Colorado River

The Colorado River is one of the principal rivers of North America, originating high in the Rocky Mountains of northern Colorado and flowing approximately 1,450 miles southwest through the arid landscapes of the American West before reaching the Gulf of California in northwestern Mexico. Rising in the Rocky Mountains of Colorado, the river flows generally west and south for 1,450 miles into the Gulf of California, and its drainage basin covers 246,000 square miles, including parts of seven states — Wyoming, Colorado, Utah, New Mexico, Nevada, Arizona, and California. Known as the "Lifeline of the Southwest," the river provides water to 40 million people and more than 5 million acres of farmland in a region encompassing some 246,000 square miles. Within Colorado itself, the river holds profound geographic, economic, and cultural importance, forming the headwater heart of one of the most heavily managed river systems in the world.

Headwaters and Course Through Colorado

The Colorado River originates on the western side of Rocky Mountain National Park in the Never Summer Mountains, with the tributaries that join to form the Colorado starting at elevations of 11,600 feet. The main river flows from 10,200 feet at La Poudre Pass, south through the Kawuneeche Valley. The river rises on the Continental Divide at La Poudre Pass, about 40 km north of Lake Granby, as a tiny stream draining a wet meadow. At the river's headwater, the Continental Divide forms the boundary between the Gulf of Mexico and Pacific Ocean watersheds of North America, between Colorado's Grand and Larimer counties.

About a mile downstream from its source, the Colorado River has carved its first canyon, the narrow, deep Little Yellowstone Canyon. It then flows through the broad Kawuneeche Valley, where it is joined by U.S. Highway 34, which parallels it to the town of Granby. It finally exits Rocky Mountain National Park, flowing into Shadow Mountain Lake and then into Lake Granby, which are portions of the Colorado-Big Thompson Project, a large trans-basin water storage and delivery project that diverts water from the Colorado River under the Front Range mountains to provide an agricultural and municipal water supply for the northern Front Range and plains of Colorado.

At Hot Sulphur Springs the river flows through Byers Canyon and is then joined by the Williams Fork. Just below Kremmling it is joined by the Blue River before flowing through Gore Canyon, famous for its challenging rapids for the sport of whitewater rafting. Below Dotsero the Colorado flows through Glenwood Canyon, emerging at the city of Glenwood Springs where the swift-flowing Roaring Fork River joins from the left. West of Glenwood Springs, the Colorado runs through a wider valley along the northern foothills of the Grand Mesa, passing the towns of New Castle, Silt, Rifle, and De Beque.

The Colorado then enters the Grand Valley, where its waters are used to irrigate over 40,000 acres of agricultural land. Here it passes Grand Junction, the largest town on the upper Colorado, where it is joined by the Gunnison River, its largest tributary within Colorado and second largest overall. From Shadow Mountain the river flows a short distance into Lake Granby, then continues southwestward until it crosses into Utah just west of Grand Junction at an elevation of about 4,400 feet.

The traditional breakdown of water usage for the river within the state is approximately 80 percent for agriculture and 10 percent for municipal and industrial consumption.

Name and Early History

The name Colorado derives from the Spanish language for "colored reddish," due to the river's heavy silt load. Until 1921, the river flowing west from the Continental Divide in Rocky Mountain National Park and winding down to the high desert of Utah was known as the Grand River. Where the Green River and the Grand River met, the Colorado River began and flowed downstream to the Gulf of California.

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. On July 25, 1921, the U.S. House of Representatives passed a joint resolution to make it official. Grand Lake, Grand County, and the city of Grand Junction are all reminders of its former name.

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 U.S. 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.

Starting in the 1860s, gold and silver strikes drew prospectors to the upper Colorado River basin. These waves of settlement dramatically increased demand on the river's resources and set the stage for the complex system of water law that would follow.

The Law of the River and Water Governance

Colorado River water is shared by states, the federal government, American Indian tribes, and Mexico, resulting in many compromises, interstate compacts, a U.S. Supreme Court decree, and an international treaty. Collectively, this is known as the Law of the River.

