HAWKESBURY HISTORY
with Michelle Nichols & Jonathan Auld
Damming the Warragamba River
Warragamba Dam provides around 80 per cent of Greater Sydney’ s water supply and is celebrating a milestone birthday.
Just as it was vital in the early days of settlement of the colony, a permanent supply of water was essential to Sydney and its metropolitan surrounds, during the 19th and 20th centuries. The Tank Stream was used as the first water supply. It drained into the Harbour at Circular Quay but was ditched in the 1820s due to the water quality.
During the nineteenth century, the government of the day were seeking ways to supplement Sydney’ s water supply. Busby’ s Bore had assisted but with the development around Sydney, access to fresh water was vital.
First noted in the 1840s when Polishborn explorer and scientist, Paul de Strzelecki( responsible for identifying and naming Mount Kosciuszko in 1840), suggested Warragamba River as an effective catchment area, which formed part of an extensive river system commencing at the Wollondilly River before joining the Coxs River then the Warragamba River.
It then joined the Nepean River becoming the Hawkesbury River at Castlereagh. The Grose, Colo and Macdonald Rivers join it before it heads into the Pacific Ocean at Broken Bay.
Plans for Warragamba resurfaced in the 1860s when a Royal Commission was established by the Government to review the water supply. Naval officer and surveyor, Thomas Woore also proposed a dam at Warragamba but instead, in 1869 a project known as the Upper Nepean Dams, was given the green light. This scheme included several dams and weirs storing water which would supply both Sydney
View of Warragamba Dam, 2021. Photo M. Nichols
Warragamba Dam Progress, 1957. Electricity Commission of NSW [ Pacific Power ].
and the Wollondilly area.
The water from this scheme was gravity fed and stored in Prospect Reservoir and the project was completed in 1888 with additional work completed in 1907 and again in 1935. Irish born Ernest Macartney de Burgh who had joined the Department of Public Works in 1885 and was employed for survey work and then later as a bridge engineer, was acting principal assistant engineer for rivers, water-supply and drainage.
In 1903 he travelled to Europe where he studied dam construction and water supply before returning to Sydney to manage the Cataract Dam project. By 1913 he was employed as the chief engineer for water supply and sewerage and‘ was responsible for the design and construction of the Cordeaux, Avon and Nepean dams.’ In 1918 he drew up plans for a dam on the Warragamba River, which he had first suggested in 1910.
Demand for a dependable water supply for Sydney re-emerged and eventually a dam at Warragamba was agreed on in 1927, to be built once the work at Nepean was completed. The commencement was held up due to the 1930s depression, as well as the intense drought of the 1930s and early 1940s, resulting in the work not getting underway until 1942. The site on the Warragamba River was selected in 1946 and initially the river diverted. Excavation commenced two years later after thousands of trees and 2.3 million tonnes of sandstone were removed.
The construction of the concrete gravity dam started in 1950 and was considered a‘ major engineering work of its time’ taking a decade to complete. In 1827, the town of Burragorang was established as a mining town and up to the 1960s was a major supplier of coal. The Burragorang township, had to be repositioned as the original valley, was flooded as part of the project.
Water from the Wollondilly and Coxs River catchment area( over 9,000 square kilometres) formed Lake Burragorang, behind the dam, storing water approximately four times the size of Sydney Harbour.
The township of Warragamba was established to house the construction workers and was home to about 3,500 people at one stage. There were about 1,800 men‘ from at least 25 nationalities, many of whom were post WWII immigrants’ employed on the site, plus shops, churches and other facilities. The workers travelled from the town via two suspension bridges but these no longer exist.
Some interesting facts about the dam include; 2,300,000 tonnes of sandstone was removed from the site during construction; 305,000 tonnes of cement plus 2,500,000 tonnes of sand and gravel were mixed to create the concrete. To control heat generation in the cement and prevent cracks, ice was mixed with the concrete. The wall was 142 metres high and 104 metres thick at the base.
It is the largest concrete dam in Australia, and at the time it was
Construction of Warragamba Dam, 1956-1960. Photo: John L. M. Dooley. Courtesy State Library of NSW.
constructed, it was considered the‘ highest concrete gravity dam in the world on sandstone foundations’ and is one of the largest domestic water supply dams in the world.
The Warragamba Dam was officially opened in October 1960 by the Hon. Robert J. Heffron MP, the then Premier of NSW. Constructed for water storage, the dam was originally used to mitigate the floodwaters in 1961 and at other major flood events.
During the late 80s the dam wall was raised five metres and strengthened. Between 1999 and 2002, an auxiliary spillway was constructed, to assist during extreme flooding. The gates on top of the dam were also enhanced in 2008. These additional measures were completed as part of floodwater management for the Hawkesbury-Nepean River system.
Over the years, there have been many discussions about the future of Warragamba including raising the dam wall,( which may result in flooding of parts of the heritage listed Blue Mountains), and introducing flood mitigation. Nothing is yet set in concrete.
WaterNSW states clearly on their website that they are“ not permitted under the regulatory framework governing Greater Sydney dams to operate Warragamba dam … for storage for flood mitigation purposes.”
Meanwhile Warragamba, Australia’ s largest urban water supply dam, is currently at 96 per cent capacity. To check the current level, go to www. waternsw. com. au / supply / regional-nsw / dam-levels
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10 ISSUE 186 // NOVEMBER 2025 theindependentmagazine. com. au THE HAWKESBURY INDEPENDENT