Baker River (Chile) in the context of Biobío River

The Biobío River (also known as Bío Bío or Bio-Bio) is the second largest river in Chile. It originates at Icalma and Galletué lakes in the Andes and flows 380 kilometres (236 mi) to the Gulf of Arauco (in Spanish) on the Pacific Ocean.

The major tributaries of the river are the Malleco and the Laja. The river is Chile's second-longest river (the longest being the Loa River) and the Biobío basin is Chile's third largest watershed, after the Loa and Baker basins. The river is also the widest river in Chile, with an average width of 1 kilometre (0.6 mi). In the Metropolitan area of Concepción, four bridges cross the river: Biobío Railroad Bridge (1889), Juan Pablo II Bridge (1973), Llacolén Bridge (2000) and Bicentennial Bridge (2010).

General Carrera Lake (Chilean part, officially renamed in 1959) or Lake Buenos Aires (Argentine part) is a deep lake located in Patagonia and shared by Argentina and Chile. Both names are internationally accepted, while the autochthonous name of the lake is Chelenko, which means "stormy waters" in Aonikenk. Another historical name is Coluguape from Mapuche, a derivative of this name is applied to Colhué Huapí Lake after Argentine explorer Francisco Moreno reached this lake in 1876 conflating it with Coluguape (General Carrera Lake).

The lake is of glacial origin and is surrounded by the Andes mountain range. The lake drains to the Pacific Ocean on the west through the Baker River. During the last glaciation the lake drained to the Atlantic through Deseado River.