The Colorado River (Spanish: Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and in northern Mexico. The 1,450-mile-long (2,330 km) river, the 5th longest in the United States, drains an expansive, arid watershed that encompasses parts of seven U.S. states and two Mexican states. The name Colorado derives from the Spanish language for "colored reddish" due to its heavy silt load. Starting in the central Rocky Mountains of Colorado, it flows generally southwest across the Colorado Plateau and through the Grand Canyon before reaching Lake Mead on the Arizona–Nevada border, where it turns south toward the international border. After entering Mexico, the Colorado approaches the mostly dry Colorado River Delta at the tip of the Gulf of California between Baja California and Sonora.
| Colorado River | |
|---|---|
 The Colorado River at Horseshoe Bend, Arizona, a few miles below Glen Canyon Dam | |
 Map of the Colorado River basin | |
 | |
| Location | |
| Country | United States, Mexico |
| States |  Colorado Utah Arizona Nevada California Baja California Sonora |
| Cities | Glenwood Springs, CO, Grand Junction, CO, Moab, UT, Page, AZ, Bullhead City, AZ, Lake Havasu City, AZ, Blythe, CA, Yuma, AZ, Las Vegas, NV, Laughlin, NV, San Luis Río Colorado, Son. |
| Physical characteristics | |
| Source | La Poudre Pass |
| • location | Rocky Mountains, Colorado, United States |
| • coordinates | 40°28′20″N 105°49′34″W / 40.47222°N 105.82611°W |
| • elevation | 10,184 ft (3,104 m) |
| Mouth | Gulf of California |
• location | Colorado River Delta, Baja California–Sonora, Mexico |
• coordinates | 31°48′54″N 114°48′00″W / 31.81500°N 114.80000°W |
• elevation | 0 ft (0 m) |
| Length | 1,450 mi (2,330 km) |
| Basin size | 246,000 sq mi (640,000 km2) |
| Discharge | |
| • location | Lees Ferry, Arizona |
| • average | 17,850 cu ft/s (505 m3/s) |
| • minimum | 750 cu ft/s (21 m3/s) |
| • maximum | 300,000 cu ft/s (8,500 m3/s) |
| Basin features | |
| Tributaries | |
| • left | Fraser River, Blue River, Eagle River, Roaring Fork River, Gunnison River, Dolores River, San Juan River, Little Colorado River, Bill Williams River, Gila River |
| • right | Green River, Dirty Devil River, Escalante River, Kanab River, Virgin River, Hardy River |
Known for its dramatic canyons, whitewater rapids, and eleven U.S. National Parks, the Colorado River and its tributaries are a vital source of water for 40 million people. An extensive system of dams, reservoirs, and aqueducts divert almost its entire flow for agricultural irrigation and urban water supply. Its large flow and steep gradient are used to generate hydroelectricity, meeting peaking power demands in much of the Intermountain West. Intensive water consumption has dried up the lower 100 miles (160 km) of the river, which has rarely reached the sea since the 1960s.
Native Americans have inhabited the Colorado River basin for at least 8,000 years. Starting around 1 CE, large agriculture-based societies were established, but a combination of drought and poor land use practices led to their collapse in the 1300s. Their descendants include tribes such as the Puebloans, while others including the Navajo settled in the Colorado Basin after the 1000s. In the 1500s, Spanish explorers began mapping and claiming the watershed, which became part of Mexico upon winning its independence from Spain in 1821. Even after most of the watershed became US territory in 1846, much of the river's course remained unknown. Several expeditions charted the Colorado in the mid-19th century—one of which, led by John Wesley Powell, was the first to run the rapids of the Grand Canyon. Large-scale settlement of the lower basin began in the mid- to late-1800s, with steamboats sailing from the Gulf of California to landings along the river that linked to wagon roads to the interior. Starting in the 1860s, gold and silver strikes drew prospectors to the upper Colorado River basin.
Large-scale river management began in the early 1900s, with major guidelines established in a series of international and US interstate treaties known as the "Law of the River". The US federal government constructed most of the major dams and aqueducts between 1910 and 1970; the largest, Hoover Dam, was completed in 1935. Numerous water projects have also involved state and local governments. With all of their waters fully allocated, both the Colorado and the neighboring Rio Grande are now considered among the most controlled and litigated river systems in the world. Since 2000, extended drought has conflicted with increasing demands for Colorado River water, and the level of human development and control of the river continues to generate controversy.
Course
The Colorado begins at La Poudre Pass in the Never Summer Mountains in Rocky Mountain National Park, 10,184 ft (3,104 m) above sea level. After a short run south, the river turns west below Grand Lake, the largest natural lake in the state. For the first 250 miles (400 km) of its course, the Colorado carves its way through the mountainous Western Slope, a sparsely populated region defined by the portion of the state west of the Continental Divide. As it flows southwest, it gains strength from many small tributaries, as well as larger ones including the Blue, Eagle and Roaring Fork rivers. After passing through De Beque Canyon, the Colorado emerges from the Rockies into the Grand Valley, a major farming and ranching region where it meets one of its largest tributaries, the Gunnison River, at Grand Junction. Most of the upper river is a swift whitewater stream ranging from 200 to 500 feet (60 to 150 m) wide, the depth ranging from 6 to 30 feet (2 to 9 m), with a few notable exceptions, such as the Blackrocks reach where the river is nearly 100 feet (30 m) deep. In a few areas, such as the marshy Kawuneeche Valley near the headwaters and the Grand Valley, it exhibits braided characteristics.
From Grand Junction, the Colorado turns northwest before cutting southwest across the eponymous Colorado Plateau, a vast area of high desert centered at the Four Corners of the southwestern United States. Here, the climate becomes significantly drier than that in the Rocky Mountains, and the river becomes entrenched in progressively deeper gorges of bare rock, beginning with Ruby Canyon and then Westwater Canyon as it enters Utah, now once again heading southwest. Farther downstream it receives the Dolores River and defines the southern border of Arches National Park, before passing Moab and flowing through "The Portal", where it exits the Moab Valley between a pair of 1,000-foot (300 m) sandstone cliffs.
In Utah, the Colorado flows primarily through the "slickrock" country, which is characterized by its narrow canyons and unique "folds" created by the tilting of sedimentary rock layers along faults. This is one of the most inaccessible regions of the continental United States. Below the confluence with the Green River, its largest tributary, in Canyonlands National Park, the Colorado enters Cataract Canyon, named for its dangerous rapids, and then Glen Canyon, known for its arches and erosion-sculpted Navajo sandstone formations. Here, the San Juan River, carrying runoff from the southern slope of Colorado's San Juan Mountains, joins the Colorado from the east. The Colorado then enters northern Arizona, where since the 1960s Glen Canyon Dam near Page has flooded the Glen Canyon reach of the river, forming Lake Powell for hydroelectricity generation.
In Arizona, the river passes Lee's Ferry, an important crossing for early explorers and settlers and since the early 20th century the principal point where Colorado River flows are measured for apportionment to the seven U.S. and two Mexican states in the basin. Downstream, the river enters Marble Canyon, the beginning of the Grand Canyon, passing under the Navajo Bridges on a now southward course. Below the confluence with the Little Colorado River, the river swings west into Granite Gorge, the most dramatic portion of the Grand Canyon, where the river cuts up to one mile (1.6 km) into the Colorado Plateau, exposing some of the oldest visible rocks on Earth, dating as long ago as 2 billion years. The 277 miles (446 km) of the river that flow through the Grand Canyon are largely encompassed by Grand Canyon National Park and are known for their difficult whitewater, separated by pools that reach up to 110 feet (34 m) in depth.
At the lower end of Grand Canyon, the Colorado widens into Lake Mead, the largest reservoir in the continental United States, formed by Hoover Dam on the border of Arizona and Nevada. Situated southeast of metropolitan Las Vegas, the dam is an integral component for management of the Colorado River, controlling floods and storing water for farms and cities in the lower Colorado River basin. Below the dam the river passes under the Mike O'Callaghan–Pat Tillman Memorial Bridge—which at nearly 900 feet (270 m) above the water is the highest concrete arch bridge in the Western Hemisphere—and then turns due south towards Mexico, defining the Arizona–Nevada and Arizona–California borders.
After leaving the confines of the Black Canyon, the river emerges from the Colorado Plateau into the Lower Colorado River Valley (LCRV), a desert region dependent on irrigation agriculture and tourism and also home to several major Indian reservations. The river widens here to a broad, moderately deep waterway averaging 500 to 1,000 feet (150 to 300 m) wide and reaching up to 0.25 miles (400 m) across, with depths ranging from 8 to 60 feet (2 to 20 m). Before channelization of the Colorado in the 20th century, the lower river was subject to frequent course changes caused by seasonal flow variations. Joseph C. Ives, who surveyed the lower river in 1861, wrote that "the shifting of the channel, the banks, the islands, the bars is so continual and rapid that a detailed description, derived from the experiences of one trip, would be found incorrect, not only during the subsequent year, but perhaps in the course of a week, or even a day."
The LCRV is one of the most densely populated areas along the river, and there are numerous towns including Bullhead City, Arizona, Needles, California, and Lake Havasu City, Arizona. Here, several large diversions draw from the river, providing water for both local uses and distant regions including the Salt River Valley of Arizona and metropolitan Southern California. The last major U.S. diversion is at Imperial Dam, where over 90 percent of the river's flow is moved into the Gila Gravity Canal and Yuma Area Project, and the much bigger All-American Canal to irrigate California's Imperial Valley, the most productive winter agricultural region in the United States.
Below Imperial Dam, only a small portion of the Colorado River makes it beyond Yuma, Arizona, and the confluence with the intermittent Gila River—which carries runoff from western New Mexico and most of Arizona–before defining 24 miles (39 km) of the Mexico–United States border. At Morelos Dam, the entire remaining flow of the Colorado is diverted to irrigate the Mexicali Valley, among Mexico's most fertile agricultural lands. Below San Luis Río Colorado, the Colorado passes entirely into Mexico, defining the Baja California–Sonora border. Since 1960, the stretch of the Colorado between here and the Gulf of California has been dry or a trickle formed by irrigation return flows. The Hardy River provides most of the flow into the Colorado River Delta, a vast alluvial floodplain covering about 3,000 square miles (7,800 km2) of northwestern Mexico. A large estuary is formed here before the Colorado empties into the Gulf about 75 miles (120 km) south of Yuma. Occasionally the International Boundary and Water Commission allows a springtime to recharge the delta.
Before 20th-century development dewatered the lower Colorado, a major tidal bore was present in the delta and estuary; the first historical record was made by the Croatian missionary in Spanish service Father Ferdinand Konščak on July 18, 1746. During spring tide conditions, the tidal bore—locally called El Burro—formed in the estuary about Montague Island in Baja California and propagated upstream.
Major tributaries
The Colorado is joined by over 25 significant tributaries, of which the Green River is the largest by both length and discharge. The Green River takes drainage from the Wind River Range of west-central Wyoming, from Utah's Uinta Mountains, and from the Rockies of northwestern Colorado. The Gila River is the second longest and drains a greater area than the Green, but has a significantly lower flow because of a more arid climate and larger diversions for irrigation and cities. Both the Gunnison and San Juan rivers, which derive most of their water from Rocky Mountains snowmelt, contribute more water than the Gila contributed naturally.
| Statistics of the Colorado's longest tributaries | ||||||||
|---|---|---|---|---|---|---|---|---|
| Name | State | Length | Watershed | Discharge | References | |||
| mi | km | mi2 | km2 | cfs | m3/s | |||
| Green River | Utah | 730 | 1,170 | 48,100 | 125,000 | 6,048 | 171.3 | |
| Gila River | Arizona | 649 | 1,044 | 58,200 | 151,000 | 247 | 7.0 | |
| San Juan River | Utah | 383 | 616 | 24,600 | 64,000 | 2,192 | 62.1 | |
| Little Colorado River | Arizona | 356 | 573 | 26,500 | 69,000 | 424 | 12.0 | |
| Dolores River | Utah | 250 | 400 | 4,574 | 11,850 | 633 | 17.9 | |
| Gunnison River | Colorado | 164 | 264 | 7,930 | 20,500 | 2,570 | 73 | |
| Virgin River | Nevada | 160 | 260 | 13,020 | 33,700 | 239 | 6.8 | |
Drainage basin
The Colorado River Basin consists of 246,000 square miles (640,000 km2), making it the seventh largest drainage basin in North America. About 238,600 square miles (618,000 km2), or 97 percent of the basin, is in the United States. The basin extends into western Colorado and New Mexico, southwestern Wyoming, eastern and southern Utah, southeastern Nevada and California, and most of Arizona. The areas drained within Baja California and Sonora in Mexico are very small and do not contribute significant runoff. Aside from the Colorado River Delta, the basin extends into Sonora at a few locations further east, including the headwaters of the Santa Cruz River and San Pedro River (both tributaries of the Gila River). For hydrological management purposes, the Colorado River Basin is divided into the Upper Basin (the drainage area above Lees Ferry), and the Lower Basin. The Upper Basin covers only 45 percent of the land area of the Colorado River Basin, but contributes 92 percent of the runoff.
The entire eastern boundary of the Colorado River Basin runs along the North American Continental Divide and is defined largely by the Rocky Mountains and the . The Wind River Range in Wyoming marks the northern extent of the basin, and is separated from the Colorado Rockies by the endorheic Great Divide Basin in southwestern Wyoming. Streams that are nearby the east side of the divide drain into the Mississippi River and Rio Grande, while nearby areas north of the Wind River Range drain into the Columbia River. The western boundary of the Colorado River Basin is formed by various ranges and plateaus that border the Great Basin, including the Uinta Mountains and Wasatch Range. Major Great Basin watersheds bordering the Colorado River Basin are the Great Salt Lake and Sevier Lake watersheds. To the south, the Colorado River Basin borders several watersheds in Mexico draining into the Gulf of California, including the Sonoyta, Concepción, and Yaqui rivers. Much of the basin is at high elevation; the mean elevation is 5,500 feet (1,700 m). Lees Ferry, more than halfway along the Colorado River from its source, is 3,150 feet (960 m) above sea level. The highest point in the Colorado River Basin is 14,321-foot (4,365 m) Uncompahgre Peak in Colorado's San Juan Mountains, while some water from the river drains via irrigation run-off into California's Salton Sea, 236 feet (72 m) below sea level.
About 72 percent of the Colorado River Basin is classified as arid, with the Sonoran and Mojave deserts covering the southern portion and the Colorado Plateau encompassing much of the central portion. The Colorado Plateau is home to most of the major canyon systems formed by the Colorado River and its tributaries, particularly those of the Green and San Juan rivers. About 23 percent of the basin is forest, with the largest area in the Rocky Mountains; other significant forested areas include the Kaibab, Aquarius, and Markagunt plateaus in southern Utah and northern Arizona, and the Mogollon Rim in central Arizona. These high plateaus and escarpments, often exceeding 9,000 feet (2,700 m) in elevation, form the northern and southern edges of the Colorado Plateau geological province. Developed land use in the basin is mostly irrigated agriculture, chiefly in the Grand Valley, the Lower Colorado River Valley, and the Salt River Valley, but the total area of crop and pasture land is only 2–3 percent of the entire basin. Urban areas cover less than 1 percent.
Climate in the Colorado River Basin ranges from subtropical hot desert at southern, lower elevations to alpine in the Rocky Mountains. Mean monthly high temperatures are 25.3 °C (77.5 °F) in the Upper Basin and 33.4 °C (92.1 °F) in the Lower Basin, and lows average −3.6 and 8.9 °C (25.5 and 48.0 °F), respectively. Annual precipitation averages 6.5 inches (164 mm), ranging from over 60 inches (1,500 mm) in some areas of the Rockies to less than 4 inches (100 mm) in dry desert valleys. The Upper Basin generally receives snow and rain during the winter and early spring, while precipitation in the Lower Basin falls mainly during intense but infrequent summer thunderstorms brought on by the North American Monsoon. Precipitation is influenced by the El Niño-Southern Oscillation (ENSO) with El Niño being associated with wetter conditions and La Niña with drier conditions. The effect of ENSO is significantly more pronounced in the Lower Basin, where it has a strong impact on monsoonal rainfall. Runoff patterns across the Colorado River Basin reflect this; most of the perennial tributaries originate in the Upper Basin, while tributaries in the Lower Basin are either ephemeral (such as the Little Colorado River) or highly seasonal (such as the Gila and Salt rivers).
As of 2010, approximately 13 million people lived within the Colorado River basin, while about 40 million people live in areas supplied by Colorado River water. Colorado River basin states are among the fastest-growing in the US; the population of Nevada alone increased by about 66 percent between 1990 and 2000 as Arizona grew by some 40 percent.Phoenix, Arizona, Las Vegas, Nevada and Mexicali, Baja California are the largest cities by population within the Colorado River Basin. Other significant cities include Tucson, Arizona, St. George, Utah and Flagstaff, Arizona. Due to the rugged and inhospitable topography through which the river flows, there are only a few major towns along the Colorado River itself, including Grand Junction, Colorado and Yuma, Arizona.
Discharge
The unimpaired annual runoff of the Colorado River at Lees Ferry, Arizona is estimated at 14.7 million acre-feet (18.1 km3), or an annualized discharge of 20,300 cu ft/s (570 m3/s), for the 1906–2023 period. River flows at the Lees Ferry stream gauge, about halfway along the length of the Colorado and 16 miles (26 km) below Glen Canyon Dam, are used to determine water allocations in the Colorado River basin. Flows originating above Lees Ferry represent the majority of Colorado River runoff. Tributaries between there and Imperial Dam near the US–Mexico border contribute a further 1.1 million acre-feet (1.4 km3), and the Gila–Salt River system historically accounted for another 1.7 million acre-feet (2.1 km3). While much of this water was lost to evaporation in the deserts of the Lower Basin, anywhere from 10 to 20 million acre-feet (12 to 25 km3) per year reached the Colorado River Delta prior to the early 20th century.
Up to 90 percent of the river's flow originates as snowmelt from the Rocky Mountains and other smaller mountain ranges of the Colorado Plateau. Natural seasonal flows at its mouth varied widely, often exceeding 100,000 cu ft/s (2,800 m3/s) in the spring melt and falling as low as 2,500 cu ft/s (71 m3/s) in winter. Snowmelt typically begins in April, peaks in May or June, and can extend into August in wet years.Monsoon rainstorms often occur in the Lower Basin from August through October, contributing much of the flow in tributaries below Lees Ferry and often causing flash flooding. Since the initial closure of Hoover Dam in 1934, lower Colorado River flows have been greatly moderated, with monthly means below the dam ranging from 16,400 cu ft/s (460 m3/s) in May to 11,200 cu ft/s (320 m3/s) in October. Upstream of the massive Hoover and Glen Canyon Dams, inflows to Lake Powell still experience distinct spring highs and winter lows, though overall volumes have been reduced due to Upper Basin water diversions. Flow regimes in a few Upper Basin tributaries, such as the Yampa River, remain almost completely unaltered.
By the 1950s, the Colorado delta was regularly drying up in fall and winter, though spring high flows often still made it to the ocean. After the initial closure of Glen Canyon Dam in 1963, these seasonal flows were almost completely eliminated, with the exception of a few very wet years, such as 1983–1987. In 1984, 16.5 million acre-feet (20.4 km3) of excess runoff reached the ocean. Flows have further declined due to evaporation from reservoirs and, particularly after 2000, reduced snowpack with warming winter temperatures in the Rockies. Water diversions have effectively removed some tributaries entirely, including the Gila River, once the Colorado's largest tributary below Lees Ferry. Most Colorado River water is diverted in the United States, with only about 2.8 million acre-feet (3.5 km3) per year reaching Mexico since 1950. At Morelos Dam, the remaining flow is diverted to irrigate the Mexicali Valley, leaving the Colorado River Delta almost entirely dry except for small amounts of agricultural wastewater.
| Discharge of the Colorado River at selected stream gauges | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Location | Annual mean discharge | Maximum peak flow | Drainage area | Period of record | Source | ||||
| cfs | m3/s | cfs | m3/s | mi2 | km2 | ||||
| Grand Lake, CO | 65.5 | 1.85 | 1,870 | 53 | 63.8 | 165 | 1953–2020 | ||
| Dotsero, CO | 2,079 | 58.9 | 22,200 | 630 | 4,390 | 11,400 | 1941–2020 | ||
| Cisco, UT | 7,048 | 199.6 | 76,800 | 2,170 | 24,100 | 62,000 | 1914–2020 | ||
| Lee's Ferry, AZ | 14,600 | 410 | 127,000 | 3,600 | 111,800 | 290,000 | 1922–2020 | ||
| Davis Dam, AZ–NV | 13,740 | 389 | 46,200 | 1,310 | 173,300 | 449,000 | 1905–2020 | ||
| Parker Dam, AZ–CA | 11,630 | 329 | 42,400 | 1,200 | 182,700 | 473,000 | 1935–2020 | ||
| Laguna Dam, AZ–CA | 1,448 | 41.0 | 30,900 | 870 | 188,600 | 488,000 | 1972–2020 | ||
| NIB (near Andrade, CA) | 3,869 | 109.6 | 40,600 | 1,150 | 246,700 | 639,000 | 1950–2020 | ||
| Monthly discharge of the Colorado at Lee's Ferry, before and after construction of Glen Canyon Dam | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Month | Jan. | Feb. | Mar. | Apr. | May | Jun. | Jul. | Aug. | Sep. | Oct. | Nov. | Dec. | |
| Pre-dam discharge (1921–1962) | cfs | 5,260 | 6,720 | 9,250 | 19,900 | 44,200 | 52,400 | 21,200 | 10,400 | 8,280 | 8,220 | 7,450 | 5,850 |
| m3/s | 149 | 190 | 262 | 564 | 1,252 | 1,484 | 600 | 294 | 234 | 233 | 211 | 166 | |
| Post-dam discharge (1963–2021) | cfs | 13,400 | 12,300 | 11,500 | 12,400 | 13,700 | 15,600 | 15,700 | 15,400 | 12,700 | 10,500 | 11,600 | 12,600 |
| m3/s | 379 | 348 | 326 | 351 | 388 | 442 | 445 | 436 | 360 | 297 | 328 | 357 | |
Geology
As recently as the Cretaceous period about 100 million years ago, much of western North America was still part of the Pacific Ocean. Tectonic forces from the collision of the Farallon Plate with the North American Plate pushed up the Rocky Mountains between 50 and 75 million years ago in a mountain-building episode known as the Laramide orogeny. The Colorado River first formed as a west-flowing stream draining the southwestern portion of the range, and the uplift also diverted the Green River, once a tributary of the Mississippi River, west towards the Colorado. About 30 to 20 million years ago, volcanic activity related to the orogeny led to the Mid-Tertiary ignimbrite flare-up, which created smaller formations such as the Chiricahua Mountains in Arizona and deposited massive amounts of volcanic ash and debris over the watershed. The Colorado Plateau first began to rise during the Eocene, between about 55 and 34 million years ago, but did not attain its present height until about 5 million years ago, about when the Colorado River established its present course into the Gulf of California.
The time scale and sequence over which the river's present course and the Grand Canyon were formed is uncertain. Before the Gulf of California was formed around 12 to 5 million years ago by faulting processes along the boundary of the North American and Pacific plates, the Colorado flowed west to an outlet on the Pacific Ocean—possibly Monterey Bay on the Central California coast, and may have played a role in the formation of the Monterey submarine canyon. Crustal extension in the Basin and Range Province began about 20 million years ago and the modern Sierra Nevada began forming about 10 million years ago, eventually diverting the Colorado southwards towards the Gulf. As the Colorado Plateau continued to rise between 5 and 2.5 million years ago, the river maintained its ancestral course (as an antecedent stream) and began to cut the Grand Canyon. Antecedence played a major part in shaping other peculiar geographic features in the watershed, including the Dolores River's bisection of Paradox Valley in Colorado and the Green River's cut through the Uinta Mountains in Utah.
Sediments carried from the plateau by the Colorado River created a vast delta made of more than 10,000 cubic miles (42,000 km3) of material that walled off the northernmost part of the gulf in approximately 1 million years. Cut off from the ocean, the portion of the gulf north of the delta eventually evaporated and formed the Salton Sink, which reached about 260 feet (79 m) below sea level. Since then the river has changed course into the Salton Sink at least three times, transforming it into Lake Cahuilla, which at maximum size flooded up the valley to present-day Indio, California. The lake took about 50 years to evaporate after the Colorado resumed flowing to the Gulf. The present-day Salton Sea can be considered the most recent incarnation of Lake Cahuilla, though on a much smaller scale.
Between 1.8 million and 10,000 years ago, massive flows of basalt from the Uinkaret volcanic field in northern Arizona dammed the Colorado River within the Grand Canyon. At least 13 lava dams were formed, the largest of which was more than 2,300 feet (700 m) high, backing the river up for nearly 500 miles (800 km) to present-day Moab, Utah. The lack of associated sediment deposits along this stretch of the Colorado River, which would have accumulated in the impounded lakes over time, suggests that most of these dams did not survive for more than a few decades before collapsing or being washed away. Failure of the lava dams caused by erosion, leaks and cavitation caused catastrophic floods, which may have been some of the largest ever to occur in North America, rivaling the late-Pleistocene Missoula Floods of the northwestern United States. Mapping of flood deposits indicate that crests as high as 700 feet (210 m) passed through the Grand Canyon, reaching peak discharges as great as 17 million cubic feet per second (480,000 m3/s).
History
Pre-colonial indigenous peoples
Small numbers of Paleo-Indians of the Clovis and Folsom cultures inhabited the Colorado Plateau as early as 10,000 BCE, with populations beginning to increase in the Desert Archaic period (6000 BCE–0 CE). While most early inhabitants were hunter-gatherers, evidence of agriculture, masonry dwellings and petroglyphs begins with the Fremont culture period (0–1300 CE). The Ancient Puebloan culture, also known as Anasazi or Hisatsinom, were descended from the Desert Archaic culture and became established in the Four Corners region around 1000 CE.
While there is much evidence of ancient habitation along the Colorado River, including stone dwellings, petroglyphs and pottery in places such as Glen Canyon, the first major agriculture-based societies arose a significant distance from the river. The Puebloan people built many multi-story pueblos or "great houses", and developed complex distribution systems to supply drinking and irrigation water in Chaco Canyon in northwestern New Mexico and Mesa Verde in southwest Colorado. The Hohokam, present in the modern Phoenix area since about 0 CE, experienced prolific growth around 600–700 CE as they constructed a large system of irrigation canals making use of the Salt River. Both civilizations supported large populations at their height, with 6,000–15,000 in Chaco Canyon and as many as 30,000–200,000 Hohokam.
| Indigenous names for the Colorado River |
| Hopi: Pisisvayu |
| Maricopa: 'Xakxwet |
| Mohave: 'Aha Kwahwat |
| Navajo: Tó Ntsʼósíkooh |
| Havasupai: Ha Ŧay Gʼam / Sil Gsvgov |
| Yavapai: ʼHakhwata |
Puebloan and Hohokam settlements were abruptly abandoned in the 1400s CE, due both to over-exploitation of natural resources such as timber, and severe drought that made it impossible to maintain irrigation systems. Many Puebloans migrated east to the Rio Grande Valley, while others persisted in smaller settlements on the Colorado Plateau. Puebloan descendants include the Hopi, Zuni, Laguna and Acoma peoples of modern Arizona and New Mexico.O'odham peoples, including the Akimel O'odham (Pima) and Maricopa who continue to live in southern Arizona, are believed to be descended from the Hohokam.
