reach the Colorado that same year. Indeed, Cárdenas is generally credited as being the first European to see the Grand Canyon.

The Colorado River was given its name by Franciscan missionaries, who were the predominant explorers of the next two centuries. The name came from the river's red tinge during the spring melt. While missionaries traveled the Colorado frequently during this period, their missions were more concerned with converting souls than they were in contributing to the geographical knowledge of the region. One exception among the Franciscans was Silvestre Vélez de Escalante, who explored the river in the 1770s.

American trappers and fur traders were the next group of Europeans to take interest in the Colorado. William H. Ashley organized the American fur trade in the Rocky Mountains and hired Jedidiah Smith, who discovered the beaver-rich Green River. Ashley himself descended the Green River—conducting the first navigation of the river—in 1825 in bullboats and provided the first authentic information regarding the upper Colorado, painting "Ashley, 1825" on a huge rock at Ashley Falls.

Whereas the early Spanish adventurers had explored the Colorado from its mouth and headed northward, the American trappers had explored the river's northern tributaries, discovering and charting the geographies of the Green River and its junction with the Colorado. The greatest explorer of the Colorado connected the two ends of the river in exploring the last unmapped part of the continental United States. John Wesley Powell, the intrepid, one-armed leader of the Colorado River Exploring Expedition, embarked on his first—and historically more significant—trip through the Grand Canyon in 1869, departing from up the Green River in western Wyoming in May. After a dangerous 900-mile journey, in which three men deserted, the party concluded its voyage at the mouth of the Virgin River, in southeastern Nevada on 29 August. Powell's subsequent expeditions were scientifically more productive than the first, and enriched by the participation of the scientific artist of such eminent geologists as Grove Karl Gilbert and Clarence Dutton as well as the archaeologist William H. Holmes. Their collaboration was instrumental in the formulation of the basic principles of structural geology. As well as the geography and geology of the Colorado River, Powell was also intensely interested in the ethnology of the region and devoted considerable time to this study. As a result of the success of the second expedition, Powell was appointed director of the Survey of the Rocky Mountain Region in 1877. In 1881 he was made bureau chief of the new U.S. Geological Survey, a position he held until 1894. The Exploration of the Colorado River of the West (1875) and The Geology of the Eastern Portion of the Uinta Mountains (1876) are among Powell's important publications from his Colorado River explorations.

While Powell might have closed the book on discovery-oriented explorations of the Colorado, the river has been explored extensively throughout the twentieth century. The damming of Glen Canyon in the 1950s required considerable analysis of sites, while recent talk of dam removal has also prompted further investigation of the river's ecology.

BIBLIOGRAPHY

Pyne, Stephen J. How the Canyon Became Grand: A Short History. New York: Viking Press, 1998.

Stegner, Wallace. Beyond the Hundredth Meridian: John Wesley Powell and the Second Opening of the West. Lincoln: University of Nebraska Press, 1982.

Worster, Donald. A River Running West: The Life of John Wesley Powell. Oxford: Oxford University Press, 2001.

MichaelEgan

See alsoExplorations and Expeditions: U.S. ; Fur Trade and Trapping .

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Colorado (rivers, United States and Mexico)

Colorado (1 kŏlərăd´ə, –răd´ō, –rä´dō 2 kŏlərā´də, –rä´də). 1 Great river of the SW United States, 1,450 mi (2,334 km) long, rising in the Rocky Mts. of N Colo., and flowing generally SW through Colo., Utah, Ariz., between Nev. and Ariz., and Ariz. and Calif., then into Mexico, flowing toward the Gulf of California; drains c.244,000 sq mi (631,960 sq km). The Gunnison, Green, San Juan, and Little Colorado are the main tributaries in the upper basin of the Colorado; the Gila is the chief tributary of the lower basin. Silt deposited by the Colorado has formed a great delta across the northern part of the Gulf of California, cutting off the head of the gulf; the Salton Sea is a flooded remnant of the severed part. The intensive use of the river's waters now usually leaves the riverbed largely dry in the delta north of its outlet, but a 2012 agreement between the United States and Mexico called for both nations to work to restore the river's delta.

