Or Gariep, chief river of South Africa, rises in the eastern highlands of Basutoland, and flows 100 m. westward to the Atlantic, receiving the Vaal and the Caledon as tributaries, and having Cape Colony on the S. bank and the Orange Free State, Griqualand West, Bechuanaland, and German Namaqualand on the N.; a bar at the mouth and the aridity of its lower course make it unfit for navigation.