The lower Colorado River valley was inhabited for thousands of years by numerous tribes of the Patayan cultures, many of which belong to the Yuman-Cochimi language group. These include the Walapai, Havasupai and Yavapai in the Grand Canyon region; the Mohave, Halchidhoma, Quechan, and Halyikwamai along the Colorado River between Black Canyon and the Mexican border, and the Cocopah around the Colorado River Delta. The Chemehuevi (a branch of the Southern Paiute) and the Kumeyaay inhabited the desert to the river's west. Those living along the lower Colorado River depended more on fishing and floodplain agriculture than on irrigation, and mostly did not live in permanent settlements. The site of modern-day Yuma has been an important river crossing since ancient times, as the channel here is much narrower compared to the expansive, swampy river bottoms to the north and south, and enabled the expansion of trade to the Pima and Maricopa in the east and coastal California tribes in the west.
The Navajo (Diné) began migrating into the Colorado River Basin around 1000–1500 CE, and eventually exercised influence over much of the Colorado Plateau. Originally hunter-gatherers, they acquired knowledge of farming from the Puebloans and adopted a more sedentary lifestyle over time, making extensive use of irrigation in their settlements. The Navajo gradually displaced Hopi settlements as they expanded into northern Arizona after the 1500s. Navajo Mountain and Rainbow Bridge in the Glen Canyon area came to hold particular religious significance for the Navajo, and the nearby confluence of the Colorado and San Juan River is regarded as the birthplace of clouds and rain.
The Ute also became established in the Colorado Plateau around 1500 CE, although they had inhabited more northerly parts of the Colorado basin (modern Wyoming and northern Colorado) since at least 0 CE. They are the first known inhabitants of this part of the Rocky Mountains, and made use of an extensive network of trails crisscrossing the mountains to move between summer and winter camps. The Ute were divided into numerous bands with separate territories but shared a common language and customs. The Uncompahgre or Tabeguache lived around the confluence of the upper Colorado and Gunnison Rivers, an area including the Grand Mesa; the Weenuchiu lived along the San Juan River, and the Parianuche and Yamparika lived in the Yampa, White and Duchesne River valleys. The Ute ranged as far as the river's headwaters; one Ute story recounts a battle with the Arapaho at Grand Lake, which they believe still hosts the spirits of the deceased.
Spanish exploration and early settlement
Starting in the 1500s, the Spanish began to explore and colonize western North America. Francisco de Ulloa may have been the first European to see the river, when in 1536 he sailed to the head of the Gulf of California. In 1540 García López de Cárdenas became the first European to see the Grand Canyon, during Coronado's expedition to find the Seven Cities of Gold ("Cibola"). Cárdenas was apparently unimpressed with the canyon, greatly underestimating its size, and left in disappointment with no gold to be found. In the same year Melchior Díaz explored the Colorado River's delta and named it Rio del Tizon ("fire brand river"), after seeing a practice used by the local people for warming themselves.
By the late 1500s or early 1600s, the Utes had acquired horses from the Spanish, and their use for hunting, trade and warfare soon became widespread among Utes and Navajo in the Colorado River basin. This conferred them a military advantage over Goshutes and Southern Paiutes that were slower to adopt horses. The Navajo also adopted a culture of livestock herding as they acquired sheep and goats from the Spanish.Juan Bautista de Anza in 1774 was the first Spaniard to reach Yuma Crossing, where he established friendly relations with the Quechan people and opened the Anza trail between Arizona and the California coast. The Spanish soon founded Mission Puerto de Purisima Concepcion and Mission San Pedro y San Pablo de Bicuner along the lower Colorado River. However, Spanish attempts to control the crossing led to the 1781 Yuma revolt, in which over 100 soldiers and colonists were killed, and the settlements were abandoned. The Quechan blocked foreigners' use of the crossing until the arrival of American mountain men and fur trappers in the 1820s.
The name Rio Colorado first appears in 1701, on the map "Paso por Tierra a la California" published by missionary Eusebio Kino, who also determined during that time that Baja California was a peninsula, not an island as previously believed. In the 1700s and early 1800s many Spanish and American explorers believed in the existence of a Buenaventura River that ran from the Rocky Mountains to the Pacific coast. In 1776, Silvestre Vélez de Escalante attached this name to the upper Green River, and a number of later maps showed this connecting to Lake Timpanogos (now Utah Lake) and flowing west to California. The Dominguez–Escalante expedition first reached the Colorado River near the junction with the Dolores River, naming the larger river "Rio San Rafael". They later forded the Colorado in southeastern Utah at Crossing of the Fathers, now submerged in Lake Powell.
American exploration
In the 1820s, American fur trappers along the upper Green River in Wyoming (known to them as the "Seedskeedee" or variants thereof), seeking a route to export furs to the coast, surmised that this and what the Spanish called the Colorado were in fact connected. William H. Ashley made an unsuccessful attempt to navigate from the Green River to the Colorado's mouth in 1825. In 1826, Jedediah Smith arrived at the lower Colorado River, referring to it as the Seedskeedee, and proceeded upstream, exploring as far as Black Canyon. During the 1830s, various fur trappers from Wyoming made it as far downstream as Cataract Canyon and Glen Canyon, but none were able to navigate the full length of the river. In 1843 John C. Frémont explored the Great Basin and conclusively determined no Buenaventura River flowed west to California; thus, the direction of river flow must be southwest.
By the early 19th century, the stretch of the Colorado above the confluence of the Green River at Cataract Canyon, Utah, became known to fur trappers as the "Grand River", though the exact origin of this name is unknown. The Grand River above the confluence with the Gunnison River was also called the Bunkara River, the Blue River, or the North Fork of the Grand River until the 1870s. By the early 1900s the name "Grand River" had been attached to the entire stream as far as Grand Lake, which was then considered its official source. Although the Grand River was renamed the Colorado in 1921, its name survives in numerous places such as Grand County and Grand Junction, Colorado.
In 1848 the U.S. Army established Fort Yuma, creating the first permanent U.S. settlement along the river. This served as a military garrison and supply point for settlers headed to California along the Southern Emigrant Trail. Due to the arduous task of ferrying supplies overland, the schooner Invincible attempted to bring supplies up the river but was thwarted by the delta's strong tides. Steamboats were brought to the river, starting in 1852 with the sidewheeler Uncle Sam, whose first voyage from the Gulf to Yuma took fifteen days.: 15 Exploration by steamboat soon advanced upriver. In 1857, George A. Johnson in the General Jesup was able to reach Pyramid Canyon, over 300 miles (480 km) north of Fort Yuma.: 16–17, 19 He was followed by Lt. Joseph Christmas Ives who used a specially built shallow-draft steamboat, Explorer, to reach Black Canyon, where Hoover Dam stands today.: Part 1, 85–87 Having set out to determine the river's suitability as a navigation route, Ives remarked: "Ours has been the first, and will doubtless be the last, party of whites to visit this profitless locality. It seems intended by nature that the Colorado River, along the greater portion of its lonely and majestic way, shall be forever unvisited and undisturbed."
The last part of the Colorado River to be surveyed was the Grand Canyon itself. In 1869, John Wesley Powell with nine men set out on an expedition from Green River Station, Wyoming. They were the first part of non-natives to travel the length of the Grand Canyon, and the first to successfully travel by boat from the upper Green River to the lower Colorado. Powell led a second expedition in 1871, with financial backing from the U.S. government, and continued to conduct geographical and botanical surveys across the region until the 1890s. Another Grand Canyon river expedition was led in 1889–1890 by Robert Brewster Stanton to survey a route for a proposed railroad through the canyon, which was never built.
We are now ready to start on our way down the Great Unknown. Our boats, tied to a common stake, are chafing each other, as they are tossed by the fretful river. They ride high and buoyant, for their loads are lighter than we could desire. We have but a month's rations remaining… The lighting of the boats has this advantage: they will ride the waves better, and we shall have little to carry when we make a portage.
We are three-quarters of a mile in the depths of the earth, and the great river shrinks into insignificance, as it dashes its angry waves against the walls and cliffs, that rise to the world above; they are but puny ripples, and we but pigmies, running up and down the sands, or lost among the boulders.
We have an unknown distance yet to run; an unknown river yet to explore. What falls there are, we know not; what rocks beset the channel, we know not; what walls rise over the river, we know not; Ah, well! we may conjecture many things. The men talk as cheerfully as ever; jests are bandied about freely this morning; but to me the cheer is somber and the jests are ghastly.
— John Wesley Powell's journal, August 1869
U.S. westward expansion and military campaigns
In 1858, gold was discovered on the Gila River east of Yuma, then along the Colorado River at El Dorado Canyon, Nevada and La Paz, Arizona. As prospectors and settlers entered the region, they became involved in skirmishes with the Mohave, spurring U.S. Army expeditions that culminated in the 1859 Battle of the Colorado River which concluded the Mohave War. In the 1870s the Mohave were moved to the Fort Mohave and Colorado River reservations. Chemehuevi and later some Hopi and Navajo peoples were also moved to the Colorado River reservation, where they today form the Colorado River Indian Tribes.
As the American frontier expanded into the Colorado Plateau, an effort to expel the Navajo from the Four Corners region was begun by General James Henry Carleton, who in 1864 enlisted mountain man Kit Carson to lead a campaign against the Navajo. Carson, with the help of the Navajo's Ute enemies, captured more than 8,000 Navajo and forcibly marched them to Fort Sumner, New Mexico. Hundreds died during what is now known as the Long Walk and while enduring appalling conditions at Fort Sumner. After the failure of the Army to maintain the reservation there, the Treaty of Bosque Redondo established the Navajo Nation in the Four Corners, where the Navajo were allowed to return in 1868.
Gold and silver were also discovered in the Upper Basin, beginning with the 1859 Blue River strike that led to the founding of Breckenridge, Colorado. Up until the 1860s, southwestern Colorado had remained relatively untouched by U.S. westward expansion, as the Americans had recognized Ute sovereignty by treaty. Following the 1861 carving out of Colorado Territory and further mineral strikes including Ouray and Telluride, Ute leaders were coerced into signing the 1873 Brunot Agreement, in which they lost rights to most of their land. A flood of mineral prospecting and settlement ensued in western Colorado. By 1881, the Army had driven out the remaining pockets of Ute resistance on the Western Slope, officially opening the Grand River country to settlement, and the town of Grand Junction was incorporated a year later. The Denver and Rio Grande Western Railroad (D&RGW) quickly expanded into this area to serve mining boomtowns, crossing the Rockies to the south via the Black Canyon of the Gunnison River. By 1883 the railroad had reached Grand Junction, and a spur up the Colorado to Glenwood Springs was completed in 1887.
In Arizona and Utah Territories, many early settlers were Mormons fleeing religious persecution in the Midwest. Mormons founded agricultural colonies at Fort Santa Clara in 1855 and St. Thomas, now flooded under Lake Mead, in 1865.Stone's Ferry, crossing the Colorado at the mouth of the Virgin River, enabled shipping of their produce by wagon to gold mining districts further south. Although the Mormons abandoned St. Thomas in 1871, a salt-mining industry persisted here, and steamboats operated up to nearby Rioville into the 1880s.: 78 In 1879 a group of Mormon settlers made their way to southeastern Utah, blasting the precarious Hole in the Rock Trail to cross the Colorado River at Glen Canyon, subsequently establishing the community of Bluff. Due to the dry climate, these settlements depended heavily on irrigation. In central Arizona, settlers uncovered and re-established canals previously used by the Hohokam.
Following tensions between Mormon settlers and the U.S. government in the Utah War, a local militia including John D. Lee perpetrated the 1857 Mountain Meadows Massacre, in which 120 non-Mormon settlers were killed. Fearing retribution, Lee moved in 1870 to the remote Pahreah Crossing in Arizona, where he took over a ferry first established in 1864 by Jacob Hamblin. This, the only river crossing for hundreds of miles not hemmed in by vertical canyon walls, became known as Lee's Ferry. While Lee was tried and subsequently executed in 1877, the ferry remained a major transportation link until the Navajo Bridge was completed nearby in 1928, rendering the ferry obsolete.
The Denver and Salt Lake Railway (D&SL), incorporated in 1902, sought to provide a more direct connection between Denver and Salt Lake City than either the transcontinental railroad through Wyoming or the D&RGW's route via Black Canyon and Durango. The D&SL completed a rail line into the upper headwaters of the Colorado River and blasted the Moffat Tunnel under the Continental Divide, but ran out of money before even reaching Utah. In 1931 the D&RGW completed the "Dotsero Cutoff" linking Glenwood Springs to the D&SL route at Bond, Colorado, finally completing the direct Denver–Salt Lake link with its acquisition of the bankrupt D&SL. The Gunnison River route was eventually abandoned in favor of the shorter Colorado River route, which today is owned by Union Pacific.
Renaming of the upper Colorado River
As late as 1921, the Colorado River upstream from the confluence with the Green River in Utah was still known as the Grand River. For over a decade, U.S. Representative Edward T. Taylor of Colorado had petitioned the Congressional Committee on Interstate and Foreign Commerce to rename the Grand River as the Colorado River. Representatives from Wyoming, Utah, and the United States Geological Survey objected, noting that the Green River was longer and drained a larger area. Taylor argued that the Grand River should be considered the main stream, as it carried the larger volume of water. Taylor felt "slighted" that the Colorado River, as named, did not begin in the state of Colorado, and "he wasn't going to let Utah or Wyoming lay claim to the river's headwaters, despite the fact that the Green River is the larger drainage basin." On July 25, 1921, President Warren G. Harding signed House Joint Resolution 32 - "To change the name of the Grand River in Colorado and Utah to the Colorado River."
Engineering and development
About 40 million people depend on the Colorado River's water for agricultural, industrial and domestic needs. The Colorado irrigates 5.5 million acres (2.2 million hectares) of farmland, and its hydroelectric plants produce 12 billion kilowatt hours (KWh) of hydroelectricity each year. Hydroelectricity from the Colorado is a key supplier of peaking power on the Southwest electric grid. Often called "America's Nile", the Colorado is so intensively managed that each drop of its water is used an average of 17 times in a single year.Southern Nevada Water Authority has called the Colorado River one of the "most controlled, controversial and litigated rivers in the world".
| Colorado River water allocations, in millions of acre-feet | ||
|---|---|---|
| User | Amount | Share |
| United States | 15.0 | 90.9% |
| California | 4.4 | 26.7% |
| Colorado | 3.88 | 23.5% |
| Arizona | 2.8 | 17.0% |
| Utah | 1.72 | 10.4% |
| Wyoming | 1.05 | 6.4% |
| New Mexico | 0.84 | 5.1% |
| Nevada | 0.3 | 1.8% |
| Mexico | 1.5 | 9.1% |
| Total | 16.5 | 100% |
In 1922, six U.S. states signed the Colorado River Compact, which divided half of the river's flow to both the Upper Basin (the drainage area above Lee's Ferry, comprising parts of Colorado, New Mexico, Utah, and Wyoming and a small portion of Arizona) and the Lower Basin (Arizona, California, Nevada, and parts of New Mexico and Utah). The Upper and Lower Basin were each allocated 7.5 million acre-feet (9.3 km3) of water per year, a figure believed to represent half of the river's annual flow at Lee's Ferry. The allotments operated under the premise that approximately 17.5 million acre-feet of water flowed through the river annually.
Arizona initially refused to ratify the compact because it feared that California would take too much of the lower basin allotment. In 1944 a compromise was reached in which Arizona was allocated 2.8 million acre-feet (3.5 km3), but with the caveat that California's 4.4-million-acre-foot (5.4 km3) allocation was prioritized during drought years. These and nine other decisions, compacts, federal acts and agreements made between 1922 and 1973 constitute what is now known as the Law of the River.
In 1944, a treaty between the U.S. and Mexico allocated 1.5 million acre-feet (1.9 km3) of Colorado River water to Mexico each year.Morelos Dam was constructed in 1950 to enable Mexico to utilize its share of the river. Water allocated to Mexico from the Colorado River is regulated by the International Boundary and Water Commission, which also apportions waters from the Rio Grande between the two countries.
Transmountain diversions
Large-scale development of Colorado River water supplies started in the late 19th century, at the river's headwaters in La Poudre Pass. The Grand Ditch, directing runoff from the river's headwaters across the Continental Divide to arid eastern Colorado, was considered an engineering marvel when completed in 1890. This was the first of twenty-four "transmountain diversions" constructed to draw water across the Rocky Mountains as the Front Range corridor increased in population. These diversions draw water from the upper Colorado and its tributaries into the South Platte River, Arkansas River and Rio Grande basins. Today, about 80 percent of Colorado's population lives on the Eastern Slope of the Rockies, while 80 percent of precipitation falls on the Western Slope.
While first planned at the same time as the Grand Ditch, construction on the Colorado-Big Thompson Project (C-BT) did not begin until the 1930s. Today, the C-BT is the largest of the transmountain diversions, delivering 230,000 acre-feet (280,000,000 m3) per year from the Colorado River to cities north of Denver. Numerous other projects followed, with the largest including the Roberts Tunnel, which delivers water from the Blue River to the city of Denver, and the Fryingpan–Arkansas Project, which diverts water from the Fryingpan River to the Arkansas River basin.
Combined, the transmountain diversions draw about 580,000 acre-feet (720,000,000 m3) of water per year out of the Colorado River basin. Historically, most of the water has been used for irrigation, although water usage is increasing for urban water supply and for recreational purposes such as snowmaking and increasing Eastern Slope streamflows for boating and fishing. Denver Water receives about 50 percent of its supply from the Colorado River basin. However, diversions have caused environmental harm to the upper Colorado River system by reducing streamflows in many tributaries. A number of reservoirs have been built to offset the impact of transmountain diversions by storing water for dry season release on the Western Slope, including Williams Fork Reservoir in 1959 and Wolford Mountain Reservoir in 1996.
The Imperial Valley and the Salton Sea
The Colorado River delta region in Mexico became a favored place for Americans to invest in agriculture in the late 19th century when Mexican President Porfirio Díaz welcomed foreign capital to develop the country. The Colorado River Land Company, formed by Los Angeles Times publisher Harry Chandler, his father-in-law Harrison Gray Otis, and others, developed the Mexicali Valley in Baja California as a thriving land company. The company headquarters was nominally based in Mexico, but its real headquarters was in Los Angeles, California. Land was leased mainly to Americans who were required to develop it. Colorado River water was used to irrigate the rich soil. The company largely escaped the turmoil of the Mexican Revolution (1910–20), but in the postrevolutionary period, the Mexican government expropriated the company's land to satisfy the demand for land reform.
In 1900, the California Development Company (CDC) envisioned irrigating the Imperial Valley, a then dry basin on the California–Mexico border, using water from the Colorado River. Due to the valley's location below sea level, water could be diverted and allowed to flow there entirely by gravity. Engineer George Chaffey was hired to design the Alamo Canal, which split from the Colorado near Pilot Knob, California and ran south into Mexico, where it joined the Alamo River, a dry arroyo which had historically carried overflowing floodwaters from the Colorado into the Salton Sink at the bottom of Imperial Valley. The scheme worked initially; by 1903, about four thousand people lived in the valley and more than 100,000 acres (40,000 ha) of farmland had been developed.
The Alamo Canal experienced continual problems due to the Colorado's high sediment content and its varying water levels. During low flows, the river often dropped below the level of the canal intake, while high flows silted up the intake, forcing the repeated excavation of new cuts. In early 1905, flooding destroyed the intake gates and water began to flow uncontrolled down the canal towards the Salton Sink. By August, the breach had grown large enough to swallow the entire flow of the river, which began to flood the bottom of the valley. The Southern Pacific Railroad attempted to dam the flow in order to protect their tracks which ran through the valley, but was hampered by repeated flooding. It took seven attempts, more than $3 million, and two years for the railroad, the CDC, and the federal government to permanently block the breach and restore the river's original course – but not before part of the Imperial Valley was flooded under a 45-mile-long (72 km) lake, today's Salton Sea. The Imperial Valley fiasco demonstrated that further economic development of the region would require a dam to control the Colorado's unpredictable flows.
Boulder Canyon Project
A large dam on the Colorado River had been envisioned since the 1920s. In 1928, Congress authorized the Reclamation Service (today's U.S. Bureau of Reclamation, or USBR) to build the Boulder Canyon Project, whose key feature would be a dam on the Colorado in Black Canyon 30 miles (48 km) southeast of Las Vegas, Nevada. On September 30, 1935, Hoover Dam was completed, forming Lake Mead, capable of holding more than two years of the Colorado's flow. Lake Mead was, and still is, the largest artificial lake in the U.S. by storage capacity. The construction of Hoover Dam stabilized the lower channel of the Colorado River, stored water for irrigation in times of drought, captured sediment and controlled floods. Hoover was the tallest dam in the world at the time of construction and also had the world's largest hydroelectric power plant.
The Boulder Canyon Project Act also authorized the All-American Canal, which was built as a permanent replacement for the Alamo Canal and follows a route entirely within the U.S. on its way to the Imperial Valley. The canal's intake is located at Imperial Dam, 20 miles (32 km) above Yuma, Arizona, which diverts the majority of the Colorado's flow with only a small portion continuing to Mexico. With a capacity of over 26,000 cubic feet per second (740 m3/s), the All-American Canal is the largest irrigation canal in the world. Because the hot, sunny climate lends to a year-round growing season, the Imperial Valley has become one of the most productive farming regions in North America, providing much of the winter produce supply in the U.S. The Imperial Irrigation District supplies water to 520,000 acres (210,000 ha) south of the Salton Sea. The Coachella Canal, which branches northward from the All-American Canal, irrigates another 78,000 acres (32,000 ha) in the Coachella Valley.
Parker Dam was initially built as the diversion point for the Colorado River Aqueduct, planned by the Metropolitan Water District of Southern California to supply water to Los Angeles. The construction of the dam was opposed by Arizona, which feared that California would take too much water from the Colorado; at one point, Arizona sent members of its National Guard to stop work on the dam. Ultimately, a compromise was reached, with Arizona dropping its objections in exchange for the USBR constructing the Gila Project, which irrigates 110,000 acres (450 km2) on the Arizona side of the river. By 1941, the 241-mile (388 km) long Colorado River Aqueduct was completed, delivering 1.2 million acre-feet (1.5 km3) of water west to Southern California. The aqueduct enabled the continued growth of Los Angeles and its suburbs, and provides water to about 10 million people today. The San Diego Aqueduct, which branches off from the Colorado River Aqueduct in Riverside County, California, opened in stages between 1954 and 1971 and provides water to another 3 million people in the San Diego metro area.
The Las Vegas Valley of Nevada experienced rapid growth after Hoover Dam, and by 1937 Las Vegas had tapped a pipeline into Lake Mead. Nevada officials, believing that groundwater resources in the southern part of the state were sufficient for future growth, were more concerned with securing a large amount of the dam's power supply than water from the Colorado; thus they settled for the smallest water allocation of all the states in the Colorado River Compact. In 2018, due to declining water levels in Lake Mead, a second pipeline was completed with a lower intake elevation.
Colorado River Storage Project
In the first half of the 20th century, the Upper Basin states, with the exception of Colorado, had developed very little of their water allocations from the Colorado River Compact. By the 1950s, however, water demand was rapidly increasing in Utah's Wasatch Front (Salt Lake City metro area) and the Rio Grande Valley of New Mexico, which both began exploring ways to divert water from the Colorado Basin. The Upper Basin states were concerned that they would not be able to use their full Compact allocations due to increasing water demands in the Lower Basin. The Compact requires the Upper Basin to deliver a minimum annual flow of 7.5 million acre-feet (9.3×109 m3) past Lee's Ferry (measured on a 10-year rolling average). Without additional reservoir storage, the Upper Basin states could not utilize their allocations without impacting water deliveries to the Lower Basin in dry years.
In 1956 Congress authorized the USBR to construct the Colorado River Storage Project (CRSP), which planned several large reservoirs on the upper Colorado, Green, Gunnison and San Juan Rivers. The initial blueprints for the CRSP included two dams on the Green River within Echo Park Canyon in Dinosaur National Monument – a move criticized by both the National Park Service and environmental groups such as the Sierra Club. The controversy received nationwide media attention, and the USBR dropped its plans for the Dinosaur dams in exchange for increasing the size of a proposed dam at Glen Canyon.
The controversy associated with Glen Canyon Dam did not build momentum until construction was well underway. Due to Glen Canyon's remote location, most of the American public did not even know of its existence; the few who did contended that it had much greater scenic value than Echo Park. The environmental movement in the American Southwest has opposed the damming and diversion of the Colorado River system due to negative effects on the ecology and natural beauty of the river and its tributaries. During the construction of Glen Canyon Dam (1956–66), environmental organizations[which?] vowed[clarification needed] to block any further development of the river, and a number of later dam and aqueduct proposals were defeated by citizen opposition. Sierra Club leader David Brower fought the dam both during the construction and for many years afterwards until his death in 2000. Brower believed that he was personally responsible for the failure to prevent Glen Canyon's flooding, calling it his "greatest mistake, greatest sin".
In addition to Glen Canyon Dam, the CRSP includes the Flaming Gorge Dam on the Green River, the Blue Mesa, Morrow Point and Crystal Dams on the Gunnison River, and the Navajo Dam on the San Juan River. A total of 22 "participating projects" (of which 16 have been constructed) were later authorized in order to develop local water supplies at various locations across the Upper Basin states. These include the Central Utah Project, which delivers 102,000 acre-feet (126,000,000 m3) per year from the Green River basin to the Wasatch Front, and the San Juan–Chama Project, which diverts 110,000 acre-feet (140,000,000 m3) per year from the San Juan River to the Rio Grande Valley. Both are multi-purpose projects serving a variety of agricultural, municipal and industrial uses.
Pacific Southwest Water Plan
By the middle of the 20th century, planners were concerned that continued growth in water demand would outstrip the available water supply from the Colorado River. After exploring a multitude of potential projects, the USBR published a study in January 1964 known as the Pacific Southwest Water Plan, which proposed diverting water from the northwestern United States into the Colorado River basin. Arizona's water allocation was a significant focus of the plan, due to the growing concern that its water supply could be curtailed due to California's seniority of water rights. In addition, the plan would guarantee full water supplies to Nevada, California and Mexico, allowing the Upper Basin states to utilize their full allocations without risking reductions in the Lower Basin. The project would cost an estimated $3.1 billion.
The first stage of this plan would divert water from Northern California's Trinity, Klamath and Eel Rivers to Southern California, allowing more Colorado River water to be used, by exchange, in Arizona. A canal system, which ultimately would become the Central Arizona Project (CAP), would be constructed to deliver Arizona's Colorado River allocation to Phoenix and Tucson, both located far away from the Colorado River in the middle of the state. At this point, central Arizona was still entirely dependent on local water supplies, such as the 1911 Theodore Roosevelt Dam, and was quickly running out of surplus water.
In order to supply the massive amount of power required to pump Colorado River water to central Arizona, two hydroelectric dams were proposed in the Grand Canyon (Bridge Canyon Dam and Marble Canyon Dam), which while not directly located in Grand Canyon National Park, would greatly impact flows of the Colorado River through the park. With the controversy over Glen Canyon Dam still ongoing, the public pressure against these dams was immense. As a result, the two Grand Canyon dams were omitted from the final CAP authorization in 1968. In addition, the boundaries of Grand Canyon National Park were redrawn to prevent future dam projects in the area. The pumping power was replaced by the building of the coal-fired Navajo Generating Station near Page, Arizona, in 1976. In 2019, the Navajo Generating Station ceased operation.
