The Colorado ( Spanish for red-colored or colored ) is the largest and most important river in Southwest North America . It is 2333 km long and has a catchment area of 635,000 km². Agriculture, drinking water, and electricity in the southwestern United States and parts of California depend heavily on the Colorado River water regime . To this end, a large number of irrigation projects of various sizes were built between the end of the 19th century and the 1980s.
The river has its source in Rocky Mountain National Park in the US state of Colorado , northwest of Denver on the western flank of the North American Continental Divide . It flows from the mountains of the Rocky Mountains to Utah and Arizona and largely forms the border between Arizona and Nevada and the entire border between Arizona and California . The Colorado River then flows into Mexico and flows into the Gulf of California between the states of Baja California and Sonora . The Colorado River has its source in an area with high regional water supply and flows through a large dry area as a result . In the US states of Utah, Nevada, Arizona and California it is therefore a so-called alien river .
Where the Colorado leaves the Rocky Mountains, the highlands of the Colorado Plateau and with it the middle course of the river begin . In this area, the Colorado with its tributaries has created many unique landscapes through erosion . Over a length of 1,600 km, the Colorado River flows through several canyons , including Glenwood Canyon in Colorado, Glen Canyon in Utah, Marble Canyon and Grand Canyon in Arizona. At the exit of the Grand Canyon, today in the reservoir area of Lake Mead , the lower reaches of the Colorado River begins. Here the river runs first through the high-lying Mojave Desert and then through the deeper Sonoran Desert . The Colorado River no longer reaches the Gulf of California year-round on the surface. Since a lot of water is taken for irrigation purposes above the estuary, the evaporation in the desert climate leads to the small remaining amounts of water seeping into the sandy soil and only flowing underground into the Gulf.
At the mouth of the Colorado River are the islands of Montague , Gore and Pelícano.
The upper reaches of the Colorado River to its confluence with the Green River was formerly called the Grand River . It was not until 1921 that the American Congress renamed it Colorado River at the request of the State of Colorado.
The historical condition of the Colorado River is largely unknown. Before the construction of the Glen Canyon Dam , which was completed in 1963, there were no comprehensive investigations. The first wave of systematic research did not begin until 1977 at the suggestion and paid for by the Bureau of Reclamation , the operator of the dam .
The river's ecosystems differ greatly in the various river sections. While the upper reaches of the Colorado River can be described as a cold and clear mountain river, it absorbs huge amounts of suspended matter through its own erosion and influx of debris from the tributaries on the Colorado Plateau. With the influx of the Gila River in Arizona, minerals and especially salts are brought into the Colorado, which change the chemical composition and salinity . In addition, the underflow is shallow due to water withdrawal and warms up strongly in the desert climate.
The extreme changes in the water regime caused by the construction of dams and the diversion of water have severely impaired the aquatic ecosystems of the middle and lower reaches. The reservoirs are deep and the flow rate is reduced to almost zero. Below the dams, the lack of bed load means that the river digs in. This makes the water colder and more tearing, which in turn results in the benthal becoming coarser. Living things that depend on warm shallow water zones lose their habitats.
The total number of original fish species in the Colorado catchment area is typically given as 49, of which four are considered locally extinct. On the other hand, at least 72 alien species were introduced into the catchment area, mainly in the interests of sport fishing . Individual votes assume only 36 or even 29 originally native species. All others would then be introduced by humans, including above all the catfish Ictalurus punctatus and the carp, which originally came from Eurasia . Both species have contributed significantly to the decline of native fish because they feed on their spawn. One of the most endangered species is Gila cypha , a carp fish that was rescued by a settlement project in Grand Canyon National Park from 2009 to 2011 .
In the 1970s, carp made up 70-80% of all fish caught in the central Colorado. Since the beginning of the 1980s the proportion has decreased massively, investigations using the same methods as before have shown only around 25% carp and this only in small schools. The cause is considered to be the changes caused by the construction of the dams, which initially strongly preferred the carp, but leveled off again over about twenty years. Furthermore, introduced species make up around 85% of the population in the best-studied section of the Grand Canyon National Park.
