Warragamba Dam

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Image:Warragamba Dam.jpg Warragamba Dam is the structure that provides the major water supply for Sydney, Australia, situated approximately 65 km to the west of Sydney in the Burragorang Valley.

Warragamba River flows through a 300-600 m wide gorge, about 100 m deep before opening out into a large valley. This allows a relatively short and high dam to impound a vast quantity of water. In 1845, Paweł Edmund Strzelecki first drew attention to Warragamba River as a water supply catchment. A dam was first proposed in 1867, with various schemes proposed and investigated between then and 1946 when the site and design of the current dam was approved.

Construction began in 1948 and was completed by 1960. It dams the Warragamba River to form Lake Burragorang which is one of the largest reservoirs for urban water supply in the world. There is also a hydroelectric power station at the dam which can generate 50 MW.

The dam wall comprises 3,000,000 tonnes (1,200,000 m³) of concrete. In order to control the temperature rise as the concrete set, ice was added to the mix (the first time this had been done in Australia) and chilled water was circulated through cooling pipes embedded in the concrete.

Between 1987 and 1989, the dam wall was raised by 5 m. Between 1998 and 2002, an auxiliary spillway was constructed on the east bank of the dam. Both these measures were undertaken following a re-evaluation of the potential rainfall and flood risks.

Although it was not designed as a flood control measure, Warragamba Dam can mitigate flooding downstream by holding floodwaters back while the reservoir fills. Its limitations, however, become apparent when the reservoir reaches capacity and water must be released through the floodgates.

Warragamba Dam is also a popular picnic spot for Sydneysiders, with up to 3000 people visiting the area on Father's Day.