The mouth of the river was seen by Francisco de Ulloa in 1539; the lower part was explored by Hernando de Alarcón in 1540. The river flows through c.1,000 mi (1,610 km) of canyons, including Arizona's Grand Canyon; many national parks, monuments, and recreational areas lie along its banks. The Colorado's waters are used for power and irrigation, especially by means of the Colorado River storage project, the Colorado–Big Thompson project, Hoover Dam, Davis Dam, Imperial Dam, the All-American Canal, Parker Dam, Glen Canyon Dam, and, in Mexico, the Morelos Dam.

Controversies over water rights on the Colorado have long raged between the United States and Mexico and among the bordering states (it supplies most of S California's water); treaties and compacts regulate the river's use. California and, to a lesser degree, Nevada have in the past drawn more water than they were designated to receive. A new compact in 2003 gave California 14 years to reduce its water usage to its legal limits. A greater problem, however, is that the 1922 Colorado River Compact that established the division of water use between the upper and lower basins was based on an estimate of the average annual flow that is 10% to 25% higher than long-term data suggest, due to the use of river gauge data from what is now known to be a relatively wet period in the river basin's history. A 2007 accord established guidelines for reducing allocations in the lower basin when shortfalls occur.

2 River, 894 mi (1,439 km) long, rising in the Llano Estacado, NW Tex., and flowing SE to Matagorda Bay, an inlet of the Gulf of Mexico; drains c.41,500 sq mi (107,485 sq km). Destructive floods, which prevented private development of the river for power, led the Texas legislature to set up the Lower, Central, and Upper Colorado River authorities to undertake projects for flood control, power plants, and irrigation. The Lower Colorado River Authority, with federal assistance, has been especially active, building five major dams (Buchanan, Roy Inks, Alvin J. Wirtz, Marble Falls, and Mansfield). These projects have benefited a large part of Texas, including the city of Austin. The scenic section of the river above Austin, which includes the lakes formed by the dams, is called Highland Lakes Country. The Central Colorado River Authority has constructed many small irrigation dams and also has jurisdiction over several city reservoirs. The Upper Colorado River Authority regulates the upper Colorado and the several branches of the Concho, a principal tributary.

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Colorado River storage project

Colorado River storage project, a multipurpose plan, undertaken by the U.S. Bureau of Reclamation in 1956, to control the flow of the upper Colorado and its tributaries and to aid in the development of the rugged, remote upper Colorado River basin; includes parts of Wyo., Utah, Colo., Ariz., and N.Mex. The Colorado River Compact of 1922 established the division between the upper and lower basins and stipulated that the upper basin's water consumption be contingent on the delivery of a set amount of water to the lower basin. Since the flow of the Colorado is erratic, a storage project was needed to maintain an even flow of water to the lower basin in dry years (the estimate of the average flow of the river, however, was based on what historically was a relatively wet period, and was 10% to 25% more than long-term estimates now indicate). A series of dams regulates stream flow, provides storage reservoirs, creates hydroelectric power, and irrigates both new and previously developed acreage. The four major units of the project are Glen Canyon Dam, on the Colorado River in Arizona; Flaming Gorge Dam, on the Green River in Utah; Navajo Dam, on the San Juan River in New Mexico; and the Curecanti dams on the Gunnison River in Colorado. The three reservoirs of the Curecanti unit are included in the Curecanti National Recreation Area (see National Parks and Monuments, table). There are 11 authorized participating projects, including the Central Utah project.

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Colorado River

Colorado River Major waterway in sw USA, which rises in the Rocky Mountains of n Colorado, and flows generally sw into the Gulf of California, passing through the Grand Canyon. There are many national parks, irrigation and hydroelectric power schemes along the river. Length: 2333km (1450mi).

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