The CAP was constructed in stages from 1973 to 1993, ultimately extending 336 miles (541 km) from the Colorado River at Parker Dam to Tucson, Arizona. It delivers 1.4 million acre-feet (1.7 km3) of water per year, irrigates 830,000 acres (3,400 km2) of farmland and provides municipal water to about 5 million people. Due to environmental concerns, most of the facilities proposed in the Pacific Southwest Water Plan were never built (though a smaller version of the Trinity River project was constructed as part of the unrelated Central Valley Project), leaving Arizona and Nevada vulnerable to future water reductions under the Compact.
Indigenous water rights
Water rights of Native Americans in the Colorado River basin were largely ignored during the extensive water resources development carried out on the river and its tributaries in the 19th and 20th centuries. The construction of dams has often had negative impacts on tribal peoples, such as the Chemehuevi when their riverside lands were flooded after the completion of Parker Dam in 1938. Ten Native American tribes in the basin now hold or continue to claim water rights to the Colorado River. The U.S. government has taken some actions to help quantify and develop the water resources of Native American reservations. The first federally funded irrigation project in the U.S. was the construction of an irrigation canal on the Colorado River Indian Reservation in 1867. Other water projects include the Navajo Indian Irrigation Project, authorized in 1962 for the irrigation of lands in part of the Navajo Nation in north-central New Mexico. The Navajo continue to seek expansion of their water rights because of difficulties with the water supply on their reservation; about 40 percent of its inhabitants must haul water by truck many miles to their homes. In the 21st century, they have filed legal claims against the governments of Arizona, New Mexico and Utah for increased water rights. Some of these claims have been successful for the Navajo, such as a 2004 settlement in which they received a 326,000-acre-foot (402,000 ML) allotment from New Mexico.
Post-2000 water supply
[The Colorado is] a 'deficit' river, as if the river were somehow at fault for its overuse.
— Marc Reisner, in Cadillac Desert
When the Colorado River Compact was drafted in the 1920s, it was based on barely 30 years of streamflow records that suggested an average annual flow of 17.5 million acre-feet (21.6 km3) past Lee's Ferry. Modern studies of tree rings revealed that those three decades were probably the wettest in the past 500 to 1,200 years and that the natural long-term annual flow past Lee's Ferry is probably closer to 13.5 million acre-feet (16.7 km3), with a natural flow at the mouth around 16.3 million acre-feet (20.1 km3). This has resulted in more water being allocated to river users than actually exists in the Colorado. Droughts have exacerbated the issue of water over-allocation.
The most severe drought on record, the southwestern North American megadrought, began in the early 21st century, in which the river basin has produced above-average runoff in only five years between 2000 and 2021. The region is experiencing a warming trend, which is accompanied by earlier snowmelt, lower precipitation and greater evapotranspiration. A 2004 study showed that a 1–6 percent decrease of precipitation would lead to runoff declining by as much as 18 percent by 2050.
Since 2000, reservoir levels have fluctuated greatly from year to year, but have experienced a steady long-term decline. The particularly dry spell between 2000 and 2004 brought Lake Powell to just a third of capacity in 2005, the lowest level on record since initial filling in 1969. In late 2010, Lake Mead was approaching the "drought trigger" elevation of 1,075 feet (328 m), at which water supplies to Arizona and Nevada would be reduced in accordance with the Colorado River Compact. Due to Arizona and Nevada's water rights being junior to California's, their allocations can legally be cut to zero before any reductions are made on the California side.
A wet winter in 2011 temporarily raised lake levels, but dry conditions returned in the next two years. In 2014, the Bureau of Reclamation cut releases from Lake Powell by 10 percent —the first such reduction since the 1960s, when Lake Powell was being filled for the first time. This resulted in Lake Mead dropping to its lowest recorded level since 1937, when it was first being filled.
Water year 2018 had a much lower-than-average snowpack. In July 2021, after two more extremely dry winters, Lake Powell fell below the previous low set in 2005. In response, the Bureau of Reclamation began releasing water from upstream reservoirs in order to keep Powell above the minimum level for hydropower generation. Lake Mead fell below the 1,075-foot (328 m) level expected to trigger federally mandated cuts to Arizona and Nevada's water supplies for the first time in history, and is expected to continue declining into 2022.
On August 16, 2021, the Bureau of Reclamation released the Colorado River Basin August 2021 24-Month Study, and for the first time declared a shortage and that because of "ongoing historic drought and low runoff conditions in the Colorado River Basin, downstream releases from Glen Canyon Dam and Hoover Dam will be reduced in 2022 due to declining reservoir levels." The Lower Basin reductions will reduce the annual apportionments – Arizona's by 18 percent, Nevada's by 7 percent, and Mexico's by 5 percent.
On June 14, 2022, Bureau of Reclamation Commissioner Camille Touton told the Senate Committee on Energy and Natural resources that additional cuts of 2–4 million acre-feet were required to stabilize reservoir levels in 2023. Touton warned that if states were unable to negotiate the requisite cuts the Interior department may use its legal authority to cut releases. When the states were unable to come to an agreement about how to share the proposed cuts, Reclamation began the legal steps to unilaterally reduce releases from Hoover and Glen Canyon Dams in 2023. As of December 2022 the lower basin states of Nevada, Arizona, and California had not agreed on how to reduce water use by the approximately 30% required to keep levels in lakes Mead and Powell from crashing. The Bureau of Reclamation has projected that water levels at Lake Powell could fall low enough that by July 2023 Glen Canyon Dam would no longer be able to generate any hydropower. Arizona proposed a plan that severely cut allocations to California, and California responded with a plan that severely cut allocations to Arizona, failing to reach consensus. In April 2023, the federal government proposed cutting allocations to Nevada, Arizona, and California evenly which would cut deliveries by as much as one-quarter to each state, rather than according to senior water rights.
In May 2023, the states finally reached a temporary agreement to prevent deadpool, reducing allocations by 3 million acre-feet over three years (until the end of 2026). 700,000 acre-feet were to be negotiated later among California, Arizona, and Nevada. The cuts were less than the federal government had demanded, and so further cuts will be needed after 2026. Fewer cuts were needed in the short term because the Colorado River Basin experienced an unusually rainy and snowy weather in early 2023.
The agreement also became easier to negotiate because many cuts are being offset by one-time federal funding. Billions of dollars in funding for programs in the Colorado River Basin to recycle water, increase efficiency, and competitive grants to pay water rights holders not to use water from the river are being provided by the Infrastructure Investment and Jobs Act and Inflation Reduction Act, and other programs funded through the United States Environmental Protection Agency and United States Department of the Interior. These are projected to reduce demand by hundreds of thousands of acre-feet per year.
Ecology
Wildlife and plants
The Colorado River and its tributaries often nourish extensive corridors of riparian growth as they traverse the arid desert regions of the watershed. Although riparian zones represent a relatively small proportion of the basin and have been affected by engineering projects and river diversion in many places, they have the greatest biodiversity of any habitat in the basin. The most prominent riparian zones along the river occur along the lower Colorado below Davis Dam, especially in the Colorado River Delta, where riparian areas support 358 species of birds despite the reduction in freshwater flow and invasive plants such as tamarisk (salt cedar). Reduction of the delta's size has also threatened animals such as jaguars and the vaquita porpoise, which is endemic to the gulf. Human development of the Colorado River has also helped to create new riparian zones by smoothing the river's seasonal flow, notably through the Grand Canyon.
More than 1,600 species of plants grow in the Colorado River watershed, ranging from the creosote bush, saguaro cactus, and Joshua trees of the Sonoran and Mojave Deserts to the forests of the Rocky Mountains and other uplands, composed mainly of ponderosa pine, subalpine fir, Douglas-fir and Engelmann spruce. Before logging in the 19th century, forests were abundant in high elevations as far south as the Mexico–U.S. border, and runoff from these areas nourished abundant grassland communities in river valleys. Some arid regions of the watershed, such as the upper Green River valley in Wyoming, Canyonlands National Park in Utah and the San Pedro River valley in Arizona and Sonora, supported extensive reaches of grassland roamed by large mammals such as buffalo and antelope as late as the 1860s. Near Tucson, Arizona, "where now there is only powder-dry desert, the grass once reached as high as the head of a man on horse back".
Rivers and streams in the Colorado basin were once home to 49 species of native fish, of which 42 were endemic. Engineering projects and river regulation have led to the extinction of four species and severe declines in the populations of 40 species.Bonytail chub, razorback sucker, Colorado pikeminnow, and humpback chub are among those considered the most at risk; all are unique to the Colorado River system and well adapted to the river's natural silty conditions and flow variations. Clear, cold water released by dams has significantly changed characteristics of habitat for these and other Colorado River basin fishes. A further 40 species that occur in the river today, notably the brown trout, were introduced during the 19th and 20th centuries, mainly for sport fishing.
Impacts of development
Historically, the Colorado transported from 85 to 100 million short tons (77,000,000 to 91,000,000 t) of sediment or silt to the Gulf of California each year – second only to the Mississippi among North American rivers. This sediment nourished wetlands and riparian areas along the river's lower course, particularly in its 3,000-square-mile (7,800 km2) delta, once the largest desert estuary on the continent. Currently, the majority of sediments carried by the Colorado River are deposited at the upper end of Lake Powell, and most of the remainder ends up in Lake Mead. Various estimates place the time it would take for Powell to completely fill with silt at 300 to 700 years. Dams trapping sediment not only pose damage to river habitat but also threaten future operations of the Colorado River reservoir system.
Reduction in flow caused by dams, diversions, water for thermoelectric power stations, and evaporation losses from reservoirs – the latter of which consumes more than 15 percent of the river's natural runoff—has had severe ecological consequences in the Colorado River Delta and the Gulf of California. Historically, the delta with its large freshwater outflow and extensive salt marshes provided an important breeding ground for aquatic species in the Gulf. Today's desiccated delta, at only a fraction of its former size, no longer provides suitable habitat, and populations of fish, shrimp and sea mammals in the gulf have seen a dramatic decline. Since 1963, the only times when the Colorado River has reached the ocean have been during El Niño events in the 1980s and 1990s.
Reduced flows have led to increases in the concentration of certain substances in the lower river that have impacted water quality. Salinity is one of the major issues and also leads to the corrosion of pipelines in agricultural and urban areas. The lower Colorado's salt content was about 50 parts per million (ppm) in its natural state, but by the 1960s, it had increased to well over 2000 ppm. By the early 1970s, there was also serious concern about salinity caused by salts leached from local soils by irrigation drainage water, which were estimated to add 10 million short tons (9,100,000 t) of excess salt to the river per year. The Colorado River Basin Salinity Control Act was passed in 1974, mandating conservation practices including the reduction of saline drainage. The program reduced the annual load by about 1.2 million short tons (1,100,000 t), but salinity remains an ongoing issue. In 1997, the USBR estimated that saline irrigation water caused crop damages exceeding $500 million in the U.S. and $100 million in Mexico. Further efforts have been made to combat the salt issue in the lower Colorado, including the construction of a desalination plant at Yuma. In 2011, the seven U.S. states agreed upon a "Plan of Implementation", which aims to reduce salinity by 644,000 short tons (584,000 t) per year by 2030. In 2013, the Bureau of Reclamation estimated that around $32 million was spent each year to prevent around 1.2 million tons of salt from entering and damaging the Colorado River.
Agricultural runoff containing pesticide residues has also been concentrated in the lower river in greater amounts. This has led to fish kills; six of these events were recorded between 1964 and 1968 alone. The pesticide issue is even greater in streams and water bodies near agricultural lands irrigated by the Imperial Irrigation District with Colorado River water. In the Imperial Valley, Colorado River water used for irrigation overflows into the New and Alamo rivers and into the Salton Sea. Both rivers and the sea are among the most polluted bodies of water in the United States, posing dangers not only to aquatic life but to contact by humans and migrating birds. Pollution from agricultural runoff is not limited to the lower river; the issue is also significant in upstream reaches such as Colorado's Grand Valley, also a major center of irrigated agriculture.
Large dams such as Hoover and Glen Canyon typically release water from lower levels of their reservoirs, resulting in stable and relatively cold year-round temperatures in long reaches of the river. The Colorado's average temperature once ranged from 85 °F (29 °C) at the height of summer to near freezing in winter, but modern flows through the Grand Canyon, for example, rarely deviate significantly from 46 °F (8 °C). Changes in temperature regime have caused declines of native fish populations, and stable flows have enabled increased vegetation growth, obstructing riverside habitat. These flow patterns have also made the Colorado more dangerous to recreational boaters; people are more likely to die of hypothermia in the colder water, and the general lack of flooding allows rockslides to build up, making the river more difficult to navigate.
Minute 319
In the 21st century, there has been renewed interest in restoring a limited water flow to the delta. In November 2012, the U.S. and Mexico reached an agreement, known as Minute 319, permitting Mexico storage of its water allotment in U.S. reservoirs during wet years, thus increasing the efficiency with which the water can be used. In addition to renovating irrigation canals in the Mexicali Valley to reduce leakage, this will make about 45,000 acre-feet (56,000,000 m3) per year available for release to the delta on average. The water will be used to provide both an annual base flow and a spring "pulse flow" to mimic the river's original snowmelt-driven regime. The first pulse flow, an eight-week release of 105,000 acre-feet (130,000,000 m3), was initiated on March 21, 2014, with the aim of revitalising 2,350 acres (950 hectares) of wetland. This pulse reached the sea on May 16, 2014, marking the first time in 16 years that any water from the Colorado flowed into the ocean, and was hailed as "an experiment of historic political and ecological significance" and a landmark in U.S.–Mexican cooperation in conservation. The pulse will be followed by the steady release of 52,000 acre-feet (64,000,000 m3) over the following three years, just a small fraction of its average flow before damming.[needs update]
Recreation
Famed for its dramatic rapids and canyons, the Colorado is one of the most well-known whitewater rivers in the United States, and its Grand Canyon section—run by more than 22,000 people annually—has been called the "granddaddy of rafting trips". Grand Canyon trips typically begin at Lee's Ferry and take out at Diamond Creek or Lake Mead; they range from one to eighteen days for commercial trips and from two to twenty-five days for private trips. Private (noncommercial) trips are extremely difficult to arrange because the National Park Service limits river traffic for environmental purposes; people who desire such a trip often have to wait more than 10 years for the opportunity.
Several other sections of the river and its tributaries are popular whitewater runs, and many of these are also served by commercial outfitters. The Colorado's Cataract Canyon and many reaches in the Colorado headwaters are even more heavily used than the Grand Canyon, and about 60,000 boaters run a single 4.5-mile (7.2 km) section above Radium, Colorado, each year. The upper Colorado also includes many of the river's most challenging rapids, including those in Gore Canyon, which is considered so dangerous that "boating is not recommended". Another section of the river above Moab, known as the Colorado "Daily" or "Fisher Towers Section", is the most visited whitewater run in Utah, with more than 77,000 visitors in 2011 alone. The rapids of the Green River's Gray and Desolation Canyons and the less difficult "Goosenecks" section of the lower San Juan River are also frequently traversed by boaters.
Eleven U.S. national parks—Arches, Black Canyon of the Gunnison, Bryce Canyon, Canyonlands, Capitol Reef, Grand Canyon, Mesa Verde, Petrified Forest, Rocky Mountain, Saguaro, and Zion—are in the watershed, in addition to many national forests, state parks, and recreation areas. Hiking, backpacking, camping, skiing, and fishing are among the multiple recreation opportunities offered by these areas. Fisheries have declined in many streams in the watershed, especially in the Rocky Mountains, because of polluted runoff from mining and agricultural activities. The Colorado's major reservoirs are also heavily traveled summer destinations. Houseboating and water-skiing are popular activities on Lakes Mead, Powell, Havasu, and Mojave, as well as Flaming Gorge Reservoir in Utah and Wyoming, and Navajo Reservoir in New Mexico and Colorado. Lake Powell and surrounding Glen Canyon National Recreation Area received more than two million visitors per year in 2007, while nearly 7.9 million people visited Lake Mead and the Lake Mead National Recreation Area in 2008. Colorado River recreation employs some 250,000 people and contributes $26 billion each year to the Southwest economy.
See also
- Colorado River Delta
- Colorado Desert
- List of Colorado River rapids and features
- List of dams in the Colorado River system
- List of largest reservoirs in the United States
- List of longest rivers of Mexico
- List of longest rivers of the United States (by main stem)
- London Bridge (Lake Havasu City)
- Moab uranium mill tailings pile
- Upper Colorado River Endangered Fish Recovery Program
Notes
- Discharge data is for Green River, Utah, 117.6 miles (189.3 km) upstream from the mouth. The stream gauge here measures flow from an area of 44,850 square miles (116,200 km2), representing about 93.2 percent of the basin.
- Before large irrigation and municipal diversions, the Gila River discharged about 1.3 million acre-feet (1.6 km3) per year, which equals a flow of nearly 2,000 cubic feet per second (57 m3/s).
- Discharge data is for Bluff, Utah, located about 113.5 miles (182.7 km) above the confluence with the Colorado. The gauge measures flow from an area of 23,000 square miles (60,000 km2), about 93.5 percent of the basin.
- Discharge data is for Littlefield, Arizona, about 66 miles (106 km) from the confluence with the Colorado, and also upstream of the confluence with its major tributary, the Muddy River. The gauge measures flow from an area of 5,090 square miles (13,200 km2), about 39.1 percent of the total basin.
- American population (9.7 million) calculated from statistics from the U.S. Census Bureau and the State of Colorado. The population in Mexico is about 3 million.
- Unimpaired runoff figures published by the Bureau of Reclamation are an estimate of unregulated river flow without any upstream water consumption.
- NIB = "Northerly International Boundary", or the point at which the Colorado begins to form the Mexico–U.S. border, south of Yuma. Also note that the SIB ("Southerly International Boundary") is the point at which the Colorado ceases to form the border and passes entirely into Mexico.
- The average discharge of the Colorado (Grand) River at Cisco, Utah, about 97 miles (156 km) upstream from the Green River confluence, is 7,181 cubic feet per second (203.3 m3/s); between here and the confluence, only a few small, intermittent tributaries join the river.The Green River has an average discharge of 6,048 cubic feet per second (171.3 m3/s) as measured at Green River, Utah, about 117.6 miles (189.3 km) above the confluence; below here the only major tributary is the San Rafael River, which contributes an average of 131 cubic feet per second (3.7 m3/s), resulting in a total of 6,169 cubic feet per second (174.7 m3/s), still significantly lower than the discharge of the Colorado at their confluence.
- The discrepancy between the natural flow at Lee's Ferry (13.5 million acre-feet or 16.65 km3) and the gauged flow between 1922 and 2020 (10.58 million acre-feet or 13.05 km3) is mostly due to water diversions above Lee's Ferry and evaporation from reservoirs, especially Lake Powell.
References
- Kammerer, J.C. (May 1990). "Largest Rivers in the United States". U.S. Geological Survey. Archived from the original on March 21, 2007. Retrieved July 2, 2010.
- "USGS Gage #09380000 Colorado River at Lees Ferry, AZ: Water-Year Summary". National Water Information System. U.S. Geological Survey. 2023. Retrieved August 11, 2024.
- "Colorado River". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. February 8, 1980. Retrieved February 18, 2012.
- "The Compact and Lees Ferry". Colorado River Streamflow: A Paleo Perspective. Western Water Assessment. Archived from the original on April 29, 2012.
- Waterman, Jonathan (February 15, 2012). "Where the Colorado Runs Dry". The New York Times. Archived from the original on August 21, 2021. Retrieved October 14, 2014.
- "Imperial Valley". Encyclopædia Britannica. 1995.
- "San Juan – Chama Project". Archived from the original on August 23, 2021. Retrieved August 23, 2021.
- Diaz, Henry F.; Anderson, Craig A. (November 28, 2003). "Precipitation Trends and Water Consumption in the Southwestern United States". Impact of Climate Change and Land Use in the Southwestern United States. U.S. Geological Survey. Archived from the original on March 9, 2012.
- Postel, Sandra (May 19, 2014). "A Sacred Reunion: The Colorado River Returns to the Sea". National Geographic. Archived from the original on January 8, 2018. Retrieved May 19, 2021.
- "La Poudre Pass". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. October 13, 1978. Retrieved March 12, 2012.
- Lindberg 2009, p. 38.
- Benke & Cushing 2005, p. 490.
- Pitlick, John; Cress, Robert (March 2000). "Longitudinal Trends in Channel Characteristics of the Colorado River and Implications for Food-Web Dynamics" (PDF). University of Colorado. Archived from the original (PDF) on December 4, 2012. Retrieved March 12, 2012.
- U.S. Geological Survey. "United States Geological Survey Topographic Maps: Fall River Pass, Colorado quad". TopoQuest. Archived from the original on July 27, 2021. Retrieved June 24, 2013.
- U.S. Geological Survey. "United States Geological Survey Topographic Maps: Westwater, Utah quad". TopoQuest. Archived from the original on July 27, 2021. Retrieved July 14, 2013.
- "Affected Environment" (PDF). Remediation of the Moab Uranium Mill Tailings, Grand and San Juan Counties, Utah Final Environmental Impact Statement. Moab, Utah, UMTRA Project. p. 28. Archived from the original (PDF) on October 15, 2011.
- Rigby, J. Keith; Hamblin, W. Kenneth; Matheny, Ray; Welsh, Stanley L. (1971). "Guidebook to the Colorado River Part 3: Moab to Hite, Utah through Canyonlands National Park" (PDF). Brigham Young University Geology Studies Volume 18 – Part 2. Brigham Young University. Archived from the original (PDF) on April 2, 2015. Retrieved July 14, 2013.
- Hopkins 2002, p. 118.
- Van Cott 1990, p. 70.
- Van Cott 1990, p. 155.
- "Rivers". Canyonlands National Park. U.S. National Park Service. June 17, 2011. Archived from the original on June 29, 2012. Retrieved February 19, 2012.
- "Lake Powell". Colorado River Storage Project. U.S. Bureau of Reclamation. November 4, 2008. Archived from the original on September 21, 2012. Retrieved February 19, 2012.
- Rusho, W.L. (1992). "Lee's Ferry, Arizona". Utah History Encyclopedia. University of Utah. Archived from the original on January 9, 2013. Retrieved February 19, 2012.
- "Grand Canyon National Park, Arizona: Geology Fieldnotes". U.S. National Park Service. Archived from the original on October 23, 2013. Retrieved July 14, 2013.
- Leopold, Luna B. "The Rapids and the Pools – Grand Canyon" (PDF). Geological Survey Professional Paper 669–D. U.S. Geological Survey. p. 133. Archived (PDF) from the original on November 4, 2013. Retrieved November 2, 2013.
- "Hoover Dam Frequently Asked Questions and Answers: Lake Mead". U.S. Bureau of Reclamation. December 2008. Archived from the original on May 20, 2012. Retrieved February 19, 2012.
- "Hoover Dam Bypass Is 2012 OCEA Winner; OPAL Lifetime Achievement Recipients Honored; Pankow, Michel Awards Presented". American Society of Civil Engineers. Archived from the original on March 27, 2013. Retrieved July 14, 2013.
- "The Colorado River Indian Tribes Reservation (C.R.I.T.) Quick Facts" (PDF). Arizona Cooperative Extension. University of Arizona. August 2010. Archived from the original (PDF) on October 21, 2011. Retrieved July 14, 2013.
- "Appendix J: Mainstem Impacts Analysis" (PDF). Draft Environmental Impact Statement: Allocation of Water Supply and Long-Term Contract Execution, Central Arizona Project. U.S. Bureau of Reclamation. Archived from the original (PDF) on January 20, 2013. Retrieved April 4, 2012.
- U.S. Geological Survey. "United States Geological Survey Topographic Maps: Blythe NE, California quad". TopoQuest. Archived from the original on July 27, 2021. Retrieved July 14, 2013.
- Gupta 2007, p. 204.
- Alles, David L., ed. (October 28, 2011). "The Lower Colorado River" (PDF). Biology Department. Western Washington University. Archived (PDF) from the original on December 7, 2012. Retrieved July 14, 2013.
- "Fighting For Water in Arid Imperial Valley". National Public Radio. February 10, 2011. Archived from the original on July 27, 2021. Retrieved February 19, 2012.
- "Border Water Source of Conflict and Cooperation: What Makes Management of Border Water Resources a Challenge?" (PDF). Arroyo. University of Arizona. 2012. Archived from the original (PDF) on November 13, 2014. Retrieved July 14, 2013.
- Valdes-Casillas, Carlos; et al. (August 1998). "Information Database and Local Outreach Program for the Restoration of the Hardy River Wetlands, Lower Colorado River Delta, Baja California and Sonora, Mexico". San Diego State University. Archived from the original on January 20, 2013. Retrieved February 19, 2012.
- (March 24, 2014). "Historic "Pulse Flow" Brings Water to Parched Colorado River Delta". National Geographic. Archived from the original on September 1, 2019.
- Chanson, Hubert (2009). Environmental, Ecological and Cultural Impacts of Tidal Bores, Benaks, Bonos and Burros. Proceedings of the International Workshop on Environmental Hydraulics IWEH09, Theoretical, Experimental and Computational Solutions. University of Queensland. Archived from the original on October 21, 2011. Retrieved November 29, 2009.
- Felger & Broyles 2007, pp. 519–520.
- "Executive Summary, Green River Basin Water Plan". Wyoming State Water Plan. February 2001. Archived from the original on November 25, 2011. Retrieved February 25, 2012.
- "Boundary Descriptions and Names of Regions, Subregions, Accounting Units and Cataloging Units". U.S. Geological Survey. Archived from the original on April 9, 2020. Retrieved February 19, 2012.
- Benke & Cushing 2005, p. 514.
- Benke & Cushing 2005, pp. 532–533.
- "Green River". Utah Rivers Council. Archived from the original on May 14, 2012. Retrieved February 26, 2012.
- "USGS Gage #09315000 on the Green River at Green River, UT" (PDF). National Water Information System. U.S. Geological Survey. 1895–2010. Archived (PDF) from the original on January 20, 2013. Retrieved February 26, 2012.
- "USGS Gage #09520000 on the Gila River near Dome, AZ" (PDF). National Water Information System. U.S. Geological Survey. 1905–2011. Archived (PDF) from the original on January 20, 2013. Retrieved February 26, 2012.
- The National Map Archived June 30, 2016, at the Wayback Machine. U.S. Geological Survey. Accessed February 25, 2012
- "USGS Gage #09379000 on the San Juan River near Bluff, UT" (PDF). National Water Information System. U.S. Geological Survey. 1914–2010. Archived (PDF) from the original on January 20, 2013. Retrieved February 26, 2012.
- "Report, Findings, and Determination Regarding the Navigability of the Little Colorado River From its Headwaters to the Confluence with the Colorado River" (PDF). Arizona Navigable Stream Adjudication Commission. 2005. Archived from the original (PDF) on April 22, 2010. Retrieved February 26, 2012.
- "USGS Gage #09402300 on the Little Colorado River Above the Mouth near Desert View, AZ" (PDF). National Water Information System. U.S. Geological Survey. 1990–2010. Archived (PDF) from the original on January 20, 2013. Retrieved February 26, 2012.
- Fielder 2002, p. 403.
- "USGS Gage #09180000 on the Dolores River near Cisco, UT" (PDF). National Water Information System. U.S. Geological Survey. 1950–2010. Archived (PDF) from the original on January 20, 2013. Retrieved February 26, 2012.
- "USGS Gage #09152000 on the Gunnison River near Grand Junction, CO" (PDF). National Water Information System. U.S. Geological Survey. 1897–2010. Archived (PDF) from the original on January 20, 2013. Retrieved February 26, 2012.
