page_title: Warragamba Dam
section_title: Spillway
hierarchical_section_title: Warragamba Dam / Overview / Spillway
caption_attribution_description: Warragamba Dam
context_page_description: Warragamba Dam is a heritage-listed dam in Warragamba, Wollondilly Shire, New South Wales, Australia. It is a concrete gravity dam, which 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 65 kilometres 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 2,031 gigalitres and is fed by a catchment area of 9,051 square kilometres. The surface area of the lake covers 75 square kilometres 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.
  The dam was devised as part of a collective engineering response to Sydney's critical water shortage during World War II and was originally known as the Warragamba Emergency Scheme.
context_section_description: The main spillway has five crest gates: A central drum gate with a 27 metres (89 ft) clear span with a pair of radial gates on each side. Each radial gate has a 12 metres (39 ft) clear span. The drum gate is hinged along the upstream edge to the upstream crest and lowers into the dam wall to allow water to flow over it. When fully open, it forms a continuation of the crest profile. All gates open automatically as the dam passes full water level, or can be manually opened. The auxiliary spillway is normally closed by a series of fuse plugs that are designed to be washed away in the event of an extreme flood event.
  As originally designed, the dam could safely withstand a peak inflow of 500,000 cubic feet per second (14,000 m³/s), leading to a peak discharge of 354,000 cubic feet per second (10,000 m³/s) down the spillway. Following a 1987 and 1989 re-evaluation of the potential rainfall and flood risks, the New South Wales Government authorised for the dam wall to be raised by 5 metres (16 ft) and constructed an auxiliary spillway on the east bank of the dam.
caption: Warragamba Dam
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