|Historical notes: ||The early growth of Sydney’s water supply followed the English (and European) practice of depending on supply from local perennially flowing rivers and streams, sometimes from behind a weir or small dam.
Australian conditions, however, are quite different from European conditions, and the eventual realisation that local supplies would always be inadequate led, in 1880, to the concept of harvesting water in the southern highlands, collecting it in major storage dams, and bringing it to Sydney by canals and pipelines. Thus, in 1888, the Upper Nepean Scheme came into being and, in later years, its progressive development followed with the construction of Cataract, Cordeaux, Avon and Nepean Dams, the latter being completed in 1935.
By that time, it was appreciated that the growth of Sydney would, in the not too distant future, require water supply augmentation of a magnitude which could be met only by the construction of a major dam on the Warragamba River.
Because of the engineering difficulties and the very high cost of that project, it was decided first to utilise the Woronora River, being the only other significant river close to Sydney and construct on it a dam of size comparable with the Upper Nepean Scheme dams, thus enabling the deferral of Warragamba.
Consequently, construction of Woronora Dam commenced in 1927, with the two objectives of providing a water supply for the Sutherland/Cronulla area and supplementing the Upper Nepean Scheme supply to the southern parts of the metropolitan area.
As a result of financial difficulties, the dam was planned in stages, with the first stage being a small dam comprising a 45 feet high (13.7m) overshot weir impounding 206 million gallons (937 megalitres). The design for this incorporated the preparation of the ground to enable the construction of the final dam at a later stage and all excavation and preparation of the foundations were done with the ultimate structure in view. A second weir at Engadine near the confluence of the Woronora River and Heathcote Creek provided a pumping pond from which water was pumped to a reservoir at Engadine. Owing to the intervention of the economic depression, the first stage was not completed until 1931 and work ceased at that point. In late 1935, construction recommenced and then continued until completion of the dam, 216 feet high (66m) impounding 15,792 million gallons (71,790 megalitres), in late 1941. When the dam and pipeline to Penshurst were completed as far as Engadine, the weir at Engadine was abandoned. It was later destroyed by explosives.
Although only 56km from Sydney, Woronora Dam was built by a day labour workforce which, in the tradition of the Upper Nepean Dams was housed in a local construction township at the dam site. The standard of these townships had improved with each successive dam and Woronora, being the last of the series, had the highest standard until the advent of the Warragamba township.
Some families went from Nepean to Woronora, then eventually moved on to Warragamba, but the tradition ended there, as no new major dams were built after that time.
When construction was completed, some half dozen of the better cottages were retained for the permanent maintenance staff, and these have since been replaced with modern cottages.
Extensive picnic areas have been provided at Woronora Dam. There are shelter sheds, barbecues, hot water urns, and well maintained toilets all set out amongst attractive gardens.
Woronora Dam is the only one of Sydney’s major water supply storage dams not part of the main Upper Nepean/Warragamba/Shoalhaven interconnected system, as it was developed to supply those southern parts of Sydney which were, at the time, beyond the effective reach of the Upper Nepean scheme. It now serves only the Sutherland/Cronulla/Heathcote areas. So great has been the population growth in recent years that Warragamba water, also, is now fed to the Sutherland/Cronulla area.