South Africa’s longest river starts as Lesotho’s Senqu
The Orange River runs 2,432 kilometres from Drakensberg heights above 3,000 metres down to the Atlantic between Oranjemund and Alexander Bay. Its catchment, counting the Vaal, covers about 973,000 square kilometres—roughly three-quarters of South Africa’s land area—yet nearly two-fifths of that basin lies outside the country.
Inside Lesotho the upper reach is called the Senqu. Winter freezes at altitude can starve downstream flows that goat and cattle herds depend on. Westward the channel skims the Free State’s south-western edge into Gariep and Vanderkloof dams, carving a deeply incised bed until flatter country opens for irrigation. Southwest of Kimberley it meets its chief tributary, the Vaal, then crosses southern Kalahari and Namaqualand wilderness toward Namibia.
From 20°E longitude it forms some 550 kilometres of international frontier with Namibia’s ǁKaras Region, crossable by road at Vioolsdrif and by ferry at Sendlingsdrif. Along the final 800 kilometres intermittent feeders such as the Fish River add little under normal conditions because the Namib ends on the north bank. Augrabies Falls drop 56 metres across an 18-kilometre stretch where the bed again cuts deep. Rapids and sandbars about 33 kilometres from the sea keep long stretches closed to boats.
Rainfall collapses from about 2,000 millimetres a year at the source to under 50 millimetres at the mouth, so dry-season evaporation shrinks the river hard, while summer turns it into a brown torrent whose sediment load threatens dams and other works. Mountain tributaries such as the Caledon, Kraai and Senqunyane drain the Maloti highlands and deliver much of the yearly flow; several are now held back by reservoirs of the Lesotho Highlands Water Project, which sends water to South Africa and generates power for Lesotho.
The name honours the Dutch House of Orange and was bestowed by the explorer Robert Jacob Gordon, but older names survive: the Khoekhoe !Garib, simply meaning river, became the Afrikaans Gariep. The Ramsar-listed estuary between Oranjemund and Alexander Bay held between roughly 20,000 and 27,000 birds of 57 species in a 1985 count, a rare perennial wetland on that dry coast.
Source: Orange River
