The Orange River (from 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 and hydroelectric power. The river was named the Orange River in honour of the Dutch ruling family, the House of Orange, by the Dutch explorer Robert Jacob Gordon. Other names include Gariep River (used by the Khoi people), Groote River or Senqu River (used in Lesotho).