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The Vaal Dam in South Africa was constructed in 1938 and lies 77 km south of OR Tambo International Airport. The lake behind the dam wall has a surface area of about 〔(【引用サイトリンク】title=VAAL DAM )〕 and is 47 meters deep. The Vaal Dam lies on the Vaal River, which is one of South Africa's strongest-flowing rivers. Other rivers flowing into the dam are the Wilge River, Klip River, Molspruit and Grootspruit.〔http://www.dwaf.gov.za/iwqs/gis_apps/dam/dams/vaal.htm〕 It has over of shoreline and is South Africa's second biggest dam by area and the fourth largest by volume. ==History== 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 above lowest foundation and a full supply capacity of . 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). The dam was subsequently raised in the early fifties to a height of which increased the capacity to . A second raising took place in 1985 when the wall was raised by a further to above lowest foundation. The capacity of the dam is currently and a further 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 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 . Flows above 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 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 long. The island was used as a secret meeting place by the apartheid government but now hosts the annual Round the Island Yacht race, a Guinness Book of World Records title of the largest inland yacht race.〔http://www.gauteng.net/attractions/entry/vaal_dam/〕 On 4 May 1948 BOAC introduced Short Solent flying boats on the UK (Southampton) to South Africa (Vaaldam) service.〔(【引用サイトリンク】title=Museum History 1940-1950 )〕 The small village of Deneysville was used as a stop-over point by the old BOAC flying boats. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Vaal Dam」の詳細全文を読む スポンサード リンク
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