Colorado River
Major river in the western United States and Mexico
The Colorado River () is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and in northern Mexico. The 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.
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 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, 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 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 wide, the depth ranging from , with a few notable exceptions, such as the Blackrocks reach where the river is nearly 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 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 into the Colorado Plateau, exposing some of the oldest visible rocks on Earth, dating as long ago as 2 billion years. The 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 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 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 wide and reaching up to across, with depths ranging from . 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 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 of northwestern Mexico. A large estuary is formed here before the Colorado empties into the Gulf about south of Yuma. Occasionally the International Boundary and Water Commission allows a springtime pulse flow 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.
Drainage basin.
The Colorado River Basin consists of , making it the seventh largest drainage basin in North America. About , 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 Rio Grande Basin. 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 . Lees Ferry, more than halfway along the Colorado River from its source, is above sea level. The highest point in the Colorado River Basin is Uncompahgre Peak in Colorado's San Juan Mountains, while some water from the river drains via irrigation run-off into California's Salton Sea, 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 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 in the Upper Basin and in the Lower Basin, and lows average , respectively. Annual precipitation averages , ranging from over in some areas of the Rockies to less than 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 , or an annualized discharge of , for the 1906–2023 period. River flows at the Lees Ferry stream gauge, about halfway along the length of the Colorado and 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 , and the Gila–Salt River system historically accounted for another . While much of this water was lost to evaporation in the deserts of the Lower Basin, anywhere from 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 in the spring melt and falling as low as 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 in May to 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, 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 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.
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 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 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 high, backing the river up for nearly 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 passed through the Grand Canyon, reaching peak discharges as great as .
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.
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. Exploration by steamboat soon advanced upriver. In 1857, George A. Johnson in the "General Jesup" was able to reach Pyramid Canyon, over north of Fort Yuma. 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. 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.
<templatestyles src="Template:Blockquote/styles.css" />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.
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. 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".
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 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 , but with the caveat that California's 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 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 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 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 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 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 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, 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 , 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 south of the Salton Sea. The Coachella Canal, which branches northward from the All-American Canal, irrigates another 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 on the Arizona side of the river. By 1941, the long Colorado River Aqueduct was completed, delivering 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 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 vowed 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 per year from the Green River basin to the Wasatch Front, and the San Juan–Chama Project, which diverts 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 from the Colorado River at Parker Dam to Tucson, Arizona. It delivers of water per year, irrigates 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 allotment from New Mexico.
Post-2000 water supply.
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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 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 , with a natural flow at the mouth around . 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 , 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 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 had 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, a scenario referred to as "dead pool". 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 a "dead pool", 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 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 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 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 , 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 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 at the height of summer to near freezing in winter, but modern flows through the Grand Canyon, for example, rarely deviate significantly from . 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 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 , was initiated on March 21, 2014, with the aim of revitalising 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 over the following three years, just a small fraction of its average flow before damming.
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 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.
Notes.
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References.
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Works cited.
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Further reading.
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Tucson, Arizona
City in Arizona, United States
Tucson (; ; ) is a city in Pima County, Arizona, United States, and its county seat. It is the second-most populous city in Arizona, behind Phoenix, with a population of 542,629 in the 2020 United States census. The Tucson metropolitan statistical area had 1.043 million residents in 2020 and forms part of the Tucson-Nogales combined statistical area. Both Tucson and Phoenix anchor the Arizona Sun Corridor. The city is southeast of Phoenix and north of the United States–Mexico border It is home to the University of Arizona.
Major incorporated suburbs of Tucson include Oro Valley and Marana northwest of the city, Sahuarita south of the city, and South Tucson in an enclave south of downtown. Communities in the vicinity of Tucson (some within or overlapping the city limits) include Casas Adobes, Catalina Foothills, Flowing Wells, Midvale Park, Tanque Verde, Tortolita, and Vail. Towns outside the Tucson metropolitan area include Three Points, Benson to the southeast, Catalina and Oracle to the north, and Green Valley to the south.
Tucson was founded as a military fort by the Spanish when Hugo O'Conor authorized the construction of Presidio San Agustín del Tucsón in 1775. It was included in the state of Sonora after Mexico gained independence from the Spanish Empire in 1821. The United States acquired a region of present-day southern Arizona and southwestern New Mexico from Mexico under the Gadsden Purchase in 1853. Tucson served as the capital of the Arizona Territory from 1867 to 1877. Tucson was Arizona's largest city by population during the territorial period and early statehood, until it was surpassed by Phoenix by 1920. Nevertheless, its population growth remained strong during the late 20th century. Tucson was the first American city to be designated a "City of Gastronomy" by UNESCO in 2015.
The Spanish name of the city, (), is derived from the O'odham (). is a stative verb meaning "(be) black, (be) dark". is (in this usage) a noun referring to the base or foundation of something. The name is commonly translated into English as "the base [of the hill] is black", a reference to a basalt-covered hill now known as Sentinel Peak. Tucson is sometimes referred to as the Old Pueblo and Optics Valley, the latter referring to its optical science and telescopes known worldwide.
History.
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Historical affiliations
 Spanish Empire 1775–1821 First Mexican Empire 1821–1823 United Mexican States 1823–1854 1854–present
The Tucson area was probably first visited by Paleo-Indians, who were known to have been in southern Arizona about 12,000 years ago. Recent archaeological excavations near the Santa Cruz River found a village site dating from 2100 BC. The floodplain of the Santa Cruz River was extensively farmed during the Early Agricultural Period, c. 1200 BC to AD 150. These people hunted, gathered wild plants and nuts, and ate corn, beans, and other crops grown using irrigation canals they constructed.
The Early Ceramic period occupation of Tucson had the first extensive use of pottery vessels for cooking and storage. The groups designated as the Hohokam lived in the area from AD 600 to 1450 and are known for their vast irrigation canal systems and their red-on-brown pottery.
Italian Jesuit missionary Eusebio Francisco Kino first visited the Santa Cruz River valley in 1692. He founded the Mission San Xavier del Bac in 1700, about upstream from the site of the settlement of Tucson. A separate Convento settlement was founded downstream along the Santa Cruz River, near the base of what is now known as "A" mountain. Hugo Oconór (Hugo O'Conor), the founding father of the city of Tucson, Arizona, authorized the construction of a military fort in that location, "Presidio San Agustín del Tucsón," on August 20, 1775 (the present downtown Pima County Courthouse was built near this site). During the Spanish period of the presidio, attacks such as the Second Battle of Tucson were repeatedly mounted by the Apache. Eventually, the town came to be called "Tucsón," a Spanish version of the O'odham word for the area. It was included in the state of Sonora after Mexico gained independence from the Kingdom of Spain and its Spanish Empire in 1821
During the Mexican–American War in 1846–1848, Tucsón was captured by Philip St. George Cooke with the Mormon Battalion, but it soon returned to Mexican control as Cooke proceeded to the west, establishing Cooke's Wagon Road to California. Tucsón was not included in the Mexican Cession to the United States following the war. Cooke's road through Tucsón became one of the important routes into California during the California Gold Rush of 1849.
The US acquired those portions of modern-day Arizona that lay south of the Gila River by treaty from Mexico in the Gadsden Purchase on June 8, 1854. Under this treaty and purchase, Tucsón became a part of the United States of America. The American military did not formally take over control until March 1856. In time, the name of the town became standardized in English in its current form, where the stress is on the first syllable, the "u" is long, and the "c" is silent.
In 1857, Tucson was established as a stage station on the San Antonio–San Diego Mail Line. In 1858, it became third division headquarters of the Butterfield Overland Mail and operated until the line was shut down in March 1861. The Overland Mail Corporation attempted to continue running, but following the Bascom Affair, devastating Apache attacks on the stations and coaches ended operations in August 1861.
Tucson was incorporated in 1877, making it the oldest incorporated city in Arizona.