The insect population in the upper reaches of the Colorado is dominated by stone flies , caddis flies and mayflies . Together with aquatic beetles and some real flies , they make up 95% of invertebrates . On the Colorado Plateau and in the lower reaches of the river, the insects are greatly reduced due to the high proportion of suspended matter in the water. Oligochaetes and the shrimp Gammarus lacustirs , as well as a variety of screw represent the largest part of invertebrates in the middle course of Colorado.
The bank vegetation is characterized by the different altitudes and the surrounding ecosystems. The tamarisk is important as a neophyte . With their high water requirements, tamarisk bushes can dominate the shore zones and displace the natural vegetation. In some of the nature reserves on the river, the species is therefore controlled by mechanical means.
The Colorado River is one of the most heavily used rivers in the world. Although its entire catchment area is only populated by an average of seven people per square kilometer, every drop of precipitation along the course of the river is statistically used around 17 times for irrigation, electricity generation or drinking water.
The Colorado Big Thompson Project
The Colorado Big Thompson Project is the largest water diversion project in Colorado. On the west side of the Rocky Mountains, water is collected in the upper reaches of the Colorado in Grand Lake , Lake Granby and in man-made reservoirs. Much of the water is channeled through the Alva B. Adams Tunnel under the Continental Divide to the east side of the mountains to the Big Thompson River , a tributary of the South Platte River . It is used to generate electricity on its way through the mountains . On the east side, it serves to irrigate around 290,000 hectares of agricultural land and supplies the cities of Fort Collins and Greeley as well as Colorado State University and several rural communities with water for industry and private consumption. The Colorado Big Thompson Project's system extends 150 miles east-west and 105 miles north-south. The water supplies through the system amount to an average of 213,000 acre-feet (approx. 263 million m³) per year.
Reservoirs and dams
There are several massive dams along the river such as the Hoover Dam , which dams Lake Mead near Las Vegas , and the Glen Canyon Dam on Lake Powell . The reservoirs are drinking water reservoirs and are used to generate electricity.
List of dams and reservoirs on the Colorado downstream:
- Shadow Mountain Dam dams Shadow Mountain Lake
- Granby Dam dams Lake Granby
- Glen Canyon Dam dams Lake Powell
- Hoover Dam dams Lake Mead
- Davis Dam dams Lake Mohave
- Parker Dam dams Lake Havasu
- Palo Verde Diversion Dam
- Imperial Dam
- Laguna Diversion Dam
- Morelos Dam
Interventions, regulations and effects
Dam constructions, especially the Glen Canyon Dam in 1966, hold back the water, so that the river south of the Morelos Dam on the border between Arizona and Mexico has been dry ever since . The lower reaches of the Colorado is an elementary part of the Pacific Flyway from Patagonia to Alaska, so that migratory birds have since had to cross the Sonoran Desert without water.
The use of river water has been regulated by a series of laws and agreements since the beginning of the 20th century, which are summarized under the name Law of the River , the administration of the use is carried out by the US federal agency Bureau of Reclamation in cooperation with the respective states . The central principle “use it or lose it!” For water allocation regulates that water that is not required may not be passed on to other parties or stored in reservoirs for a long time without the consent of the partners can be used by anyone else. This principle prevents incentives to save water and led to the fact that agriculture in the regions was continuously intensified in order to use up allocated water.
Below the Hoover Dam the following distribution applies:
- 1.5 MAF (Million Acre Feet ) for Mexico,
- 4.4 for California,
- 2.8 Arizona,
- 0.3 Nevada.
Since the annual inflow is 1.2 MAF less than the legally required levy, the water level in Lake Mead is falling continuously. In 2014 the lake still held 12 MAF, so that if the water regime remained unchanged, the reservoir would be empty in ten years and those entitled under it could no longer use the granted water rights. Emergency measures are initiated beforehand if the water level of Lake Mead falls below certain thresholds.
It is noteworthy that with intelligent use, the water would not only be sufficient for all uses, including the expected increase in population, but also enough water would still be available for restoration projects on the Colorado River. The city of Tucson , Arizona, for example, uses half as much water per inhabitant as Phoenix . Crucially, in Tucson, lawns in private gardens have been banned since the 1990s. This resulted in a change in awareness that also spread to other areas of water use. Las Vegas now processes all of the water in the sewer system and pumps the clarified water back into Lake Mead. Only about 10% of the water used in Las Vegas for irrigation purposes is lost to the cycle.
