The Avon Dam is a heritage-listed dam in Avon, Wingecarribee Shire, New South Wales, Australia. It is one of four dams and weirs in the catchment of the Upper Nepean Scheme, providing water to the Macarthur and Illawarra regions, the Wollondilly Shire, and metropolitan Sydney. The arch dam across the Avon River was completed in 1927 under the supervision of Ernest Macartney de Burgh, the dam is currently managed by the Sydney Catchment Authority and is listed on the New South Wales State Heritage Register. History The Upper Nepean Scheme was commenced in 1880 after it was realised that the Botany Swamps scheme was insufficient to meet Sydney's water supply needs. The Nepean project consisted of the construction of a weir across the Nepean River to divert the rivers Cataract, Cordeaux, Avon and Nepean, to the Prospect Reservoir. By 1902 the original Nepean scheme was found also to be inadequate, after a severe drought had again depleted the water supply. A Royal Commission was appointed in 1902 to report on the water supply situation and in that same year, it recommended the construction of the Cataract Dam, to impound the waters of the Cataract River at a site upstream of Broughton's Pass. Construction of the dam was completed about the end of 1907. From 1907, rainfall on the catchment area was very low and it was not until January 1911 that Cataract Dam first filled to capacity. This, together with the greatly increased rate of consumption of water, stressed the need for additional water storage. The Nepean River watershed, from a topographical standpoint, was found to be very favourable for the construction of large water storage works at moderate cost. Rivers such as the Cordeaux, Avon and Nepean, located in narrow gorges, provided very suitable dam sites, with solid rock foundations at a shallow depth. Sandstone could easily be quarried into rough rectangular blocks and used for the construction. These features led to the recommendation that more dams be built. A site for a second storage dam, Cordeaux, to be built on the Cordeaux River, was selected by the Water Board in the latter part of the 1911 and a gauging weir was constructed. Preliminary plans and estimates were prepared and the foundations tested. Following this, further investigations were carried out by the Public Works Department. Good rainfall occurred throughout the succeeding years (except for a dry period in 1915–1916)