From 1877 to 1878, the area suffered a rash of stagecoach robberies. Most notable were the two holdups committed by masked road agent William Whitney Brazelton. Brazelton held up two stages in the summer of 1878 near Point of Mountain Station, about northwest of Tucson. John Clum, of Tombstone, Arizona, fame, was one of the passengers. Pima County Sheriff Charles A. Shibell and his citizen posse killed Brazelton on August 19, 1878, in a mesquite bosque along the Santa Cruz River south of Tucson. Brazelton had been suspected of highway robbery in the Tucson area, the Prescott region, and the Silver City, New Mexico area. Because of the crimes and threats to his business, John J. Valentine Sr. of Wells, Fargo & Co. had sent Bob Paul, a special agent and future Pima County sheriff, to investigate. The US Army established Fort Lowell, then east of Tucson, to help protect settlers and travelers from Apache attacks.
In 1882, Morgan Earp was fatally shot, in what was later referred to in the press as the "Earp–Clanton Tragedy". Marietta Spence, wife of Pete Spence, one of the Cochise County Cowboys, testified at the coroner's inquest on Earp's killing and implicated Frank Stilwell in the murder. The coroner's jury concluded Pete Spence, Stilwell, Frederick Bode, and Florentino "Indian Charlie" Cruz were the prime suspects in the assassination of Morgan Earp.
Deputy U.S. Marshal Wyatt Earp gathered a few trusted friends and accompanied Virgil Earp and his family as they traveled to Benson to take a train to California. They found Stilwell apparently lying in wait for Virgil Earp at the Tucson station and killed Stilwell on the tracks. After killing Stilwell, Wyatt deputized others and conducted a vendetta, killing three more cowboys over the next few days before leaving the territory.
Jim Leavy had built a reputation of having fought in at least 16 gunfights. On June 5, 1882, Leavy had an argument with faro dealer John Murphy in Tucson. The two agreed to have a duel on the Mexican border, but after hearing of Leavy's exploits as a gunfighter, Murphy decided to ambush Leavy instead. Together with two of his friends, Murphy ambushed Leavy as he was leaving the Palace Hotel, killing him. According to Wright, the three co-defendants in Leavy's murder later escaped from the Pima County Jail, but were later recaptured. Murphy and Gibson were found in Fenner, California, living under assumed names; they were retried for the murder before being found not guilty. Moyer was captured in Denver and sentenced to life in Yuma Territorial Prison, but was pardoned in 1888.
Post-frontier life.
As other settlers tried to overcome violent frontier society, in 1885, the territorial legislature founded the University of Arizona as a land-grant college on what was overgrazed ranchland between Tucson and Fort Lowell.
In 1890, Asians made up 4.2% of the city's population. They were predominantly Chinese men who had been recruited as workers on the railroads.
By 1900, 7,531 people lived in Tucson. By 1910, the population increased to 13,913. About this time, the U.S. Veterans Administration had begun construction of the present Veterans Hospital. The city's clean, dry air made it a destination for many veterans who had been gassed in World War I and needed respiratory therapy. In addition, these dry and high-altitude conditions were thought to be ideal for the treatment of tuberculosis, for which no cures were known before antibiotics were developed against it.
The city continued to grow, with the population increasing to 20,292 in 1920 and 36,818 in 1940. In 2006, the estimated population of Pima County, in which Tucson is located, passed one million, while the City of Tucson's population was 535,000.
In 1912, Arizona was admitted as a state. This increased the number of flags that had been flown over Tucson to five: Spanish, Mexican, United States, Confederate, and the State of Arizona.
During the territorial and early statehood periods, Tucson was Arizona's largest city and commercial center, while Phoenix was the seat of state government (beginning in 1889) and agriculture. The development of Tucson Municipal Airport increased the city's prominence. Between 1910 and 1920, though, Phoenix surpassed Tucson in population, and has continued to outpace Tucson in growth. In recent years, both Tucson and Phoenix have had some of the highest growth rates of any jurisdiction in the United States.
Geography.
According to the United States Census Bureau, as of 2010, the City of Tucson has a land area of . The city's elevation is above sea level (as measured at the Tucson International Airport). Tucson is on an alluvial plain in the Sonoran Desert, surrounded by five minor ranges of mountains: the Santa Catalina Mountains and the Tortolita Mountains to the north, the Santa Rita Mountains to the south, the Rincon Mountains to the east, and the Tucson Mountains to the west. Tucson Mountains include Wasson Peak. The highest point in the area is Mount Wrightson, found in the Santa Rita Mountains at above sea level.
Tucson is southeast of Phoenix and north of the United States–Mexico border. The 2020 United States census puts the city's population at 542,629 with a metropolitan area population at 1,043,433. In 2020, Tucson ranked as the 33rd-largest city and 53rd-largest metropolitan area in the United States. A major city in the Arizona Sun Corridor, Tucson is the largest city in southern Arizona, and the second-largest in the state after Phoenix. It is also the largest city in the area of the historic Gadsden Purchase. As of 2015, the Greater Tucson Metro area has exceeded a population of 1 million.
The city is built along the Santa Cruz River, formerly a perennial river. Now a dry riverbed for much of the year, it regularly floods during significant seasonal rains.
Interstate 10 runs northwest through town, connecting Tucson to Phoenix to the northwest (on the way to its western terminus in Santa Monica, California), and to Las Cruces, New Mexico and El Paso, Texas to the southeast. (Its eastern terminus is in Jacksonville, Florida).
I-19 runs south from Tucson toward Nogales and the U.S.–Mexico border. I-19 is the only Interstate highway that uses "kilometer posts" instead of "mileposts". However, speed limits are marked in miles per hour and kilometers per hour.
Neighborhoods.
Downtown and Central Tucson.
Similar to many other cities in the Western US, Tucson was developed by European Americans on a grid plan starting in the late 19th century, with the city center at Stone Avenue and Broadway Boulevard. While this intersection was initially near the geographic center of Tucson, the center has shifted as the city has expanded far to the east. Development to the west was effectively blocked by the Tucson Mountains. Covering a large geographic area, Tucson has many distinct neighborhoods.
Tucson's earliest neighborhoods, some of which were redeveloped and covered by the Tucson Convention Center (TCC), include:
Other historical neighborhoods near downtown include:
At the end of the 2010s, city planners and the business community worked to redevelop downtown Tucson. The primary project was Rio Nuevo, a large retail and community center that had been stalled in planning for more than a decade. One Rio Nuevo project that was successful is Mission Garden. Related to Tucson's City of Gastronomy designation, this living agricultural museum at the base of Sentinel Peak west of downtown grows heritage crops and heirloom trees that represent people who have lived in the area for thousands of years. Downtown is generally regarded as the area bordered by 17th Street to the south, I-10 to the west, and 6th Street to the north, and Toole Avenue and the Union Pacific (formerly Southern Pacific) railroad tracks, site of the historic train depot on the east side. Downtown is divided into the Presidio District, the Barrio Viejo, and the Congress Street Arts and Entertainment District. Some authorities include the 4th Avenue shopping district, northeast of the rest of downtown and connected by an underpass beneath the UPRR tracks.
Historic attractions downtown with rich architecture include the Hotel Congress designed in 1919, the Art Deco Fox Theatre designed in 1929, the Rialto Theatre opened in 1920, and St. Augustine Cathedral completed in 1896. Included on the National Register of Historic Places is the old Pima County Courthouse, designed by Roy Place in 1928. El Charro Café, Tucson's oldest restaurant, operates its main location downtown.
As one of the oldest parts of town, Central Tucson is anchored by the Broadway Village shopping center, designed by local architect Josias Joesler at the intersection of Broadway Boulevard and Country Club Road. The 4th Avenue Shopping District between downtown, the university, and the Lost Barrio just east of downtown, also has many unique and popular stores. Local retail business in Central Tucson is densely concentrated along Fourth Avenue and the Main Gate Square on University Boulevard near the UA campus. El Con Mall is also in the eastern part of midtown.
