Orange River

The Augrabies Falls in full flow

In the dry winter, 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 about 2,000 mm per annum, but precipitation decreases as the river flows westward; at its mouth, the rainfall is less than 50 mm per year. The factors that support evaporation, though, tend to increase in a westerly direction. 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.[9]

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). Around 366,000 km² (38%), however, are situated outside the country in Lesotho, Botswana, and Namibia.

Some of the earliest precolonial inhabitants called the river ǂNūǃarib, referring to its black colour, or sometimes just Kai !Arib ("Great River"), from which is derived the Afrikaans version Gariep, and translation "Groote Rivier".[8] The early Dutch name for the river was just that translation, Groote Rivier, meaning "Great River".[10] The river was named the Orange River by Colonel Robert Gordon, commander of the United East India Company (VOC) garrison at Cape Town, on a trip to the interior in 1779.[8] Gordon named the river in honor of William V of Orange.[8] 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, itself derived from the name ǀHaiǃarib "pale 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.[8] In Lesotho, where the river rises, it is known as the Senqu River, derived from the original Khoemana name.

Panorama taken from a fluorspar-rich hill overlooking a bend in the River, which was in flood due to above-normal rains

The Eastern Cape Geographical Names Committee has advertised its intention to consider a name change from the colonial name, for that portion of the river that forms the border between the Eastern Cape and the Free State, with suggestions being IGqili or Senqu.[11][12] The advertisement placed in the Aliwal Weekblad newspaper states that the "present name is perceived to have a strong association with the history of colonial subjugation and has therefore no place under the current democratic dispensation."[12]

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 use 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 hydroelectric power,
• to provide a reliable water supply for users in the Orange River basin, and
• to give a new lease on life to water-deficient areas in the Eastern Cape, such as the Great Fish and Sundays River valleys.

The Gariep Dam near Colesberg, previously 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 hydroelectric 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.

The Gariep Dam on the Orange River is the largest dam in South Africa, and was a key part of the Orange River Project.

Eskom operates hydroelectric power stations at both the Gariep Dam and the Vanderkloof Dam. The hydroelectric 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.

View over the eastern part of the dam, with the water intake at Oviston

A vineyard on the Orange River

Various irrigation projects along the river

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 Gariepand Vanderkloof Dams. Old, established irrigation schemes such as those at Buchuberg, Upington, Kakamas, and Vioolsdrif have also benefitted because regulation of the flow is now possible. On the Namibian side of the river, Aussenkehr produces grapes with the help of water from the Orange.

In recent years, the wine-producing areas along the Orange River have grown in importance. Irrigation in the Eastern Cape has also received a tremendous boost, not only from the additional water 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.

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 used the Sterkfontein Dam, located near Harrismith in the Free State.

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 on the Orange River is a popular tourist activity.

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.

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 not indigenous. Another exotic species, rainbow trout, is found in the river headwaters in Lesotho.

The smallmouth yellowfish (Labeobarbus aeneus) is a popular sport fish endemic to the Orange-Vaal River system.

Seven species are endemic to the Vaal-Orange River system:[13]

• Rock-catfish (Austroglanis sclateri)
• Maluti redfin or Maloti minnow (Pseudobarbus quathlambae)
• Namaquab barb (Barbus hospes)
• River sardine (Mesobola brevianalis)
• Smallmouth yellowfish (Labeobarbus aeneus)
• Largemouth yellowfish (Labeobarbus kimberlyensis)
• Orange River Mudfish (Labeo capensis)

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.[14]

Twin Falls in Augrabies Falls National Park