Colorado River (Aha Kwahwat in
Mojave), or the
River, is a river in the southwestern
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
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.
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
Canyon. The river then passes through the city of
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
The Colorado here ranges from wide and from
in depth with occasional deeper areas.
Cataract, Glen and Grand Canyons
turns southwest near Fruita, Colorado,
and is joined by the Dolores River
soon after entering Utah. It partially forms the southern border of
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.
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.
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
Here, the Colorado ranges from in width and
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
Canyon, which is 349 km long (217 miles) and from 6 to 30
km (4 to 20 miles) between the upper cliffs.
high, drop in successive escarpments of , banded in splendid colors
toward the narrow gorge of the present river.
confluence of the Virgin River in
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
Verde Diversion Dam and Imperial
Here, the Colorado River ranges in width
from and from in depth.
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.
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
Sink, Coachella 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.
course of the river, which forms the border between Baja
essentially a trickle or a dry stream today due to use of the river
as the Imperial Valley's irrigation source.
from the mouth, the Hardy River
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
conditions, the tidal bore
formed in the estuary about Montague
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.
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
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
Downstream view of the Colorado River
at river mile 175 in the Grand Canyon
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.
next seen by Hernando de Alarcon
who in 1540 led the maritime contingent of Coronado's
The plan was to meet the land based force and resupply them.
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
("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
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
, and Brazo de Mira flores p
.. The latter of these
three is the longest. Later references suggest that Brazo de
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
persisted for more than a century, especially among
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
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
Gila with separate mouths. Upriver from a tributary of the
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
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
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
. 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
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
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
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.
Approximate heights above sea level at several key locations:
the significant difference between the present height of the rim of
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
Estimates for the beginning of this
erosion/upheaval process range from 5 to 70 million years
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.
Glen Canyon Dam and Bridge
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
. Several dams have been built along the
Colorado River, beginning with Glen Canyon Dam near the Utah-Arizona border. Other dams include
Dam, Davis Dam, Palo Verde
Diversion Dam, and Imperial
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
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.
canal's waters are used to irrigate the parched but fertile
Valley, where several years can pass between measurable
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
Mead, which provides water for irrigation and the
generation of hydroelectric
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
("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'
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.
the railroads arrived, the lower Colorado River from the sea to
near present-day Laughlin,
Nevada was an important means of transportation via large
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
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
$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
The Colorado River basin is home to fourteen native species of
fish. Four are endemic
: Colorado pikeminnow
(formerly Colorado squawfish), razorback sucker
, bonytail chub, and
humpback chub. The Upper
Colorado River Endangered Fish Recovery Program
controversial effort by the US Fish and Wildlife
, in conjunction with the Arizona Game and Fish
, the Colorado Division Of Wildlife
and the Utah Department Of
to recover these endangered fish.
- Munro, P et al.. A Mojave Dictionary Los Angeles:
- Morrison, Samuel Eliot, The European Discovery of America -
the Southern Voyages 1492-1616, Oxford University Press, New
York, 1974 (page 623),
- Morrison, op cit, page 625
- Many of these can be viewed at the Library of
Congress web site.
- 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".
- 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).
- Many years ago, the Colorado River was just
Grand, retrieved January 5, 2008.