The University of Arizona, chartered in 1885, is in midtown and includes Arizona Stadium and McKale Center (named for J.F. "Pop" McKale, a prominent coach and athletics administrator at the university).
The historic Tucson High School (designed by Roy Place in 1924) was featured in the 1987 film "Can't Buy Me Love". The Arizona Inn (built in 1930) and the Tucson Botanical Gardens are also in Central Tucson.
Tucson's largest park, Reid Park, is in midtown and includes Reid Park Zoo and Hi Corbett Field. Speedway Boulevard, a major east–west arterial road in central Tucson, was named the "ugliest street in America" by "Life" in the early 1970s, quoting Tucson Mayor James Corbett.
In the late 1990s, Speedway Boulevard was awarded "Street of the Year" by "Arizona Highways." Speedway Boulevard was named after an historic horse racetrack, known as the Harlem River Speedway, and more commonly called "The Speedway", in New York City. The Tucson street was called "The Speedway" from 1904 to about 1906, when "The" was removed from the title.
As of the early 21st century, Central Tucson is considered bicycle-friendly. To the east of the University of Arizona, Third Street is bike-only except for local traffic; it passes by the historic homes of the Sam Hughes neighborhood. To the west, East University Boulevard leads to the Fourth Avenue Shopping District. To the North, North Mountain Avenue has a full bike-only lane for half of the to the Rillito River Park bike and walk multi-use path. To the south, North Highland Avenue leads to the Barraza-Aviation Parkway bicycle path.
Southern Tucson.
South Tucson is the name of an independent, incorporated town of south of downtown. It is surrounded by the City of Tucson and was incorporated in 1936 and reincorporated in 1940.
The population is about 83% Mexican-American and 10% Native American, as residents self-identify in the census. South Tucson is widely known for its many Mexican restaurants and architectural styles. Bright murals have been painted on some walls, but city policy discourages this and many have been painted over.
The south side of the city of Tucson is generally considered to be the area around south of 22nd Street, east of I-19, west of Davis Monthan Air Force Base and southwest of Aviation Parkway, and north of Los Reales Road. The Tucson International Airport and Tucson Electric Park are located here.
Western Tucson.
The West Side has areas of both urban and suburban development. It is generally defined as the area west of I-10. Western Tucson encompasses the banks of the Santa Cruz River and the foothills of the Tucson Mountains. Area attractions include the International Wildlife Museum and Sentinel Peak. The Marriott Starr Pass Resort and Spa serves travelers and residents. As travelers pass the Tucson Mountains, they enter the area commonly referred to as "west of" Tucson or "Old West Tucson". In this large, undulating plain extending south into the Altar Valley, rural residential development predominates. Attractions include Saguaro National Park West, and movie set/theme park developed at the Old Tucson Studios.
On Sentinel Peak, just west of downtown, a giant "A" was installed in honor of the University of Arizona, resulting in the nickname "A" Mountain. Starting in about 1915, an annual tradition developed for freshmen to whitewash the A, which was visible for miles. After the September 11 terrorist attacks, the A was painted red, white, and blue. At the beginning of the Iraq War in 2003, antiwar activists painted the A black. Competition ensued, with various sides repainting the A in different colors until the city council intervened and made the red, white, and blue colors official. In 2013, the color scheme changed back to white. Another color may be decided by a biennial election. With the tricolor scheme, some observers complain the shape of the A is hard to distinguish from the background of the peak. Since 1993, the A has been painted green for St. Patrick's Day. It has also been given other color schemes for different causes.
Northern Tucson.
North Tucson includes the urban neighborhoods of Amphitheater and Flowing Wells. Usually considered the area north of Fort Lowell Road, North Tucson includes some of Tucson's primary commercial zones (Tucson Mall and the Oracle Road Corridor). Many of the city's most upscale boutiques, restaurants, and art galleries are also on the north side, including St. Philip's Plaza. The plaza is directly adjacent to the historic St. Philip's in the Hills Episcopal Church (built in 1936).
The north side also is home to the suburban community of Catalina Foothills, in the foothills of the Santa Catalina Mountains just north of the city limits. This community includes many of the area's most expensive homes, sometimes multimillion-dollar estates. The Foothills area is generally defined as north of River Road, east of Oracle Road and west of Sabino Creek. Some of the Tucson area's major resorts are in the Catalina Foothills, including Hacienda Del Sol, Westin La Paloma Resort, Loews Ventana Canyon Resort and Canyon Ranch Resort. La Encantada, an outdoor shopping mall, is also in the Foothills.
The DeGrazia Gallery of the Sun is near the intersection of Swan Road and Skyline Drive. Built by artist Ted DeGrazia starting in 1951, the property is listed on the National Register of Historic Places and features an eclectic chapel, an art gallery, and a museum.
The expansive area northwest of the city limits is diverse, ranging from the rural communities of Catalina and parts of the town of Marana, the small suburb of Picture Rocks, the town of Oro Valley in the western foothills of the Santa Catalina Mountains, and residential areas in the northeastern foothills of the Tucson Mountains. Continental Ranch (Marana), Dove Mountain (Marana), and Rancho Vistoso (Oro Valley), and Saddlebrooke (North Oro Valley) are all master planned communities in the northwest that have thousands of residents.
The community of Casas Adobes is also on the Northwest side, with the distinction of being Tucson's first suburb, established in the late 1940s. Casas Adobes is centered on the historic Casas Adobes Plaza (built in 1948). Casas Adobes is also home to Tohono Chul Park, which is now within the town of Oro Valley, (a nature preserve) near the intersection of North Oracle Road and West Ina Road. The attempted assassination of Representative Gabby Giffords, which resulted in the murders of chief judge for the U.S. District Court for Arizona, John Roll, and five other people on January 8, 2011, occurred at the La Toscana Village in Casas Adobes. The Foothills Mall is also on the northwest side in Casas Adobes.
This area is home to many of the Tucson area's golf courses and resorts, including the Preserve and Mountainview Golf Clubs at Saddlebrooke, Hilton El Conquistador Golf & Tennis Resort in Oro Valley, the Omni Tucson National Resort & Spa, and Westward Look Resort. The Ritz Carlton at Dove Mountain, the second Ritz Carlton resort in Arizona, which also includes a golf course, opened in the foothills of the Tortolita Mountains in northeast Marana in 2009.
Eastern Tucson.
East Tucson is relatively new compared to other parts of the city, developed between the 1950s and the 1970s, with developments such as Desert Palms Park. It is generally classified as the area of the city east of Swan Road, with above-average real estate values relative to the rest of the city. The area includes urban and suburban development near the Rincon Mountains. East Tucson includes Saguaro National Park East. Tucson's "Restaurant Row" is also on the east side, along with a significant corporate and financial presence. Restaurant Row is sandwiched by three of Tucson's storied Vicinages: Harold Bell Wright Estates, named after the author's ranch which occupied some of that area before the depression; the Tucson Country Club (the third to bear the name Tucson Country Club), and the Dorado Country Club. Tucson's largest office building is 5151 East Broadway in east Tucson, completed in 1975. The first phases of Williams Centre, a mixed-use, master-planned development on Broadway near Craycroft Road, were opened in 1987. Park Place, a recently renovated shopping center, is also along Broadway (west of Wilmot Road).
Near the intersection of Craycroft and Ft. Lowell Roads are the remnants of the Historic Fort Lowell. This area has become one of Tucson's iconic neighborhoods. In 1891, the Fort was abandoned and much of the interior was stripped of their useful components and it quickly fell into ruin. In 1900, three of the officer buildings were purchased for use as a sanitarium. The sanitarium was then sold to Harvey Adkins in 1928. The Bolsius family – Pete, Nan and Charles – purchased and renovated surviving adobe buildings of the Fort, transforming them into spectacular artistic southwestern architectural examples. Their woodwork, plaster treatment and sense of proportion drew on their Dutch heritage and New Mexican experience.
