What is the region south of the Colorado River in Argentina?

Answer 1

The Colorado River (Spanish: Río Colorado) is a river in the south of Argentina. It has its sources on the eastern slopes of the Andes in the latitude of the Chilean volcano Tinguiririca (about 34° 48' S.), and pursues a general east-southeast course to the Atlantic Ocean, where it discharges through several channels of a delta of the Unión Bay extending from latitude 39° 30' to 39° 50' S. Its total length is about 1000 kilometres (620 miles), of which about 300 kilometres (200 miles), from the coast up to Pichi Mahuida, are navigable for vessels of up to 2 metres (7 ft.) draft.

The river has been usually described as being formed by the confluence of the Grande and Barrancas, 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 Salado (or Curacó) from La Pampa Province, and is considered to be part of the ancient outlet of the now closed lacustrine basin of Urre Lauquen. 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.

Answer 2

"Patagonia is the portion of South America mostly in Argentina and partly of Chile made up of the Andes mountains to the west and south and plateaus and low plains to the east. To the east of the Andes, it lies south of the Neuquén River and Colorado rivers..."

The region south of the Colorado River is called Patagonia.