In the spring of 2014, water was released for the first time for a renaturation project in the lower reaches of the river, which had fallen dry for decades. Morelos Dam was open from March 23rd to May 21st. The experiment was made possible because an earthquake destroyed Mexican irrigation canals in 2010. The United States then signed an agreement with Mexico according to which the water intended for Mexico would be withheld in Lake Mead and Lake Powell until Mexico could use it again. This confidence-building measure allowed further negotiations between the otherwise divided parties to the contracts. The USA subsequently supported Mexico in repairing and improving the sewer system, which will save water in the future. Some of the water saved will be used to renaturate the river.
In 2000, the river began to carry less and less water due to comparatively little rainfall. After geological research over the past 800 years, however, geologists found that, conversely, over the past hundred years there had been above-average rainfall in the western United States. Failure to do so would jeopardize the entire water and energy supply of the American West, which depends on the Colorado River. This danger is compounded by the rapidly growing population in the area. The Lake Powell has lost over 60 percent of its water since 2000th The volume of Lake Mead has shrunk about 40 percent in the same time. According to a study from 2012, the rainfall in the catchment area of the river is no longer sufficient to cover the discharges, so that the reserves in the reservoirs are dwindling.
In 2013, the Colorado River was ranked # 1 in the top ten most endangered rivers in the United States.
Tributaries and places
The major tributaries of the Colorado include (north to south):
- Gunnison River (left - Colorado)
- Dolores River (left - Colorado, Utah)
- Green River (right - Wyoming, Colorado, Utah)
- Dirty Devil River (right - Utah)
- Escalante River (right - Utah)
- San Juan River (left - New Mexico, Utah)
- Paria River (right - Utah, Arizona)
- Little Colorado River (left - Arizona)
- Kanab Creek (right - Utah, Arizona)
- Virgin River (right - Utah, Arizona, Nevada)
- Gila River (left - Arizona)
Places on the Colorado River include:
- Glenwood Springs, Colorado
- Grand Junction, Colorado
- Moab (Utah)
- Page (Arizona)
- Boulder City (Nevada)
- Lake Havasu City (Arizona)
- Yuma (Arizona)
- San Luis Río Colorado (Sonora)
The landscape around the Colorado River, especially the Grand Canyon, inspired many visual artists and musicians to take an artistic look at it. Among other things, two pieces of music, from the classical and the rock area, were created, which have the river and the gorge as their theme:
- Ferde Grofé : Grand Canyon Suite (1929–1931) with the sentences Sunrise, The Painted Desert, On the Trail, Sunset and Cloudburst. Analog recording in vinyl with the London Festival Orchestra under the direction of Stanley Black: Liner SPC 21002.
- Refugee : Grand Canyon , rock suite on the Refugee album (1973).
- Johnny Cash : You wild Colorado , folk song on the album Orange Blossom Special (1965).
- Drive-by truckers : Grand Canyon , from the album English Oceans (2014)
- Water is the future: The Colorado - A river is looking for its mouth. 53-minute television documentary by Frank Nischk (Arte, Germany 2017).
- The Colorado River - A throttled giant. 44-minute television documentary by Katja Esson (rbb, Germany 2016).
- USA: The southwest is drying up | ARTE report | Available on the Arte Youtube Channel , 2019
- Dean W. Blinn, N. Leroy Poff: Colorado River Basin . In: Artur C. Benke, Colbert E. Cushing: Rivers of North America . Elsevier, 2005, ISBN 0-12-088253-1 , pages 482-539
- Steven W. Carothers, Bryan T. Brown: The Colorado River through Grand Canyon . University of Arizona Press, 1991, ISBN 0-8165-1232-9
- Largest Rivers in the United States , USGS, May 1990
- Spanish Dictionary , PONS.eu
- Meaning of the word: colorado
- Blinn, Poff, pp. 491–495
- Grand Canyon National Park - Humpback Chub Translocation Experiment in Shinumo Creek , National Park Service
- Carothers, Brown, p. 84 with further references
- Blinn, Poff, p. 489
- The Day We Set the Colorado River Free , Outside magazine, June 10, 2014
- Law of the River ( Memento of the original from June 26, 2012 on WebCite ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , US Bureau of Reclamation
- Reclaimed Water ( Memento of the original dated June 2, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , City of Tucson
- Endangered Rivers 2013 - Colorado River , American Rivers