Other artists and academics throughout the middle of the 20th century, including Win Ellis, Jack Maul, Madame Germaine Cheruy and René Cheruy, Giorgio Belloli, Charles Bode, Veronica Hughart, Edward H. Spicer and Rosamond Spicer, Hazel Larson Archer and Ruth Brown, renovated adobes, built homes and lived in the area. The artist colony attracted writers and poets including beat generation Alan Harrington and Jack Kerouac whose visit is documented in his iconic book "On the Road". This rural pocket in the middle of the city is listed on the National Register of Historic Places. Each year in February the vicinage celebrates its history in the City Landmark it owns and restored the San Pedro Chapel.
Situated between the Santa Catalina Mountains and the Rincon Mountains near Redington Pass northeast of the city limits is the affluent community of Tanque Verde. The Arizona National Golf Club, Forty-Niners Country Club, and the historic Tanque Verde Guest Ranch are also in northeast Tucson.
Southeast Tucson continues to experience rapid residential development. The area includes Davis-Monthan Air Force Base. The area is considered to be south of Golf Links Road. It is the home of Santa Rita High School, Chuck Ford Park (Lakeside Park), Lakeside Lake, Lincoln Park (upper and lower), The Lakecrest Vicinagess, and Pima Community College East Campus. The Atterbury Wash with its access to excellent bird watching is also in the Southeast Tucson area. The suburban community of Rita Ranch houses many of the military families from Davis-Monthan, and is near the southeasternmost expansion of the current city limits. Close by Rita Ranch and also within the city limits lies Civano, a planned development meant to showcase ecologically sound building practices and lifestyles.
Climate.
Tucson has a hot desert climate (Köppen "BWh"), with two major seasons, a hot summer and mild winter. Tucson averages of precipitation per year, concentrated during the Pacific storms of winter and the North American Monsoon of summer. Fall and spring tend to be sunny and dry. Despite being at a more southerly latitude than Phoenix, Tucson is slightly cooler and wetter due to a variety of factors, including elevation and orographic lift in surrounding mountains, though Tucson does occasionally see warmer daytime temperatures in the winter.
Summer is characterized by average daily high temperatures between and low temperatures between . Early summer is characterized by low humidity and clear skies; mid- and late summer are characterized by higher humidity, cloudy skies, and frequent rain. The sun is intense in Tucson during part of the year, and those who spend time outdoors need protection. Recent studies show that the rate of skin cancer in Arizona is at least three times higher than in more northerly regions. Additionally, heat stroke is a concern for hikers, mountain bikers, and adventurers who explore canyons, open desert lands, and other exposed areas.
While monsoon season officially begins on June 15, the arrival of the North American Monsoon is unpredictable, as it varies from year to year. On average, Tucson receives its first monsoon storms around July 3. Monsoon activity generally persists through August and often into September. During the monsoon, the humidity is much higher than the rest of the year. It begins with clouds building up from the south in the early afternoon, followed by intense thunderstorms and rainfall, which can cause flash floods. The evening sky at this time of year is often pierced with dramatic lightning strikes. Large areas of the city do not have storm sewers, so monsoon rains flood the main thoroughfares, usually for no longer than a few hours. A few underpasses in Tucson have "feet of water" scales painted on their supports to discourage fording by automobiles during a rainstorm. Arizona traffic code Title 28–910, the so-called "Stupid Motorist Law", was instituted in 1995 to discourage people from entering flooded roadways. If the road is flooded and a barricade is in place, motorists who drive around the barricade can be charged up to $2000 for costs involved in rescuing them. Despite the warnings and precautions, three Tucson drivers have drowned between 2004 and 2010.
The weather in the fall is much like spring, dry, with warm/cool nights and warm/hot days. Temperatures above are possible into early October. Temperatures decline at the quickest rate in October and November, and are normally the coolest in late December and early January.
Winters in Tucson are mild relative to other parts of the United States. Average daytime highs range between , with overnight lows between . Tucson typically averages three hard freezes per winter season, with temperatures dipping to the mid- or low 20 degrees F (−4 to −7 °C), but this is typically limited to only a very few nights. Although rare, snow occasionally falls in lower elevations in Tucson and is common in the Santa Catalina Mountains. The most recent snowfall was on March 2, 2023, when a winter storm caused snow to fall throughout most of the southwest. Tucson airport recorded of snow, the seventh heaviest March snowfall on record.
Early spring is characterized by gradually rising temperatures and several weeks of vivid wildflower blooms beginning in late February and into March. During this time of year the diurnal temperature variation occurs with a temperature change often surpassing daily.
Since records began in 1894, the record maximum temperature was on June 27, 1990, and the record minimum temperature was on January 7, 1913. There are an average of 158 days annually with highs of or higher and an average of 12 days with lows reaching or below the freezing mark. Average annual precipitation is . On average, 47.4 days have measurable precipitation. The wettest year was 1905, with and the driest year was 2020 with . The most precipitation in one month was in July 2021. The most precipitation in 24 hours was on July 29, 1958. Annual snowfall averages . The most snow in one winter was in winter 1971–1972. The most snow in one month was in December 1971.
Demographics.
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According to 2020 United States census, the racial composition of Tucson was:
According to the 2010 American Census Bureau, the racial composition of Tucson was:
2020 census.
As of the census of 2010, 520,116 people, 229,762 households, and 112,455 families resided in the city. The population density was . The 209,609 dwelling units had an average density of . The racial makeup of the city was 69.7% White (down from 94.8% in 1970), 5.0% Black or African-American, 2.7% Native American, 2.9% Asian, 0.2% Pacific Islander, 16.9% from other races, and 3.8% from two or more races. Hispanics or Latinos of any race were 41.6% of the population. Non-Hispanic Whites were 47.2% of the population in 2010, down from 72.8% in 1970.
The largest ancestries reported in Tucson according to 2022 estimates were Mexican (39.9%), German (11%), English (7.7%), Italian (3.4%), American (2.8%), and Polish (1.8%).
According to research by demographer William H. Frey using data from the 2010 United States census, Tucson has the lowest level of Black-White segregation of any of the 100 largest metropolitan areas in the United States.
Of the 192,891 households, 29.0% had children under 18 living with them, 39.7% were married couples living together, 13.8% had a female householder with no husband present, and 41.7% were not families. About 32.3% of all households were made up of individuals, and 9.3% had someone living alone who was 65 or older. The average household size was 2.42, and the average family size was 3.12.
In the inner city, the population has 24.6% under 18, 13.8% from 18 to 24, 30.5% from 25 to 44, 19.2% from 45 to 64, and 11.9% who were 65 or older. The median age was 32 years. For every 100 females, there were 96.0 males. For every 100 females 18 and over, there were 93.3 males.
The median income for a household in the city was $30,981, and for a family was $37,344. Males had a median income of $28,548 versus $23,086 for females. The per capita income for the city was $16,322. About 13.7% of families and 18.4% of the population were below the poverty line, including 23.6% of those under 18 and 11.0% of those 65 or over.
Economy.
Much of Tucson's economic development has centered on the development of the University of Arizona, which is the city's largest employer. Davis-Monthan Air Force Base, on the city's southeastern edge, also provides many jobs for Tucson residents. Its presence, as well as the presence of the US Army Intelligence Center (Fort Huachuca, the region's largest employer, in nearby Sierra Vista), has led to the development of many high-technology industries, including government contractors. The city of Tucson is also a major hub for the Union Pacific Railroad's Sunset Route that links the Los Angeles ports with the South/Southeast regions of the country.
