At a length of 1,300 miles (2,100 kilometers), the Orange River is one of the longest rivers in Africa. From its source in Lesotho, near the Indian Ocean, it flows 1,300 miles (2,100 kilometers) to the Atlantic Ocean. After flowing west across South Africa, the river forms a large part of the border between that country and Namibia.
The Orange River begins 10,800 feet (3,300 meters) above sea level on a plateau in the highlands of Lesotho. The plateau lies between the Drakensberg mountain range and the Maloti Mountains. In Lesotho the Orange River is called the Sinqu (or Senqu) River. Near the river’s headwaters, the rainfall is about 32 inches (80 centimeters) per year.
The Orange River then flows through the Eastern Cape, Free State, and Northern Cape provinces of South Africa. Two of its biggest tributaries are the Caledon and Vaal rivers. Both enter from the north. Farther west in its course, the river is recognized as the southern boundary of the Kalahari Desert. On its way to the Atlantic Ocean at Alexander Bay, the river passes through the coastal region called the Namib Desert. In this area the annual rainfall is less than 2 inches (5 centimeters).
Big riverboats and ships cannot navigate on the Orange River because the river has too many waterfalls and rapids. There are no large cities on its banks, but the river still plays an important role in the economies of Lesotho and South Africa. Dams and tunnels have been built in connection with several large-scale Orange River development schemes. The dams and tunnels store river water, move it to places where it can irrigate crops or serve urban populations, and harness its flow to generate electric power. The Katse Dam in Lesotho is part of the Lesotho Highlands Water Project. It is the highest dam above sea level in the Southern Hemisphere. The Gariep Dam and the Vanderkloof Dam, both in South Africa, are elements in the Orange River Project.
The river also attracts tourists. Augrabies Falls is a group of waterfalls and rapids on the Orange River that is a famous natural wonder. The falls are the main tourist attraction at Augrabies Falls National Park in South Africa.
The Orange River was originally called the Gariep. Gariep is the Khoi word for “river.” This name is sometimes still used. In 1779 the Dutch officer Robert Jacob Gordon explored the river. He named it the Orange River in honor of the Dutch royal family, which is called the house of Orange. European settlers also called the river Grootrivier, which means “great river” in Afrikaans.
Throughout the 19th century the Orange River marked the northern limit of British power in southern Africa. Beginning in the 1830s, the Boers (Afrikaners) crossed it in search of land and freedom from British rule. They named their first republic—the Orange Free State—for the river.