The Colorado River (Aha Kwahwat in Mojave), or the Red River, is a river in the southwestern United States and northwestern Mexico, approximately long, draining a part of the arid regions on the western slope of the Rocky Mountains. The natural course of the river flows from north of Grand Lake, Colorado into the Gulf of California, but the heavy use of the river as an irrigation source for the Imperial Valley has desiccated the lower course of the river in Mexico such that it no longer consistently reaches the sea.

The watershed of the Colorado River covers in parts of seven U.S. states and two Mexican states. Total flows of the river range from in droughts to in severe floods. With the construction of massive power dams on the lower course of the river, flows of over are unusual. The mean flow of the river was during the period between 1903-34. From 1951-80, the average flow was less than . Historically the flow was much higher before water usage began in the basin.

Course

Headwaters

The Colorado River's source is located high in Rocky Mountain National Park, near Lulu City, just west of the Continental Divide. Below Rocky Mountain National Park, the river flows through the Kawuneeche Valley, also part of the Park. Grand Lake, Colorado's largest and deepest natural lake, is just downstream of the river's headwaters, and, like it, is formed by melting snow and small tributaries. However, the Colorado River actually flows into Shadow Mountain Reservoir where it encounters the first of many dams in its journey to the Gulf of California and the Sea of Cortez. The physical connection between Shadow Mountain Reservoir and Grand Lake is not the course of the Colorado River, but a logistical piece of a larger trans-basin water storage and delivery project, the Colorado-Big Thompson Project that diverts the headwaters of the Colorado River to Colorado's Front Range and Eastern Plains on the other side of the Continental Divide. The next stop on the river's journey, Lake Granby, is another reservoir in this same project. From Lake Granby, the river passes just north of the Town of Granby and through a third dam at Windy Gapy. From there, U.S. Highway 40 roughly parallels the river to the town of Kremmling, where it enters Gore Canyon, just west of its confluence with the Blue River.

Most of the river's tributaries within Colorado are small. However there are exceptions, such as the Gunnison and Roaring Fork Rivers, in which massive amounts of water flow. About a hundred miles later it meets the Eagle River in the town of Dotsero, Colorado, and where I-70 parallels the river through Glenwood Canyon. The river then passes through the city of Glenwood Springs where it is joined by the swift flowing Roaring Fork River. West of Glenwood Springs, the Colorado runs through the Grand Valley and is joined by the Gunnison River in Grand Junction. From there it flows westward to the Utah border and Westwater Canyon. The Colorado here ranges from wide and from in depth with occasional deeper areas.

Cataract, Glen and Grand Canyons

The river turns southwest near Fruita, Colorado, and is joined by the Dolores River soon after entering Utah. It partially forms the southern border of Arches National Park near Moab, Utah, and then passes by Dead Horse Point State Park and through Canyonlands National Park where it is met by one of its primary tributaries, the Green River. The Colorado then flows into Lake Powell, formed by the Glen Canyon Dam. Below the dam, water released from the bottom of Lake Powell makes the river clear, clean, and cold. Just south of the town of Page, Arizona, the river forms the dramatic Horseshoe Bend, then at Lees Ferry is joined by another tributary, the warm, shallow, muddy Paria River, and begins its course through Marble Canyon. Here, the Colorado ranges from in width and in depth.

At the southern end of Marble Canyon, the river is joined by another tributary, the Little Colorado, and the river then turns abruptly west directly across the folds and fault line of the plateau, through the Grand Canyon, which is 349 km long (217 miles) and from 6 to 30 km (4 to 20 miles) between the upper cliffs. The walls, high, drop in successive escarpments of , banded in splendid colors toward the narrow gorge of the present river.

Below the confluence of the Virgin River in Nevada, the Colorado abruptly turns southward. Hoover Dam, built during the Great Depression, forms Lake Mead, a popular recreation site as well as the supplier of most of the water for Las Vegas. From Hoover Dam, the river flows south and forms part of the boundary between Arizona and Nevada and between Arizona and California. Along the California-Arizona reach of the river, four additional dams are operated to divert water for agricultural irrigation and for recreation. Lake Mohave, formed by Davis Dam, lies in the southern portion of the Lake Mead National Recreation Area. Lake Havasu, formed by Parker Dam, provides recreation as well as the home of the retired New London Bridge. The two remaining dams supply irrigation water: Palo Verde Diversion Dam and Imperial Dam. Here, the Colorado River ranges in width from and from in depth.

