|Gariep, Oranje, Senqu|
|Countries||Lesotho, South Africa, Namibia|
|- right||Caledon River, Vaal River, Fish River (Namibia)|
|Landmarks||Gariep Dam, Augrabies Falls|
|Source||Thaba Putsoa |
|- location||Maloti Mountains (Drakensberg), Lesotho|
|- elevation||3,350 m (10,991 ft)|
|- location||Atlantic Ocean|
|Length||2,200 km (1,367 mi)|
|Basin||973,000 km2 (375,677 sq mi)|
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).
The Orange River (Afrikaans/Dutch: Oranjerivier), Gariep River, Groote River or Senqu River is the longest river in South Africa. 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, Kimberly, and Aggeneys, 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.
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. While in Lesotho, the river is known as the Senqu and parts of it freeze in winter, because of the high altitude there. This creates droughts downstream of it which mainly affects goat and cattle production.
The river then 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, southwest 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 the 20th degree of east longitude. From here 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 Vioolsdrif, the main border post between South Africa and Namibia.
In the last 800 km (500 mi) of its course the Orange receives many intermittent streams and several large wadis lead into it. In this section, the Namib Desert terminates 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 Hundred Falls or Augrabies Falls are located on this section of the Orange, where the river descends 122 m (400 ft) in a course of 26 km (16 mi).
The Orange empties into the Atlantic Ocean at Alexander Bay, which lies about equidistant between Cape Town and Walvis Bay. 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.
The river has a total length of 2,200 km (1,400 mi).
Catchment and rainfall 
In the dry winter months the volume of the water in the river is considerably reduced because of the rapid run-off and evaporation. At the source of the Orange the rainfall is approximately 2,000 mm per annum but precipitation decreases as the river flows westward; at its mouth the rainfall is less than 50 mm per annum. The factors that support evaporation, on the other hand, tend to increase in a westerly direction. However, in the wet season (summer) the Orange river becomes an impetuous, brown torrent. The huge mass of sediment carried constitutes a long-term threat to all engineering projects on the river.
The total catchment of the Orange River (including the Vaal) extends over 973,000 km², i.e. equivalent to about 77% of the land area of South Africa (1,268,5358 km²). Approximately 366,000 km² (38%), however, is situated outside the country in Lesotho, Botswana and Namibia.
Name of the river 
The earliest pre-colonial inhabitants called the river Gariep'. The river was named the Orange River by Colonel Robert Gordon, commander of the Dutch East India Company garrison at Cape Town, on a trip to the interior in 1779. Gordon named the river in honor of William V of Orange. A popular but incorrect belief is that the river was named after the supposedly orange color of its water, as opposed to the color its tributary, the Vaal River ( 'vaal' being Afrikaans for pale or grey). Since the end of apartheid, the name "Gariep" has had greater favour in official correspondence in South Africa, although the name "Orange" has greater international recognition. In Lesotho, where the river rises, it is known as the Senqu River.
As the collection point for the majority of South Africa's water, the Orange River plays a major role in supporting agriculture, industry and mining. To assist in this, two large water schemes have been created, the Orange River Project and the Lesotho Highlands Water Project. Historically, the river played an important role in the South African diamond rush, with the first diamonds in the country being discovered in alluvial deposits on the Orange. Today, several commercial diamond mines operate along the final stretch of the Orange River and around its mouth. Finally, because of the lack of dangerous animals and high water levels during summer, the river is used for recreational canoeing and rafting. Orange River Rafting has become very popular with many companies using their camps along the river to operate from. The most popular trips are a 4 day and a 6 day river trips that take place either along the Gorge or along the Richtervelt area.
Orange River Project 
The Orange River Project (ORP) was one of the largest and most imaginative projects of its kind in South Africa. It was constructed by Hendrik Verwoerd's government at the height of the apartheid era. The ORP was built to utilise the unused water of the Orange River — which, without the Vaal River, represents some 14.1% of the total runoff in South Africa — and in the process, to satisfy an increasing demand for water. The main objectives of the project were:
- to stabilise river flow,
- the generation and transmission of hydro-electric power,
- to provide a reliable water supply for users in the Orange river basin, and
- to give a new lease of life to water-deficient areas in the Eastern Cape such as the Great Fish and Sundays River valleys.
The Gariep Dam near Colesberg, named the Hendrik Verwoerd Dam when built, is the main storage structure within the Orange River. From here the water is supplied in two directions: westward along the Orange River (via hydro-electric power generators) to the Vanderkloof Dam which was previously named the PK le Roux Dam, and southward through the Orange-Fish Tunnel to the Eastern Cape.
