| Vaal Dam | |
|---|---|
| Official name | Vaal Dam |
| Location | Gauteng Free State |
| Dam and spillways | |
| Impounds | Vaal River |
| Reservoir | |
| Creates | Vaal Dam |
| Capacity | 2,536,000,000 cubic metres (8.96×1010 cu ft)[1] |
| Surface area | 320 square kilometres (120 sq mi)[1] |
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Vaal Dam
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The Vaal Dam in South Africa was constructed in 1938 and lies 77 km south of OR Tambo International Airport Formerly Jan Smuts Airport, then renamed Johannesburg International Airport in 1994, before being renamed yet again on 27 October 2006 as ORT. The lake behind the dam wall has a surface area of about 320 square kilometres (120 sq mi)[1] and is 47 meters deep. The Vaal Dam lies on the Vaal River, which is one of South Africa's strongest-flowing rivers. It has over 800 kilometres (500 mi) of shoreline and is South Africa's second biggest dam by area and the third largest by volume.
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The construction of Vaal Dam started during the depression of the early thirties and the dam was completed in 1938 with a wall height of 54.2 metres (178 ft) above lowest foundation and a full supply capacity of 994,000,000 cubic metres (3.51×1010 cu ft). The dam is a concrete gravity structure with an earthfill section on the right flank. It was built as a joint venture by Rand Water and the Department of Irrigation (now known as the Department of Water Affairs and Forestry).
The dam was subsequently raised in the early fifties to a height of 60.3 metres (198 ft) which increased the capacity to 2,188,000,000 cubic metres (7.73×1010 cu ft). A second raising took place in 1985 when the wall was raised by a further 3.05 metres (10.0 ft) to 63.4 metres (208 ft) above lowest foundation. The capacity of the dam is currently 2,536,000,000 cubic metres (8.96×1010 cu ft) and a further 663,000,000 cubic metres (2.34×1010 cu ft) or 26% can be stored temporarily for flood attenuation.
The flood attenuation properties of the dam were severely tested in February 1996 when the largest flood ever recorded at the Vaal Dam site was experienced. An inflow of over 4,700 cubic metres per second (170,000 cu ft/s) was measured into the Vaal Dam which was already at full capacity due to good rains and it was only through the expert management of the Hydrology staff at DWAF that the maximum flood released from the dam was limited to 2,300 cubic metres per second (81,000 cu ft/s). Flows above 2,300 cubic metres per second (81,000 cu ft/s) would have caused serious damage downstream of Vaal Dam and the situation during the 1996 flood became extremely tense as the storage in the reservoir peaked at 118.5% of Full Supply Capacity on 19 February 1996 i.e. only 194,000,000 cubic metres (6.9×109 cu ft) of flood absorption capacity remained before the full inflow would have been released causing massive damage.
The Lesotho Highlands Water Project pumps water into the system in order to supply water to the people and industrial complex of Gauteng. This water is piped from Lesotho into the Liebenbergsvlei and Wilge Rivers.
The Sterkfontein Dam forms part of the Tugela-Vaal water transfer scheme for the interbasin transfer of water from the Thukela River in KwaZulu-Natal to boost the levels in the Vaal River System. Water from the Sterkfontein Dam is released once the Vaal Dam drops to below 16%.
The dam has its own island some 5 km (3 mi) long. The island was used as a secret meeting place by the apartheid government but now hosts the annual Round the Yacht race, a Guinness Book of World Records title of the largest inland yacht race. [2]
On 4 May 1948 BOAC introduced Short Solent flying boats on the UK (Southampton) to South Africa (Vaaldam) service.[3] The small village of Deneysville was used as a stop-over point by the old BOAC flying boats.
Many world class watersport events are held here including the annual "Round The Island" yacht race organized by Lake Deneys Yacht Club—[4] a race that has been in the Guinness Book of Records for being the "Longest Inland Yacht Race in the World". Several large events take place here including Keelboat Week and the Bayshore 200 km jetski race, and now the Bayshore Marina Vaal Dam Treasure Hunt.
Three provinces make up the Dam's shoreline - the Free State is the largest by area, Mpumalanga has a beautiful and relatively unspoilt shoreline, while the most despoiled by far is that of Gauteng. The dam was commissioned in 1939, has a capacity of 2.536 cubic kilometres (2,056,000 acre·ft),[1] and a surface area of 320 square kilometres (120 sq mi),[1] the dam wall is 63 metres (207 ft) high. Due to the large lake size reservoir there is a problem with evaporation, see Sterkfontein Dam for more details.
Deneysville is the largest town on the Vaal Dam and provides the shopping centre for the Dam. There are Three yacht clubs and two Marinas the famous "Round The Island" yacht race is held at the Lake Deneys Yacht Club. This race has entered the Guinness Book of Records for the most boats in an inland yacht race.
More information on Deneysville including types of Accommodation available as well as information can be had from http://www.deneysville.com
| External images | |
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| Vaal Dam from the DWAF | |
| Vaal Dam from the DWAF | |