Raytheon Missiles and Defense (formerly Hughes Aircraft Co.), Texas Instruments, IBM, Intuit Inc., Universal Avionics, Honeywell Aerospace, Sunquest Information Systems, Sanofi-Aventis, Ventana Medical Systems, Inc., and Bombardier Aerospace all have a large presence in Tucson. Roughly 150 Tucson companies are involved in the design and manufacture of optics and optoelectronics systems, earning Tucson the nickname "Optics Valley". Much of this comes from the Steward Observatory at the University of Arizona, which is one of few locations in the world that can cast the enormous mirrors used in telescopes around the world and in space.
Tourism is another major industry in Tucson. The city's many resorts, hotels, and attractions bring in $2 billion and over 3.5 million visitors annually.
One of the major annual attractions is the Tucson Gem and Mineral Show, and its associated shows, all held generally in the first two weeks of February. These associated shows (such as gems, jewelry, beads, and fossils) are held throughout the city, with 43 different shows in 2010. This makes Tucson's the largest such exposition in the world. Its yearly economic impact in 2015 was evaluated at $120 million.
In addition to vacationers, many winter residents, or "snowbirds", are attracted to Tucson's mild winters and live here on a seasonal basis. They also contribute to the local economy. Snowbirds often purchase second homes in Tucson and nearby areas, contributing significantly to the property tax base.
Top employers.
According to Tucson's 2023 Annual Comprehensive Financial Report, the top employers in the city are:
Arts and culture.
Annual cultural events and fairs.
Tucson Gem and Mineral Show.
The Tucson Gem & Mineral Show is one of the largest gem and mineral shows in the world and has been held for over 50 years. The show is only one part of the gem, mineral, fossil and bead gathering held across more than 45 different sites in Tucson. The shows run from late January to mid-February, with the official show lasting two weeks in February.
Tucson Festival of Books.
Since 2009, the Tucson Festival of Books has been held annually over a two-day period in March at the University of Arizona. By 2010 it had become the fourth largest book festival in the United States, with 450 authors and 80,000 attendees. In addition to readings and lectures, it features a science fair, varied entertainment, food, and exhibitors ranging from local retailers and publishers to regional and national nonprofit organizations.
El Tour de Tucson.
El Tour de Tucson is a cycling race that has been happening in Tucson since 1983. The race tends to happen in the month of November, before American Thanksgiving. There are a number of distances available to ride, from 1-mile fun rides to a long distance ride that spans the whole city resulting in 102 miles. In addition to being a competitive race, this race also allows non-profit charities to raise funds for their organizations. The race was first held by the Perimeter Bicycling Association in 1983 with less than 200 cyclists, and raised $4,500; by 2023 there have been close to 9,000 cyclists and raised $5.8 million. It was recently named a top 10 road race in the United States, ranking at #4.
Tucson Folk Festival.
For the past 33 years, the Tucson Folk Festival has taken place the first Saturday and Sunday of May in downtown Tucson's El Presidio Park. In addition to nationally known headline acts each evening, the Festival highlights over 100 local and regional musicians on five stages and is one of the largest free festivals in the country. All stages are within easy walking distance. Organized by the Tucson Kitchen Musicians' Association, volunteers make this festival possible. KXCI 91.3-FM, Arizona's only community radio station, is a major partner, broadcasting from the Plaza Stage throughout the weekend. There are also many workshops, events for children, sing-alongs, and a popular singer-songwriter contest. Musicians typically play 30-minute sets, supported by professional audio staff volunteers. A variety of food and crafts are available at the festival, as well as local microbrews. All proceeds help fund future festivals.
Fourth Avenue Street Fair.
There are two Fourth Avenue Street Fairs, in December and late March/early April, staged between 9th Street and University Boulevard, that feature arts and crafts booths, food vendors and street performers. The fairs began in 1970 when Fourth Avenue, which at the time had half a dozen thrift shops, several New Age bookshops and the Food Conspiracy Co-Op, was a gathering place for hippies, and a few merchants put tables in front of their stores to attract customers before the holidays.
These days, the street fair has grown into a large corporate event, with most tables owned by outside merchants. It hosts mostly traveling craftsmen selling various arts such as pottery, paintings, wood working, metal decorations, candles, and many others.
Tucson Rodeo (Fiesta de los Vaqueros).
Another popular event held in February, which is early spring in Tucson, is the Fiesta de los Vaqueros, or rodeo week, founded by winter visitor, Leighton Kramer. While at its heart the Fiesta is a sporting event, it includes what is billed as "the world's largest non-mechanized parade". The Rodeo Parade is a popular event as most schools give two rodeo days off instead of Presidents' Day. The exception is Presidio High (a non-public charter school), which does not get either. Western wear is seen throughout the city as corporate dress codes are cast aside during the Fiesta. The Fiesta de los Vaqueros marks the beginning of the rodeo season in the United States.
Tucson Meet Yourself.
Every October for the past 30 years, the Tucson Meet Yourself festival has celebrated the city's many ethnic groups. For one weekend, the downtown area features dancing, singing, artwork, and food from more than 30 different ethnicities. The event is held at and around the Jacome Plaza, located in front of the Joel D. Valdez Main Library. All performers are from Tucson and the surrounding area, in keeping with the idea of "meeting yourself". The records of the Tucson Meet Yourself Festival reside at the University of Arizona Special Collections Library.
Tucson Modernism Week.
Since 2012, during the first two weekends of October, the Tucson Historic Preservation Foundation hosts Tucson Modernism Week. The event includes more than 30 programs including tours, lectures, exhibits, films and parties. The events are in mid-century modern buildings and neighborhoods throughout the city and highlight the work of significant architects and designers who contributed to the development and history of southern Arizona including: architect Arthur Brown, fashion designer Dolores Gonzales, architect Bob Swaim, architect Anne Rysdale, textile designers Harwood and Sophie Steiger, architect Nick Sakellar, architectural designer Tom Gist, furniture designer Max Gottschalk, architect Ned Nelson, landscape architect Guy Green, architect Juan Worner Baz, and many others.
All Souls Procession Weekend.
The All Souls Procession, held in early November, is one of Tucson's largest festivals. Modeled on the Mexican holiday Dia de los Muertos (Day of the Dead), it combines aspects of many different cultural traditions. The first All Souls Procession was organized by local artist Susan Kay Johnson in 1990 and involved 35 participants; by 2013, participation was estimated at 50,000.
The Procession, held at sundown, consists of a non-motorized parade through downtown Tucson featuring many floats, sculptures, and memorials, in which the community is encouraged to participate. The parade is followed by performances on an outdoor stage, culminating in the burning of an urn in which written prayers have been collected from participants and spectators. The event is organized and funded by the non-profit arts organization Many Mouths One Stomach, with the help of volunteers and donations from the public and local businesses.
Cyclovia Tucson.
Cyclovia Tucson is an annual event supported by Living Streets Alliance that invites people of all ages and abilities to walk, bike, and roll down car-free streets for a day. Cyclovia is an Open Streets initiative designed to maximize the enormous amount of space taken up by roads in sprawling cities like Tucson. Since 2012, Cyclovia transforms the streets of metro Tucson into a block party atmosphere to socialize, incorporating partnerships with small businesses, and giving people the opportunity to move freely through the streets without moving cars. Cyclovia happens twice a year, typically in the spring and in the fall.
Cultural and other attractions.
Cultural and other attractions include:
Fourth Avenue, near the University of Arizona, is home to many shops, restaurants, and bars, and hosts the annual 4th Avenue Street Fair every December and March. University Boulevard, leading directly to the UA Main Gate, is also the center of numerous bars, retail shops, and restaurants most commonly frequented by the large student population of the UA.
El Tiradito is a religious shrine in the downtown area. The shrine dates back to the early days of Tucson. It is based on a love story of revenge and murder. People stop by the shrine to light a candle for someone in need, a place for people to go give hope.
Biosphere 2 is a educational facility designed to mimic a tropical or sub-tropical climate-controlled environment.
Literary arts.
