Colorado River: Encyclopedia II - Colorado River - Course

Colorado River - Course

The Colorado River's headwaters are located in Rocky Mountain National Park, just west of the Continental Divide. The river's course then follows the Kewuneeche Valley to Shadow Mountain Reservoir, near the town of Granby, then flows into Lake Granby. Most of the river's first tributaries are small. However there are exceptions, such as the Roaring Fork and Gunnison Rivers, in which massive amounts of water flow. The river then roughly parallels US 40 to the town of Kremling, then enters Gore Canyon. Shortly thereafter, the river roughly parallels I-70 through Glenwood Canyon and the city of Glenwood Springs, where it is joined by the swift flowing Roaring Fork River. Below Glenwood, the Colorado runs through the Grand Valley to Grand Junction, where it is joined by the Gunnison River; from there it flows on to the Utah border. The Colorado here ranges from 200 - 1200 feet wide and from 6 - 30 feet in depth with occasional deeper areas. Once inside Utah, the river turns south, and goes through Arches National Park, then Dead Horse Point State Park and Canyonlands National Park, where it is met by one of its primary tributaries, the Green River. The river then flows into Lake Powell, formed by the Glen Canyon Dam. Below the dam, water released from the bottom of Lake Powell makes the river clear, clean, and cold. Just south of the town of Page, Arizona, the river forms the dramatic Horseshoe Bend, then at Lees Ferry is joined by another tributary, the warm, shallow, muddy Paria River, and begins its course through Marble Canyon. Here, the Colorado ranges from 300 - 2000 feet in width and 9 - 130 feet in depth.

At the southern end of Marble Canyon, the river is joined by another tributary, the Little Colorado, and the river then turns abruptly west directly athwart the folds and fault line of the plateau, through the Grand Canyon, which is 217 miles long and from 4 to 20 miles wide between the upper cliffs. The walls, 4000 to 6000 feet high, drop in successive escarpments of 500 to 1600 feet, banded in splendid colours, toward the gloomy narrow gorge of the present river.

Below the confluence of the Virgin River of Nevada the Colorado abruptly turns southward, and forms part of the boundary between Arizona and Nevada, and the border between Arizona and California. Along the California-Arizona reach of the river, two additional dams are operated to divert water for agricultural irrigation supplies: Palo Verde Diversion Dam and Imperial Dam. Here, the Colorado River ranges in width from 700 - 2500 feet and from 8 - 100 feet in depth.

Below the Black Canyon the river lessens in gradient, and in its lower course flows in a broad sedimentary valley's distinct estuarine plain upriver from Yuma, where it joined by the Gila River. The channel through much of this region is bedded in a dyke-like embankment lying above the floodplain over which the escaping water spills in time of flood. This dyke cuts off the flow of the river to the remarkable low area in southern California known as the Salton Sink, Coahuila Valley, or Imperial Valley. The Salton Sink is located below sea level; therefore, the descent from the river near Yuma is very much greater than the descent from Yuma to the gulf.

The lower course of the river, which forms the border between Baja California and Sonora, is essentially a dry stream today due to use of the river as a water source. Prior to the mid 20th century, the Colorado River Delta provided a rich estuarine marshland that is now essentially desiccated, but nonetheless is an important ecological resource.

Adapted from the Wikipedia article "Course", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki