- Olifants River (Western Cape)
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Coordinates: 31°42′01″S 18°11′15″E / 31.7002°S 18.1876°E
The Olifants River is a river in the Western Cape Province of South Africa. The river is approximately 285 km long with a catchment area of 46, are220 km² and flows into the Atlantic Ocean. The major towns in the Olifants/Doring river catchment include Lutzville, Vredendal and Vanrhynsdorp situated in the lower catchment area and Clanwilliam and Citrusdal in the middle catchment areas. The upper and main catchment area of the Olifants river is Ceres and the Cederberg mountains. The Clanwilliam and Bulshoek dams are located in the river and provide water for the towns and farms along the river.
Watershed
The Olifants River rises in the Agter Witzenberg Mountains north of Ceres. The mainstem is about 250 km long. The river flows to the north-west through a deep, narrow valley that widens and flattens into a wide floodplain below Clanwilliam. The tributaries flowing from the east (Ratel River, Thee River, Noordhoek River, Boontjies River, Rondegat River, Jan Dissels River) are typically perennial, while those flowing from the west (Seekoeivlei River) are seasonal and do not contribute much to the flow in the system. The river eventually drains into the Atlantic Ocean near Papendorp.
Dams in[verification needed] the Olifants River:
- Clanwilliam Dam, with a storage capacity of 127,000,000 cubic metres (4.5×109 cu ft)
- Bulshoek Dam, with a storage capacity of 7,500,000 cubic metres (260,000,000 cu ft)
Ecology
The upper Olifants River is one of the main dwelling places of adult Sawfins ("Barbus" serra). This local endemic is classified as Endangered by the IUCN. At present it is so rare as to be jeopardized by angling or fishing and may not be killed or caught; a long-lived species, it needs several years to grow undisturbed but reaches an adult almost 40 cm after a decade. CapeNature has done trials to adapt it for aquaculture or fishery, but this requires better conservation of the river ecosystem. The Clanwilliam Redfin ("B." calidus) is another threatened and legally protected species found in the Olifants River; it is more[1]
The Clanwilliam Yellowfish (Labeobarbus capensis) is another large cyprinid endemic to the Western Cape region. It has been subject to some captive breeding effort and its stocks are in better shape. However, it may have gone extinct in the Olifants River, and at least is almost certainly gone from between Olifants Gorge and Clanwilliam Dam. Whether it will be reintroduced is unclear, as Sawfin and Clanwilliam Yellowfish adults are probably ecological competitors, and until the Olifants River is sufficiently restored ecologically might not be able to thrive both.[2]
The most severe biological threat to the river's ecosystem is probably the Smallmouth Bass (Micropterus dolomieu). Originally introduced for sport fishing, is has become something of a pest by depleting the stocks of other fish species. Its eradication is encouraged under the Cape Action for People and the Environment program.
Non-biological threats are mainly excessive removal of river water for irrigation, and the resultant toxic surface runoff from plantations (especially agrumes). These are often grown right up to the river bank, without leaving sufficient natural vegetation to filter out pesticides and fertilizer and halt erosion, and thus causing both river and adjacent cropland to degrade.[3]
Footnotes
References
- Impson, D. & Swartz, E. (2007a). Barbus calidus. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 20 September 2009.
- Impson, D. & Swartz, E. (2007b). Barbus serra. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 21 September 2009.
- Impson, D. & Swartz, E. (2007c). Labeobarbus capensis. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 21 September 2009.
Categories:- Rivers of the Western Cape
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