In 1922, Herbert Hoover (who later became president of the U.S.) and representatives from the seven basin states signed the Colorado River Compact, which allocates the amount of water that Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming can legally use. The compact divides the states into two basins — the Upper Basin (Colorado, New Mexico, Utah, and Wyoming) and the Lower Basin (Arizona, California, and Nevada) — with Colorado River water equitably shared between the basins.

In 1948, the Upper Colorado River Basin Compact created the Upper Colorado River Commission and apportioned the Upper Basin's allocation proportionally among the four Upper Basin states: Colorado received 51.75%, New Mexico 11.25%, Utah 23%, and Wyoming 14%. Colorado's dominant share reflects the fact that the river's headwaters lie within its borders, and that the state contributes the lion's share of the system's runoff.

In 1944, the U.S. and Mexico signed a treaty to annually allocate 1.5 million acre-feet of Colorado River water to Mexico in normal years. In 1956, the Colorado River Storage Project Act approved multiple projects in the Upper Basin, including Flaming Gorge Dam and Glen Canyon Dam.

Delph E. Carpenter (1877–1951), known as the "Father of Interstate River Compacts," served the state of Colorado as a lawyer, state senator, and river commissioner. Documents in historical collections related to his work include drafts, letters, and reports for the Colorado River Compact (1922) and Upper Colorado River Compact (1948).

Denver Water receives about 50 percent of its supply from the Colorado River basin. Combined, transmountain diversions draw about 580,000 acre-feet of water per year out of the Colorado River basin.

Ecology and Conservation

Human use of water has severely altered the river, leading one writer to describe it as "a river no more." The combined effects of numerous dams and extensive diversions of water from the river have so significantly altered natural flows that many of the plants and animals native to the river are gradually disappearing from the drainage basin, and most years the river no longer reaches the Pacific Ocean.

Four of the 14 fish species native to the river — the Colorado pikeminnow, razorback sucker, bonytail, and humpback chub — are endangered or threatened. Federal and state agencies in the upper basin, along with several tribal nations and NGOs, have created a recovery program to restore and protect aquatic habitat.

A Colorado water consultant began working on the Colorado Water Congress Special Project in 1983 to assist in the resolution of potential conflicts between water development and management activities and protection of four fish species in the Colorado River Basin listed as endangered under the federal Endangered Species Act. In early 1985, recovery of the endangered fish species was proposed as the solution, leading to development of the Upper Colorado River Endangered Fish Recovery Implementation Program.

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.

In Colorado, the river runs through high-altitude forests home to elk, moose, bears, and mountain lions. Farther south, mountain sheep and coyotes roam the arid landscapes, while bird species vary by region and climate.

Recreation and Economic Importance

Passing through no less than 11 different national parks and monuments as it tumbles through the varied landscapes of seven states and two countries, the Colorado River is a critical water supply for agriculture, industry, and municipalities, from Denver to Tijuana, fueling a $1.4 trillion annual economy. Fishing, whitewater paddling, boating, backpacking, wildlife viewing, hiking, and myriad other recreational opportunities contribute some $26 billion alone.

Just below Kremmling the river flows through Gore Canyon, famous for its challenging rapids for the sport of whitewater rafting, and drops significantly until State Highway 131 crosses at the village of State Bridge. The river's pace varies dramatically, shifting from calm stretches to thrilling whitewater rapids, making it a hub for outdoor adventure. Popular recreation spots include Fisher Towers, Westwater Canyon, Cataract Canyon, and the Grand Canyon.

Recreation is also a significant part of the Colorado River system. The Colorado River Basin is used by millions of people annually for activities ranging from rafting to snow sports and generates billions of dollars in revenue.

At its widest point, in Grand Junction, Colorado, the river stretches 200 feet across and is thought to be its deepest — nearly 90 feet — near Phantom Ranch in the Grand Canyon in Arizona. The river corridor through Colorado also supports a thriving tourism economy in communities such as Glenwood Springs, Grand Junction, and Kremmling, each of which relies on river-based recreation for significant portions of local income.