Spanning the Woronora River, this concrete wall stands as a testament to engineering ingenuity. Today we are going to delve into the story of the Woronora Dam.
The Woronora Dam is more than just a water source. It is a piece of Sydney’s history. Its primary role is to supply potable water to Sydney’s southern suburbs and the northern Illawarra region. The reservoir impounds 71790 megalitres of water. You might hear people incorrectly call it Lake Woronora.
Construction of the Woronora Dam started in 1927. It was the fifth dam built as part of Sydney’s water supply. The Metropolitan Water Sewerage and Drainage Board of NSW oversaw its construction. However the Great Depression intervened in 1930. Work was suspended. Men sought work elsewhere leaving their families behind. Funds were released in 1931 to build a weir for water to Sutherland and Cronulla. Work resumed on the Woronora Dam itself four years later.
Finally the Woronora Dam was completed in 1941. It cost about A$13 million. Interestingly the Woronora Dam is not connected to the Upper Nepean Warragamba Shoalhaven system. It was built to supplement Sydney’s water while the larger Warragamba Dam was under construction. After completion six cottages were kept for on-site maintenance staff. The rest of the township became picnic and recreational areas.
Look closely at the dam’s structure. It is a curved mass gravity dam. This means it stays in place due to its own weight. The dam wall is 66 metres high and 390 metres long. The lower levels use cyclopean masonry. These are massive sandstone blocks quarried on-site. Blue metal and gravel concrete make up the 285000-cubic-metre main wall. Inside there are two inspection galleries.
Notice the separate serpentine spillway. It releases floodwater at 1470 cubic metres per second. This flows through a concrete-lined cutting into the river downstream. In 1988 the Woronora Dam was upgraded. A$2.9 million was spent on wall and foundation drains. This ensured it met international safety standards.
The Woronora Dam’s catchment area spans 75 square kilometres. The Sydney Catchment Authority manages the dam and its facilities. No towns exist in the catchment area. However the Princes Highway, Heathcote Road, and the Illawarra railway line pass through it. Sutherland and Campbelltown are also nearby.
Raw water from the Woronora Dam is pumped to the adjacent Woronora Water Filtration Plant. This plant is one of nine in Sydney. It’s operated by Sydney Water or private contractors. The Woronora Dam and filtration plant supply water south of the Georges River. This includes Sutherland Helensburgh Otford and Bundeena.
The Maritime Operations Division even uses the reservoir for sonar testing. Their testing station sits on a pontoon in the middle of the reservoir.
You can experience the Woronora Dam firsthand. There is a walking trail across the dam wall. A picnic area and carpark are also available.
The building of the Woronora Dam even made its way into popular culture. It featured in the comedy drama Dad Rudd MP. Construction scenes were filmed here employing workers and their families as extras.
The Woronora Dam is a state heritage site. It was added to the New South Wales State Heritage Register on 18 November 1999. This recognizes its significance to Sydney’s water supply. The design and construction of the dam involved prominent engineers. Gerald Haskins Stanley T Farnsworth and William Hudson all contributed.
The Woronora Dam stands as a picturesque scene. The long curved wall complements the wide valley of the Woronora River. The forested hillsides add to its beauty. The crest house and valve house showcase Inter-war Stripped Classical style.
The Woronora Dam is more than just a dam. It is a testament to engineering history. It also offers insight into the lives of those who built it. Take a moment to appreciate this vital part of Sydney’s water supply. Enjoy the views and reflect on the Woronora Dam’s enduring legacy.