- Annerino 1999, p. 8.
- "USGS Gage #09415000 on the Virgin River at Littlefield, AZ" (PDF). National Water Information System. U.S. Geological Survey. 1929–2010. Archived (PDF) from the original on January 20, 2013. Retrieved February 26, 2012.
- Benke & Cushing 2005, pp. 483–486.
- "Watersheds (map)". Commission for Environmental Cooperation. 2006. Archived from the original on April 14, 2008.
- "Current Understanding of Colorado River Basin Climate and Hydrology" (PDF). Western Water Assessment. April 2020. Archived (PDF) from the original on January 20, 2022. Retrieved May 24, 2022.
- "River Basins of Mexico". University of Texas. 1975. Archived from the original on November 7, 2011. Retrieved February 19, 2012.
- Fassnacht, S.R. (2004). "Streamflow Predictability in the Upper Versus Lower Colorado River Sub-Basins" (PDF). Eastern Snow Conference. Archived from the original (PDF) on June 23, 2012. Retrieved February 19, 2012.
- "Lees Ferry (historical)". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. February 8, 1980. Retrieved May 25, 2022.
- "Annual Report on the Salton Sea Management Program" (PDF). California Natural Resources Agency. March 2021. Archived (PDF) from the original on April 1, 2022. Retrieved May 26, 2022.
- Singh, Ramesh K.; Senay, Gabriel B.; Velpuri, Naga Manohar; Kagone, Stephanie (January 2014). "Actual Evapotranspiration (Water Use) Assessment of the Colorado River Basin at the Landsat Resolution Using the Operational Simplified Surface Energy Balance Model". Remote Sensing. 6 (1): 233–256. doi:10.3390/rs6010233. Archived from the original on March 1, 2024. Retrieved May 26, 2022.
- Benke & Cushing 2005, pp. 483–489.
- Baker Jr., Malchus B.; Ffolliott, Peter F. (2000). "Contributions of Watershed Management Research to Ecosystem-Based Management in the Colorado River Basin" (PDF). USDA Forest Service Proceedings RMRS–P–13. U.S. Forest Service. Archived (PDF) from the original on October 23, 2020. Retrieved June 24, 2013.
- Climate and Hydrology of the Colorado River Basin Region. National Academies Press. 2007. doi:10.17226/11857. ISBN 978-0-309-10524-8. Archived from the original on May 26, 2022. Retrieved May 23, 2022.
- "Features and Dynamics of Colorado River Basin Climate". Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability. National Academies Press. 2007. doi:10.17226/11857. ISBN 978-0-309-10524-8. Archived from the original on January 20, 2013. Retrieved February 19, 2012.
- "State and County QuickFacts". U.S. Census Bureau. Archived from the original on March 4, 2012. Retrieved March 4, 2012.
- "Population and Demographics". Colorado Data Book. State of Colorado. September 2007. Archived from the original (PDF) on January 20, 2013.
- "Colorado River Basin Salinity Control Program". Natural Resources Conservation Service. U.S. Department of Agriculture. July 12, 2010. Archived from the original on June 10, 2021. Retrieved March 4, 2012.
- "Colorado River Basin Water Management: Evaluating and Adjusting to Hydroclimatic Variability (Report in Brief)" (PDF). Division on Earth & Life Studies. National Academies. February 2007. Archived from the original (PDF) on September 15, 2012. Retrieved February 19, 2012.
- "Colorado River Basin Natural Flow and Salt Data". U.S. Bureau of Reclamation. April 22, 2024. Retrieved August 11, 2024.
- "Water-Year Summary for Site USGS 09380000 Colorado River at Lees Ferry, AZ". National Water Information System. U.S. Geological Survey. 1922–2020. Archived from the original on June 24, 2021. Retrieved May 17, 2021.
- "USGS Gage #09380000 on the Colorado River at Lee's Ferry, AZ". National Water Information System. U.S. Geological Survey. 1921–2010. Archived from the original on February 22, 2016. Retrieved April 21, 2012.
- Schmidt, J. C., Yackulic, C. B., & Kuhn, E. (2023). The Colorado River water crisis: Its origin and the future. WIREs Water, 10(6), e1672. https://doi.org/10.1002/wat2.1672
- Thomsen, B.W.; Eychaner, J.H. (1991). "Predevelopment hydrology of the Gila River Indian Reservation, South-Central Arizona" (PDF). Arizona Navigable Stream Adjudication Commission. Retrieved August 11, 2024.
- Phillips, Daniel H.; Reinink, Yvonne; Skarupa, Timothy E.; Ester III, Charles E.; and Skindlov, Jon A. (April 29, 2009). "Water resources planning and management at the Salt River Project, Arizona, USA" (PDF). TreeFlow. Retrieved August 11, 2024.
{{cite web}}: CS1 maint: multiple names: authors list (link) - Anderson, D. Larry (2002). "The Colorado River: Utah's Perspective" (PDF). Utah Division of Water Resources. Retrieved August 11, 2024.
- "Climatic Fluctuations, Drought, and Flow in the Colorado River Basin". USGS Fact Sheet 2004-3062. U.S. Geological Survey. August 2004. Archived from the original on October 19, 2012. Retrieved April 17, 2012.
- Wiltshire, Gilbert & Rogers 2010, pp. 101–102.
- Wahl, Kenneth L.; Collins, Dannie L.; Aldridge, Byron N. "Runoff in the Upper Colorado River Basin Water Years, 1983–85, and Comparisons with Forecasts of Runoff to Lake Powell" (PDF). Western Snow Conference. Archived from the original (PDF) on July 14, 2012.
- Preston, Ben (March 22, 2010). "The Risky Business of Slicing the Pie". Miller–McCune. Archived from the original on July 27, 2021. Retrieved June 27, 2013.
- "USGS Gage #09421500 on the Colorado River below Hoover Dam". National Water Information System. U.S. Geological Survey. 1934–2021. Retrieved August 11, 2024.
- Richard, Gigi A. and Anderson, Richard M. (2007). "Channel-forming discharge on the Dolores River and Yampa River, Colorado" (PDF). Colorado Parks and Wildlife. Retrieved August 11, 2024.
{{cite web}}: CS1 maint: multiple names: authors list (link) - Christensen, Niklas S.; Wood, Andrew W.; Voisin, Nathalie; Lettenmaier, Dennis P.; Palmer, Richard N. (2004). "The Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin" (PDF). Climatic Change. 62 (337–363): 345. doi:10.1023/b:clim.0000013684.13621.1f. S2CID 53533021. Archived from the original (PDF) on May 1, 2014. Retrieved July 13, 2013.
- Cohen, Michael J.; Henges-Jeck, Christine; Castillo-Moreno, Gerardo (2001). "A Preliminary Water Balance for the Colorado River Delta, 1992–1998" (PDF). Journal of Arid Environments. 49 (1): 35–48. Bibcode:2001JArEn..49...35C. doi:10.1006/jare.2001.0834. Archived (PDF) from the original on October 10, 2015. Retrieved June 27, 2013.
- "For A Few Weeks The Colorado River Reached The Ocean. Will It Happen Again?". KPBS Public Media. February 19, 2018. Archived from the original on March 24, 2022. Retrieved February 27, 2022.
- "USGS Gage #09522200 on the Colorado River at NIB, Above Morelos Dam, AZ – Annual Statistics". National Water Information System. U.S. Geological Survey. 1951–1992. Archived from the original on September 19, 2015. Retrieved April 27, 2012.
- Zimmerman, Janet (October 6, 2010). "Colorado River Drought Threatens Power Production". The Press-Enterprise. Riverside, California. Archived from the original on January 20, 2013. Retrieved February 18, 2012.
- Stark, Mike (April 21, 2009). "Study: Shortages Likely on Colorado River by 2050". USA Today. Associated Press. Archived from the original on July 18, 2013. Retrieved June 27, 2013.
- Hoerling, Martin; Eischeid, Jon. "Past Peak Water in the Southwest" (PDF). Western Water Assessment. Archived from the original (PDF) on June 9, 2010.
- McKinnon, Shaun (August 9, 2006). "Mines, Farms Put Gila River on Life Support: Despite Lack of Regulation, Some Trying to Restore River to Its Natural Beauty and Wonder". Arizona Republic. Archived from the original on January 17, 2013. Retrieved February 19, 2012.
- "Water-Year Summary for Site USGS 09522000 Colorado River at Northerly International Boundary, above Morelos Dam, near Andrade, CA". National Water Information System. U.S. Geological Survey. 1950–2020. Archived from the original on August 24, 2021. Retrieved May 17, 2021.
- "Reclamation". Colorado River Water Users Association. Archived from the original on November 4, 2013. Retrieved November 2, 2013.
- "Water-Year Summary for Site USGS 09010500 Colorado River below Baker Gulch near Grand Lake, CO". National Water Information System. U.S. Geological Survey. 1953–2020. Archived from the original on August 24, 2021. Retrieved May 17, 2021.
- "Water-Year Summary for Site USGS 09070500 Colorado River near Dotsero, CO". National Water Information System. U.S. Geological Survey. 1941–2020. Archived from the original on August 24, 2021. Retrieved May 17, 2021.
- "Water-Year Summary for Site USGS 09180500 Colorado River near Cisco, UT". National Water Information System. U.S. Geological Survey. 1914–2020. Archived from the original on August 24, 2021. Retrieved May 17, 2021.
- "Water-Year Summary for Site USGS 09423000 Colorado River below Davis Dam, AZ–NV". National Water Information System. U.S. Geological Survey. 1905–2020. Archived from the original on August 24, 2021. Retrieved May 17, 2021.
- "Water-Year Summary for Site USGS 09427520 Colorado River below Parker Dam, AZ–CA". National Water Information System. U.S. Geological Survey. 1935–2020. Archived from the original on August 24, 2021. Retrieved May 17, 2021.
- "Water-Year Summary for Site USGS 09429600 Colorado River below Laguna Dam, AZ–CA". National Water Information System. U.S. Geological Survey. 1972–2020. Archived from the original on August 24, 2021. Retrieved May 17, 2021.
- Prisciantelli 2002, p. 56.
- Cannon, Eric (April 28, 2002). "The Mid-Tertiary Ignimbrite Flare-Up". University of Colorado, Boulder. Archived from the original on July 16, 2012. Retrieved February 19, 2012.
- Foos, Annabelle. "Geology of the Colorado Plateau" (PDF). U.S. National Park Service. Archived from the original (PDF) on September 8, 2015. Retrieved February 19, 2012.
- Martin-Barajas, Arturo; et al. (July 2009). "The Tectonic Evolution of the Gulf of California". Division of Geological and Planetary Sciences. California Institute of Technology. Archived from the original on January 20, 2013. Retrieved February 19, 2012.
- Young & Spamer 2001, p. 193.
- Davis, Jim (January 2009). "Why Does a River Run Through It?". Survey Notes. 41 (1). Utah Geological Survey. Archived from the original on November 8, 2010. Retrieved February 19, 2012.
- Prisciantelli 2002, p. 62.
- Alles, David L., ed. (October 28, 2011). "Geology of the Salton Trough" (PDF). Western Washington University. Archived (PDF) from the original on March 2, 2012. Retrieved February 29, 2012.
- Buckles, Joseph E.; Krantz, Timothy. "Reconstruction of Prehistoric Shorelines for Cultural Restraints using GIS". Salton Sea Database Program. ESRI. Archived from the original on November 27, 2011. Retrieved February 19, 2012.
- Fenton, Cassie; Webb, Bob. "A Fresh Look at Western Grand Canyon Lava Dams: Introduction". Grand Canyon River Guides. Archived from the original on June 23, 2012. Retrieved February 19, 2012.
- Rugg, Scott H.; Austin, Steven A. (August 1998). "Evidence for Rapid Formation and Failure of Pleistocene "Lava Dams" of the Western Grand Canyon, Arizona" (PDF). Institute for Creation Research. Archived from the original (PDF) on January 21, 2012. Retrieved February 19, 2012.
- Fenton, Cassandra R.; Poreda, Robert J.; Nash, Barbara P.; Webb, Robert H.; Cerling, Thure E.; et al. (2004). "Geochemical Discrimination of Five Pleistocene Lava-Dam Outburst-Flood Deposits, Western Grand Canyon, Arizona" (PDF). Journal of Geology. 112 (1): 91–110. Bibcode:2004JG....112...91F. doi:10.1086/379694. S2CID 53339467. Archived (PDF) from the original on January 20, 2013. Retrieved February 19, 2012.
- Fenton, Cassandra R.; Webb, Robert H; Cerling, Thure E. (May 6, 2005). "Peak Discharge of a Pleistocene Lava-Dam Outburst Flood in Grand Canyon, Arizona, USA" (PDF). Quaternary Research. 65 (2). U.S. Geological Survey: 324. Bibcode:2006QuRes..65..324F. doi:10.1016/j.yqres.2005.09.006. S2CID 128533268. Archived from the original (PDF) on October 15, 2011. Retrieved February 19, 2012.
- "People of the Colorado Plateau". Land Use History of North America. Northern Arizona University. Archived from the original on June 29, 2015. Retrieved April 9, 2012.
- "Formative Era/Fremont Culture". U.S. Bureau of Land Management. August 31, 2009. Archived from the original on June 23, 2012. Retrieved April 9, 2012.
- "Fremont Culture". Dinosaur National Monument. U.S. National Park Service. Archived from the original on August 15, 2012. Retrieved April 9, 2012.
- Vess, Deborah. "The Anasazi". Georgia College and State University. Archived from the original on June 8, 2011.
- Sevigny, Melissa (May 12, 2022). "Archaeological sites once thought lost under Lake Powell reappear as water drops". Arizona Public Radio. Retrieved August 11, 2024.
- "Water Development, Extraction, and Diversion". Land Use History of North America: Colorado Plateau. Northern Arizona University. p. 2. Archived from the original on February 14, 2015. Retrieved October 21, 2014.
- "Ancestral Pueblo People and Their World" (PDF). U.S. National Park Service. Retrieved August 20, 2024.
- Nobles 1998, p. 26.
- Logan 2006, pp. 21–22.
- Hopi Dictionary/Hopìikwa Lavàytutuveni:. Hopi-English Dictionary of the Third Mesa Dialect. The Hopi Dictionary Project. Tucson: University of Arizona Press, 1997.
- Antone, Caroline. Piipayk m'iim. Salt River: Oʼodham Piipaash Language Program, 2000.
- Gupta 2010, p. 362.
- Hinton, Leanne (1984). A Dictionary of the Havasupai Language. Supai, Arizona: Havasupai Tribe. OCLC 12358778.
- William Alan Shaterian (1983). Phonology and Dictionary of Yavapai (PhD dissertation). University of California, Berkeley. OCLC 13197420.
- "Ancient Forest Management in the Chaco Canyon – From 600 AD to 1300 AD". Tenthmil. Archived from the original on December 24, 2010.
- Schwinning, Susan; Belnap, Jayne; Bowling, David R. & Ehleringer, James R. (2008). "Sensitivity of the Colorado Plateau to Change: Climate, Ecosystems and Society". Ecology and Society. 13 (2): 28. doi:10.5751/ES-02412-130228. hdl:10535/2863.
- Andrews, John P.; Bostwick, Todd W. "Desert Farmers at the River's Edge: The Hohokam and Pueblo Grande". Pueblo Grande Museum Archaeological Park. City of Phoenix. Archived from the original on May 8, 2012. Retrieved April 10, 2012.
- Shaw, Anne Moore. "A Pima Past". Salt River Pima-Maricopa Indian Community. Archived from the original on January 20, 2013. Retrieved April 10, 2012.
- Kroeber, Clifton B. and Fontana, Bernard L. "Yuman Antagonists: Maricopas, Quechans and Mohaves to 1857". Massacre on the Gila: An Account of the Last Major Battle Between American Indians, with Reflections on the Origin of War. University of Arizona Press. Retrieved August 20, 2024.
{{cite web}}: CS1 maint: multiple names: authors list (link) - "California: Mohave". Southwest Indian Relief Council. Archived from the original on December 13, 2012. Retrieved April 10, 2012.
- "The Navajo: A Brief History" (PDF). The Navajo Nation Division of Economic Development. Archived (PDF) from the original on September 4, 2012. Retrieved April 10, 2012.
- Hassell, Hank (2001). "Navajo Mountain Religion: Rainbow Bridge through Indian Eyes". Johns Hopkins University. Retrieved August 20, 2024.
- "Ute". Land Use History of North America. Northern Arizona University. Archived from the original on February 5, 2012. Retrieved April 9, 2012.
- Benke & Cushing 2005, p. 486.
- "History". Southern Ute Indian Tribe. Retrieved August 20, 2024.
- "John Wesley Powell's Exploration of the Colorado River". U.S. Geological Survey. March 28, 2006. Archived from the original on April 5, 2015. Retrieved February 19, 2012.
- Axelrod & Phillips 2008, p. 4.
- Lankford 2010, pp. 100–101.
- Flint, Richard; Flint, Shirley Cushing. "Diaz, Melchior". New Mexico Office of the State Historian. Archived from the original on October 10, 2013.
- Pritzker 1998, p. 309.
- "Arizona: Yuma Crossing National Heritage Area". U.S. National Park Service. April 22, 2019. Retrieved August 20, 2024.
- Bolton 2017, pp. 440.
- Gudde & Bright 2004, p. 50.
- Anthony, Alex. "Crossing of the Fathers". Intermountain Histories. Retrieved August 20, 2024.
- "Before Powell: Exploration of the Colorado River".
- Dellenbaugh 1909, p. 60.
- Rolle 1999, p. 54.
- Indian Affairs: Treaties. U.S. Government Printing Office. 1904.
- "Renaming the Grand River, Colo." (PDF), Hearing Before the Committee on Interstate and Foreign Commerce of the House of Representatives, Sixty Sixth Congress, Third Session, on HJ 460, Government Printing Office, February 18, 1921, archived (PDF) from the original on August 5, 2021, retrieved May 16, 2023
- A Complete Pronouncing Gazetteer or Geographical Dictionary of the World: Containing the Most Recent and Authentic Information Respecting the Countries, Cities, Towns, Resorts, Islands, Rivers, Mountains, Seas, Lakes, Etc., in Every Portion of the Globe. J. B. Lippincott Company. 1906.
- Gemaehlich, Tammy (September 4, 2023). "What's in a Name: Grand Junction and the rivers that run through it". The Grand Junction Daily Sentinel. Retrieved August 17, 2024.
- "Overland Monthly and Out West Magazine". A. Roman and Company. August 11, 1895. Archived from the original on March 1, 2024. Retrieved August 31, 2016 – via Google Books.
- Richard E. Lingenfelter (1978). Steamboats on the Colorado River, 1852–1916 (PDF). Tucson: University of Arizona Press. Archived from the original (PDF) on January 18, 2016.
- "Autobiography and Reminiscence of George Alonzo Johnson, San Diego, 1901". oac.cdlib.org. Archived from the original on August 3, 2020. Retrieved August 11, 2022.
- Ives, Joseph C. (August 11, 1861). "Report Upon the Colorado River of the West". U.S. Government Printing Office – via Google Books.
- Dellenbaugh 1909, p. 170.
- Schmidt 1993, p. 12.
- Dolnick 2002, p. 5.
- Leuchtenburg 2000, p. 360.
- "Historic 3D Photographs of the Second Powell Expedition (1871–1872)". Geology of National Parks. U.S. Geological Survey. February 13, 2012. Archived from the original on March 11, 2012. Retrieved February 20, 2012.
- "The J.W. Powell Survey (1871-1894)". Smithsonian Institution Archives. Retrieved August 20, 2024.
- Hekkers, Jim (1980). "The Colorado River Railroad Survey" (PDF). Colorado Outdoors. Retrieved August 17, 2024.
- Dolnick 2002, p. 238.
- Keeler, Preston. "Nelson, Nevada Ghost Town and El Dorado Canyon". Intermountain Histories. Retrieved August 20, 2024.
- Johnson, Weldon B. (September 10, 2018). "Arizona's mining history: Danger for many, riches for a few". The Arizona Republic.
- Kessel & Wooster 2005, p. 217.
- "Fort Mojave Reservation". Tribal Library Census and Needs Assessment. California State University San Marcos. June 12, 2001. Archived from the original on May 14, 2013.
- "About the Mohave, Chemehuevi, Hopi and Navajo Tribes". Colorado River Indian Tribes. 2009. Archived from the original on August 12, 2021. Retrieved April 10, 2012.
- "The Colorado River Indian Tribes (C.R.I.T.) Reservation and Extension Programs" (PDF). University of Arizona College of Agriculture and Life Sciences. Indian Country Extension. October 2008. Archived from the original (PDF) on January 20, 2013. Retrieved April 10, 2012.
- "Navajo Nation". Indian Health Service. Archived from the original on June 23, 2012. Retrieved April 10, 2012.
- "Treaty Between the United States of America and the Navajo Tribe of Indians". Historic Documents. New Mexico State University. 1868. Archived from the original on March 11, 2002. Retrieved April 10, 2012.
- "Navajo Nation – Facts at a Glance". The Navajo Nation. 2004. Archived from the original on March 8, 2012. Retrieved April 10, 2012.
- Brown 1972, pp. 52–53.
- Casey 2007, p. 251.
- Lindberg 2009, pp. 134–135.
- "Chapter 5: The Utes in Southwestern Colorado: A Confrontation of Cultures". Frontier in Transition: A History of Southwestern Colorado. U.S. National Park Service. Retrieved May 15, 2017.
- "GJ HISTORY: Grand Junction town founder George A. Crawford — A witness to early American history". The Post-Independent. September 26, 2013. Retrieved August 20, 2024.
- "Glenwood Canyon time travel: A journey back through the history of travel through the 'Grand River Cañon' passage". August 15, 2021.
- "St. Thomas, Nevada". U.S. National Park Service. December 15, 2022. Retrieved August 20, 2024.
- Glass & Glass 1983, pp. 162–163.
- "Hole-in-the-Rock". U.S. National Park Service. July 28, 2023. Retrieved August 20, 2024.
- Howard, Jerry B. "Hohokam Legacy: Desert Canals". WaterHistory.org. Archived from the original on January 24, 2012. Retrieved April 9, 2012.
- Williams, O.A. (1937). "Settlement and Growth of the Gila Valley as a Mormon Colony, 1879–1900" (PDF). University of Arizona. Archived from the original (PDF) on January 20, 2013. Retrieved February 20, 2012.
- "Lees Ferry History". Glen Canyon National Recreational Area. U.S. National Park Service. August 11, 2006. Archived from the original on April 14, 2012. Retrieved February 20, 2012.
- "Lees Ferry". Arizona State University. July 8, 2010. Archived from the original on June 3, 2012. Retrieved February 20, 2012.
- "The "Moffat Road" and Northwestern Colorado, 1903-1948". BLM Cultural Resource Series: An Isolated Empire: A History of Northwest Colorado. U.S. National Park Service. Retrieved August 20, 2024.
- "Black Canyon of the Gunnison: Narrow Gauge Railroad". U.S. National Park Service. December 2, 2022. Retrieved August 20, 2024.
- Colorado River Water Conservation District (December 23, 2003). "Many Years Ago, the Colorado River Was Just Grand". SummitDaily. Archived from the original on April 30, 2011. Retrieved January 5, 2008.
- Barnes 1988, p. 104.
- "USGS Gage #09328500 on the San Rafael River near Green River, Utah" (PDF). National Water Information System. U.S. Geological Survey. 1910–2012. Archived (PDF) from the original on September 19, 2015. Retrieved June 22, 2013.
- Runyon, Luke (December 20, 2017). "How the 'Grand' Became the 'Colorado' And What It Says About Our Relationship To Nature". KUNC. University of Colorado Boulder. Retrieved August 20, 2024.
- "House Joint Resolution 32 - To change the name of the Grand River in Colorado and Utah to the Colorado River" (PDF). Congressional Record. Sixty-seventh United States Congress. July 25, 1921. p. 4274. Archived (PDF) from the original on May 16, 2023. Retrieved May 29, 2023.
- "Colorado River Basin Water Supply and Demand Study" (PDF). U.S. Bureau of Reclamation. December 2012. Archived (PDF) from the original on May 20, 2022. Retrieved May 18, 2022.
- Davis, Eric F. "The Colorado River Controversy" (PDF). Michigan State University. Archived from the original (PDF) on October 1, 2004.
- "Low Water May Halt Hoover Dam's Power". Circle of Blue. September 22, 2010. Archived from the original on January 20, 2013. Retrieved October 8, 2012.
- "Hydropower". Glen Canyon Dam Adaptive Management Program. November 18, 2010. Archived from the original on May 22, 2012. Retrieved May 12, 2012.
- Waterman, Jonathan (August 11, 2010). "Restoring floods to America's Nile". National Geographic. Archived from the original on March 24, 2012. Retrieved March 2, 2012.
- Nabhan, Gary Paul (January 16, 2007). "The Beginning and the End of the Colorado River: Protecting the Sources, Ensuring its Courses". Northern Arizona University. Archived from the original on December 25, 2011. Retrieved February 20, 2012.
- Reisner 1993, p. 120.
- "Colorado River Law". Southern Nevada Water Authority. Archived from the original on April 26, 2012. Retrieved February 20, 2012.
- "Colorado River Compact, 1922" (PDF). U.S. Bureau of Reclamation. Archived from the original (PDF) on September 15, 2012. Retrieved February 20, 2012.
- "Utilization of Waters of the Colorado and Tijuana Rivers and of the Rio Grande: Treaty Between the United States of America and Mexico" (PDF). International Boundary and Water Commission. February 3, 1944. Archived from the original (PDF) on September 15, 2012. Retrieved February 20, 2012.
- "Colorado River". GOOD Magazine. Archived from the original on July 20, 2012. Retrieved February 26, 2012.
- "Big changes are coming for the Colorado River soon—and they could get messy". Environment. August 15, 2022. Archived from the original on August 15, 2022. Retrieved August 16, 2022.
- Anderson, Larry (May 2002). "Utah's Perspective: The Colorado River" (PDF). Utah Division of Water Resources. Archived from the original (PDF) on April 9, 2014. Retrieved February 20, 2012.
- "The Law of the River". U.S. Bureau of Reclamation. March 2008. Archived from the original on June 26, 2012. Retrieved February 18, 2012.
- "Dams Along the Lower Colorado River". U.S. Bureau of Reclamation. Archived from the original on May 17, 2022. Retrieved May 18, 2022.
- "Appendix I: The Past, Present and Future of Transmountain Diversion Projects" (PDF). Roaring Fork Watershed Plan. Roaring Fork Conservancy. Archived from the original (PDF) on January 20, 2013. Retrieved March 18, 2012.
- "Transmountain Water Diversions" (PDF). Colorado River District. July 2011. Archived from the original (PDF) on December 1, 2011. Retrieved March 18, 2012.
- Citizen's Guide to Colorado's Transbasin Diversions. Water Education Colorado. 2014. Archived from the original on May 19, 2022. Retrieved May 19, 2022.
- "Transmountain Diversions". Roaring Fork Conservancy. Archived from the original on May 18, 2022. Retrieved May 18, 2022.
- "Colorado-Big Thompson Project". U.S. Bureau of Reclamation. October 18, 2011. Archived from the original on November 12, 2011. Retrieved February 20, 2012.
- "Moving Water in the Watershed". Blue River Watershed Group. Archived from the original on March 29, 2012. Retrieved May 18, 2012.
