river in southern Argentina, rising in the Andes Mountains south of San Carlos de Bariloche in Río Negro provincia. It flows southward and then eastward, emerging from the Andes in northwestern Chubut province. It then flows generally southeastward to the Pass of Indios, where it continues east-northeastward across Patagonia and past Las Plumas, Trelew, and Rawson. It empties into the Atlantic Ocean at Punta Castro. The river, 503 miles (810 km) long, is not navigable, but its lower course irrigates the adjacent valley (producing apples and cherries).