Final course

Below the Black Canyon the river lessens in gradient and in its lower course flows in a broad sedimentary valley's distinct estuarine plain upriver from Yuma, where it is joined by the Gila River. The channel through much of this region is bedded in a dike-like embankment lying above the floodplain over which the escaping water spills in time of flood. This dike cuts off the flow of the river to the remarkable low area in southern California known as the Salton Sink, Coachella Valley, or Imperial Valley. The Salton Sink is located below sea level; therefore, the descent from the river near Yuma is very much greater than the descent from Yuma to the gulf.

The lower course of the river, which forms the border between Baja California and Sonora, is essentially a trickle or a dry stream today due to use of the river as the Imperial Valley's irrigation source. Several miles from the mouth, the Hardy River enters, giving the river a little more water before it reaches the ocean. Prior to the mid 20th century, the Colorado River Delta provided a rich estuarine marshland that is now essentially desiccated, but nonetheless is an important ecological resource.

The estuary of the Colorado River was subjected to a major tidal bore that almost disappeared with the drastic reduction in the freshwater flow following the damming of the Colorado River, and to a lesser extent because of some dredging of the estuary channel. The first historical record of the tidal bore was that of the Spanish missionary Father Ferdinand Consac on 18 July 1746. During spring tide conditions, the tidal bore formed in the estuary about Montague Island and propagated upstream. It was called locally 'El Burro' or 'burro'. Today the tidal bore is rarely seen although there are still some anecdotic observations.

Climate change

According to the Natural Resources Defense Council, the Colorado River Basin, which stretches from Wyoming to Mexico, is at the center of hotter climate changes in the Western United States. Since the 1970s, rising temperatures have contributed to earlier snowmelts, and the basin has warmed more than any other area in the contiguous United States.

As a result, the volume of water in the basin is decreasing. The years 2000 to 2004 were the only five consecutive years in recorded history with water flow below average. Lake Powell, one of the basin's main reservoirs, is only 45 percent full. "Hotter and Drier: The West's Changed Climate." Natural Resource Defense Council. Mar. 2008. 25 July 2008 /www.nrdc.org/globalwarming/west/fwest.pdf>.

History

Early records

The existence of the Colorado River was first noted in the records of written history in September, 1539, when Francisco de Ulloa sailed to the head of the Gulf of California and rowed a short distance upstream. It was next seen by Hernando de Alarcon who in 1540 led the maritime contingent of Coronado's expedition. The plan was to meet the land based force and resupply them. Alarcon ascended the river about 85 Spanish miles to the limit of navigation near present-day Yuma, Arizona. He waited for Coronado, but eventually despaired, cached some supplies and correspondence, left a note on a tree, and departed. Coronado's land forces never reached that location, but Melchior Diaz, on his third expedition, went to see if he could establish contact with Alarcon. By the time he reached the Colorado, however, Alarcon had already left. The Native Americans told him what they knew of Alarcon's presence and that he had left a cache of supplies. Diaz found the note and the supplies. Diaz named the river Rio del Tizon ("River of Embers" or "Firebrand River") based on a practice used by the natives for warming themselves. Meanwhile, Coronado (who at the time was near Zuni, New Mexico) had learned from one of his scouting parties that the natives spoke of a large river to the west. He sent Garcia Lopez de Cardenas to lead a contingent of men to find this river. They did find it at what is now known as the Grand Canyon, becoming the first people of European background to see it. Their failed attempts at reaching the river led them to conclude that it would not be possible to be supplied via the Gulf of California and the river.

The following year, Francisco de Bolanos sailed to the mouth of the river on the Gulf of California. One of his pilots, Domingo del Castillo, prepared a map of the Mexican coast. He charted three rivers at the head of the gulf and named them Brazo de laguna p., Rio de buena Guia p., and Brazo de Mira flores p.. The latter of these three is the longest. Later references suggest that Brazo de Mira flores referred to what is now called the Gila River, and that Rio de buena Guia was his name for the Colorado. (In spite of these records, the error that California was an island persisted for more than a century, especially among European cartographers.)