- Wahlstrom, Ernest E. (1974). "History of Geologic Investigations, Engineering Design, and Construction Methods of the Harold D. Roberts Tunnel, Colorado" (PDF). Geological Survey Professional Paper 831–A. U.S. Geological Survey. Archived (PDF) from the original on August 19, 2021. Retrieved May 18, 2012.
- "Fryingpan–Arkansas Project". U.S. Bureau of Reclamation. May 10, 2011. Archived from the original on August 27, 2014. Retrieved May 18, 2012.
- "Williams Fork Reservoir". Denver Water. Archived from the original on May 22, 2022. Retrieved May 18, 2022.
- "Wolford Mountain Reservoir". Colorado River District. Archived from the original on May 20, 2022. Retrieved May 18, 2022.
- Dwyer, John J. The Agrarian Dispute: The Expropriation of American-Owned Rural Land in Postrevolutionary Mexico. Durham: Duke University Press 2008
- Kerig, Dorothy P. "Yankee Enclave: The Colorado River Land Company and Mexican Agrarian Reform in Baja California, 1902-1944." PhD diss. University of California, Irvine 1988.
- Castillo-Muñoz, Verónica. The Other California: Land, Identities, and Politics on the Mexican Borderlands. Oakland: University of California Press 2017.
- Billington, Jackson & Melosi 2005, p. 140.
- Sperry, Robert L. (Winter 1975). "When The Imperial Valley Fought For Its Life". The Journal of San Diego History. 21 (1). San Diego History Center. Archived from the original on June 26, 2023. Retrieved June 25, 2023.
- Patten, McCaskie and Unitt, pp. 4–5
- "Origin of the Salton Sea". Suburban Emergency Management Project. Archived from the original on July 18, 2011.
- Billington, Jackson & Melosi 2005, pp. 141–142.
- "Boulder Canyon Project – Hoover Dam". U.S. Bureau of Reclamation. February 1, 2012. Archived from the original on October 11, 2012. Retrieved October 9, 2012.
- "The Colorado River and Hoover Dam: Facts and Figures". U.S. Bureau of Reclamation. January 2012. Archived from the original on May 14, 2012. Retrieved February 20, 2012.
- "Boulder Canyon Project Act (1928)". National Archives. September 21, 2021. Archived from the original on May 18, 2022. Retrieved May 18, 2022.
- "All-American Canal, California–Mexico border". Earth Observatory. National Aeronautics and Space Administration. February 23, 2009. Archived from the original on August 19, 2021. Retrieved February 20, 2012.
- "About IID Water". Imperial Irrigation District. Archived from the original on May 6, 2022. Retrieved May 18, 2022.
- "CRBSCP - Coachella Canal Unit - Title I". U.S. Bureau of Reclamation. Archived from the original on May 19, 2022. Retrieved May 18, 2022.
- "Parker Dam". Parker-Davis Project. U.S. Bureau of Reclamation. June 29, 2009. Archived from the original on September 27, 2012. Retrieved February 20, 2012.
- Marie Bell, Tina (1997). "Gila Project" (PDF). U.S. Bureau of Reclamation. Archived from the original (PDF) on February 24, 2012. Retrieved February 28, 2012.
- "The Colorado River: A Regional Solution". Los Angeles Department of Water and Power. Archived from the original on March 4, 2012. Retrieved February 28, 2012.
- "San Diego Project". U.S. Bureau of Reclamation. January 11, 2012. Archived from the original on March 16, 2012. Retrieved March 16, 2012.
- "Nevada". Colorado River Water Users Association. Archived from the original on November 4, 2013. Retrieved November 2, 2013.
- Fradkin 1996, p. 191.
- "Colorado River Storage Project". U.S. Bureau of Reclamation. Archived from the original on November 8, 2019. Retrieved May 18, 2022.
- "Chapter IX: Dinosaur National Monument". A Survey of the Recreational Resources of the Colorado River Basin. U.S. National Park Service. September 6, 2004. Archived from the original on November 3, 2013. Retrieved February 20, 2012.
- "Historic Opposition to Glen Canyon Dam". The End of Lake Powell Campaign. Colorado Riverkeeper. July 20, 2004. Archived from the original on December 28, 2013. Retrieved November 2, 2013.
- "Resurrection: Buried Treasure". National Audubon Society. 2006. Archived from the original on January 20, 2013. Retrieved February 20, 2012.
- "The Central Utah Project - An Overview". U.S. Department of the Interior. April 3, 2019. Archived from the original on May 20, 2022. Retrieved May 18, 2022.
- Glaser, Leah S. "San Juan-Chama Project". U.S. Bureau of Reclamation. Archived from the original on March 8, 2022. Retrieved May 18, 2022.
- "Pacific Southwest Water Plan" (PDF). U.S. Bureau of Reclamation. January 1964. Archived (PDF) from the original on September 4, 2021. Retrieved May 18, 2022.
The Colorado River Spanish Rio Colorado is one of the principal rivers along with the Rio Grande in the Southwestern United States and in northern Mexico The 1 450 mile long 2 330 km river the 5th longest in the United States drains an expansive arid watershed that encompasses parts of seven U S states and two Mexican states The name Colorado derives from the Spanish language for colored reddish due to its heavy silt load Starting in the central Rocky Mountains of Colorado it flows generally southwest across the Colorado Plateau and through the Grand Canyon before reaching Lake Mead on the Arizona Nevada border where it turns south toward the international border After entering Mexico the Colorado approaches the mostly dry Colorado River Delta at the tip of the Gulf of California between Baja California and Sonora Colorado RiverThe Colorado River at Horseshoe Bend Arizona a few miles below Glen Canyon DamMap of the Colorado River basinLocationCountryUnited States MexicoStatesColorado Utah Arizona Nevada California Baja California SonoraCitiesGlenwood Springs CO Grand Junction CO Moab UT Page AZ Bullhead City AZ Lake Havasu City AZ Blythe CA Yuma AZ Las Vegas NV Laughlin NV San Luis Rio Colorado Son Physical characteristicsSourceLa Poudre Pass locationRocky Mountains Colorado United States coordinates40 28 20 N 105 49 34 W 40 47222 N 105 82611 W 40 47222 105 82611 elevation10 184 ft 3 104 m MouthGulf of California locationColorado River Delta Baja California Sonora Mexico coordinates31 48 54 N 114 48 00 W 31 81500 N 114 80000 W 31 81500 114 80000 elevation0 ft 0 m Length1 450 mi 2 330 km Basin size246 000 sq mi 640 000 km2 Discharge locationLees Ferry Arizona average17 850 cu ft s 505 m3 s minimum750 cu ft s 21 m3 s maximum300 000 cu ft s 8 500 m3 s Basin featuresTributaries leftFraser River Blue River Eagle River Roaring Fork River Gunnison River Dolores River San Juan River Little Colorado River Bill Williams River Gila River rightGreen River Dirty Devil River Escalante River Kanab River Virgin River Hardy River Known for its dramatic canyons whitewater rapids and eleven U S National Parks the Colorado River and its tributaries are a vital source of water for 40 million people An extensive system of dams reservoirs and aqueducts divert almost its entire flow for agricultural irrigation and urban water supply Its large flow and steep gradient are used to generate hydroelectricity meeting peaking power demands in much of the Intermountain West Intensive water consumption has dried up the lower 100 miles 160 km of the river which has rarely reached the sea since the 1960s Native Americans have inhabited the Colorado River basin for at least 8 000 years Starting around 1 CE large agriculture based societies were established but a combination of drought and poor land use practices led to their collapse in the 1300s Their descendants include tribes such as the Puebloans while others including the Navajo settled in the Colorado Basin after the 1000s In the 1500s Spanish explorers began mapping and claiming the watershed which became part of Mexico upon winning its independence from Spain in 1821 Even after most of the watershed became US territory in 1846 much of the river s course remained unknown Several expeditions charted the Colorado in the mid 19th century one of which led by John Wesley Powell was the first to run the rapids of the Grand Canyon Large scale settlement of the lower basin began in the mid to late 1800s with steamboats sailing from the Gulf of California to landings along the river that linked to wagon roads to the interior Starting in the 1860s gold and silver strikes drew prospectors to the upper Colorado River basin Large scale river management began in the early 1900s with major guidelines established in a series of international and US interstate treaties known as the Law of the River The US federal government constructed most of the major dams and aqueducts between 1910 and 1970 the largest Hoover Dam was completed in 1935 Numerous water projects have also involved state and local governments With all of their waters fully allocated both the Colorado and the neighboring Rio Grande are now considered among the most controlled and litigated river systems in the world Since 2000 extended drought has conflicted with increasing demands for Colorado River water and the level of human development and control of the river continues to generate controversy CourseHeadwaters of the Colorado River in Rocky Mountain National Park Colorado The Colorado begins at La Poudre Pass in the Never Summer Mountains in Rocky Mountain National Park 10 184 ft 3 104 m above sea level After a short run south the river turns west below Grand Lake the largest natural lake in the state For the first 250 miles 400 km of its course the Colorado carves its way through the mountainous Western Slope a sparsely populated region defined by the portion of the state west of the Continental Divide As it flows southwest it gains strength from many small tributaries as well as larger ones including the Blue Eagle and Roaring Fork rivers After passing through De Beque Canyon the Colorado emerges from the Rockies into the Grand Valley a major farming and ranching region where it meets one of its largest tributaries the Gunnison River at Grand Junction Most of the upper river is a swift whitewater stream ranging from 200 to 500 feet 60 to 150 m wide the depth ranging from 6 to 30 feet 2 to 9 m with a few notable exceptions such as the Blackrocks reach where the river is nearly 100 feet 30 m deep In a few areas such as the marshy Kawuneeche Valley near the headwaters and the Grand Valley it exhibits braided characteristics From Grand Junction the Colorado turns northwest before cutting southwest across the eponymous Colorado Plateau a vast area of high desert centered at the Four Corners of the southwestern United States Here the climate becomes significantly drier than that in the Rocky Mountains and the river becomes entrenched in progressively deeper gorges of bare rock beginning with Ruby Canyon and then Westwater Canyon as it enters Utah now once again heading southwest Farther downstream it receives the Dolores River and defines the southern border of Arches National Park before passing Moab and flowing through The Portal where it exits the Moab Valley between a pair of 1 000 foot 300 m sandstone cliffs Colorado River in the Grand Canyon seen from Pima Point near Hermit s Rest In Utah the Colorado flows primarily through the slickrock country which is characterized by its narrow canyons and unique folds created by the tilting of sedimentary rock layers along faults This is one of the most inaccessible regions of the continental United States Below the confluence with the Green River its largest tributary in Canyonlands National Park the Colorado enters Cataract Canyon named for its dangerous rapids and then Glen Canyon known for its arches and erosion sculpted Navajo sandstone formations Here the San Juan River carrying runoff from the southern slope of Colorado s San Juan Mountains joins the Colorado from the east The Colorado then enters northern Arizona where since the 1960s Glen Canyon Dam near Page has flooded the Glen Canyon reach of the river forming Lake Powell for hydroelectricity generation In Arizona the river passes Lee s Ferry an important crossing for early explorers and settlers and since the early 20th century the principal point where Colorado River flows are measured for apportionment to the seven U S and two Mexican states in the basin Downstream the river enters Marble Canyon the beginning of the Grand Canyon passing under the Navajo Bridges on a now southward course Below the confluence with the Little Colorado River the river swings west into Granite Gorge the most dramatic portion of the Grand Canyon where the river cuts up to one mile 1 6 km into the Colorado Plateau exposing some of the oldest visible rocks on Earth dating as long ago as 2 billion years The 277 miles 446 km of the river that flow through the Grand Canyon are largely encompassed by Grand Canyon National Park and are known for their difficult whitewater separated by pools that reach up to 110 feet 34 m in depth At the lower end of Grand Canyon the Colorado widens into Lake Mead the largest reservoir in the continental United States formed by Hoover Dam on the border of Arizona and Nevada Situated southeast of metropolitan Las Vegas the dam is an integral component for management of the Colorado River controlling floods and storing water for farms and cities in the lower Colorado River basin Below the dam the river passes under the Mike O Callaghan Pat Tillman Memorial Bridge which at nearly 900 feet 270 m above the water is the highest concrete arch bridge in the Western Hemisphere and then turns due south towards Mexico defining the Arizona Nevada and Arizona California borders Satellite view of the Colorado River valley near Yuma Arizona Interstate 8 runs from left to right just below center After leaving the confines of the Black Canyon the river emerges from the Colorado Plateau into the Lower Colorado River Valley LCRV a desert region dependent on irrigation agriculture and tourism and also home to several major Indian reservations The river widens here to a broad moderately deep waterway averaging 500 to 1 000 feet 150 to 300 m wide and reaching up to 0 25 miles 400 m across with depths ranging from 8 to 60 feet 2 to 20 m Before channelization of the Colorado in the 20th century the lower river was subject to frequent course changes caused by seasonal flow variations Joseph C Ives who surveyed the lower river in 1861 wrote that the shifting of the channel the banks the islands the bars is so continual and rapid that a detailed description derived from the experiences of one trip would be found incorrect not only during the subsequent year but perhaps in the course of a week or even a day The LCRV is one of the most densely populated areas along the river and there are numerous towns including Bullhead City Arizona Needles California and Lake Havasu City Arizona Here several large diversions draw from the river providing water for both local uses and distant regions including the Salt River Valley of Arizona and metropolitan Southern California The last major U S diversion is at Imperial Dam where over 90 percent of the river s flow is moved into the Gila Gravity Canal and Yuma Area Project and the much bigger All American Canal to irrigate California s Imperial Valley the most productive winter agricultural region in the United States Colorado River as it exits the United States into Mexico beneath the San Luis Colorado Colonia Miguel Aleman Bridge September 2009 Below Imperial Dam only a small portion of the Colorado River makes it beyond Yuma Arizona and the confluence with the intermittent Gila River which carries runoff from western New Mexico and most of Arizona before defining 24 miles 39 km of the Mexico United States border At Morelos Dam the entire remaining flow of the Colorado is diverted to irrigate the Mexicali Valley among Mexico s most fertile agricultural lands Below San Luis Rio Colorado the Colorado passes entirely into Mexico defining the Baja California Sonora border Since 1960 the stretch of the Colorado between here and the Gulf of California has been dry or a trickle formed by irrigation return flows The Hardy River provides most of the flow into the Colorado River Delta a vast alluvial floodplain covering about 3 000 square miles 7 800 km2 of northwestern Mexico A large estuary is formed here before the Colorado empties into the Gulf about 75 miles 120 km south of Yuma Occasionally the International Boundary and Water Commission allows a springtime to recharge the delta Before 20th century development dewatered the lower Colorado a major tidal bore was present in the delta and estuary the first historical record was made by the Croatian missionary in Spanish service Father Ferdinand Konscak on July 18 1746 During spring tide conditions the tidal bore locally called El Burro formed in the estuary about Montague Island in Baja California and propagated upstream Major tributaries The San Juan River near Mexican Hat UtahThe Green River at Mineral Bottom just north of Canyonlands National Park The Colorado is joined by over 25 significant tributaries of which the Green River is the largest by both length and discharge The Green River takes drainage from the Wind River Range of west central Wyoming from Utah s Uinta Mountains and from the Rockies of northwestern Colorado The Gila River is the second longest and drains a greater area than the Green but has a significantly lower flow because of a more arid climate and larger diversions for irrigation and cities Both the Gunnison and San Juan rivers which derive most of their water from Rocky Mountains snowmelt contribute more water than the Gila contributed naturally Statistics of the Colorado s longest tributariesName State Length Watershed Discharge Referencesmi km mi2 km2 cfs m3 sGreen River Utah 730 1 170 48 100 125 000 6 048 171 3Gila River Arizona 649 1 044 58 200 151 000 247 7 0San Juan River Utah 383 616 24 600 64 000 2 192 62 1Little Colorado River Arizona 356 573 26 500 69 000 424 12 0Dolores River Utah 250 400 4 574 11 850 633 17 9Gunnison River Colorado 164 264 7 930 20 500 2 570 73Virgin River Nevada 160 260 13 020 33 700 239 6 8Drainage basinMap showing the Upper and Lower Colorado River Basin and adjacent areas supplied by Colorado River water The Colorado River Basin consists of 246 000 square miles 640 000 km2 making it the seventh largest drainage basin in North America About 238 600 square miles 618 000 km2 or 97 percent of the basin is in the United States The basin extends into western Colorado and New Mexico southwestern Wyoming eastern and southern Utah southeastern Nevada and California and most of Arizona The areas drained within Baja California and Sonora in Mexico are very small and do not contribute significant runoff Aside from the Colorado River Delta the basin extends into Sonora at a few locations further east including the headwaters of the Santa Cruz River and San Pedro River both tributaries of the Gila River For hydrological management purposes the Colorado River Basin is divided into the Upper Basin the drainage area above Lees Ferry and the Lower Basin The Upper Basin covers only 45 percent of the land area of the Colorado River Basin but contributes 92 percent of the runoff The entire eastern boundary of the Colorado River Basin runs along the North American Continental Divide and is defined largely by the Rocky Mountains and the The Wind River Range in Wyoming marks the northern extent of the basin and is separated from the Colorado Rockies by the endorheic Great Divide Basin in southwestern Wyoming Streams that are nearby the east side of the divide drain into the Mississippi River and Rio Grande while nearby areas north of the Wind River Range drain into the Columbia River The western boundary of the Colorado River Basin is formed by various ranges and plateaus that border the Great Basin including the Uinta Mountains and Wasatch Range Major Great Basin watersheds bordering the Colorado River Basin are the Great Salt Lake and Sevier Lake watersheds To the south the Colorado River Basin borders several watersheds in Mexico draining into the Gulf of California including the Sonoyta Concepcion and Yaqui rivers Much of the basin is at high elevation the mean elevation is 5 500 feet 1 700 m Lees Ferry more than halfway along the Colorado River from its source is 3 150 feet 960 m above sea level The highest point in the Colorado River Basin is 14 321 foot 4 365 m Uncompahgre Peak in Colorado s San Juan Mountains while some water from the river drains via irrigation run off into California s Salton Sea 236 feet 72 m below sea level The Black Suspension Bridge crosses the Colorado River in the Grand Canyon at Phantom Ranch Arizona About 72 percent of the Colorado River Basin is classified as arid with the Sonoran and Mojave deserts covering the southern portion and the Colorado Plateau encompassing much of the central portion The Colorado Plateau is home to most of the major canyon systems formed by the Colorado River and its tributaries particularly those of the Green and San Juan rivers About 23 percent of the basin is forest with the largest area in the Rocky Mountains other significant forested areas include the Kaibab Aquarius and Markagunt plateaus in southern Utah and northern Arizona and the Mogollon Rim in central Arizona These high plateaus and escarpments often exceeding 9 000 feet 2 700 m in elevation form the northern and southern edges of the Colorado Plateau geological province Developed land use in the basin is mostly irrigated agriculture chiefly in the Grand Valley the Lower Colorado River Valley and the Salt River Valley but the total area of crop and pasture land is only 2 3 percent of the entire basin Urban areas cover less than 1 percent Climate in the Colorado River Basin ranges from subtropical hot desert at southern lower elevations to alpine in the Rocky Mountains Mean monthly high temperatures are 25 3 C 77 5 F in the Upper Basin and 33 4 C 92 1 F in the Lower Basin and lows average 3 6 and 8 9 C 25 5 and 48 0 F respectively Annual precipitation averages 6 5 inches 164 mm ranging from over 60 inches 1 500 mm in some areas of the Rockies to less than 4 inches 100 mm in dry desert valleys The Upper Basin generally receives snow and rain during the winter and early spring while precipitation in the Lower Basin falls mainly during intense but infrequent summer thunderstorms brought on by the North American Monsoon Precipitation is influenced by the El Nino Southern Oscillation ENSO with El Nino being associated with wetter conditions and La Nina with drier conditions The effect of ENSO is significantly more pronounced in the Lower Basin where it has a strong impact on monsoonal rainfall Runoff patterns across the Colorado River Basin reflect this most of the perennial tributaries originate in the Upper Basin while tributaries in the Lower Basin are either ephemeral such as the Little Colorado River or highly seasonal such as the Gila and Salt rivers As of 2010 approximately 13 million people lived within the Colorado River basin while about 40 million people live in areas supplied by Colorado River water Colorado River basin states are among the fastest growing in the US the population of Nevada alone increased by about 66 percent between 1990 and 2000 as Arizona grew by some 40 percent Phoenix Arizona Las Vegas Nevada and Mexicali Baja California are the largest cities by population within the Colorado River Basin Other significant cities include Tucson Arizona St George Utah and Flagstaff Arizona Due to the rugged and inhospitable topography through which the river flows there are only a few major towns along the Colorado River itself including Grand Junction Colorado and Yuma Arizona DischargeAnnual Colorado River discharge volumes at Lee s Ferry between 1895 and 2004 The unimpaired annual runoff of the Colorado River at Lees Ferry Arizona is estimated at 14 7 million acre feet 18 1 km3 or an annualized discharge of 20 300 cu ft s 570 m3 s for the 1906 2023 period River flows at the Lees Ferry stream gauge about halfway along the length of the Colorado and 16 miles 26 km below Glen Canyon Dam are used to determine water allocations in the Colorado River basin Flows originating above Lees Ferry represent the majority of Colorado River runoff Tributaries between there and Imperial Dam near the US Mexico border contribute a further 1 1 million acre feet 1 4 km3 and the Gila Salt River system historically accounted for another 1 7 million acre feet 2 1 km3 While much of this water was lost to evaporation in the deserts of the Lower Basin anywhere from 10 to 20 million acre feet 12 to 25 km3 per year reached the Colorado River Delta prior to the early 20th century Up to 90 percent of the river s flow originates as snowmelt from the Rocky Mountains and other smaller mountain ranges of the Colorado Plateau Natural seasonal flows at its mouth varied widely often exceeding 100 000 cu ft s 2 800 m3 s in the spring melt and falling as low as 2 500 cu ft s 71 m3 s in winter Snowmelt typically begins in April peaks in May or June and can extend into August in wet years Monsoon rainstorms often occur in the Lower Basin from August through October contributing much of the flow in tributaries below Lees Ferry and often causing flash flooding Since the initial closure of Hoover Dam in 1934 lower Colorado River flows have been greatly moderated with monthly means below the dam ranging from 16 400 cu ft s 460 m3 s in May to 11 200 cu ft s 320 m3 s in October Upstream of the massive Hoover and Glen Canyon Dams inflows to Lake Powell still experience distinct spring highs and winter lows though overall volumes have been reduced due to Upper Basin water diversions Flow regimes in a few Upper Basin tributaries such as the Yampa River remain almost completely unaltered By the 1950s the Colorado delta was regularly drying up in fall and winter though spring high flows often still made it to the ocean After the initial closure of Glen Canyon Dam in 1963 these seasonal flows were almost completely eliminated with the exception of a few very wet years such as 1983 1987 In 1984 16 5 million acre feet 20 4 km3 of excess runoff reached the ocean Flows have further declined due to evaporation from reservoirs and particularly after 2000 reduced snowpack with warming winter temperatures in the Rockies Water diversions have effectively removed some tributaries entirely including the Gila River once the Colorado s largest tributary below Lees Ferry Most Colorado River water is diverted in the United States with only about 2 8 million acre feet 3 5 km3 per year reaching Mexico since 1950 At Morelos Dam the remaining flow is diverted to irrigate the Mexicali Valley leaving the Colorado River Delta almost entirely dry except for small amounts of agricultural wastewater Discharge of the Colorado River at selected stream gaugesLocation Annual mean discharge Maximum peak flow Drainage area Period of record Sourcecfs m3 s cfs m3 s mi2 km2Grand Lake CO 65 5 1 85 1 870 53 63 8 165 1953 2020Dotsero CO 2 079 58 9 22 200 630 4 390 11 400 1941 2020Cisco UT 7 048 199 6 76 800 2 170 24 100 62 000 1914 2020Lee s Ferry AZ 14 600 410 127 000 3 600 111 800 290 000 1922 2020Davis Dam AZ NV 13 740 389 46 200 1 310 173 300 449 000 1905 2020Parker Dam AZ CA 11 630 329 42 400 1 200 182 700 473 000 1935 2020Laguna Dam AZ CA 1 448 41 0 30 900 870 188 600 488 000 1972 2020NIB near Andrade CA 3 869 109 6 40 600 1 150 246 700 639 000 1950 2020Monthly discharge of the Colorado at Lee s Ferry before and after construction of Glen Canyon DamMonth Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Pre dam discharge 1921 1962 cfs 5 260 6 720 9 250 19 900 44 200 52 400 21 200 10 400 8 280 8 220 7 450 5 850m3 s 149 190 262 564 1 252 1 484 600 294 234 233 211 166Post dam discharge 1963 2021 cfs 13 400 12 300 11 500 12 400 13 700 15 600 15 700 15 400 12 700 10 500 11 600 12 600m3 s 379 348 326 351 388 442 445 436 360 297 328 357GeologyAs recently as the Cretaceous period about 100 million years ago much of western North America was still part of the Pacific Ocean Tectonic forces from the collision of the Farallon Plate with the North American Plate pushed up the Rocky Mountains between 50 and 75 million years ago in a mountain building episode known as the Laramide orogeny The Colorado River first formed as a west flowing stream draining the southwestern portion of the range and the uplift also diverted the Green River once a tributary of the Mississippi River west towards the Colorado About 30 to 20 million years ago volcanic activity related to the orogeny led to the Mid Tertiary ignimbrite flare up which created smaller formations such as the Chiricahua Mountains in Arizona and deposited massive amounts of volcanic ash and debris over the watershed The Colorado Plateau first began to rise during the Eocene between about 55 and 34 million years ago but did not attain its present height until about 5 million years ago about when the Colorado River established its present course into the Gulf of California The time scale and sequence over which the river s present course and the Grand Canyon were formed is uncertain Before the Gulf of California was formed around 12 to 5 million years ago by faulting processes along the boundary of the North American and Pacific plates the Colorado flowed west to an outlet on the Pacific Ocean possibly Monterey Bay on the Central California coast and may have played a role in the formation of the Monterey submarine canyon Crustal extension in the Basin and Range Province began about 20 million years ago and the modern Sierra Nevada began forming about 10 million years ago eventually diverting the Colorado southwards towards the Gulf As the Colorado Plateau continued to rise between 5 and 2 5 million years ago the river maintained its ancestral course as an antecedent stream and began to cut the Grand Canyon Antecedence played a major part in shaping other peculiar geographic features in the watershed including the Dolores River s bisection of Paradox Valley in Colorado and the Green River s cut through the Uinta Mountains in Utah Remnants of basalt flows from the Uinkaret volcanic field are seen here descending into the Grand Canyon where they dammed the Colorado over 10 times in the past 2 million years Sediments carried from the plateau by the Colorado River created a vast delta made of more than 10 000 cubic miles 42 000 km3 of material that walled off the northernmost part of the gulf in approximately 1 million years Cut off from the ocean the portion of the gulf north of the delta eventually evaporated and formed the Salton Sink which reached about 260 feet 79 m below sea level Since then the river has changed course into the Salton Sink at least three times transforming it into Lake Cahuilla which at maximum size flooded up the valley to present day Indio California The lake took about 50 years to evaporate after the Colorado resumed flowing to the Gulf The present day Salton Sea can be considered the most recent incarnation of Lake Cahuilla though on a much smaller scale Between 1 8 million and 10 000 years ago massive flows of basalt from the Uinkaret volcanic field in northern Arizona dammed the Colorado River within the Grand Canyon At least 13 lava dams were formed the largest of which was more than 2 300 feet 700 m high backing the river up for nearly 500 miles 800 km to present day Moab Utah The lack of associated sediment deposits along this stretch of the Colorado River which would have accumulated in the impounded lakes over time suggests that most of these dams did not survive for more than a few decades before collapsing or being washed away Failure of the lava dams caused by erosion leaks and cavitation caused catastrophic floods which may have been some of the largest ever to occur in North America rivaling the late Pleistocene Missoula Floods of the northwestern United States Mapping of flood deposits indicate that crests as high as 700 feet 210 m passed through the Grand Canyon reaching peak discharges as great as 17 million cubic feet per second 480 000 m3 s HistoryPre colonial indigenous peoples Cliff Palace Mesa Verde National Park Small numbers of Paleo Indians of the Clovis and Folsom cultures inhabited the Colorado Plateau as early as 10 000 BCE with populations beginning to increase in the Desert Archaic period 6000 BCE 0 CE While most early inhabitants were hunter gatherers evidence of agriculture masonry dwellings and petroglyphs begins with the Fremont culture period 0 1300 CE The Ancient Puebloan culture also known as Anasazi or Hisatsinom were descended from the Desert Archaic culture and became established in the Four Corners region around 1000 CE While there is much evidence of ancient habitation along the Colorado River including stone dwellings petroglyphs and pottery in places such as Glen Canyon the first major agriculture based societies arose a significant distance from the river The Puebloan people built many multi story pueblos or great houses and developed complex distribution systems to supply drinking and irrigation water in Chaco Canyon in northwestern New Mexico and Mesa Verde in southwest Colorado The Hohokam present in the modern Phoenix area since about 0 CE experienced prolific growth around 600 700 CE as they constructed a large system of irrigation canals making use of the Salt River Both civilizations supported large populations at their height with 6 000 15 000 in Chaco Canyon and as many as 30 000 200 000 Hohokam Indigenous names for the Colorado RiverHopi PisisvayuMaricopa XakxwetMohave Aha KwahwatNavajo To NtsʼosikoohHavasupai Ha Ŧay Gʼam Sil GsvgovYavapai ʼHakhwata Puebloan and Hohokam settlements were abruptly abandoned in the 1400s CE due both to over exploitation of natural resources such as timber and severe drought that made it impossible to maintain irrigation systems Many Puebloans migrated east to the Rio Grande Valley while others persisted in smaller settlements on the Colorado Plateau Puebloan descendants include the Hopi Zuni Laguna and Acoma peoples of modern Arizona and New Mexico O odham peoples including the Akimel O odham Pima and Maricopa who continue to live in southern Arizona are believed to be descended from the Hohokam The lower Colorado River valley was inhabited for thousands of years by numerous tribes of the Patayan cultures many of which belong to the Yuman Cochimi language group These include the Walapai Havasupai and Yavapai in the Grand Canyon region the Mohave Halchidhoma Quechan and Halyikwamai along the Colorado River between Black Canyon and the Mexican border and the Cocopah around the Colorado River Delta The Chemehuevi a branch of the Southern Paiute and the Kumeyaay inhabited the desert to the river s west Those living along the lower Colorado River depended more on fishing and floodplain agriculture than on irrigation and mostly did not live in permanent settlements The site of modern day Yuma has been an important river crossing since ancient times as the channel here is much narrower compared to the expansive swampy river bottoms to the north and south and enabled the expansion of trade to the Pima and Maricopa in the east and coastal California tribes in the west Navajo woman and child photographed by Ansel Adams c 1944 The Navajo Dine began migrating into the Colorado River Basin around 1000 1500 CE and eventually exercised influence over much of the Colorado Plateau Originally hunter gatherers they acquired knowledge of farming from the Puebloans and adopted a more sedentary lifestyle over time making extensive use of irrigation in their settlements The Navajo gradually displaced Hopi settlements as they expanded into northern Arizona after the 1500s Navajo Mountain and Rainbow Bridge in the Glen Canyon area came to hold particular religious significance for the Navajo and the nearby confluence of the Colorado and San Juan River is regarded as the birthplace of clouds and rain The Ute also became established in the Colorado Plateau around 1500 CE although they had inhabited more northerly parts of the Colorado basin modern Wyoming and northern Colorado since at least 0 CE They are the first known inhabitants of this part of the Rocky Mountains and made use of an extensive network of trails crisscrossing the mountains to move between summer and winter camps The Ute were divided into numerous bands with separate territories but shared a common language and customs The Uncompahgre or Tabeguache lived around the confluence of the upper Colorado and Gunnison Rivers an area including the Grand Mesa the Weenuchiu lived along the San Juan River and the Parianuche and Yamparika lived in the Yampa White and Duchesne River valleys The Ute ranged as far as the river s headwaters one Ute story recounts a battle with the Arapaho at Grand Lake which they believe still hosts the spirits of the deceased Spanish exploration and early settlement La conquista del Colorado 2017 by Augusto Ferrer Dalmau depicts Francisco Vazquez de Coronado s 1540 1542 expedition Garcia Lopez de Cardenas can be seen overlooking the Grand Canyon Starting in the 1500s the Spanish began to explore and colonize western North America Francisco de Ulloa may have been the first European to see the river when in 1536 he sailed to the head of the Gulf of California In 1540 Garcia Lopez de Cardenas became the first European to see the Grand Canyon during Coronado s expedition to find the Seven Cities of Gold Cibola Cardenas was apparently unimpressed with the canyon greatly underestimating its size and left in disappointment with no gold to be found In the same year Melchior Diaz explored the Colorado River s delta and named it Rio del Tizon fire brand river after seeing a practice used by the local people for warming themselves By the late 1500s or early 1600s the Utes had acquired horses from the Spanish and their use for hunting trade and warfare soon became widespread among Utes and Navajo in the Colorado River basin This conferred them a military advantage over Goshutes and Southern Paiutes that were slower to adopt horses The Navajo also adopted a culture of livestock herding as they acquired sheep and goats from the Spanish Juan Bautista de Anza in 1774 was the first Spaniard to reach Yuma Crossing where he established friendly relations with the Quechan people and opened the Anza trail between Arizona and the California coast The Spanish soon founded Mission Puerto de Purisima Concepcion and Mission San Pedro y San Pablo de Bicuner along the lower Colorado River However Spanish attempts to control the crossing led to the 1781 Yuma revolt in which over 100 soldiers and colonists were killed and the settlements were abandoned The Quechan blocked foreigners use of the crossing until the arrival of American mountain men and fur trappers in the 1820s The name Rio Colorado first appears in 1701 on the map Paso por Tierra a la California published by missionary Eusebio Kino who also determined during that time that Baja California was a peninsula not an island as previously believed In the 1700s and early 1800s many Spanish and American explorers believed in the existence of a Buenaventura River that ran from the Rocky Mountains to the Pacific coast In 1776 Silvestre Velez de Escalante attached this name to the upper Green River and a number of later maps showed this connecting to Lake Timpanogos now Utah Lake and flowing west to California The Dominguez Escalante expedition first reached the Colorado River near the junction with the Dolores River naming the larger river Rio San Rafael They later forded the Colorado in southeastern Utah at Crossing of the Fathers now submerged in Lake Powell American exploration Boats of John Wesley Powell s second Colorado River expedition in Marble Canyon 1872 In the 1820s American fur trappers along the upper Green River in Wyoming known to them as the Seedskeedee or variants thereof seeking a route to export furs to the coast surmised that this and what the Spanish called the Colorado were in fact connected William H Ashley made an unsuccessful attempt to navigate from the Green River to the Colorado s mouth in 1825 In 1826 Jedediah Smith arrived at the lower Colorado River referring to it as the Seedskeedee and proceeded upstream exploring as far as Black Canyon During the 1830s various fur trappers from Wyoming made it as far downstream as Cataract Canyon and Glen Canyon but none were able to navigate the full length of the river In 1843 John C Fremont explored the Great Basin and conclusively determined no Buenaventura River flowed west to California thus the direction of river flow must be southwest By the early 19th century the stretch of the Colorado above the confluence of the Green River at Cataract Canyon Utah became known to fur trappers as the Grand River though the exact origin of this name is unknown The Grand River above the confluence with the Gunnison River was also called the Bunkara River the Blue River or the North Fork of the Grand River until the 1870s By the early 1900s the name Grand River had been attached to the entire stream as far as Grand Lake which was then considered its official source Although the Grand River was renamed the Colorado in 1921 its name survives in numerous places such as Grand County and Grand Junction Colorado In 1848 the U S Army established Fort Yuma creating the first permanent U S settlement along the river This served as a military garrison and supply point for settlers headed to California along the Southern Emigrant Trail Due to the arduous task of ferrying supplies overland the schooner Invincible attempted to bring supplies up the river but was thwarted by the delta s strong tides Steamboats were brought to the river starting in 1852 with the sidewheeler Uncle Sam whose first voyage from the Gulf to Yuma took fifteen days 15 Exploration by steamboat soon advanced upriver In 1857 George A Johnson in the General Jesup was able to reach Pyramid Canyon over 300 miles 480 km north of Fort Yuma 16 17 19 He was followed by Lt Joseph Christmas Ives who used a specially built shallow draft steamboat Explorer to reach Black Canyon where Hoover Dam stands today Part 1 85 87 Having set out to determine the river s suitability as a navigation route Ives remarked Ours has been the first and will doubtless be the last party of whites to visit this profitless locality It seems intended by nature that the Colorado River along the greater portion of its lonely and majestic way shall be forever unvisited and undisturbed Route of Powell s first expedition 1869 The last part of the Colorado River to be surveyed was the Grand Canyon itself In 1869 John Wesley Powell with nine men set out on an expedition from Green River Station Wyoming They were the first part of non natives to travel the length of the Grand Canyon and the first to successfully travel by boat from the upper Green River to the lower Colorado Powell led a second expedition in 1871 with financial backing from the U S government and continued to conduct geographical and botanical surveys across the region until the 1890s Another Grand Canyon river expedition was led in 1889 1890 by Robert Brewster Stanton to survey a route for a proposed railroad through the canyon which was never built We are now ready to start on our way down the Great Unknown Our boats tied to a common stake are chafing each other as they are tossed by the fretful river They ride high and buoyant for their loads are lighter than we could desire We have but a month s rations remaining The lighting of the boats has this advantage they will ride the waves better and we shall have little to carry when we make a portage We are three quarters of a mile in the depths of the earth and the great river shrinks into insignificance as it dashes its angry waves against the walls and cliffs that rise to the world above they are but puny ripples and we but pigmies running up and down the sands or lost among the boulders We have an unknown distance yet to run an unknown river yet to explore What falls there are we know not what rocks beset the channel we know not what walls rise over the river we know not Ah well we may conjecture many things The men talk as cheerfully as ever jests are bandied about freely this morning but to me the cheer is somber and the jests are ghastly John Wesley Powell s journal August 1869 U S westward expansion and military campaigns Lithograph of Fort Yuma c 1875 In 1858 gold was discovered on the Gila River east of Yuma then along the Colorado River at El Dorado Canyon Nevada and La Paz Arizona As prospectors and settlers entered the region they became involved in skirmishes with the Mohave spurring U S Army expeditions that culminated in the 1859 Battle of the Colorado River which concluded the Mohave War In the 1870s the Mohave were moved to the Fort Mohave and Colorado River reservations Chemehuevi and later some Hopi and Navajo peoples were also moved to the Colorado River reservation where they today form the Colorado River Indian Tribes As the American frontier expanded into the Colorado Plateau an effort to expel the Navajo from the Four Corners region was begun by General James Henry Carleton who in 1864 enlisted mountain man Kit Carson to lead a campaign against the Navajo Carson with the help of the Navajo s Ute enemies captured more than 8 000 Navajo and forcibly marched them to Fort Sumner New Mexico Hundreds died during what is now known as the Long Walk and while enduring appalling conditions at Fort Sumner After the failure of the Army to maintain the reservation there the Treaty of Bosque Redondo established the Navajo Nation in the Four Corners where the Navajo were allowed to return in 1868 Gold and silver were also discovered in the Upper Basin beginning with the 1859 Blue River strike that led to the founding of Breckenridge Colorado Up until the 1860s southwestern Colorado had remained relatively untouched by U S westward expansion as the Americans had recognized Ute sovereignty by treaty Following the 1861 carving out of Colorado Territory and further mineral strikes including Ouray and Telluride Ute leaders were coerced into signing the 1873 Brunot Agreement in which they lost rights to most of their land A flood of mineral prospecting and settlement ensued in western Colorado By 1881 the Army had driven out the remaining pockets of Ute resistance on the Western Slope officially opening the Grand River country to settlement and the town of Grand Junction was incorporated a year later The Denver and Rio Grande Western Railroad D amp RGW quickly expanded into this area to serve mining boomtowns crossing the Rockies to the south via the Black Canyon of the Gunnison River By 1883 the railroad had reached Grand Junction and a spur up the Colorado to Glenwood Springs was completed in 1887 In Arizona and Utah Territories many early settlers were Mormons fleeing religious persecution in the Midwest Mormons founded agricultural colonies at Fort Santa Clara in 1855 and St Thomas now flooded under Lake Mead in 1865 Stone s Ferry crossing the Colorado at the mouth of the Virgin River enabled shipping of their produce by wagon to gold mining districts further south Although the Mormons abandoned St Thomas in 1871 a salt mining industry persisted here and steamboats operated up to nearby Rioville into the 1880s 78 In 1879 a group of Mormon settlers made their way to southeastern Utah blasting the precarious Hole in the Rock Trail to cross the Colorado River at Glen Canyon subsequently establishing the community of Bluff Due to the dry climate these settlements depended heavily on irrigation In central Arizona settlers uncovered and re established canals previously used by the Hohokam Historic photograph of the cable ferry at Lee s Ferry prior to construction of the Navajo Bridge Following tensions between Mormon settlers and the U S government in the Utah War a local militia including John D Lee perpetrated the 1857 Mountain Meadows Massacre in which 120 non Mormon settlers were killed Fearing retribution Lee moved in 1870 to the remote Pahreah Crossing in Arizona where he took over a ferry first established in 1864 by Jacob Hamblin This the only river crossing for hundreds of miles not hemmed in by vertical canyon walls became known as Lee s Ferry While Lee was tried and subsequently executed in 1877 the ferry remained a major transportation link until the Navajo Bridge was completed nearby in 1928 rendering the ferry obsolete The Denver and Salt Lake Railway D amp SL incorporated in 1902 sought to provide a more direct connection between Denver and Salt Lake City than either the transcontinental railroad through Wyoming or the D amp RGW s route via Black Canyon and Durango The D amp SL completed a rail line into the upper headwaters of the Colorado River and blasted the Moffat Tunnel under the Continental Divide but ran out of money before even reaching Utah In 1931 the D amp RGW completed the Dotsero Cutoff linking Glenwood Springs to the D amp SL route at Bond Colorado finally completing the direct Denver Salt Lake link with its acquisition of the bankrupt D amp SL The Gunnison River route was eventually abandoned in favor of the shorter Colorado River route which today is owned by Union Pacific Renaming of the upper Colorado River As late as 1921 the Colorado River upstream from the confluence with the Green River in Utah was still known as the Grand River For over a decade U S Representative Edward T Taylor of Colorado had petitioned the Congressional Committee on Interstate and Foreign Commerce to rename the Grand River as the Colorado River Representatives from Wyoming Utah and the United States Geological Survey objected noting that the Green River was longer and drained a larger area Taylor argued that the Grand River should be considered the main stream as it carried the larger volume of water Taylor felt slighted that the Colorado River as named did not begin in the state of Colorado and he wasn t going to let Utah or Wyoming lay claim to the river s headwaters despite the fact that the Green River is the larger drainage basin On July 25 1921 President Warren G Harding signed House Joint Resolution 32 To change the name of the Grand River in Colorado and Utah to the Colorado River Engineering and developmentHoover Dam releasing water in 1998 About 40 million people depend on the Colorado River s water for agricultural industrial and domestic needs The Colorado irrigates 5 5 million acres 2 2 million hectares of farmland and its hydroelectric plants produce 12 billion kilowatt hours KWh of hydroelectricity each year Hydroelectricity from the Colorado is a key supplier of peaking power on the Southwest electric grid Often called America s Nile the Colorado is so intensively managed that each drop of its water is used an average of 17 times in a single year Southern Nevada Water Authority has called the Colorado River one of the most controlled controversial and litigated rivers in the world Colorado River water allocations in millions of acre feetUser Amount ShareUnited States 15 0 90 9 California 4 4 26 7 Colorado 3 88 23 5 Arizona 2 8 17 0 Utah 1 72 10 4 Wyoming 1 05 6 4 New Mexico 0 84 5 1 Nevada 0 3 1 8 Mexico 1 5 9 1 Total 16 5 100 In 1922 six U S states signed the Colorado River Compact which divided half of the river s flow to both the Upper Basin the drainage area above Lee s Ferry comprising parts of Colorado New Mexico Utah and Wyoming and a small portion of Arizona and the Lower Basin Arizona California Nevada and parts of New Mexico and Utah The Upper and Lower Basin were each allocated 7 5 million acre feet 9 3 km3 of water per year a figure believed to represent half of the river s annual flow at Lee s Ferry The allotments operated under the premise that approximately 17 5 million acre feet of water flowed through the river annually Arizona initially refused to ratify the compact because it feared that California would take too much of the lower basin allotment In 1944 a compromise was reached in which Arizona was allocated 2 8 million acre feet 3 5 km3 but with the caveat that California s 4 4 million acre foot 5 4 km3 allocation was prioritized during drought years These and nine other decisions compacts federal acts and agreements made between 1922 and 1973 constitute what is now known as the Law of the River In 1944 a treaty between the U S and Mexico allocated 1 5 million acre feet 1 9 km3 of Colorado River water to Mexico each year Morelos Dam was constructed in 1950 to enable Mexico to utilize its share of the river Water allocated to Mexico from the Colorado River is regulated by the International Boundary and Water Commission which also apportions waters from the Rio Grande between the two countries Transmountain diversions Large scale development of Colorado River water supplies started in the late 19th century at the river s headwaters in La Poudre Pass The Grand Ditch directing runoff from the river s headwaters across the Continental Divide to arid eastern Colorado was considered an engineering marvel when completed in 1890 This was the first of twenty four transmountain diversions constructed to draw water across the Rocky Mountains as the Front Range corridor increased in population These diversions draw water from the upper Colorado and its tributaries into the South Platte River Arkansas River and Rio Grande basins Today about 80 percent of Colorado s population lives on the Eastern Slope of the Rockies while 80 percent of precipitation falls on the Western Slope The Grand Ditch one of the earliest water diversions of the Colorado River is still in use today While first planned at the same time as the Grand Ditch construction on the Colorado Big Thompson Project C BT did not begin until the 1930s Today the C BT is the largest of the transmountain diversions delivering 230 000 acre feet 280 000 000 m3 per year from the Colorado River to cities north of Denver Numerous other projects followed with the largest including the Roberts Tunnel which delivers water from the Blue River to the city of Denver and the Fryingpan Arkansas Project which diverts water from the Fryingpan River to the Arkansas River basin Combined the transmountain diversions draw about 580 000 acre feet 720 000 000 m3 of water per year out of the Colorado River basin Historically most of the water has been used for irrigation although water usage is increasing for urban water supply and for recreational purposes such as snowmaking and increasing Eastern Slope streamflows for boating and fishing Denver Water receives about 50 percent of its supply from the Colorado River basin However diversions have caused environmental harm to the upper Colorado River system by reducing streamflows in many tributaries A number of reservoirs have been built to offset the impact of transmountain diversions by storing water for dry season release on the Western Slope including Williams Fork Reservoir in 1959 and Wolford Mountain Reservoir in 1996 The Imperial Valley and the Salton Sea The Colorado River delta region in Mexico became a favored place for Americans to invest in agriculture in the late 19th century when Mexican President Porfirio Diaz welcomed foreign capital to develop the country The Colorado River Land Company formed by Los Angeles Times publisher Harry Chandler his father in law Harrison Gray Otis and others developed the Mexicali Valley in Baja California as a thriving land company The company headquarters was nominally based in Mexico but its real headquarters was in Los Angeles California Land was leased mainly to Americans who were required to develop it Colorado River water was used to irrigate the rich soil The company largely escaped the turmoil of the Mexican Revolution 1910 20 but in the postrevolutionary period the Mexican government expropriated the company s land to satisfy the demand for land reform In 1900 the California Development Company CDC envisioned irrigating the Imperial Valley a then dry basin on the California Mexico border using water from the Colorado River Due to the valley s location below sea level water could be diverted and allowed to flow there entirely by gravity Engineer George Chaffey was hired to design the Alamo Canal which split from the Colorado near Pilot Knob California and ran south into Mexico where it joined the Alamo River a dry arroyo which had historically carried overflowing floodwaters from the Colorado into the Salton Sink at the bottom of Imperial Valley The scheme worked initially by 1903 about four thousand people lived in the valley and more than 100 000 acres 40 000 ha of farmland had been developed The Alamo Canal experienced continual problems due to the Colorado s high sediment content and its varying water levels During low flows the river often dropped below the level of the canal intake while high flows silted up the intake forcing the repeated excavation of new cuts In early 1905 flooding destroyed the intake gates and water began to flow uncontrolled down the canal towards the Salton Sink By August the breach had grown large enough to swallow the entire flow of the river which began to flood the bottom of the valley The Southern Pacific Railroad attempted to dam the flow in order to protect their tracks which ran through the valley but was hampered by repeated flooding It took seven attempts more than 3 million and two years for the railroad the CDC and the federal government to permanently block the breach and restore the river s original course but not before part of the Imperial Valley was flooded under a 45 mile long 72 km lake today s Salton Sea The Imperial Valley fiasco demonstrated that further economic development of the region would require a dam to control the Colorado s unpredictable flows Boulder Canyon Project Hoover Dam under construction 1934The Imperial Dam bottom right diverts water into the All American Canal center running towards Imperial Valley A large dam on the Colorado River had been envisioned since the 1920s In 1928 Congress authorized the Reclamation Service today s U S Bureau of Reclamation or USBR to build the Boulder Canyon Project whose key feature would be a dam on the Colorado in Black Canyon 30 miles 48 km southeast of Las Vegas Nevada On September 30 1935 Hoover Dam was completed forming Lake Mead capable of holding more than two years of the Colorado s flow Lake Mead was and still is the largest artificial lake in the U S by storage capacity The construction of Hoover Dam stabilized the lower channel of the Colorado River stored water for irrigation in times of drought captured sediment and controlled floods Hoover was the tallest dam in the world at the time of construction and also had the world s largest hydroelectric power plant The Boulder Canyon Project Act also authorized the All American Canal which was built as a permanent replacement for the Alamo Canal and follows a route entirely within the U S on its way to the Imperial Valley The canal s intake is located at Imperial Dam 20 miles 32 km above Yuma Arizona which diverts the majority of the Colorado s flow with only a small portion continuing to Mexico With a capacity of over 26 000 cubic feet per second 740 m3 s the All American Canal is the largest irrigation canal in the world Because the hot sunny climate lends to a year round growing season the Imperial Valley has become one of the most productive farming regions in North America providing much of the winter produce supply in the U S The Imperial Irrigation District supplies water to 520 000 acres 210 000 ha south of the Salton Sea The Coachella Canal which branches northward from the All American Canal irrigates another 78 000 acres 32 000 ha in the Coachella Valley Parker Dam was initially built as the diversion point for the Colorado River Aqueduct planned by the Metropolitan Water District of Southern California to supply water to Los Angeles The construction of the dam was opposed by Arizona which feared that California would take too much water from the Colorado at one point Arizona sent members of its National Guard to stop work on the dam Ultimately a compromise was reached with Arizona dropping its objections in exchange for the USBR constructing the Gila Project which irrigates 110 000 acres 450 km2 on the Arizona side of the river By 1941 the 241 mile 388 km long Colorado River Aqueduct was completed delivering 1 2 million acre feet 1 5 km3 of water west to Southern California The aqueduct enabled the continued growth of Los Angeles and its suburbs and provides water to about 10 million people today The San Diego Aqueduct which branches off from the Colorado River Aqueduct in Riverside County California opened in stages between 1954 and 1971 and provides water to another 3 million people in the San Diego metro area The Las Vegas Valley of Nevada experienced rapid growth after Hoover Dam and by 1937 Las Vegas had tapped a pipeline into Lake Mead Nevada officials believing that groundwater resources in the southern part of the state were sufficient for future growth were more concerned with securing a large amount of the dam s power supply than water from the Colorado thus they settled for the smallest water allocation of all the states in the Colorado River Compact In 2018 due to declining water levels in Lake Mead a second pipeline was completed with a lower intake elevation Colorado River Storage Project In the first half of the 20th century the Upper Basin states with the exception of Colorado had developed very little of their water allocations from the Colorado River Compact By the 1950s however water demand was rapidly increasing in Utah s Wasatch Front Salt Lake City metro area and the Rio Grande Valley of New Mexico which both began exploring ways to divert water from the Colorado Basin The Upper Basin states were concerned that they would not be able to use their full Compact allocations due to increasing water demands in the Lower Basin The Compact requires the Upper Basin to deliver a minimum annual flow of 7 5 million acre feet 9 3 109 m3 past Lee s Ferry measured on a 10 year rolling average Without additional reservoir storage the Upper Basin states could not utilize their allocations without impacting water deliveries to the Lower Basin in dry years Glen Canyon Dam the largest dam of the Colorado River Storage Project In 1956 Congress authorized the USBR to construct the Colorado River Storage Project CRSP which planned several large reservoirs on the upper Colorado Green Gunnison and San Juan Rivers The initial blueprints for the CRSP included two dams on the Green River within Echo Park Canyon in Dinosaur National Monument a move criticized by both the National Park Service and environmental groups such as the Sierra Club The controversy received nationwide media attention and the USBR dropped its plans for the Dinosaur dams in exchange for increasing the size of a proposed dam at Glen Canyon The controversy associated with Glen Canyon Dam did not build