Upper Nepean dams
The dams of the Upper Nepean collect water from the catchments of the Cataract, Cordeaux, Avon and Nepean rivers, which are tributaries of the Upper Hawkesbury-Nepean River. These systems supply water to the Macarthur and Illawarra regions, the Wollondilly Shire, and metropolitan Sydney.
Why were the Upper Nepean Dams built?
The innovative Upper Nepean Scheme was Sydney's fourth source of water supply. Completed in 1888, the scheme diverted water from a series of weirs on the Cataract, Cordeaux, Avon and Nepean rivers to Prospect Reservoir via 64 kilometres of tunnels, canals and aqueducts collectively known as the Upper Canal. The Upper Canal System, which relies on gravity to divert water, was a remarkable feat of the time, and functions as efficiently today as it did more than 100 years ago.
However, the Upper Nepean Scheme brought only temporary relief to Sydney's water supply problems. After two Royal Commissions into Sydney's water supply, the authorities agreed to build a dam on Cataract River. The successive building of Cataract, Cordeaux, Avon and Nepean dams between 1907 and 1935 greatly improved the Upper Nepean Scheme's capacity.