What states does the Colorado River flow through?

The Colorado River flows through three states, Colorado, Utah and Arizona, then forms the border between Arizona and Nevada and between Arizona and California before it crosses into Mexico. Seven states hold a share of its water: Colorado, New Mexico, Utah and Wyoming in the Upper Basin above Lee Ferry, and Arizona, California and Nevada in the Lower Basin below it, with a guaranteed share for Mexico.

The chart is the river at Lees Ferry, Arizona, the gauge just above the point where the 1922 Colorado River Compact divides the river between its two basins.

The route, source to Mexico

The river rises in the mountains of north-central Colorado and runs southwest more than 1,400 miles toward the Gulf of California, per Reclamation. It crosses western Colorado, picking up the Gunnison, and enters Utah, where it meets the Green River in Canyonlands. Glen Canyon Dam, just inside Arizona, holds it back as Lake Powell, which reaches far up into Utah and also takes in the San Juan River. Below the dam it passes Lees Ferry and runs through the Grand Canyon to Lake Mead, the reservoir behind Hoover Dam on the Nevada-Arizona line. From Lake Mead down it is a border: Arizona and Nevada along Lake Mead and Lake Mohave, then Arizona and California past Lake Havasu and down to Yuma, before it enters Mexico.

Two of the seven states never touch the main stem. Wyoming's share reaches the Colorado down the Green River, which rises in Wyoming, and New Mexico's down the San Juan. Reclamation counts six major tributaries in all: the Green, the Gunnison, the San Juan, the Virgin, the Little Colorado and the Gila. Together they drain 242,000 square miles of the United States, about one-twelfth of the country's continental land area, plus 2,000 square miles of Mexico.

How the water is divided

The 1922 Compact names the states of the Upper Division (Colorado, New Mexico, Utah and Wyoming) and of the Lower Division (Arizona, California and Nevada), and splits the river at Lee Ferry, a point one mile below the mouth of the Paria River in Arizona. Each basin gets the use of 7,500,000 acre-feet a year, and the Lower Basin may increase its use by 1,000,000 more. The basins follow drainage, not state lines, so Arizona has land in the Upper Basin, and New Mexico and Utah have land in the Lower Basin.

The Compact's delivery rule sits at the same point: the Upper Division states agree not to cause the flow at Lee Ferry to fall below 75,000,000 acre-feet in any ten consecutive years. The 1948 Upper Colorado River Basin Compact then divided the Upper Basin's share by percentage, and the Boulder Canyon Project Act of 1928 split the Lower Basin's. The 1944 Water Treaty guarantees Mexico 1,500,000 acre-feet a year.

Water that leaves the basin

Several states carry part of their share out of the river's drainage altogether:

• Colorado. Reclamation's Colorado-Big Thompson Project moves West Slope water under the Continental Divide, supplying supplemental irrigation for 615,000 acres east of the Divide and municipal water for more than 1 million people in northeastern Colorado.
• Utah. The Central Utah Project's Bonneville Unit diverts Colorado River system water into the Bonneville Basin, on the Wasatch Front side of the mountains.
• New Mexico. The San Juan-Chama Project tunnels water from the Navajo, Little Navajo and Blanco rivers, upper tributaries of the San Juan, into the Rio Grande basin, about 89,800 acre-feet a year on average over 1991 to 2020. Albuquerque holds the largest contract, 48,200 acre-feet. The Rio Grande is the river that fills Elephant Butte Reservoir farther south.
• Arizona. The Central Arizona Project lifts water out of Lake Havasu and carries it about 336 miles to a terminus southwest of Tucson, serving Phoenix and Tucson.
• California. Metropolitan Water District's Colorado River Aqueduct also draws from Lake Havasu, and the All-American Canal takes water at Imperial Dam to about 530,000 acres in the Imperial Valley, with the Coachella Canal serving about 78,530 acres in the Coachella Valley.

Agriculture accounts for about 70 percent of the river's use, and between 35 and 40 million people rely on it for some or all of their municipal water, per Reclamation.

Worked example: water year 2026 against the paper split

On paper the Compact and the treaty divide 16.5 million acre-feet a year: 7.5 million to each basin and 1.5 million to Mexico, before the Lower Basin's extra million. Reclamation's Sep 15, 2026 24-Month Study forecast water year 2026's unregulated inflow to Lake Powell, the river's natural flow from the Upper Basin, at 3.52 million acre-feet, 37% of the 1991-2020 average, after an April-July runoff of 1.14 million acre-feet, 18% of average. Reclamation cut Glen Canyon Dam's release for the year from 7.48 to 6.00 million acre-feet.

Downstream, the same study projected calendar 2026 diversions of 0.985 million acre-feet for the Central Arizona Project and 0.788 million for Metropolitan Water District, and 0.201 million acre-feet of Nevada's consumptive use above Hoover Dam. Those numbers sit inside Arizona's 2.8 million, California's 4.4 million and Nevada's 0.3 million acre-feet; the rest of each state's use is along the river itself.

Lake Powell stood at 3,519.79 feet above sea level on Oct 15, 2026, and Lake Mead at 1,037.53 feet above sea level on Oct 15, 2026. Operating year 2027 runs under new 2027-2028 Operating Guidelines issued under a 2026 Record of Decision, with a shortage condition governing Lake Mead in 2027 and Mexico's deliveries also governed by International Boundary and Water Commission Minute No. 334, per the same study. The Colorado River system in charts follows the two reservoirs that hold most of the river's stored water.