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Warragamba Dam, a concrete gravity dam, creates Lake Burragorang, the primary reservoir for water supply for the Australian city of Sydney, New South Wales. The dam impounds the Coxs, Kowmung, Nattai, Wingecarribee, Wollondilly, and Warragamba rivers, within the Hawkesbury-Nepean catchment; and the dam wall is located approximately to the southwest of Sydney central business district, near the town of Wallacia. Constructed between 1948 and 1960, the dam created capacity for a reservoir of and is fed by a catchment area of . The surface area of the lake covers of the now flooded Burragorang Valley. Enhancements to the dam were completed in 2009, including the addition of an auxiliary spillway to manage extreme flood events. A small hydroelectric power station is incorporated into the design of the dam and may operate at times of peak discharge; but has rarely generated power in recent years. In early March 2012, the dam spilled for the first time in fourteen years, as a result of heavy rainfall in the catchment during February 2012. This spill followed a period of prolonged drought which saw the dam fall to historic lows of below 33 percent in 2007. == Overview == The Warragamba River flows through a gorge that varies in width from to , and is in depth. This gorge opens at its upper end into a large valley, the Burragorang Valley. This river configuration allows for a relatively short but high dam wall, in the gorge, to impound a vast quantity of water.〔 An account of the development and history of the water supply, sewerage, and drainage systems of Sydney and the near south coast from their beginnings with the first settlement to 1960.〕 In 1845, Paweł Strzelecki drew attention to the Warragamba River as a water supply catchment; in 1867, supporters proposed a dam. Between 1867 and 1946, supporters proposed various schemes before the site and design of the current dam received approval. In 1940, a weir and pumping station, known as the Warragamba Emergency Scheme, reached completion, just downstream of the main dam site.〔 In 1943 the Metropolitan Water, Sewerage and Drainage Board invited the geologist William Browne to investigate a proposed site. Browne found a more suitable site and continued as geological adviser until completion. The site was reviewed and approved by Dr John Savage, considered the pre-eminent expert in this field, and formally accepted by the Metropolitan Water, Sewerage and Drainage Board on 2 October 1946.〔 The Board appointed Thomas Upton as the engineer. Dam construction began in 1948 and was completed in 1960. The resulting dam of the Warragamba River formed Lake Burragorang, which is one of the largest reservoirs for urban water supply in the world. The dam wall comprises of concrete. It was laid as interlocking blocks roughly on each side, which were later grouted together to form a continuous, monolithic wall. It is so large that engineers had to use two techniques to prevent the temperature from becoming too hot as the concrete set. One was to add ice to the wet concrete, the first application of this technique in Australia. The other was to embed cooling pipes into the concrete and circulate chilled water through the pipes. As a result, the dam wall was cooled in a few months instead of the estimated 100 years it would have taken to cool naturally.〔 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「Warragamba Dam」の詳細全文を読む スポンサード リンク
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