The Loa River is a U-shaped river in Chile's northern Antofagasta Region. At 440 km long, it is the country's longest river and the main watercourse in the Atacama Desert. The Loa's sources are located on Andean mountain slopes at the foot of Miño Volcano. The upper Loa basin is flanked on the west by a ridge with elevations that reach above 4,50…The Loa River is a U-shaped river in Chile's northern Antofagasta Region. At 440 km long, it is the country's longest river and the main watercourse in the Atacama Desert. The Loa's sources are located on Andean mountain slopes at the foot of Miño Volcano. The upper Loa basin is flanked on the west by a ridge with elevations that reach above 4,500 m, whereas to the east lies a volcanic chain, which separates it from endorheic basins as that of Salar de Ascotán.