Orange River
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The Orange River (Afrikaans: Oranjerivier, German: Oranjefluss or just Oranje), in the past also sometimes known as the Gariep or as the Grootrivier, is the major river of South Africa. The river was first discovered by indigenous people but only explored by Europeans in 1760 and named by Colonel Robert Gordon after the House of Orange. Another account of its naming suggests that it may have been called after the supposedly orangy colour of its water, as opposed to the colour of the water of the Vaal River ( 'vaal' being Afrikaans for pale or grey).
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[edit] Geography
The Orange rises in the Drakensberg mountains along the border between South Africa and Lesotho, about 193 km (120 miles) from the Indian Ocean and at an altitude of over 3000m. While in Lesotho, the river is known as the Senqu and parts of it freeze in winter, owing to the altitude there. It then runs 2200 km (1367 mi) westwards, at first along the south-western boundary of the Free State and then through the Northern Cape province and eventually discharges into the Atlantic Ocean in the west where it forms the southern border of Namibia with South Africa's Northern Cape Province
The most notable tributary is the Vaal River, which leads to the Wilge River and also rises in the Drakensberg where a source is known as the Ash River and is situated about 30 km north of Clarens in the Free State (Orange Free State). The Vaal River flows westwards towards Johannesburg and forms the boundary between the Transvaal and the Free State before joining the Orange southwest of Kimberley. Below its confluence with the Vaal, the Orange flows through the arid wilderness of the southern Kalahari region and Namaqualand. Here it forms the international border between South Africa and Namibia's Karas Region. The Namib Desert terminates at the river.
In the last 800 km (500 miles) of its course the Orange receives many intermittent streams and several large wadis lead into it. The area being desert, under normal circumstances the volume of water added by these tributaries is negligible. The Hundred Falls or Augrabies Falls are located on this section of the Orange. Here the river descends 122 m (400 ft) in a course of 26 km (16 miles).
The Orange empties into the Atlantic Ocean at Alexander Bay, which lies about equidistant between Cape Town and Walvis Bay. Some 33 km (20 miles) from its mouth it is completely obstructed by rapids and is generally not navigable for long stretches at any point, owing to sand bars and the like.
In the dry winter months the volume of the water in the river is considerably reduced because of the rapid run-off and due to evaporation. At the source of the Orange the rainfall is approximately 2000 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.
From the border of Lesotho to below the Van der Kloof Dam the river bed is deeply incised. Further downstream the land is flatter, with large areas under irrigation. Still further down, at Augrabies and at Vioolsdrif, the bed of the river is once again deeply incised. The total catchment of the Orange River (including the Vaal) extends over 973 000 km², i.e. about 77% of the land area of the RSA (1 268 535 km²). Approximately 366 000 km² (38%), however, is situated outside the country in Lesotho, Botswana and Namibia.
[edit] Water catchment
The water catchment of the Orange now supports two large water schemes, the Orange River Project and the Lesotho Highlands Water Project.
[edit] Orange River Project
The Orange River Project (ORP) was one of the largest and most imaginative projects of its kind in South Africa was constructed by 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.
[edit] Hydro-electricity
Eskom operates hydro-electric power-stations at both the 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.
[edit] Irrigation
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.
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.
[edit] 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 30km 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.
[edit] Miscellaneous
- There are important deposits of alluvial diamonds along the Orange River and around its mouth.
- In pre-colonial times the river almost certainly was home to the hippopotamus but, if so, these disappeared long ago.
- Because of the river's geographical position, it is too cold in winter to support crocodiles.
- Because of the lack of dangerous animals and high water levels during summer, the river is a great venue for canoeing; during the temperate months of March and April, given good rains and the sluices of the dams being open one 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.
