COLORADO RIVER, a stream in the south of the Argen tine Republic. It has its sources on the eastern slopes of the Andes in the latitude of the Chilean volcano Tinguiririca (about 48' S.), and pursues a general east-south-east course to the Atlantic, where it discharges through several channels of a delta extending from lat. 39° 3o' to 39° 50' S. Its total length is about 62o m., of which about 200 m. from the coast up to Pichemahuida is navigable for vessels of 7 ft. draught. It has been usually de scribed as being formed by the confluence of the Grande and Bar rancas, but as the latter is only a small stream compared with the Grande it is better described as a tributary, and the Grande as a part of the main river under another name. After leaving the vicinity of the Andes the Colorado flows through a barren, arid territory and receives no tributary of note except the Curaco, which has its sources in the Pampa territory and is considered to be part of the ancient outlet of the now closed lacustrine basin of southern Mendoza. The bottom lands of the Colorado in its course across Patagonia are fertile and wooded, but their area is too limited to support more than a small, scattered population.