The accomplished and awarded writers (poets, novelists, dramatists, nonfiction writers) who have lived in Tucson include Edward Abbey, Erskine Caldwell, Barbara Kingsolver and David Foster Wallace. Some were associated with the University of Arizona, but many were independent writers who chose to make Tucson their home. The city is particularly active in publishing and presenting contemporary innovative poetry in various ways. Examples are the Chax Press, a publisher of poetry books in trade and book arts editions, and the University of Arizona Poetry Center, which has a sizable poetry library and presents readings, conferences, and workshops.
Performing arts.
Theater groups include the Arizona Theatre Company, which performs in the Temple of Music and Art, and Arizona Onstage Productions, a not-for-profit theater company devoted to musical theater. Broadway in Tucson presents the touring reproductions of many Broadway-style events. The Gaslight Theater produces musical melodrama parodies in the old Jerry Lewis Theater and has been in Tucson since 1977.
Tucson is home to the Tucson Symphony Orchestra, the oldest performing arts organization in the state of Arizona.
The annual Tucson Fringe Festival, held in various local venues in and around Downtown Tucson, offers non-traditional artistic performances at low cost to the public. The festival is held in early January each year.
Music.
Musical organizations include the Tucson Symphony Orchestra (founded in 1929) and Arizona Opera (founded as the Tucson Opera Company in 1971). The Tucson Arizona Boys Chorus, founded in 1939 and performing a wide-ranging repertoire that incorporates rope tricks, has represented the city as "Ambassadors in Levi's" at local, national, and international concerts. The Tucson Girls Chorus runs six choirs and numerous satellite choirs which perform locally, nationally, and internationally.
Tucson is considered an influential center for Mariachi music and is home to a large number of Mariachi musicians and singers. The Tucson International Mariachi Conference, hosted annually since 1982, involves several hundred mariachi bands and folklorica dance troops during a three-day festival in April. The Norteño Festival and Street Fair in the enclave city of South Tucson is held annually at the end of summer.
Tucson is also known nationally for its punk scene. Since the late 1970s punk subculture has flourished in Tucson. At present there are multiple punk bars downtown and house venues in the surrounding neighborhoods.
Prominent musicians based in Tucson or with ties to the city include Linda Ronstadt, Lalo Guerrero, The Dusty Chaps, Howe Gelb, Bob Log III, Calexico, Giant Sand, Hipster Daddy-O and the Handgrenades, The Bled, AJJ, Ramshackle Glory, and Tucson's official troubadour Ted Ramirez. The Tucson Area Music Awards, or TAMMIES, are an annual event.
Television and film.
Tucson has been the setting and filming location for multiple films. Some notable films that have been filmed in Tucson include "Revenge of the Nerds", "Can't Buy Me Love", "Major League", "Tombstone", and "Tin Cup". The city is also a common filming location and setting for Western films, most were filmed at Old Tucson. The television show "Hey Dude" was filmed at Tanque Verde Ranch. Additionally, the fictional motorcycle clubs the Sons of Anarchy and Mayans from the television shows "Sons of Anarchy" and "Mayans M.C." both have Tucson chapters that are featured in the show. In the season 4 "Sons of Anarchy" episode "Una Venta", the cast travels to Tucson to discuss an issue with the Tucson chapter. The upcoming TV series "Duster" began filming in Tucson in October 2021. The series is specifically being filmed in downtown Tucson and the Tucson Mountains region of Saguaro National Park.
Cuisine.
Tucson is well known for its Sonoran-style Mexican food. Since the turn of the century, other ethnic restaurants and fine dining choices have proliferated.
In 2015 the United Nations Educational, Scientific and Cultural Organization (UNESCO) designated Tucson a "world city of gastronomy" under the Creative Cities Network program, becoming thus the first city of gastronomy in the United States. The city's focus on food includes Mission Garden, a living agricultural museum that showcases the crops and trees that have been grown in the area for over 4000 years.
The Sonoran hot dog is very popular in Tucson. A hot dog is wrapped in bacon and grilled, served on a bolillo-style hot dog bun, and topped with pinto beans, onions, tomatoes, and a variety of additional condiments, often including mayonnaise, mustard, and jalapeño salsa. Tucson also has a strong, though contested, claim to being the place of origin of the chimichanga.
Nicknames.
Tucson is commonly known as "The Old Pueblo". While the exact origin of this nickname is uncertain, it is commonly traced back to Mayor R. N. "Bob" Leatherwood. When rail service was established to the city on March 20, 1880, Leatherwood celebrated the fact by sending telegrams to various leaders, including the President of the United States and the Pope, announcing the "ancient and honorable pueblo" of Tucson was now connected by rail to the outside world. The term became popular with newspaper writers who often abbreviated it as "A. and H. Pueblo". This in turn transformed into the current form of "The Old Pueblo".
In the early 1980s, city leaders ran a contest searching for a new nickname. The winning entry was the "Sunshine Factory". The new nickname never gained popular acceptance, allowing the old name to remain in common use. Tucson was dubbed "Optics Valley" in 1992 when "Business Week" ran a cover story on the Arizona Optics Industry Association.
Sports.
Tucson is not represented in any of the five major sports leagues of the United States: the NFL, MLB, the NBA, the NHL, or MLS.
The University of Arizona's athletic teams, most notably the men's basketball, football, baseball, and softball teams, have strong local interest. The men's basketball team, formerly coached by Hall of Fame head coach Lute Olson and currently coached by Tommy Lloyd, made 25 straight NCAA Tournaments appearances (1985–2009) and won the 1997 National Championship. Arizona's softball team has reached the NCAA National Championship game 12 times and has won 8 times, most recently in 2007. Arizona's baseball team won NCAA National Championships in 1976, 1980, 1986, and 2012. The university's swim teams have gained international recognition, with swimmers coming from as far as Japan and Africa to train with coach Frank Busch, who has also worked with the U.S. Olympic swim team for numerous years. Both men's and women's swim teams won the 2008 NCAA National Championships.
In ice hockey, the Tucson Roadrunners of the American Hockey League began play during the 2016–2017 season after relocating to Tucson in 2016. They play at the Tucson Convention Center Arena from October to April, and are the top affiliate of the Utah Hockey Club. Between 1975 and 1979, there were three professional ice hockey teams in Arizona. The Tucson Mavericks of the Central Hockey League from 1975 to 1976, the Tucson Icemen of the Southwest Hockey League from 1976 to 1977, and the Tucson Rustlers of the Pacific Hockey League from 1978 to 1979. Later in 1997, the Tucson Gila Monsters were unvieled and played from 1997 to 1999 in the West Coast Hockey League. After the Gila Monsters folded in 1999 a team was announced that were to begin play for the Western Professional Hockey League called the Tucson Scorch they never played a game due to the owner not posting a financial guarantee which was required for a team to begin play in the league.
In American football, the Indoor Football League announced in 2018 they were bringing an expansion team to Tucson to play at the Tucson Convention Center's newly renovated Tucson Arena starting in 2019. That team would be announced as the Tucson Sugar Skulls.
In baseball, the Tucson Saguaros of the independent Pecos League began play in 2016 and play at the Kino Veterans Memorial Stadium. They won the league in their inaugural season and won two more championships in 2020 and 2021. The Tucson Padres played at Kino Veterans Memorial Stadium from 2011 to 2013. They served as the AAA affiliate of the San Diego Padres. The team, formerly known as the Portland Beavers, temporarily moved to Tucson from Portland while the team awaited a new stadium in Escondido. Legal issues derailed the plans to build the Escondido stadium, so they moved to El Paso, Texas for the 2014 season and onward. Previously, the Tucson Sidewinders, a triple-A affiliate of the Arizona Diamondbacks from 1998 to 2008, won the Pacific Coast League championship and unofficial AAA championship in 2006. The Sidewinders played at Tucson Electric Park (now called Kino Sports Complex) and were in the Pacific Conference South of the PCL. The Sidewinders were sold in 2007 and moved to Reno, Nevada after the 2008 season. They now compete as the Reno Aces, who have served as a triple-A affiliate for the Arizona Diamondbacks since 2009.