momentum until construction was well underway Due to Glen Canyon s remote location most of the American public did not even know of its existence the few who did contended that it had much greater scenic value than Echo Park The environmental movement in the American Southwest has opposed the damming and diversion of the Colorado River system due to negative effects on the ecology and natural beauty of the river and its tributaries During the construction of Glen Canyon Dam 1956 66 environmental organizations which vowed clarification needed to block any further development of the river and a number of later dam and aqueduct proposals were defeated by citizen opposition Sierra Club leader David Brower fought the dam both during the construction and for many years afterwards until his death in 2000 Brower believed that he was personally responsible for the failure to prevent Glen Canyon s flooding calling it his greatest mistake greatest sin In addition to Glen Canyon Dam the CRSP includes the Flaming Gorge Dam on the Green River the Blue Mesa Morrow Point and Crystal Dams on the Gunnison River and the Navajo Dam on the San Juan River A total of 22 participating projects of which 16 have been constructed were later authorized in order to develop local water supplies at various locations across the Upper Basin states These include the Central Utah Project which delivers 102 000 acre feet 126 000 000 m3 per year from the Green River basin to the Wasatch Front and the San Juan Chama Project which diverts 110 000 acre feet 140 000 000 m3 per year from the San Juan River to the Rio Grande Valley Both are multi purpose projects serving a variety of agricultural municipal and industrial uses Pacific Southwest Water Plan The main canal of the Central Arizona Project crossing the Sonoran Desert By the middle of the 20th century planners were concerned that continued growth in water demand would outstrip the available water supply from the Colorado River After exploring a multitude of potential projects the USBR published a study in January 1964 known as the Pacific Southwest Water Plan which proposed diverting water from the northwestern United States into the Colorado River basin Arizona s water allocation was a significant focus of the plan due to the growing concern that its water supply could be curtailed due to California s seniority of water rights In addition the plan would guarantee full water supplies to Nevada California and Mexico allowing the Upper Basin states to utilize their full allocations without risking reductions in the Lower Basin The project would cost an estimated 3 1 billion The first stage of this plan would divert water from Northern California s Trinity Klamath and Eel Rivers to Southern California allowing more Colorado River water to be used by exchange in Arizona A canal system which ultimately would become the Central Arizona Project CAP would be constructed to deliver Arizona s Colorado River allocation to Phoenix and Tucson both located far away from the Colorado River in the middle of the state At this point central Arizona was still entirely dependent on local water supplies such as the 1911 Theodore Roosevelt Dam and was quickly running out of surplus water In order to supply the massive amount of power required to pump Colorado River water to central Arizona two hydroelectric dams were proposed in the Grand Canyon Bridge Canyon Dam and Marble Canyon Dam which while not directly located in Grand Canyon National Park would greatly impact flows of the Colorado River through the park With the controversy over Glen Canyon Dam still ongoing the public pressure against these dams was immense As a result the two Grand Canyon dams were omitted from the final CAP authorization in 1968 In addition the boundaries of Grand Canyon National Park were redrawn to prevent future dam projects in the area The pumping power was replaced by the building of the coal fired Navajo Generating Station near Page Arizona in 1976 In 2019 the Navajo Generating Station ceased operation The CAP was constructed in stages from 1973 to 1993 ultimately extending 336 miles 541 km from the Colorado River at Parker Dam to Tucson Arizona It delivers 1 4 million acre feet 1 7 km3 of water per year irrigates 830 000 acres 3 400 km2 of farmland and provides municipal water to about 5 million people Due to environmental concerns most of the facilities proposed in the Pacific Southwest Water Plan were never built though a smaller version of the Trinity River project was constructed as part of the unrelated Central Valley Project leaving Arizona and Nevada vulnerable to future water reductions under the Compact Indigenous water rights Water rights of Native Americans in the Colorado River basin were largely ignored during the extensive water resources development carried out on the river and its tributaries in the 19th and 20th centuries The construction of dams has often had negative impacts on tribal peoples such as the Chemehuevi when their riverside lands were flooded after the completion of Parker Dam in 1938 Ten Native American tribes in the basin now hold or continue to claim water rights to the Colorado River The U S government has taken some actions to help quantify and develop the water resources of Native American reservations The first federally funded irrigation project in the U S was the construction of an irrigation canal on the Colorado River Indian Reservation in 1867 Other water projects include the Navajo Indian Irrigation Project authorized in 1962 for the irrigation of lands in part of the Navajo Nation in north central New Mexico The Navajo continue to seek expansion of their water rights because of difficulties with the water supply on their reservation about 40 percent of its inhabitants must haul water by truck many miles to their homes In the 21st century they have filed legal claims against the governments of Arizona New Mexico and Utah for increased water rights Some of these claims have been successful for the Navajo such as a 2004 settlement in which they received a 326 000 acre foot 402 000 ML allotment from New Mexico Post 2000 water supply The Colorado is a deficit river as if the river were somehow at fault for its overuse Marc Reisner in Cadillac Desert When the Colorado River Compact was drafted in the 1920s it was based on barely 30 years of streamflow records that suggested an average annual flow of 17 5 million acre feet 21 6 km3 past Lee s Ferry Modern studies of tree rings revealed that those three decades were probably the wettest in the past 500 to 1 200 years and that the natural long term annual flow past Lee s Ferry is probably closer to 13 5 million acre feet 16 7 km3 with a natural flow at the mouth around 16 3 million acre feet 20 1 km3 This has resulted in more water being allocated to river users than actually exists in the Colorado Droughts have exacerbated the issue of water over allocation Lake Mead in 2010 showing the bathtub ring left behind by low water levels The most severe drought on record the southwestern North American megadrought began in the early 21st century in which the river basin has produced above average runoff in only five years between 2000 and 2021 The region is experiencing a warming trend which is accompanied by earlier snowmelt lower precipitation and greater evapotranspiration A 2004 study showed that a 1 6 percent decrease of precipitation would lead to runoff declining by as much as 18 percent by 2050 Since 2000 reservoir levels have fluctuated greatly from year to year but have experienced a steady long term decline The particularly dry spell between 2000 and 2004 brought Lake Powell to just a third of capacity in 2005 the lowest level on record since initial filling in 1969 In late 2010 Lake Mead was approaching the drought trigger elevation of 1 075 feet 328 m at which water supplies to Arizona and Nevada would be reduced in accordance with the Colorado River Compact Due to Arizona and Nevada s water rights being junior to California s their allocations can legally be cut to zero before any reductions are made on the California side A wet winter in 2011 temporarily raised lake levels but dry conditions returned in the next two years In 2014 the Bureau of Reclamation cut releases from Lake Powell by 10 percent the first such reduction since the 1960s when Lake Powell was being filled for the first time This resulted in Lake Mead dropping to its lowest recorded level since 1937 when it was first being filled Water year 2018 had a much lower than average snowpack In July 2021 after two more extremely dry winters Lake Powell fell below the previous low set in 2005 In response the Bureau of Reclamation began releasing water from upstream reservoirs in order to keep Powell above the minimum level for hydropower generation Lake Mead fell below the 1 075 foot 328 m level expected to trigger federally mandated cuts to Arizona and Nevada s water supplies for the first time in history and is expected to continue declining into 2022 On August 16 2021 the Bureau of Reclamation released the Colorado River Basin August 2021 24 Month Study and for the first time declared a shortage and that because of ongoing historic drought and low runoff conditions in the Colorado River Basin downstream releases from Glen Canyon Dam and Hoover Dam will be reduced in 2022 due to declining reservoir levels The Lower Basin reductions will reduce the annual apportionments Arizona s by 18 percent Nevada s by 7 percent and Mexico s by 5 percent On June 14 2022 Bureau of Reclamation Commissioner Camille Touton told the Senate Committee on Energy and Natural resources that additional cuts of 2 4 million acre feet were required to stabilize reservoir levels in 2023 Touton warned that if states were unable to negotiate the requisite cuts the Interior department may use its legal authority to cut releases When the states were unable to come to an agreement about how to share the proposed cuts Reclamation began the legal steps to unilaterally reduce releases from Hoover and Glen Canyon Dams in 2023 As of December 2022 the lower basin states of Nevada Arizona and California had not agreed on how to reduce water use by the approximately 30 required to keep levels in lakes Mead and Powell from crashing The Bureau of Reclamation has projected that water levels at Lake Powell could fall low enough that by July 2023 Glen Canyon Dam would no longer be able to generate any hydropower Arizona proposed a plan that severely cut allocations to California and California responded with a plan that severely cut allocations to Arizona failing to reach consensus In April 2023 the federal government proposed cutting allocations to Nevada Arizona and California evenly which would cut deliveries by as much as one quarter to each state rather than according to senior water rights In May 2023 the states finally reached a temporary agreement to prevent deadpool reducing allocations by 3 million acre feet over three years until the end of 2026 700 000 acre feet were to be negotiated later among California Arizona and Nevada The cuts were less than the federal government had demanded and so further cuts will be needed after 2026 Fewer cuts were needed in the short term because the Colorado River Basin experienced an unusually rainy and snowy weather in early 2023 The agreement also became easier to negotiate because many cuts are being offset by one time federal funding Billions of dollars in funding for programs in the Colorado River Basin to recycle water increase efficiency and competitive grants to pay water rights holders not to use water from the river are being provided by the Infrastructure Investment and Jobs Act and Inflation Reduction Act and other programs funded through the United States Environmental Protection Agency and United States Department of the Interior These are projected to reduce demand by hundreds of thousands of acre feet per year EcologyWildlife and plants Heavily forested banks of the Colorado River near Topock Arizona The Colorado River and its tributaries often nourish extensive corridors of riparian growth as they traverse the arid desert regions of the watershed Although riparian zones represent a relatively small proportion of the basin and have been affected by engineering projects and river diversion in many places they have the greatest biodiversity of any habitat in the basin The most prominent riparian zones along the river occur along the lower Colorado below Davis Dam especially in the Colorado River Delta where riparian areas support 358 species of birds despite the reduction in freshwater flow and invasive plants such as tamarisk salt cedar Reduction of the delta s size has also threatened animals such as jaguars and the vaquita porpoise which is endemic to the gulf Human development of the Colorado River has also helped to create new riparian zones by smoothing the river s seasonal flow notably through the Grand Canyon More than 1 600 species of plants grow in the Colorado River watershed ranging from the creosote bush saguaro cactus and Joshua trees of the Sonoran and Mojave Deserts to the forests of the Rocky Mountains and other uplands composed mainly of ponderosa pine subalpine fir Douglas fir and Engelmann spruce Before logging in the 19th century forests were abundant in high elevations as far south as the Mexico U S border and runoff from these areas nourished abundant grassland communities in river valleys Some arid regions of the watershed such as the upper Green River valley in Wyoming Canyonlands National Park in Utah and the San Pedro River valley in Arizona and Sonora supported extensive reaches of grassland roamed by large mammals such as buffalo and antelope as late as the 1860s Near Tucson Arizona where now there is only powder dry desert the grass once reached as high as the head of a man on horse back Rivers and streams in the Colorado basin were once home to 49 species of native fish of which 42 were endemic Engineering projects and river regulation have led to the extinction of four species and severe declines in the populations of 40 species Bonytail chub razorback sucker Colorado pikeminnow and humpback chub are among those considered the most at risk all are unique to the Colorado River system and well adapted to the river s natural silty conditions and flow variations Clear cold water released by dams has significantly changed characteristics of habitat for these and other Colorado River basin fishes A further 40 species that occur in the river today notably the brown trout were introduced during the 19th and 20th centuries mainly for sport fishing Impacts of development Most of the Colorado River basin water used by humans is used to grow feed for livestock more than four times the amount used for crops for direct human consumption The Colorado was named for the reddish color caused by its natural sediment loads but damming the river has caused it to acquire a clear green hue as seen here in lower Glen Canyon Historically the Colorado transported from 85 to 100 million short tons 77 000 000 to 91 000 000 t of sediment or silt to the Gulf of California each year second only to the Mississippi among North American rivers This sediment nourished wetlands and riparian areas along the river s lower course particularly in its 3 000 square mile 7 800 km2 delta once the largest desert estuary on the continent Currently the majority of sediments carried by the Colorado River are deposited at the upper end of Lake Powell and most of the remainder ends up in Lake Mead Various estimates place the time it would take for Powell to completely fill with silt at 300 to 700 years Dams trapping sediment not only pose damage to river habitat but also threaten future operations of the Colorado River reservoir system Reduction in flow caused by dams diversions water for thermoelectric power stations and evaporation losses from reservoirs the latter of which consumes more than 15 percent of the river s natural runoff has had severe ecological consequences in the Colorado River Delta and the Gulf of California Historically the delta with its large freshwater outflow and extensive salt marshes provided an important breeding ground for aquatic species in the Gulf Today s desiccated delta at only a fraction of its former size no longer provides suitable habitat and populations of fish shrimp and sea mammals in the gulf have seen a dramatic decline Since 1963 the only times when the Colorado River has reached the ocean have been during El Nino events in the 1980s and 1990s Reduced flows have led to increases in the concentration of certain substances in the lower river that have impacted water quality Salinity is one of the major issues and also leads to the corrosion of pipelines in agricultural and urban areas The lower Colorado s salt content was about 50 parts per million ppm in its natural state but by the 1960s it had increased to well over 2000 ppm By the early 1970s there was also serious concern about salinity caused by salts leached from local soils by irrigation drainage water which were estimated to add 10 million short tons 9 100 000 t of excess salt to the river per year The Colorado River Basin Salinity Control Act was passed in 1974 mandating conservation practices including the reduction of saline drainage The program reduced the annual load by about 1 2 million short tons 1 100 000 t but salinity remains an ongoing issue In 1997 the USBR estimated that saline irrigation water caused crop damages exceeding 500 million in the U S and 100 million in Mexico Further efforts have been made to combat the salt issue in the lower Colorado including the construction of a desalination plant at Yuma In 2011 the seven U S states agreed upon a Plan of Implementation which aims to reduce salinity by 644 000 short tons 584 000 t per year by 2030 In 2013 the Bureau of Reclamation estimated that around 32 million was spent each year to prevent around 1 2 million tons of salt from entering and damaging the Colorado River Agricultural runoff containing pesticide residues has also been concentrated in the lower river in greater amounts This has led to fish kills six of these events were recorded between 1964 and 1968 alone The pesticide issue is even greater in streams and water bodies near agricultural lands irrigated by the Imperial Irrigation District with Colorado River water In the Imperial Valley Colorado River water used for irrigation overflows into the New and Alamo rivers and into the Salton Sea Both rivers and the sea are among the most polluted bodies of water in the United States posing dangers not only to aquatic life but to contact by humans and migrating birds Pollution from agricultural runoff is not limited to the lower river the issue is also significant in upstream reaches such as Colorado s Grand Valley also a major center of irrigated agriculture Large dams such as Hoover and Glen Canyon typically release water from lower levels of their reservoirs resulting in stable and relatively cold year round temperatures in long reaches of the river The Colorado s average temperature once ranged from 85 F 29 C at the height of summer to near freezing in winter but modern flows through the Grand Canyon for example rarely deviate significantly from 46 F 8 C Changes in temperature regime have caused declines of native fish populations and stable flows have enabled increased vegetation growth obstructing riverside habitat These flow patterns have also made the Colorado more dangerous to recreational boaters people are more likely to die of hypothermia in the colder water and the general lack of flooding allows rockslides to build up making the river more difficult to navigate Minute 319 In the 21st century there has been renewed interest in restoring a limited water flow to the delta In November 2012 the U S and Mexico reached an agreement known as Minute 319 permitting Mexico storage of its water allotment in U S reservoirs during wet years thus increasing the efficiency with which the water can be used In addition to renovating irrigation canals in the Mexicali Valley to reduce leakage this will make about 45 000 acre feet 56 000 000 m3 per year available for release to the delta on average The water will be used to provide both an annual base flow and a spring pulse flow to mimic the river s original snowmelt driven regime The first pulse flow an eight week release of 105 000 acre feet 130 000 000 m3 was initiated on March 21 2014 with the aim of revitalising 2 350 acres 950 hectares of wetland This pulse reached the sea on May 16 2014 marking the first time in 16 years that any water from the Colorado flowed into the ocean and was hailed as an experiment of historic political and ecological significance and a landmark in U S Mexican cooperation in conservation The pulse will be followed by the steady release of 52 000 acre feet 64 000 000 m3 over the following three years just a small fraction of its average flow before damming needs update RecreationA rafting party on the Colorado River Famed for its dramatic rapids and canyons the Colorado is one of the most well known whitewater rivers in the United States and its Grand Canyon section run by more than 22 000 people annually has been called the granddaddy of rafting trips Grand Canyon trips typically begin at Lee s Ferry and take out at Diamond Creek or Lake Mead they range from one to eighteen days for commercial trips and from two to twenty five days for private trips Private noncommercial trips are extremely difficult to arrange because the National Park Service limits river traffic for environmental purposes people who desire such a trip often have to wait more than 10 years for the opportunity Several other sections of the river and its tributaries are popular whitewater runs and many of these are also served by commercial outfitters The Colorado s Cataract Canyon and many reaches in the Colorado headwaters are even more heavily used than the Grand Canyon and about 60 000 boaters run a single 4 5 mile 7 2 km section above Radium Colorado each year The upper Colorado also includes many of the river s most challenging rapids including those in Gore Canyon which is considered so dangerous that boating is not recommended Another section of the river above Moab known as the Colorado Daily or Fisher Towers Section is the most visited whitewater run in Utah with more than 77 000 visitors in 2011 alone The rapids of the Green River s Gray and Desolation Canyons and the less difficult Goosenecks section of the lower San Juan River are also frequently traversed by boaters Eleven U S national parks Arches Black Canyon of the Gunnison Bryce Canyon Canyonlands Capitol Reef Grand Canyon Mesa Verde Petrified Forest Rocky Mountain Saguaro and Zion are in the watershed in addition to many national forests state parks and recreation areas Hiking backpacking camping skiing and fishing are among the multiple recreation opportunities offered by these areas Fisheries have declined in many streams in the watershed especially in the Rocky Mountains because of polluted runoff from mining and agricultural activities The Colorado s major reservoirs are also heavily traveled summer destinations Houseboating and water skiing are popular activities on Lakes Mead Powell Havasu and Mojave as well as Flaming Gorge Reservoir in Utah and Wyoming and Navajo Reservoir in New Mexico and Colorado Lake Powell and surrounding Glen Canyon National Recreation Area received more than two million visitors per year in 2007 while nearly 7 9 million people visited Lake Mead and the Lake Mead National Recreation Area in 2008 Colorado River recreation employs some 250 000 people and contributes 26 billion each year to the Southwest economy See alsoArizona portalCalifornia portalColorado portalMexico portalUnited States portalUtah portalColorado River Delta Colorado Desert List of Colorado River rapids and features List of dams in the Colorado River system List of largest reservoirs in the United States List of longest rivers of Mexico List of longest rivers of the United States by main stem London Bridge Lake Havasu City Moab uranium mill tailings pile Upper Colorado River Endangered Fish Recovery ProgramNotesDischarge data is for Green River Utah 117 6 miles 189 3 km upstream from the mouth The stream gauge here measures flow from an area of 44 850 square miles 116 200 km2 representing about 93 2 percent of the basin Before large irrigation and municipal diversions the Gila River discharged about 1 3 million acre feet 1 6 km3 per year which equals a flow of nearly 2 000 cubic feet per second 57 m3 s Discharge data is for Bluff Utah located about 113 5 miles 182 7 km above the confluence with the Colorado The gauge measures flow from an area of 23 000 square miles 60 000 km2 about 93 5 percent of the basin Discharge data is for Littlefield Arizona about 66 miles 106 km from the confluence with the Colorado and also upstream of the confluence with its major tributary the Muddy River The gauge measures flow from an area of 5 090 square miles 13 200 km2 about 39 1 percent of the total basin American population 9 7 million calculated from statistics from the U S Census Bureau and the State of Colorado The population in Mexico is about 3 million Unimpaired runoff figures published by the Bureau of Reclamation are an estimate of unregulated river flow without any upstream water consumption NIB Northerly International Boundary or the point at which the Colorado begins to form the Mexico U S border south of Yuma Also note that the SIB Southerly International Boundary is the point at which the Colorado ceases to form the border and passes entirely into Mexico The average discharge of the Colorado Grand River at Cisco Utah about 97 miles 156 km upstream from the Green River confluence is 7 181 cubic feet per second 203 3 m3 s between here and the confluence only a few small intermittent tributaries join the river The Green River has an average discharge of 6 048 cubic feet per second 171 3 m3 s as measured at Green River Utah about 117 6 miles 189 3 km above the confluence below here the only major tributary is the San Rafael River which contributes an average of 131 cubic feet per second 3 7 m3 s resulting in a total of 6 169 cubic feet per second 174 7 m3 s still significantly lower than the discharge of the Colorado at their confluence The discrepancy between the natural flow at Lee s Ferry 13 5 million acre feet or 16 65 km3 and the gauged flow between 1922 and 2020 10 58 million acre feet or 13 05 km3 is mostly due to water diversions above Lee s Ferry and evaporation from reservoirs especially Lake Powell ReferencesKammerer J C May 1990 Largest Rivers in the United States U S Geological Survey Archived from the original on March 21 2007 Retrieved July 2 2010 USGS Gage 09380000 Colorado River at Lees Ferry AZ Water Year Summary National Water Information System U S Geological Survey 2023 Retrieved August 11 2024 Colorado River Geographic Names Information System United States Geological Survey United States Department of the Interior February 8 1980 Retrieved February 18 2012 The Compact and Lees Ferry Colorado River Streamflow A Paleo Perspective Western Water Assessment Archived from the original on April 29 2012 Waterman Jonathan February 15 2012 Where the Colorado Runs Dry The New York Times Archived from the original on August 21 2021 Retrieved October 14 2014 Imperial Valley Encyclopaedia Britannica 1995 San Juan Chama Project Archived from the original on August 23 2021 Retrieved August 23 2021 Diaz Henry F Anderson Craig A November 28 2003 Precipitation Trends and Water Consumption in the Southwestern United States Impact of Climate Change and Land Use in the Southwestern United States U S Geological Survey Archived from the original on March 9 2012 Postel Sandra May 19 2014 A Sacred Reunion The Colorado River Returns to the Sea National Geographic Archived from the original on January 8 2018 Retrieved May 19 2021 La Poudre Pass Geographic Names Information System United States Geological Survey United States Department of the Interior October 13 1978 Retrieved March 12 2012 Lindberg 2009 p 38 Benke amp Cushing 2005 p 490 Pitlick John Cress Robert March 2000 Longitudinal Trends in Channel Characteristics of the Colorado River and Implications for Food Web Dynamics PDF University of Colorado Archived from the original PDF on December 4 2012 Retrieved March 12 2012 U S Geological Survey United States Geological Survey Topographic Maps Fall River Pass Colorado quad TopoQuest Archived from the original on July 27 2021 Retrieved June 24 2013 U S Geological Survey United States Geological Survey Topographic Maps Westwater Utah quad TopoQuest Archived from the original on July 27 2021 Retrieved July 14 2013 Affected Environment PDF Remediation of the Moab Uranium Mill Tailings Grand and San Juan Counties Utah Final Environmental Impact Statement Moab Utah UMTRA Project p 28 Archived from the original PDF on October 15 2011 Rigby J Keith Hamblin W Kenneth Matheny Ray Welsh Stanley L 1971 Guidebook to the Colorado River Part 3 Moab to Hite Utah through Canyonlands National Park PDF Brigham Young University Geology Studies Volume 18 Part 2 Brigham Young University Archived from the original PDF on April 2 2015 Retrieved July 14 2013 Hopkins 2002 p 118 Van Cott 1990 p 70 Van Cott 1990 p 155 Rivers Canyonlands National Park U S National Park Service June 17 2011 Archived from the original on June 29 2012 Retrieved February 19 2012 Lake Powell Colorado River Storage Project U S Bureau of Reclamation November 4 2008 Archived from the original on September 21 2012 Retrieved February 19 2012 Rusho W L 1992 Lee s Ferry Arizona Utah History Encyclopedia University of Utah Archived from the original on January 9 2013 Retrieved February 19 2012 Grand Canyon National Park Arizona Geology Fieldnotes U S National Park Service Archived from the original on October 23 2013 Retrieved July 14 2013 Leopold Luna B The Rapids and the Pools Grand Canyon PDF Geological Survey Professional Paper 669 D U S Geological Survey p 133 Archived PDF from the original on November 4 2013 Retrieved November 2 2013 Hoover Dam Frequently Asked Questions and Answers Lake Mead U S Bureau of Reclamation December 2008 Archived from the original on May 20 2012 Retrieved February 19 2012 Hoover Dam Bypass Is 2012 OCEA Winner OPAL Lifetime Achievement Recipients Honored Pankow Michel Awards Presented American Society of Civil Engineers Archived from the original on March 27 2013 Retrieved July 14 2013 The Colorado River Indian Tribes Reservation C R I T Quick Facts PDF Arizona Cooperative Extension University of Arizona August 2010 Archived from the original PDF on October 21 2011 Retrieved July 14 2013 Appendix J Mainstem Impacts Analysis PDF Draft Environmental Impact Statement Allocation of Water Supply and Long Term Contract Execution Central Arizona Project U S Bureau of Reclamation Archived from the original PDF on January 20 2013 Retrieved April 4 2012 U S Geological Survey United States Geological Survey Topographic Maps Blythe NE California quad TopoQuest Archived from the original on July 27 2021 Retrieved July 14 2013 Gupta 2007 p 204 Alles David L ed October 28 2011 The Lower Colorado River PDF Biology Department Western Washington University Archived PDF from the original on December 