Below its junction with the Gila, and thence up the middle of the Colorado river to the boundary line between Mexico and California.
By far the greater part of the high plateau district is drained by the Colorado river and its branches, the most important of which are the Green, Grand and San Juan, portions of whose courses lie in canyons of remarkable grandeur.
Similarly, near Yuma in Arizona, a project was undertaken for carrying the waters of the main canal on the California side under the Colorado river by a siphon.
RIO NEGRO, a territory of Argentina lying between the Colorado river and the 42nd parallel S.
The region of the Colorado river is largely desert, with occasional buttes and spurs.
Near the Colorado river the dissected cuesta of the Grand Prairie passes southward, by a change to a more nearly horizontal structure, into the dissected Edwards plateau (to be referred to again as part of the Great Plains), which terminates in a maturely dissected fault scarp, 300 or 400 ft.
Deep, hardly wider at the top than at the bottom, in the heavy Triassic sandstones of southern Utah; but the most famous example is the Grand Canyon (qv.) of Arizona, eroded by the Colorado river across the uplifted platform of Carboniferous limestone.
Existing documents seem to indicate that Francisco Vasquez de Coronado, the Spanish explorer, sent out an expedition of twelve men under Captain Garcia Lopez de Cardenas in 1540, which succeeded in reaching the Colorado river at a point now within the state of Utah.
In 1900 the Colorado river (q.v.) was tapped south of the Mexican boundary for water wherewith to irrigate land in the Imperial Valley along the Southern Pacific railway, adjoining Salton Sea.
Its depth is not great, at least as compared with the canyons upon the Colorado river system; it ranges from 600 ft.