In soccer, Tucson is host to the Mobile Mini Sun Cup, the largest pre-season Major League Soccer (MLS) tournament in the country. As many as 11 MLS soccer clubs train in Tucson every winter. Tucson is also host to FC Tucson, a professional soccer club that plays at the Kino Sports Complex North Stadium in the third-tier USL League Two.
The United States Handball Association Hall of Fame is in Tucson.
Tracks include Tucson Raceway Park and Rillito Downs. Tucson Raceway Park hosts NASCAR-sanctioned auto racing events and is one of only two asphalt short tracks in Arizona. Rillito Downs is an in-town destination on weekends in January and February each year. This historic track held the first organized quarter horse races in the world, and they are still racing there. The racetrack is threatened by development. The Moltacqua racetrack, was another historic horse racetrack on what is now Sabino Canyon Road and Vactor Ranch Trail, but it no longer exists.
Parks and recreation.
The city has more than 120 parks, from small and local to larger parks with ballfields, natural areas, lakes, 5 public golf courses, and Reid Park Zoo. The Loop is a popular system of shared-use paths encircling the city primarily along washes and is usually well-separated from traffic. Several scenic parks and points of interest are also nearby, including the Tucson Botanical Gardens, Tohono Chul Park, Saguaro National Park, Sabino Canyon, and Biosphere 2 (just north of the city, near the town of Oracle).
Tumamoc Hill is an active research site maintained by the University of Arizona and Pima County that doubles as a popular walking/running trail. The paved trail on Tumamoc Hill is 1.5 miles uphill (3 miles full trip), divided into two parts. The lower half is a much more gradual slope compared to the steep upper half reaching a final elevation of 2,340 ft where it overlooks most of the city of Tucson. The trail attracts around 1500 visits a day from various demographics of the Tucson area.
Mt. Lemmon is north (by the Catalina Highway) and over above Tucson in the Santa Catalina Mountains in the Coronado National Forest. Outdoor activities in the Catalinas include hiking, mountain biking, birding, rock climbing, picnicking, camping, swimming in mountain stream pools, sky rides at Ski Valley, fishing, and photography. In winter with enough snow, the sky ride converts back to skiing at the southernmost ski resort in the continental United States. Summerhaven, a community near the top of Mt. Lemmon, is also a popular destination.
The League of American Bicyclists gave Tucson a gold rating for bicycle friendliness in late April 2007. Tucson hosts the largest perimeter cycling event in the United States. The ride, called "El Tour de Tucson", takes place each November on the Saturday before Thanksgiving. El Tour de Tucson produced and promoted by Perimeter Bicycling has had as many as 10,000 participants from all over the world. In 2019, ridership is expected to be 6,000 cyclists. Tucson is one of only nine cities in the U.S. to receive a gold rating or higher for cycling friendliness from the League of American Bicyclists. The city is known for its winter cycling opportunities, with teams and riders from around the world spending a portion of the year training in Tucson's year-round biking climate. Popular mountain biking areas include Tucson Mountain Park, Sweetwater Preserve, the Tortolita Mountain trail systems, and Fantasy Island. Road cyclists take on Catalina Highway's steep climb year-round.
Government.
Pima County supported John Kerry 53% to 47% in the 2004 U.S. Presidential Election, and Barack Obama 54% to 46% in the 2008 U.S. Presidential Election. In the latter year, Pima was the only county to vote against Arizona's gay marriage ban. In 2013, Tucson became the second city in Arizona to approve of civil unions for same-sex partners. The city was the first in the state to pass a domestic partnership registry earlier in 2003.
In general, Tucson and Pima County support the Democratic Party, while the state's largest metropolitan area, greater Phoenix, has traditionally supported the Republican Party. Congressional redistricting in 2013, following the publication of the 2010 Census, divided the Tucson area into three Federal Congressional districts (the first, second and third of Arizona). The city center is in the 7th District, represented by Raul Grijalva, a Democrat, since 2003, while the more affluent residential areas to the east are in the 6th District, represented by Republican Juan Ciscomani since 2022, and the exurbs north and west between Tucson and Phoenix in the 2nd District are represented by Republican Eli Crane since 2022.
The United States Postal Service operates post offices in Tucson. The Tucson Main Post Office is at 1501 South Cherrybell Stravenue.
City government.
Tucson follows the "weak mayor" model of the council-manager form of local government. The six-member city council holds exclusive legislative authority, and shares executive authority with the mayor, who is elected by the voters independently of the council. An appointed city manager is responsible for the day-to-day operations of the city. Tucson is the only city in Arizona that holds officially partisan elections for city offices, with candidates nominated through party primaries.
Both the council members and the mayor serve four-year terms; none face term limits. Council members are nominated by their wards via a ward-level primary held in August. The top vote-earners from each party then compete at-large for their ward's seat on the November ballot. In other words, on election day the whole city votes on all the council races up for that year. Council elections are severed: Wards 1, 2, and 4 (as well as the mayor) are up for election in the same year (most recently 2015), while Wards 3, 5, and 6 share another year (most recently 2017).
Tucson is known for being a trailblazer in voluntary partial publicly financed campaigns. Since 1985, both mayoral and council candidates have been eligible to receive matching public funds from the city. To become eligible, council candidates must receive 200 donations of $10 or more (300 for a mayoral candidate). Candidates must then agree to spending limits equal to 33¢ for every registered Tucson voter, or $79,222 in 2005 (the corresponding figures for mayor are 64¢ per registered voter, or $142,271 in 2003). In return, candidates receive matching funds from the city at a 1:1 ratio of public money to private donations. The only other limitation is that candidates may not exceed 75% of the limit by the date of the primary. Many cities, such as San Francisco and New York City, have copied this system, albeit with more complex spending and matching formulas.
Mayor Regina Romero (D) was sworn into office on December 2, 2019, succeeding Jonathan Rothschild (D) who was sworn into office on December 5, 2011, succeeding Robert E. Walkup (R), who took office in 1999. Walkup was preceded by George Miller (D), 1991–1999; Tom Volgy (D), 1987–1991; Lew Murphy (R), 1971–1987; and Jim Corbett (D), 1967–1971.
Education.
Primary and secondary schools.
Primarily, students of the Tucson area attend public schools in the Tucson Unified School District (TUSD). TUSD has the second highest enrollment of any school district in Arizona, behind Mesa Unified School District in the Phoenix metropolitan area. There are also many publicly funded charter schools with a specialized curriculum. Other notable districts include Sunnyside Unified School District, Marana Unified School District, Amphitheater Unified School District, Vail Unified School District, and Flowing Wells Unified School District.
In 1956, Tucson High School had the largest enrollment of any secondary school in the United States, with a total of more than 6,800 students. In 2018, Tucson High School enrollment was just over 3,000. The facility operated on a two-shift basis while construction went on for two other high schools that opened within a year to educate children in the rapidly booming Tucson population.
Media.
Print.
Tucson has one daily newspaper, the morning "Arizona Daily Star". Wick Communications publishes the daily legal paper "The Daily Territorial", while Boulder, Colo.-based 10/13 Communications publishes "Tucson Weekly" (an "alternative" publication), "Inside Tucson Business" and the "Explorer". TucsonSentinel.com is a nonprofit independent online news organization. "Tucson Lifestyle Magazine", "Lovin' Life in Tucson", "DesertLeaf", and "Zócalo Magazine" are monthly publications covering arts, architecture, decor, fashion, entertainment, business, history, and other events. The "Arizona Daily Wildcat" is the University of Arizona's student newspaper, and the "Aztec News" is the Pima Community College student newspaper. "Catholic Outlook" is the newspaper for the Roman Catholic Diocese of Tucson, and the "Arizona Jewish Post" is the newspaper of the Jewish Federation of Southern Arizona.
Television.
The Tucson metro area is served by many local television stations and is the 65th largest designated market area (DMA) in the U.S. with 433,330 homes (0.39% of the total U.S.). It is limited to the three counties of southeastern Arizona (Pima, Santa Cruz, and Cochise)
The major television networks serving Tucson are:
Infrastructure.
Energy.
Tucson's primary electrical power source is a natural gas power plant managed by Tucson Electric Power that is within the city limits on the southwestern boundary of Davis-Monthan Air-force base adjacent to Interstate 10. The air pollution generated has raised some concerns as the Sundt operating station has been online since 1962 and is exempt from many pollution standards and controls due to its age.
Solar has been gaining ground in Tucson with its ideal over 300 days of sunshine climate. Federal, state, and even local utility credits and incentives have also enticed residents to equip homes with solar systems.
Davis-Monthan AFB has a 3.3 Megawatt (MW) ground-mounted solar photovoltaic (PV) array and a 2.7 MW rooftop-mounted PV array, both of which are in the Base Housing area. The base will soon have the largest solar-generating capacity in the United States Department of Defense after awarding a contract on September 10, 2010, to SunEdison to construct a 14.5 MW PV field on the northwestern side of the base.
Global Solar Energy, which is at the University of Arizona's science and technology park, is one of the planet's largest CIGS solar fields at 750 kilowatts.
Light pollution.
Tucson and Pima County adopted dark sky ordinances to control light pollution in support of the region's astronomical observatories in 1972. Last amended in 2012, the City of Tucson/Pima County Outdoor Lighting Code establishes maximum illumination levels, shielding requirements, and limits on signage in "continuing support of astronomical activity and minimizing wasted energy, while not compromising the safety, security, and well-being of persons engaged in outdoor nighttime activities."
Water.
Less than 100 years ago, the Santa Cruz River flowed nearly year-round through Tucson. This supply of water has slowly disappeared, causing Tucson to seek alternative sources.
In 1881, water was pumped from a well on the banks of the Santa Cruz River and flowed by gravity through pipes into the distribution system.
Tucson currently draws water from two main sources: Central Arizona Project (CAP) water and groundwater. In 1992, Tucson Water delivered CAP water to some customers that was unacceptable due to discoloration, bad odor and flavor, as well as problems it caused with some customers' plumbing and appliances. Tucson's city water currently consists of CAP water mixed with groundwater.
In an effort to conserve water, Tucson is recharging groundwater supplies by running part of its share of CAP water into various open portions of local rivers to seep into their aquifer. Additional study is scheduled to determine how much water is lost through evaporation from the open areas, especially during the summer. The City of Tucson provides reclaimed water to its inhabitants, but it is only used for "applications such as irrigation, dust control, and industrial uses". These resources have been in place for more than 27 years, and deliver to over 900 locations.
To prevent further loss of groundwater, Tucson has been involved in water conservation and groundwater preservation efforts, shifting away from its reliance on a series of Tucson area wells in favor of conservation, consumption-based pricing for residential and commercial water use, and new wells in the more sustainable Avra Valley aquifer, northwest of the city. An allocation from the Central Arizona Project Aqueduct (CAP), which passes more than across the desert from the Colorado River, has been incorporated into the city's water supply, annually providing over 20 million gallons of "recharged" water which is pumped into the ground to replenish water pumped out. Since 2001, CAP water has allowed the city to remove or turn off over 80 wells.
Water harvesting.
The city of Tucson, Arizona provides financial incentives for residents to harvest their rainwater. Tucson's water supply, like many Western cities, is drawn from two main sources: surface water that is pumped more than 300 miles from the Colorado River and groundwater. The pump expends a significant amount of energy and the Colorado River is diminishing as a result of climate change and overuse.
In 2012, the city began a program that rebates residents as much as $2,000 for the purchase of water harvesting systems. "Water harvesting" refers to rainwater, which is gathered from building surfaces, and stormwater"," which collects nonpotable storm runoff from streets and earth. The program is financed by a water bill fee of 10 cents per 748 gallons of city water used. In the first few years, the rebate program was not conserving water as efficiently as they anticipated. But in fiscal year 2018 to 2019, the rebate program saved 52.1 million gallons of water. That is enough water to meet the annual usage of 160 households. The city has been trying to grow the approximately 250 people who obtain active rebates each year by introducing a loan program to bring rebates within reach of lower-income residents.
The city government has an ambitious goal to be carbon neutral by 2030 and is integrating changes that will help change local resident's conventional thinking and practices. On May 1, 2020, Tucson began charging residents and businesses within city limits a monthly Green Stormwater Infrastructure fee (13 cents per 748 gallons of city water used), which is projected to raise some $3 million a year for public stormwater capture installations and other projects. But this comes at a time when unemployment is rising and the number of low income residents facing unaffordable bills between 2010 and 2018 doubled to 46% as the average bill increased by 119% in Tucson. Additionally, as part of the citywide climate resiliency effort, Mayor Regina Romero recently announced the planting of a million trees over the next decade.
Transportation.
Public transit.
Tucson's Sun Tran bus system serves greater Tucson with standard, express, regional shuttle, and on-demand shuttle bus service. It was awarded Best Transit System in 1988 and 2005. A streetcar line, Sun Link, connects the University of Arizona campus with 4th Avenue, downtown, and the Mercado District west of Interstate 10 and the Santa Cruz River. Ten-minute headway passenger service began July 25, 2014. The streetcar uses Sun Tran's card payment and transfer system, connecting with the University of Arizona's CatTran shuttles, Amtrak, and Greyhound intercity bus service. Sun Tran has been fare-free since the spring of 2020. Initially this change was made to limit contact between riders and drivers due to the COVID-19 pandemic, but the city council voted to eliminate fares indefinitely in 2023.
Rail.
Amtrak, the national passenger rail system, provides service to Tucson three times weekly in both directions, operating its "Sunset Limited" between Los Angeles, California and New Orleans, Louisiana; and "Texas Eagle" service between Los Angeles and Chicago, Illinois.
Airport.
Tucson International Airport (), is south of the city's center. TIA is the second-largest commercial airport in Arizona, providing nonstop flights to 15 destinations throughout the United States. In addition to passenger and freight service, TIA supports the 162nd Fighter Wing's fleet of seventy F-16s stationed at the Tucson Air National Guard Base. There are two general aviation reliever airports in the area. The city of Tucson operates Ryan Airfield southwest of the city center, and the town of Marana operates Marana Regional Airport to the northwest. Pinal Airpark is also within the metropolitan area.
Roadways.
There are two Interstate highways in the metropolitan area. Interstate 10 runs southeast from Phoenix through Marana, passes west of downtown, and continues east toward El Paso. Interstate 19 leaves the I-10 south of downtown and heads south to the Mexican border. Arizona State Route 210 is a shorter expressway that links downtown with Davis-Monthan Air Force Base and Tucson's southeast side. Tucson does not have a beltway system, and relies almost entirely on surface streets.
Freeways and state highways in Tucson include:
Cycling.
Cycling is popular in Tucson. Tucson and Pima County maintain an extensive network of marked bike routes, signal crossings, on-street bike lanes, mountain-biking trails, and dedicated shared-use paths. The Loop is a network of seven linear parks, built mainly along river beds, comprising of paved, vehicle-free trails that encircles the majority of the city with links to Marana and Oro Valley. The Tucson–Pima County Bicycle Advisory Committee (TPCBAC) serves in an advisory capacity to local governments on issues relating to bicycle recreation, transportation, and safety. The League of American Bicyclists awarded Tucson a gold rating for bicycle-friendliness in 2006.
Sister cities.
Tucson's sister cities are:
References.
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Further reading.
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