The Orange River is the longest river in South Africa (total length of 2,200 km)
The Orange River Basin extends extensively into Namibia and Botswana to the north. It rises in the Drakensberg mountains in Lesotho, flowing westward 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 hydro-electric 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 Orange River runs westward through South Africa, forming the south-western boundary of the Free State province. In this section, the river flows first into the Gariep Dam (the largest in the country) and later into the Vanderkloof Dam. From the border of Lesotho to below the Van der Kloof Dam, the river bed is deeply incised. Further downstream the land is flatter and the river is used extensively for irrigation.
At the western point of the Free State, south-west of Kimberley, the Orange meets with its main tributary, the Vaal River, which itself forms much of the northern border of the province. From here the river flows further westward through the arid wilderness of the southern Kalahari region and Namaqualand in the Northern Cape province to meet with Namibia at 20°E longitude where it flows westward for 550 km, forming the international border between the province and Namibia's Karas Region. On the border, the river passes the town of Vioolsdrift, the main border post between South Africa and Namibia.
For the last 800 km (500 mi) of its course the Orange River receives many intermittent streams and several large ravines lead into it. In this section the Namib Desert ends on the north bank of the river, so under normal circumstances, the volume of water added by these tributaries is negligible. Here the bed of the river is once again deeply incised. The Augrabies Falls is located on this section of the Orange River where the river descends 122 m (400 ft) in a course of 26 km (16 mi).
The last 100 km or so of the Orange River, where gravel deposits in the river bed and along the banks, it is rich with diamonds and several diamond mines operate along this stretch.
The Orange empties into the Atlantic Ocean between the small towns of Oranjemund (meaning "Orange mouth") in Namibia and Alexander Bay in South Africa, about halfway between Walvis Bay and Cape Town. Some 33 km (21 mi) from its mouth it is completely obstructed by rapids and sand bars and is generally not navigable for long stretches.
During the temperate months of March and April, given good rains and the sluices of the dams being open, a canoeist (or rafter) can easily travel 30 km per day. The lower reaches of the river are most popular because of the spectacular topography. Commercial tours are available and some of the expeditions depart between Henkries and Goodhouse and others from the border town Vioolsdrift.
The Orange River has a relative rareness of species diversity. A 2011 survey of 13,762 fish found only 16 species of fish present. Three of these, the common Carp, the Mozambique Tilapia, and the Western Mosquitofish are not indigenous. Another exotic species, Rainbow Trout, is found in the river headwaters in Lesotho.
Seven species are endemic to the Vaal-Orange River system:
Over 120 species have been identified on our routes.The most common species are the African Darter (snakebird), Fish Eagle, Kingfisher, Grey- and Goliath Heron, Red-eyed Bulbul, Hadeda-Ibis, Sacred Reed-, White-breasted- and Bank Cormorant, Yellow Finch (Geelvink), Great White- and Cattle Egret, Cape Robin, Pied- and Cape Wagtail, Blacksmith Plover (Kiewiet), Cape White-eye, Mousebird, Hamerkop, Olive Thrush, Karoo Thrush, Spoonbill, White-tipped starling, Diederick Cuckoo, Cardinal Woodpecker, Barn Owl, Acacia Pied Barbet, Freckled Nightjar, African Hoopoe and the Orange River White-eye, to name but a few.
The coastal plains are home to many raptors, such as the Lanner- and Peregrine Falcon, Black-breasted Snake Eagle, and Rock Kestrel. In these vast, open plains you may also see about eight species of Lark, as well as the Booted and Verreaux’s (Black) Eagle, Ludwig’s Bustard, Dusky Sunbird, Ground Woodpecker and Southern Grey Tit.
The Orange River has no large animals. It lies outside the range of the Nile crocodile, and although hippopotami were once abundant, they were hunted to extermination in the 1800s.