<Tr> <Td> - average </Td> <Td> 365 m / s (12,890 cu ft / s) </Td> </Tr> <Tr> <Td_colspan="2"> The course and watershed of the Orange River, Caledon River and Vaal River . This map shows a conservative border for the watershed . Specifically, the Kalahari basin is excluded, as some sources say it is endorheic . Some other sources using computational methods show a basin which includes parts of Botswana (and hence of the Kalahari). </Td> </Tr> <P> The Orange River (Afrikaans / Dutch: Oranjerivier) is the longest river in South Africa and the Orange River Basin extends extensively into Namibia and Botswana to the north . It rises in the Drakensberg mountains in Lesotho, flowing westwards through South Africa to the Atlantic Ocean . The river forms part of the international borders between South Africa and Namibia and between South Africa and Lesotho, as well as several provincial borders within South Africa . Except for Upington, it does not pass through any major cities . The Orange River plays an important role in the South African economy by providing water for irrigation, as well as hydroelectric power . The river was named by Robert Jacob Gordon after the Dutch Royal House . Other names include Gariep River (used by the Khoi people), Groote River or Senqu River (used in Lesotho). The official name, however, is the Orange River . </P> <P> The Orange rises in the Drakensberg mountains along the border between South Africa and Lesotho, about 193 km (120 mi) west of the Indian Ocean and at an altitude of over 3,000 m . The extremity of the Orange River inside Lesotho is known as the Senqu . Parts of the Senqu River freeze in winter because of the high altitude there . This creates droughts downstream of it which mainly affect goat and cattle production . </P>

Which international border does the gariep-orange follow before it enters the sea