Its large flow and steep gradient are used for generating hydroelectric power, and its major dams regulate peaking power demands in much of the Intermountain West.
Intensive water consumption has dried up the lower 100 miles (160 km) of the river, which has rarely reached the sea since the 1960s.
Most of the upper river is a swift whitewater stream ranging from 200 to 500 feet (60 to 150 m) wide, the depth ranging from 6 to 30 feet (2 to 9 m), with a few notable exceptions, such as the Blackrocks reach where the river is nearly 100 feet (30 m) deep.
Farther downstream it receives the Dolores River and defines the southern border of Arches National Park, before passing Moab and flowing through "The Portal", where it exits the Moab Valley between a pair of 1,000-foot (300 m) sandstone cliffs.
In Utah, the Colorado flows primarily through the "slickrock" country, which is characterized by its narrow canyons and unique "folds" created by the tilting of sedimentary rock layers along faults.
This is one of the most inaccessible regions of the continental United States.
Large engineering works began around the start of the 20th century, with major guidelines established in a series of international and U. interstate treaties known as the "Law of the River". Most of the major dams were built between 19; the system keystone, Hoover Dam, was completed in 1935.
The Colorado is now considered among the most controlled and litigated rivers in the world, with every drop of its water fully allocated.
Here, many 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. 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 about 24 miles (39 km) of the Mexico–United States border.