The Calder River rises in the Otway Ranges in southwest Victoria, near Bateman Ridge and flows generally south by west through the Port Campbell National Park towards the settlement of Horden Vale where the river enters Lake Costin and then Lake Craven, before reaching its confluence with the Aire River shortly before the Aire enters Bass Strait, northwest of Cape Otway. From its highest point, the Calder River descends 393 metres (1,289 ft) over its 14-kilometre (8.7 mi) course.[3]