7 2012 Retrieved July 14 2013 Fighting For Water in Arid Imperial Valley National Public Radio February 10 2011 Archived from the original on July 27 2021 Retrieved February 19 2012 Border Water Source of Conflict and Cooperation What Makes Management of Border Water Resources a Challenge PDF Arroyo University of Arizona 2012 Archived from the original PDF on November 13 2014 Retrieved July 14 2013 Valdes Casillas Carlos et al August 1998 Information Database and Local Outreach Program for the Restoration of the Hardy River Wetlands Lower Colorado River Delta Baja California and Sonora Mexico San Diego State University Archived from the original on January 20 2013 Retrieved February 19 2012 March 24 2014 Historic Pulse Flow Brings Water to Parched Colorado River Delta National Geographic Archived from the original on September 1 2019 Chanson Hubert 2009 Environmental Ecological and Cultural Impacts of Tidal Bores Benaks Bonos and Burros Proceedings of the International Workshop on Environmental Hydraulics IWEH09 Theoretical Experimental and Computational Solutions University of Queensland Archived from the original on October 21 2011 Retrieved November 29 2009 Felger amp Broyles 2007 pp 519 520 Executive Summary Green River Basin Water Plan Wyoming State Water Plan February 2001 Archived from the original on November 25 2011 Retrieved February 25 2012 Boundary Descriptions and Names of Regions Subregions Accounting Units and Cataloging Units U S Geological Survey Archived from the original on April 9 2020 Retrieved February 19 2012 Benke amp Cushing 2005 p 514 Benke amp Cushing 2005 pp 532 533 Green River Utah Rivers Council Archived from the original on May 14 2012 Retrieved February 26 2012 USGS Gage 09315000 on the Green River at Green River UT PDF National Water Information System U S Geological Survey 1895 2010 Archived PDF from the original on January 20 2013 Retrieved February 26 2012 USGS Gage 09520000 on the Gila River near Dome AZ PDF National Water Information System U S Geological Survey 1905 2011 Archived PDF from the original on January 20 2013 Retrieved February 26 2012 The National Map Archived June 30 2016 at the Wayback Machine U S Geological Survey Accessed February 25 2012 USGS Gage 09379000 on the San Juan River near Bluff UT PDF National Water Information System U S Geological Survey 1914 2010 Archived PDF from the original on January 20 2013 Retrieved February 26 2012 Report Findings and Determination Regarding the Navigability of the Little Colorado River From its Headwaters to the Confluence with the Colorado River PDF Arizona Navigable Stream Adjudication Commission 2005 Archived from the original PDF on April 22 2010 Retrieved February 26 2012 USGS Gage 09402300 on the Little Colorado River Above the Mouth near Desert View AZ PDF National Water Information System U S Geological Survey 1990 2010 Archived PDF from the original on January 20 2013 Retrieved February 26 2012 Fielder 2002 p 403 USGS Gage 09180000 on the Dolores River near Cisco UT PDF National Water Information System U S Geological Survey 1950 2010 Archived PDF from the original on January 20 2013 Retrieved February 26 2012 USGS Gage 09152000 on the Gunnison River near Grand Junction CO PDF National Water Information System U S Geological Survey 1897 2010 Archived PDF from the original on January 20 2013 Retrieved February 26 2012 Annerino 1999 p 8 USGS Gage 09415000 on the Virgin River at Littlefield AZ PDF National Water Information System U S Geological Survey 1929 2010 Archived PDF from the original on January 20 2013 Retrieved February 26 2012 Benke amp Cushing 2005 pp 483 486 Watersheds map Commission for Environmental Cooperation 2006 Archived from the original on April 14 2008 Current Understanding of Colorado River Basin Climate and Hydrology PDF Western Water Assessment April 2020 Archived PDF from the original on January 20 2022 Retrieved May 24 2022 River Basins of Mexico University of Texas 1975 Archived from the original on November 7 2011 Retrieved February 19 2012 Fassnacht S R 2004 Streamflow Predictability in the Upper Versus Lower Colorado River Sub Basins PDF Eastern Snow Conference Archived from the original PDF on June 23 2012 Retrieved February 19 2012 Lees Ferry historical Geographic Names Information System United States Geological Survey United States Department of the Interior February 8 1980 Retrieved May 25 2022 Annual Report on the Salton Sea Management Program PDF California Natural Resources Agency March 2021 Archived PDF from the original on April 1 2022 Retrieved May 26 2022 Singh Ramesh K Senay Gabriel B Velpuri Naga Manohar Kagone Stephanie January 2014 Actual Evapotranspiration Water Use Assessment of the Colorado River Basin at the Landsat Resolution Using the Operational Simplified Surface Energy Balance Model Remote Sensing 6 1 233 256 doi 10 3390 rs6010233 Archived from the original on March 1 2024 Retrieved May 26 2022 Benke amp Cushing 2005 pp 483 489 Baker Jr Malchus B Ffolliott Peter F 2000 Contributions of Watershed Management Research to Ecosystem Based Management in the Colorado River Basin PDF USDA Forest Service Proceedings RMRS P 13 U S Forest Service Archived PDF from the original on October 23 2020 Retrieved June 24 2013 Climate and Hydrology of the Colorado River Basin Region National Academies Press 2007 doi 10 17226 11857 ISBN 978 0 309 10524 8 Archived from the original on May 26 2022 Retrieved May 23 2022 Features and Dynamics of Colorado River Basin Climate Colorado River Basin Water Management Evaluating and Adjusting to Hydroclimatic Variability National Academies Press 2007 doi 10 17226 11857 ISBN 978 0 309 10524 8 Archived from the original on January 20 2013 Retrieved February 19 2012 State and County QuickFacts U S Census Bureau Archived from the original on March 4 2012 Retrieved March 4 2012 Population and Demographics Colorado Data Book State of Colorado September 2007 Archived from the original PDF on January 20 2013 Colorado River Basin Salinity Control Program Natural Resources Conservation Service U S Department of Agriculture July 12 2010 Archived from the original on June 10 2021 Retrieved March 4 2012 Colorado River Basin Water Management Evaluating and Adjusting to Hydroclimatic Variability Report in Brief PDF Division on Earth amp Life Studies National Academies February 2007 Archived from the original PDF on September 15 2012 Retrieved February 19 2012 Colorado River Basin Natural Flow and Salt Data U S Bureau of Reclamation April 22 2024 Retrieved August 11 2024 Water Year Summary for Site USGS 09380000 Colorado River at Lees Ferry AZ National Water Information System U S Geological Survey 1922 2020 Archived from the original on June 24 2021 Retrieved May 17 2021 USGS Gage 09380000 on the Colorado River at Lee s Ferry AZ National Water Information System U S Geological Survey 1921 2010 Archived from the original on February 22 2016 Retrieved April 21 2012 Schmidt J C Yackulic C B amp Kuhn E 2023 The Colorado River water crisis Its origin and the future WIREs Water 10 6 e1672 https doi org 10 1002 wat2 1672 Thomsen B W Eychaner J H 1991 Predevelopment hydrology of the Gila River Indian Reservation South Central Arizona PDF Arizona Navigable Stream Adjudication Commission Retrieved August 11 2024 Phillips Daniel H Reinink Yvonne Skarupa Timothy E Ester III Charles E and Skindlov Jon A April 29 2009 Water resources planning and management at the Salt River Project Arizona USA PDF TreeFlow Retrieved August 11 2024 a href wiki Template Cite web title Template Cite web cite web a CS1 maint multiple names authors list link Anderson D Larry 2002 The Colorado River Utah s Perspective PDF Utah Division of Water Resources Retrieved August 11 2024 Climatic Fluctuations Drought and Flow in the Colorado River Basin USGS Fact Sheet 2004 3062 U S Geological Survey August 2004 Archived from the original on October 19 2012 Retrieved April 17 2012 Wiltshire Gilbert amp Rogers 2010 pp 101 102 Wahl Kenneth L Collins Dannie L Aldridge Byron N Runoff in the Upper Colorado River Basin Water Years 1983 85 and Comparisons with Forecasts of Runoff to Lake Powell PDF Western Snow Conference Archived from the original PDF on July 14 2012 Preston Ben March 22 2010 The Risky Business of Slicing the Pie Miller McCune Archived from the original on July 27 2021 Retrieved June 27 2013 USGS Gage 09421500 on the Colorado River below Hoover Dam National Water Information System U S Geological Survey 1934 2021 Retrieved August 11 2024 Richard Gigi A and Anderson Richard M 2007 Channel forming discharge on the Dolores River and Yampa River Colorado PDF Colorado Parks and Wildlife Retrieved August 11 2024 a href wiki Template Cite web title Template Cite web cite web a CS1 maint multiple names authors list link Christensen Niklas S Wood Andrew W Voisin Nathalie Lettenmaier Dennis P Palmer Richard N 2004 The Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin PDF Climatic Change 62 337 363 345 doi 10 1023 b clim 0000013684 13621 1f S2CID 53533021 Archived from the original PDF on May 1 2014 Retrieved July 13 2013 Cohen Michael J Henges Jeck Christine Castillo Moreno Gerardo 2001 A Preliminary Water Balance for the Colorado River Delta 1992 1998 PDF Journal of Arid Environments 49 1 35 48 Bibcode 2001JArEn 49 35C doi 10 1006 jare 2001 0834 Archived PDF from the original on October 10 2015 Retrieved June 27 2013 For A Few Weeks The Colorado River Reached The Ocean Will It Happen Again KPBS Public Media February 19 2018 Archived from the original on March 24 2022 Retrieved February 27 2022 USGS Gage 09522200 on the Colorado River at NIB Above Morelos Dam AZ Annual Statistics National Water Information System U S Geological Survey 1951 1992 Archived from the original on September 19 2015 Retrieved April 27 2012 Zimmerman Janet October 6 2010 Colorado River Drought Threatens Power Production The Press Enterprise Riverside California Archived from the original on January 20 2013 Retrieved February 18 2012 Stark Mike April 21 2009 Study Shortages Likely on Colorado River by 2050 USA Today Associated Press Archived from the original on July 18 2013 Retrieved June 27 2013 Hoerling Martin Eischeid Jon Past Peak Water in the Southwest PDF Western Water Assessment Archived from the original PDF on June 9 2010 McKinnon Shaun August 9 2006 Mines Farms Put Gila River on Life Support Despite Lack of Regulation Some Trying to Restore River to Its Natural Beauty and Wonder Arizona Republic Archived from the original on January 17 2013 Retrieved February 19 2012 Water Year Summary for Site USGS 09522000 Colorado River at Northerly International Boundary above Morelos Dam near Andrade CA National Water Information System U S Geological Survey 1950 2020 Archived from the original on August 24 2021 Retrieved May 17 2021 Reclamation Colorado River Water Users Association Archived from the original on November 4 2013 Retrieved November 2 2013 Water Year Summary for Site USGS 09010500 Colorado River below Baker Gulch near Grand Lake CO National Water Information System U S Geological Survey 1953 2020 Archived from the original on August 24 2021 Retrieved May 17 2021 Water Year Summary for Site USGS 09070500 Colorado River near Dotsero CO National Water Information System U S Geological Survey 1941 2020 Archived from the original on August 24 2021 Retrieved May 17 2021 Water Year Summary for Site USGS 09180500 Colorado River near Cisco UT National Water Information System U S Geological Survey 1914 2020 Archived from the original on August 24 2021 Retrieved May 17 2021 Water Year Summary for Site USGS 09423000 Colorado River below Davis Dam AZ NV National Water Information System U S Geological Survey 1905 2020 Archived from the original on August 24 2021 Retrieved May 17 2021 Water Year Summary for Site USGS 09427520 Colorado River below Parker Dam AZ CA National Water Information System U S Geological Survey 1935 2020 Archived from the original on August 24 2021 Retrieved May 17 2021 Water Year Summary for Site USGS 09429600 Colorado River below Laguna Dam AZ CA National Water Information System U S Geological Survey 1972 2020 Archived from the original on August 24 2021 Retrieved May 17 2021 Prisciantelli 2002 p 56 Cannon Eric April 28 2002 The Mid Tertiary Ignimbrite Flare Up University of Colorado Boulder Archived from the original on July 16 2012 Retrieved February 19 2012 Foos Annabelle Geology of the Colorado Plateau PDF U S National Park Service Archived from the original PDF on September 8 2015 Retrieved February 19 2012 Martin Barajas Arturo et al July 2009 The Tectonic Evolution of the Gulf of California Division of Geological and Planetary Sciences California Institute of Technology Archived from the original on January 20 2013 Retrieved February 19 2012 Young amp Spamer 2001 p 193 Davis Jim January 2009 Why Does a River Run Through It Survey Notes 41 1 Utah Geological Survey Archived from the original on November 8 2010 Retrieved February 19 2012 Prisciantelli 2002 p 62 Alles David L ed October 28 2011 Geology of the Salton Trough PDF Western Washington University Archived PDF from the original on March 2 2012 Retrieved February 29 2012 Buckles Joseph E Krantz Timothy Reconstruction of Prehistoric Shorelines for Cultural Restraints using GIS Salton Sea Database Program ESRI Archived from the original on November 27 2011 Retrieved February 19 2012 Fenton Cassie Webb Bob A Fresh Look at Western Grand Canyon Lava Dams Introduction Grand Canyon River Guides Archived from the original on June 23 2012 Retrieved February 19 2012 Rugg Scott H Austin Steven A August 1998 Evidence for Rapid Formation and Failure of Pleistocene Lava Dams of the Western Grand Canyon Arizona PDF Institute for Creation Research Archived from the original PDF on January 21 2012 Retrieved February 19 2012 Fenton Cassandra R Poreda Robert J Nash Barbara P Webb Robert H Cerling Thure E et al 2004 Geochemical Discrimination of Five Pleistocene Lava Dam Outburst Flood Deposits Western Grand Canyon Arizona PDF Journal of Geology 112 1 91 110 Bibcode 2004JG 112 91F doi 10 1086 379694 S2CID 53339467 Archived PDF from the original on January 20 2013 Retrieved February 19 2012 Fenton Cassandra R Webb Robert H Cerling Thure E May 6 2005 Peak Discharge of a Pleistocene Lava Dam Outburst Flood in Grand Canyon Arizona USA PDF Quaternary Research 65 2 U S Geological Survey 324 Bibcode 2006QuRes 65 324F doi 10 1016 j yqres 2005 09 006 S2CID 128533268 Archived from the original PDF on October 15 2011 Retrieved February 19 2012 People of the Colorado Plateau Land Use History of North America Northern Arizona University Archived from the original on June 29 2015 Retrieved April 9 2012 Formative Era Fremont Culture U S Bureau of Land Management August 31 2009 Archived from the original on June 23 2012 Retrieved April 9 2012 Fremont Culture Dinosaur National Monument U S National Park Service Archived from the original on August 15 2012 Retrieved April 9 2012 Vess Deborah The Anasazi Georgia College and State University Archived from the original on June 8 2011 Sevigny Melissa May 12 2022 Archaeological sites once thought lost under Lake Powell reappear as water drops Arizona Public Radio Retrieved August 11 2024 Water Development Extraction and Diversion Land Use History of North America Colorado Plateau Northern Arizona University p 2 Archived from the original on February 14 2015 Retrieved October 21 2014 Ancestral Pueblo People and Their World PDF U S National Park Service Retrieved August 20 2024 Nobles 1998 p 26 Logan 2006 pp 21 22 Hopi Dictionary Hopiikwa Lavaytutuveni Hopi English Dictionary of the Third Mesa Dialect The Hopi Dictionary Project Tucson University of Arizona Press 1997 Antone Caroline Piipayk m iim Salt River Oʼodham Piipaash Language Program 2000 Gupta 2010 p 362 Hinton Leanne 1984 A Dictionary of the Havasupai Language Supai Arizona Havasupai Tribe OCLC 12358778 William Alan Shaterian 1983 Phonology and Dictionary of Yavapai PhD dissertation University of California Berkeley OCLC 13197420 Ancient Forest Management in the Chaco Canyon From 600 AD to 1300 AD Tenthmil Archived from the original on December 24 2010 Schwinning Susan Belnap Jayne Bowling David R amp Ehleringer James R 2008 Sensitivity of the Colorado Plateau to Change Climate Ecosystems and Society Ecology and Society 13 2 28 doi 10 5751 ES 02412 130228 hdl 10535 2863 Andrews John P Bostwick Todd W Desert Farmers at the River s Edge The Hohokam and Pueblo Grande Pueblo Grande Museum Archaeological Park City of Phoenix Archived from the original on May 8 2012 Retrieved April 10 2012 Shaw Anne Moore A Pima Past Salt River Pima Maricopa Indian Community Archived from the original on January 20 2013 Retrieved April 10 2012 Kroeber Clifton B and Fontana Bernard L Yuman Antagonists Maricopas Quechans and Mohaves to 1857 Massacre on the Gila An Account of the Last Major Battle Between American Indians with Reflections on the Origin of War University of Arizona Press Retrieved August 20 2024 a href wiki Template Cite web title Template Cite web cite web a CS1 maint multiple names authors list link California Mohave Southwest Indian Relief Council Archived from the original on December 13 2012 Retrieved April 10 2012 Dine History and Facts University of California Irvine Donald Bren School of Information and Computer Sciences Archived from the original on December 11 2012 Retrieved April 10 2012 The Navajo A Brief History PDF The Navajo Nation Division of Economic Development Archived PDF from the original on September 4 2012 Retrieved April 10 2012 Hassell Hank 2001 Navajo Mountain Religion Rainbow Bridge through Indian Eyes Johns Hopkins University Retrieved August 20 2024 Ute Land Use History of North America Northern Arizona University Archived from the original on February 5 2012 Retrieved April 9 2012 Benke amp Cushing 2005 p 486 History Southern Ute Indian Tribe Retrieved August 20 2024 John Wesley Powell s Exploration of the Colorado River U S Geological Survey March 28 2006 Archived from the original on April 5 2015 Retrieved February 19 2012 Axelrod amp Phillips 2008 p 4 Lankford 2010 pp 100 101 Flint Richard Flint Shirley Cushing Diaz Melchior New Mexico Office of the State Historian Archived from the original on October 10 2013 Pritzker 1998 p 309 Arizona Yuma Crossing National Heritage Area U S National Park Service April 22 2019 Retrieved August 20 2024 Bolton 2017 pp 440 Gudde amp Bright 2004 p 50 Anthony Alex Crossing of the Fathers Intermountain Histories Retrieved August 20 2024 Before Powell Exploration of the Colorado River Dellenbaugh 1909 p 60 Rolle 1999 p 54 Indian Affairs Treaties U S Government Printing Office 1904 Renaming the Grand River Colo PDF Hearing Before the Committee on Interstate and Foreign Commerce of the House of Representatives Sixty Sixth Congress Third Session on HJ 460 Government Printing Office February 18 1921 archived PDF from the original on August 5 2021 retrieved May 16 2023 A Complete Pronouncing Gazetteer or Geographical Dictionary of the World Containing the Most Recent and Authentic Information Respecting the Countries Cities Towns Resorts Islands Rivers Mountains Seas Lakes Etc in Every Portion of the Globe J B Lippincott Company 1906 Gemaehlich Tammy September 4 2023 What s in a Name Grand Junction and the rivers that run through it The Grand Junction Daily Sentinel Retrieved August 17 2024 Overland Monthly and Out West Magazine A Roman and Company August 11 1895 Archived from the original on March 1 2024 Retrieved August 31 2016 via Google Books Richard E Lingenfelter 1978 Steamboats on the Colorado River 1852 1916 PDF Tucson University of Arizona Press Archived from the original PDF on January 18 2016 Autobiography and Reminiscence of George Alonzo Johnson San Diego 1901 oac cdlib org Archived from the original on August 3 2020 Retrieved August 11 2022 Ives Joseph C August 11 1861 Report Upon the Colorado River of the West U S Government Printing Office via Google Books Dellenbaugh 1909 p 170 Schmidt 1993 p 12 Dolnick 2002 p 5 Leuchtenburg 2000 p 360 Historic 3D Photographs of the Second Powell Expedition 1871 1872 Geology of National Parks U S Geological Survey February 13 2012 Archived from the original on March 11 2012 Retrieved February 20 2012 The J W Powell Survey 1871 1894 Smithsonian Institution Archives Retrieved August 20 2024 Hekkers Jim 1980 The Colorado River Railroad Survey PDF Colorado Outdoors Retrieved August 17 2024 Dolnick 2002 p 238 Keeler Preston Nelson Nevada Ghost Town and El Dorado Canyon Intermountain Histories Retrieved August 20 2024 Johnson Weldon B September 10 2018 Arizona s mining history Danger for many riches for a few The Arizona Republic Kessel amp Wooster 2005 p 217 Fort Mojave Reservation Tribal Library Census and Needs Assessment California State University San Marcos June 12 2001 Archived from the original on May 14 2013 About the Mohave Chemehuevi Hopi and Navajo Tribes Colorado River Indian Tribes 2009 Archived from the original on August 12 2021 Retrieved April 10 2012 The Colorado River Indian Tribes C R I T Reservation and Extension Programs PDF University of Arizona College of Agriculture and Life Sciences Indian Country Extension October 2008 Archived from the original PDF on January 20 2013 Retrieved April 10 2012 Navajo Nation Indian Health Service Archived from the original on June 23 2012 Retrieved April 10 2012 Treaty Between the United States of America and the Navajo Tribe of Indians Historic Documents New Mexico State University 1868 Archived from the original on March 11 2002 Retrieved April 10 2012 Navajo Nation Facts at a Glance The Navajo Nation 2004 Archived from the original on March 8 2012 Retrieved April 10 2012 Brown 1972 pp 52 53 Casey 2007 p 251 Lindberg 2009 pp 134 135 Chapter 5 The Utes in Southwestern Colorado A Confrontation of Cultures Frontier in Transition A History of Southwestern Colorado U S National Park Service Retrieved May 15 2017 GJ HISTORY Grand Junction town founder George A Crawford A witness to early American history The Post Independent September 26 2013 Retrieved August 20 2024 Glenwood Canyon time travel A journey back through the history of travel through the Grand River Canon passage August 15 2021 St Thomas Nevada U S National Park Service December 15 2022 Retrieved August 20 2024 Glass amp Glass 1983 pp 162 163 Hole in the Rock U S National Park Service July 28 2023 Retrieved August 20 2024 Howard Jerry B Hohokam Legacy Desert Canals WaterHistory org Archived from the original on January 24 2012 Retrieved April 9 2012 Williams O A 1937 Settlement and Growth of the Gila Valley as a Mormon Colony 1879 1900 PDF University of Arizona Archived from the original PDF on January 20 2013 Retrieved February 20 2012 Lees Ferry History Glen Canyon National Recreational Area U S National Park Service August 11 2006 Archived from the original on April 14 2012 Retrieved February 20 2012 Lees Ferry Arizona State University July 8 2010 Archived from the original on June 3 2012 Retrieved February 20 2012 The Moffat Road and Northwestern Colorado 1903 1948 BLM Cultural Resource Series An Isolated Empire A History of Northwest Colorado U S National Park Service Retrieved August 20 2024 Black Canyon of the Gunnison Narrow Gauge Railroad U S National Park Service December 2 2022 Retrieved August 20 2024 Colorado River Water Conservation District December 23 2003 Many Years Ago the Colorado River Was Just Grand SummitDaily Archived from the original on April 30 2011 Retrieved January 5 2008 Barnes 1988 p 104 USGS Gage 09328500 on the San Rafael River near Green River Utah PDF National Water Information System U S Geological Survey 1910 2012 Archived PDF from the original on September 19 2015 Retrieved June 22 2013 Runyon Luke December 20 2017 How the Grand Became the Colorado And What It Says About Our Relationship To Nature KUNC University of Colorado Boulder Retrieved August 20 2024 House Joint Resolution 32 To change the name of the Grand River in Colorado and Utah to the Colorado River PDF Congressional Record Sixty seventh United States Congress July 25 1921 p 4274 Archived PDF from the original on May 16 2023 Retrieved May 29 2023 Colorado River Basin Water Supply and Demand Study PDF U S Bureau of Reclamation December 2012 Archived PDF from the original on May 20 2022 Retrieved May 18 2022 Davis Eric F The Colorado River Controversy PDF Michigan State University Archived from the original PDF on October 1 2004 Low Water May Halt Hoover Dam s Power Circle of Blue September 22 2010 Archived from the original on January 20 2013 Retrieved October 8 2012 Hydropower Glen Canyon Dam Adaptive Management Program November 18 2010 Archived from the original on May 22 2012 Retrieved May 12 2012 Waterman Jonathan August 11 2010 Restoring floods to America s Nile National Geographic Archived from the original on March 24 2012 Retrieved March 2 2012 Nabhan Gary Paul January 16 2007 The Beginning and the End of the Colorado River Protecting the Sources Ensuring its Courses Northern Arizona University Archived from the original on December 25 2011 Retrieved February 20 2012 Reisner 1993 p 120 Colorado River Law Southern Nevada Water Authority Archived from the original on April 26 2012 Retrieved February 20 2012 Colorado River Compact 1922 PDF U S Bureau of Reclamation Archived from the original PDF on September 15 2012 Retrieved February 20 2012 Utilization of Waters of the Colorado and Tijuana Rivers and of the Rio Grande Treaty Between the United States of America and Mexico PDF International Boundary and Water Commission February 3 1944 Archived from the original PDF on September 15 2012 Retrieved February 20 2012 Colorado River GOOD Magazine Archived from the original on July 20 2012 Retrieved February 26 2012 Big changes are coming for the Colorado River soon and they could get messy Environment August 15 2022 Archived from the original on August 15 2022 Retrieved August 16 2022 Anderson Larry May 2002 Utah s Perspective The Colorado River PDF Utah Division of Water Resources Archived from the original PDF on April 9 2014 Retrieved February 20 2012 The Law of the River U S Bureau of Reclamation March 2008 Archived from the original on June 26 2012 Retrieved February 18 2012 Dams Along the Lower Colorado River U S Bureau of Reclamation Archived from the original on May 17 2022 Retrieved May 18 2022 Appendix I The Past Present and Future of Transmountain Diversion Projects PDF Roaring Fork Watershed Plan Roaring Fork Conservancy Archived from the original PDF on January 20 2013 Retrieved March 18 2012 Transmountain Water Diversions PDF Colorado River District July 2011 Archived from the original PDF on December 1 2011 Retrieved March 18 2012 Citizen s Guide to Colorado s Transbasin Diversions Water Education Colorado 2014 Archived from the original on May 19 2022 Retrieved May 19 2022 Transmountain Diversions Roaring Fork Conservancy Archived from the original on May 18 2022 Retrieved May 18 2022 Colorado Big Thompson Project U S Bureau of Reclamation October 18 2011 Archived from the original on November 12 2011 Retrieved February 20 2012 Moving Water in the Watershed Blue River Watershed Group Archived from the original on March 29 2012 Retrieved May 18 2012 Wahlstrom Ernest E 1974 History of Geologic Investigations Engineering Design and Construction Methods of the Harold D Roberts Tunnel Colorado PDF Geological Survey Professional Paper 831 A U S Geological Survey Archived PDF from the original on August 19 2021 Retrieved May 18 2012 Fryingpan Arkansas Project U S Bureau of Reclamation May 10 2011 Archived from the original on August 27 2014 Retrieved May 18 2012 Williams Fork Reservoir Denver Water Archived from the original on May 22 2022 Retrieved May 18 2022 Wolford Mountain Reservoir Colorado River District Archived from the original on May 20 2022 Retrieved May 18 2022 Dwyer John J The Agrarian Dispute The Expropriation of American Owned Rural Land in Postrevolutionary Mexico Durham Duke University Press 2008 Kerig Dorothy P Yankee Enclave The Colorado River Land Company and Mexican Agrarian Reform in Baja California 1902 1944 PhD diss University of California Irvine 1988 Castillo Munoz Veronica The Other California Land Identities and Politics on the Mexican Borderlands Oakland University of California Press 2017 Billington Jackson amp Melosi 2005 p 140 Sperry Robert L Winter 1975 When The Imperial Valley Fought For Its Life The Journal of San Diego History 21 1 San Diego History Center Archived from the original on June 26 2023 Retrieved June 25 2023 Patten McCaskie and Unitt pp 4 5 Origin of the Salton Sea Suburban Emergency Management Project Archived from the original on July 18 2011 Billington Jackson amp Melosi 2005 pp 141 142 Boulder Canyon Project Hoover Dam U S Bureau of Reclamation February 1 2012 Archived from the original on October 11 2012 Retrieved October 9 2012 The Colorado River and Hoover Dam Facts and Figures U S Bureau of Reclamation January 2012 Archived from the original on May 14 2012 Retrieved February 20 2012 Boulder Canyon Project Act 1928 National Archives September 21 2021 Archived from the original on May 18 2022 Retrieved May 18 2022 All American Canal California Mexico border Earth Observatory National Aeronautics and Space Administration February 23 2009 Archived from the original on August 19 2021 Retrieved February 20 2012 About IID Water Imperial Irrigation District Archived from the original on May 6 2022 Retrieved May 18 2022 CRBSCP Coachella Canal Unit Title I U S Bureau of Reclamation Archived from the original on May 19 2022 Retrieved May 18 2022 Parker Dam Parker Davis Project U S Bureau of Reclamation June 29 2009 Archived from the original on September 27 2012 Retrieved February 20 2012 Marie Bell Tina 1997 Gila Project PDF U S Bureau of Reclamation Archived from the original PDF on February 24 2012 Retrieved February 28 2012 The Colorado River A Regional Solution Los Angeles Department of Water and Power Archived from the original on March 4 2012 Retrieved February 28 2012 San Diego Project U S Bureau of Reclamation January 11 2012 Archived from the original on March 16 2012 Retrieved March 16 2012 Nevada Colorado River Water Users Association Archived from the original on November 4 2013 Retrieved November 2 2013 Fradkin 1996 p 191 Colorado River Storage Project U S Bureau of Reclamation Archived from the original on November 8 2019 Retrieved May 18 2022 Chapter IX Dinosaur National Monument A Survey of the Recreational Resources of the Colorado River Basin U S National Park Service September 6 2004 Archived from the original on November 3 2013 Retrieved February 20 2012 Historic Opposition to Glen Canyon Dam The End of Lake Powell Campaign Colorado Riverkeeper July 20 2004 Archived from the original on December 28 2013 Retrieved November 2 2013 Resurrection Buried Treasure National Audubon Society 2006 Archived from the original on January 20 2013 Retrieved February 20 2012 The Central Utah Project An Overview U S Department of the Interior April 3 2019 Archived from the original on May 20 2022 Retrieved May 18 2022 Glaser Leah S San Juan Chama Project U S Bureau of Reclamation Archived from the original on March 8 2022 Retrieved May 18 2022 Pacific Southwest Water Plan PDF U S Bureau of Reclamation January 1964 Archived PDF from the original on September 4 2021 Retrieved May 18 2022
