Avon Dam was the third and largest of the four dams constructed to collect water from the Illawarra Plateau. Created by damming the Avon River and completed in 1927, Avon Dam’s main role today is to supply water to the Illawarra region. It is Sydney’s second largest dam after Warragamba (nearly 150 GL operating capacity), but has a small catchment (142 square kms).
When I began the series of articles of the Dams of Greater Sydney in early 2021, we visited every dam except Avon Dam, which was closed due to a bridge that needed to be maintained as a result of heavy rain. Sydney then went into lockdown due to COVID19 in early August so there hasn’t been an opportunity to visit this dam until very recently.
Work on Avon Dam began in 1921 and was completed in 1927. The curved dam wall (72m high and 223m in length) was built using cyclopean masonry. This consisted of sandstone blocks, quarried from the site, fitted into an irregular pattern and packed with sandstone concrete. The blocks were lifted into place by electric powered cranes.
The massive stone gateways at either end of the dam wall were inspired by the popularity of all things Egyptian following the discovery of King Tutankhamun’s tomb in 1922. The picnic area has remnant features that evoke images of an Egyptian revival landscape. These include remnants of fountains and ponds and an old fernery.
The rock was quarried to make a deep cut through a ridge to a neighbouring creek to provide the dam’s spillway, which discharges into the Avon River 800 metres downstream.
Avon Dam was strengthened in 1971 and again in the 1980s. A tunnel linking Avon and Nepean dams, to enable the transfer of water between dams in either direction, was completed in 1973.
When we visited, the spillway was not in operation but has an interesting serpentine design. There was also an area next to the dam wall which contained a number of buildings that was marked as “No Access” on the map but I walked around anyway.