Comparisons of 17th, 18th, and early 19th-century maps reveal a parade of names being applied to the Colorado and its tributaries, as well as a variety of courses, as cartographers learned or made up the geography of the region. On a map by Nicholas Sanson (1650) the R. del Tecon and the R. de Coral share a common mouth on the gulf. A number of maps show the Gila River (sometimes just the lower, sometimes the whole) as the Rio Grande de las Apostoles. A 1763 map by Emanuel Bowen equates the Apostles with the del Coral. A 1720 map by Fer Nicholas labels the main body of the Colorado as Rio del Tison, and a tributary of the Apostles/Gila as Rio Colorade. In 1703 Guillaume de L'Isle showed a Rio de buena esperanza as a major tributary of the Tison, but it is not clear if this tributary corresponds better with the Little Colorado or the San Juan. A map by Herman Moll (1720) charts the Tison and the Gila with separate mouths. Upriver from a tributary of the Tison that would appear to correspond with today's Virgin River, the name for the main channel is given as R. of Good Hope. On other maps Good Hope/Buena Esperanza are transferred to a tributary of the Gila. A map of 1757 gives the name of the main course as Rio Colorado de los Martyres. A map of 1781 by Jonathan Carver charts a major split in the river and labels the eastern branch "Colorado" and the western branch Martyres. A map from 1758 by Didier Robert de Vaugondy applies the name Colorado to a river that reaches north to the headwaters of the Missouri, best corresponding to today's Green River. When Jedediah Smith first reached the lower Colorado in 1826, he first called it the Seedskeedee, as the headwaters of the Green River were known to the trappers, but also noted that the natives called it the Colorado.

It is not clear when or why the name "Colorado" first replaced "Tizon" (Tecon/Tison), which had been the most common name on maps since 1540. Among the maps in the Library of Congress, every use of "Colorado" (or Colorade) from 1720 and before is applied to a tributary of what is now the Gila River that seems best to correspond with today's Verde River. The earliest map in that collection that replaces "Tizon" with "Colorado" is a map from 1743.

The map that resulted from Escalante's expedition in 1776 labels the main channel as the Colorado up to the confluence of the Nabajoo and Zaguananas rivers. The associated information leads one to conclude that the Nabajoo corresponds to the San Juan and the Zaguananas to the Colorado from there to the Dolores River. On this map the Colorado above the Dolores is called the Rafael, and the Green River (named Buenaventura River) is erroneously diverted to the southwest and to what is now called Sevier Lake. Where Escalante's journal records his crossing of the San Rafael, he notes that the Native Americans knew this river as the Colorado. He also notes that the natives said this river had it source in a distant lake, but the lake is not charted on the resulting map. It is evident from a number of maps of the period that people were not aware of the distance between the Colorado's confluence with the Dolores and the western slopes of the Front Range. On a map from 1847 by John Disturnell, the Rafael is replaced with the Green River, while the upper Colorado (or more correctly, what would be called the Grand River) is not shown at all.

Grand River

"Grand River" is the name once applied to the Colorado River from its headwaters in Rocky Mountain National Park to its confluence with the Green River in Utah.Early explorers identified the Gunnison River in Colorado as the headwaters of the Colorado River. The Grand River in Colorado was later identified as the headwaters of the river, and also provides hydroelectric power and irrigation. Finally in 1916, E.C. LaRue, Chief Hydrologist of the United States Geological Survey, identified the Green River in Wyoming as the actual headwaters of the Colorado River. This gave rise to several now orphaned names including Grand Lake, Grand Valley, Grand Junction, Grand County, Colorado, and Grand County, Utah. The earliest appearance of this name on a map could be on the map by Henry Schenck Tanner (1836). The name there replaces the name of Rio Rafael, which appears on many earlier maps. The head of this branch of the Colorado is shown as at about the same latitude as Longs Peak in Colorado. There is nothing charted that corresponds to the Green River, nothing that corresponds with the course of the Dolores (even though some earlier maps did show the Dolores with reasonable accuracy), and the headwaters of both the Rio Grande ("Rio del Norte") and especially the Arkansas River are shown to reach to a higher latitude.

