Warragamba Dam
Available storage - the available storage in Sydney's water supply reservoirs. The figure is updated every Thursday after 3pm.
Weekly storage reports - providing more detailed weekly information including temperature, rainfall, supply and available storage in each of the dams and reservoirs.
Catchment rainfall - providing detail on average rainfall in the drinking water catchments for the 24 hours to 9am each working day.
Warragamba Dam
Located about 65 kilometres west of Sydney in a narrow gorge on the Warragamba River, Warragamba Dam is one of the largest domestic water supply dams in the world.
Water is collected from the catchments of the Wollondilly and Coxs River systems covering an area of 9,050 square kilometres to form Lake Burragorang and Warragamba Dam.
Lake Burragorang is the largest urban water supply in Australia, containing four times the volume of water of Sydney Harbour. It provides about 80 per cent of the water supply for nearly four million people in the Sydney region.
The Dams of Greater Sydney and Surrounds - Warragamba booklet outlines why and how the dam was built, how the dam works, recreational facilities at Warragamba Dam, and information on the Special Areas surrounding the dam. The Warragamba Dam 50th anniversary 1960-2010 booklet commemorates the 50th anniversary of the dam's opening.
Why Warragamba Dam was built
The Warragamba River had two important advantages as a site for a major dam. It had a large catchment area and the river flowed through a long and narrow gorge. The government could build a tall and narrow dam that could impound a vast amount of water.
Its potential was identified as early as 1845, but plans were deferred while the Upper Nepean dams were built between 1907 and 1935. An increasing demand for water from the expanding population, and a record drought from 1934 to 1942, forced the the government to develop Warragamba Dam to ensure a reliable water supply.
How the dam was built
Constructed between 1948 and 1960, Warragamba Dam was a major engineering feat of the mid 20th Century. Workers removed more than 2,300,000 tonnes of sandstone from the site. Concrete was mixed on site using 305,000 tonnes of cement and 2,500,000 tonnes of sand and gravel.
The dam was built in a series of interlocking concrete blocks. A system of overhead cableways lifting 18 tonne buckets was used to place the concrete.
Ice was mixed with the concrete to control the heat generated by the setting concrete and to prevent cracks forming. One of the first pre-stressed concrete towers in Australia was built to house the ice-making plant.
How the dam works
Warragamba Dam supplies bulk water to three Sydney Water filtration plants (Prospect, Orchard Hills and Warragamba), where it is filtered and distributed to people living in Sydney and the lower Blue Mountains.
The best quality water is selected and drawn through screens on three outlets in the upstream face of the dam. Water flows by gravity through a valve house into two pipelines that feed the raw water to Prospect Water Filtration Plant and via off-takes to the smaller filtration plants at Orchard Hills and Warragamba.
Eraring Energy owns and operates the 50 megawatt hydro-electric power station which generates power only when there is a high level of water in the lake.
How the dam is monitored
SCA officers inspect and monitor Warragamba Dam through a network of more than five kilometres of galleries inside the dam wall. They monitor water pressure, seepage and any physical changes in the dam wall and its foundations to ensure they fall within acceptable limits.
Warragamba Dam was designed to deflect slightly as the lake level rises and falls. These deflections are measured regularly using precise surveying techniques. Sensitive seismic equipment in the dam and surrounding catchment area monitors earth movements. The SCA regularly inspects and maintains crest gates, valves, pipelines, and associated equipment.
Safeguarding the dam
When rainfall and flood event studies showed that the dam could experience floods much larger than originally estimated, the height of the dam wall was raised by five metres as the first step in a two-stage solution to make the dam meet modern international dam safety standards. Between 1987 and 1989 the dam wall was raised and strengthened using post-tensioned steel cables, tying the upper portion of the wall to its base.
In late 1998, work began on stage two of the dam safety program, which involved building an auxiliary spillway on the east bank of the dam. The auxiliary spillway was completed in June 2002.
During rare and extreme floods, the auxiliary spillway will allow floodwaters to pass safely around the dam, reducing the pressure on the dam wall. This will protect the areas downstream of the dam from the devastating effects of a dambreak, and will safeguard Sydney’s water supply.