Eskom operates hydro-electric power-stations at both the Gariep Dam and the Vanderkloof Dam. The hydro-electric power station at the Vanderkloof Dam was the first power-generation station in South Africa situated entirely underground. The towns Oviston and Oranjekrag were established to facilitate the construction and operation of the new infrastructure.
Irrigation in the vast area downstream of the Vanderkloof Dam, which has turned thousands of hectares of arid veld into highly productive agricultural land, was made possible by the construction of the Gariep Dam and the Vanderkloof Dam. Old, established irrigation schemes such as those at Buchuberg, Upington, Kakamas and Vioolsdrif have also benefitted because regulation of the flow is now possible.
In recent years the wine producing areas along the Orange River have also grown in importance. See the article Northern Cape wine.
Irrigation in the Eastern Cape has also received a tremendous boost, not only from the additional water that is being made available but also owing to improvement in water quality. Without this improvement the citrus farmers along the Lower Sundays River would almost certainly have continued to suffer losses of productivity.
Lesotho Highlands Water Project 
The Lesotho Highlands Water Project was conceived to supplement the water supply in the Vaal River System. Water is delivered to South Africa by means of the Delivery Tunnel which passes under the Lesotho South Africa border at the Caledon River and then under the Little Caledon River south of Clarens in the Free State and discharges into the Ash River about 30 km further to the north. The scheme became viable when water demands in Gauteng reached levels that could no longer be supported economically by alternative schemes such as the Tugela River-Vaal River pumped storage scheme, which utilized the Sterkfontein Dam, located near Harrismith in the Free State.
Alluvial diamonds 
In 1867, the first diamond discovered in South Africa, the Eureka Diamond, was found near Hopetown on the Orange River. Two years later, a much larger diamond known as the Star of South Africa was found in the same area, causing a diamond rush. This was soon eclipsed by the diamond rush to mine diamonds directly from kimberlite at Kimberley in 1871, although alluvial diamonds continued to be found in the Orange. Today, several commercial diamond mines operate on the last stretch of the river, as well as the beaches around its mouth. Diamond mines also operate on the middle stretch of the river.
Rafting and canoeing 
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 these expeditions depart from the border town of Vioolsdrif.
Fish species 
The Orange River has a relative paucity 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 non-indigenous. Another exotic species, rainbow trout, are found in the river headwaters in Lesotho.
- Rock-catfish (Austroglanis sclateri)
- Maloti minnow (Pseudobarbus quathalambe)
- Namaqua barb (Barbus hospes)
- River sardine (Mesobola brevianalis)
- Smallmouth yellowfish (Labeobarbus aeneus)
- Largemouth yellowfish (Labeobarbus kimberlyensis)
- Orange River Mudfish (Labeo capensis)
Larger animals 
- Thomas Kruchem: Orange~Senqu. Artery of Life. Deutsche Gesellschaft für internationale Zusammenarbeit (GIZ), Eschborn, Germany 2012, ISBN 978-3-86099-884-7.
See also 
- List of rivers in South Africa
- List of international border rivers
- List of crossings of the Orange River
- Dams on the Orange River (or tributaries)
- Waterfalls on the Orange River
- Augrabies Falls
- Twin falls
- Key rivers of South Africa
- Swanevelder, C. J. (1981), Utilising South Africa's largest river: The physiographic background to the Orange River scheme, GeoJournal vol 2 supp 2 pg 29-40
- Revenga, C.; Murray, S.; Abramovitz, J. and Hammond, A . (1998) Watersheds of the world: Ecological value and vulnerability, World Resources Institute, ISBN 1-56973-254-X
- Earle, Anton et al. (2005), A preliminary basin profile of the Orange/Senqu River (pdf), African Centre for Water Research, retrieved 30 June 2007
- The Northern Ephemeral Rivers of the Orange-Senqu River Basin
- Ramollo, P. P. (2011). "Freshwater Fish Abundance and Distribution in the Orange River, South Africa". Journal of Fisheries International 6: 13–14. doi:10.3923/jfish.2011.13.17.
- G.C. Shortridge (1934). The mammals of South West Africa. William Heinemann Ltd.
|Wikimedia Commons has media related to: Orange River|
- Orange-Senqu River Commission (ORASECOM)
- Orange-Senqu River Awareness Kit - knowledge hub for the Orange-Senqu River basin
- Map of the Orange River basin at Water Resources eAtlas
- Map of portion of Orange River basin forming part of South Africa
- Information on the Orange River from the South African Department of Water Affairs and Forestry