A map by David H. Burr (1839) shows the "Colorado River of the West" flowing from the headwaters of the Green River to the Gulf of California, with the "Grand River" as a tributary branching to the east, the third tributary upriver from the Nabajoo (San Juan). The Green River is not separately named. The headwaters of the Grand are depicted as being very close to the headwaters of the Rio Grande (which is labeled "Rio Bravo del Norte") as well as those of the Arkansas River. A textual note on the map indicates that little is known of this area.

In 1921, U.S. Representative Edward T. Taylor petitioned the Congressional Committee on Interstate and Foreign Commerce to rename the Grand River as the Colorado River. On July 25, 1921 the name change was made official in House Joint Resolution 460 of the 66th Congress, over the objections of representatives from Wyoming and Utah and the United States Geological Survey which noted that the drainage basin of the Green River was more than 70% more extensive than that of the Grand River, although the Grand carried a slightly higher volume of water at its confluence with the Green.

Elevation summary

Approximate heights above sea level at several key locations:

Feet	Meters	Location
9000	2750	Colorado headwaters (Rocky Mountains)
6100	1850	midway to Colorado-Utah border
4300	1300	Colorado-Utah border
3850	1170	midway to Utah-Arizona border
3700	1130	Utah-Arizona border (Wahweap Bay)
3000	900	midway to Grand Canyon (Rider Point)
2800	850	Grand Canyon North Rim
2500	760	Grand Canyon South Rim
1200	365	Lake Mead (above Hoover Dam)
600	183	below Hoover Dam
485	150	California-Nevada-Arizona border
100	30	California-Arizona-Mexico border

Note that the significant difference between the present height of the rim of the Grand Canyon (about 2440 m; 8000 ft) and the levels at which the river enters/exits it gives rise to the geologic theory that its upheaval must have begun around the same time the river began flowing through it and eroding it (since rivers do not run uphill, it would have otherwise followed some other path around the upheaval). Estimates for the beginning of this erosion/upheaval process range from 5 to 70 million years ago.

Engineering

In the autumn of 1904, the river's waters escaped into a diversion canal a few miles below Yuma, Arizona, creating the New River and Alamo River. The rivers re-created in California a great inland sea in an area that it had frequently inundated before, for example, in 1884 and 1891, when it had for a time practically abandoned its former course through Mexican territory to the Sea of Cortez. However, it was effectively dammed in the early part of 1907 and returned to its normal course, from which, however, there was still much leakage to the Salton Sea. In July 1907, the permanent dam was completed. From the Black Canyon towards the sea the Colorado normally flows through a desert-like basin.

The Colorado River is a major and in some cases life-sustaining source of water for irrigation, drinking, and other uses by people living in the arid American southwest. Allocation of the river's water is governed by the Colorado River Compact. Several dams have been built along the Colorado River, beginning with Glen Canyon Dam near the Utah-Arizona border. Other dams include Hoover Dam, Parker Dam, Davis Dam, Palo Verde Diversion Dam, and Imperial Dam. Since the completion of the dams, the majority of the river in normal hydrologic years is diverted for agricultural and municipal water supply. The Colorado's last drops evaporate in the Sonoran Desert, miles before the river reaches the Gulf of California. Almost 90% of all water diverted from the river is for irrigation purposes. The All-American Canal is the largest irrigation canal in the world and carries a volume of water from 420 to 850 m³/s (15,000 to 30,000 ft³/s), making it larger in volume than New York's Hudson River. The canal's waters are used to irrigate the parched but fertile Imperial Valley, where several years can pass between measurable rainfalls. Hydrology transport models are used to assess management of the river's flow and water quality.

Hoover Dam (originally Boulder Dam, and the first dam of its type) was completed in 1936. Its impoundment of the river in the Mojave Desert creates Lake Mead, which provides water for irrigation and the generation of hydroelectric power.

Several cities such as Los Angeles, Las Vegas, San Bernardino, San Diego, Phoenix, and Tucson have aqueducts leading all the way back to the Colorado River. One such aqueduct is the Central Arizona Project ("CAP") canal, which was begun in the 1970s and finished in the 1990s. The canal begins at Parker Dam and runs all the way to Phoenix and then Tucson to supplement those cities' water needs.

The lower Colorado is navigable by moderate to large-sized craft. The lower river from Davis Dam to Yuma is navigable by large paddlewheel boats and river barges, but commercial navigation on the river is unimportant because the river is cut off from the sea, making other means of transportation more efficient in the region. Before the railroads arrived, the lower Colorado River from the sea to near present-day Laughlin, Nevada was an important means of transportation via large steamers. Most of the rest of the river, excluding the rapids in the canyons, is navigable by small to moderate-sized river craft and power boats.

Moab uranium tailings

Atlas Mineral Corporation operated a uranium processing mill in the area of Moab, Utah, on the north bank of the Colorado River just under 5 km (about 3 miles) from downtown Moab. As a byproduct of uranium processing activities, an estimated 16 million ton pile of chemically and radioactively hazardous tailings exists. The pile is located about 700-800 feet from the Colorado River. Although no contamination has been detected, the proximity of the material to the watershed has been a concern. The Senate has authorized the U.S. Department of Energy to budget $22.8 million in 2007 to begin the project of moving the uranium tailings farther from the river. The plan is to move the contaminated materials north to a disposal site located at Crescent Junction, Utah. The project is expected to be completed by 2028 with current funding plans, at total estimated cost of US$720 million.

Wildlife

The Colorado River basin is home to fourteen native species of fish. Four are endemic and endangered: Colorado pikeminnow (formerly Colorado squawfish), razorback sucker, bonytail chub, and humpback chub. The Upper Colorado River Endangered Fish Recovery Program is a controversial effort by the US Fish and Wildlife Service, in conjunction with the Arizona Game and Fish Department, the Colorado Division Of Wildlife, and the Utah Department Of Wildlife to recover these endangered fish.

Fish species

• Brook Trout
• Catfish
• Carp
• Crappie
• Largemouth Bass
• Rainbow Trout
• Striped Bass
• Sunfish
• Sturgeon
• Colorado Pikeminnow
• Humpback Chub
• Razorback Sucker
• Bonytail Chub

See also

• All-American Canal Bridge
• Colorado River Compact
• Colorado River Delta
• Glen Canyon Dam
• Hoover Dam
• List of tributaries of the Colorado River
• List of Colorado River rapids and features
• List of flora of the Lower Colorado River Valley

References

1. Munro, P et al.. A Mojave Dictionary Los Angeles: UCLA, 1992
2. Morrison, Samuel Eliot, The European Discovery of America - the Southern Voyages 1492-1616, Oxford University Press, New York, 1974 (page 623),
3. [1]
4. Morrison, op cit, page 625
5. Many of these can be viewed at the Library of Congress web site[2].
6. Moody, Ralph The Old Trails West, Thomas Y. Crowell Company, New York, 1963 (page 179); and Jedediah Smith's letter to William Clark as printed in the Thursday, October 11, 1827 edition of the Missouri Republican (Saint Louis), which is reproduced as an image in the Time-Life series The Old West, The Trailblazers, Time-Life Books, New York, 1973, (page 107). Jedediah Smith's spelling there is "Seeds Keeder".
7. [3]
8. [4]
9. [5]
10. [6]
11. It should be noted that a number of the rivers of the American southwest at one time or another had the word "Grand" as a part of their names, including the Rio Grande (Rio Grande del Norte) and the Gila (Rio Grande de las Apostoles).
12. Many years ago, the Colorado River was just Grand, retrieved January 5, 2008.

External links

• Federal Department of Energy site on uranium mine tailing site.
• State of Utah site on uranium mine tailings.
• Bibliography on Water Resources and International Law Peace Palace Library
• Arizona Boating Locations Facilities Map
• Arizona Fishing Locations Map
• Where to Fish in Arizona Species Information
• Drought Watch Campaign - map of the Colorado River system showing the fill levels of major reservoirs. Last updated July 2004.