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.

[1] 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.

[1] Good rainfall occurred throughout the succeeding years (except for a dry period in 1915–1916) and, because of this and the intervention of World War I, construction on the Cordeaux Dam was not commenced until 1918.

In November of that year a Special Board of Experts consisting of engineers from the Public Authorities was appointed by the Government to draw up recommendations for the amplification of the Sydney water supply.

Like its predecessors, Avon also had the upstream face of the dam sheathed with a layer of basaltic concrete (2 feet thick) for watertightness and to resist wave and other erosion forces.

All the plant was electrically operated and the current obtained from the State Power Station at Port Kembla by transmission lines 19 miles (31 km) in length.

This was cut at a special sawmill erected at the Dam and a fleet of punts and launches transported the logs down the river to the mill.

However, in this case the rock was quarried to make a deep cut through a ridge to a neighbouring creek to provide the spillway for the dam.

Like its predecessors, Avon also had the upstream face of the dam sheathed with a layer of basaltic concrete (2 feet thick) for watertightness and to resist wave and other erosion forces.

Each end of the dam wall is flanked by massive Egyptian style pylons complete with decorative lotus columns.

[1] The cliffline landscape includes shelters with stone and cement-rendered seating, some cement faux rockwork walling, plantings of Wisteria, palms, Cordyline sp., Cyathea sp.

The entry features a pair of stone piers incorporating the words AVON DAM in quartz pebbles and a central path that leads to various picnic tables.

There are plantings of Swamp Cypress (Taxodium distichum), Hoop Pine (Araucaria cunninghamii), Syzygium, Podocarpus, Acer, Camellia, Flowering Cherry and Liquidambar.

Nearby is a very large Scribbly Gum which, as part of the indigenous vegetation, long predates any use of the site for Sydney's water supply.

The loop road, giving access to the area along the ridge, is edged by a low stone retaining wall that also dates to the late 1920s-1930s period.

Along the main entry road to the dam site near an old gate are clumps of Agave americana and Flax which may indicate the earlier presence of a cottage now demolished.

It was designed by the NSW Public Works Department under the direction of one of Australia's leading water supply engineers, E.M. De Burgh.

The completion of the Avon Dam was a significant step in the continuing process of providing a reliable water supply for Sydney and surrounding areas as part of the Upper Nepean Scheme.

Even by the international standards of the time, Avon was a high dam with a large impoundment of water and was a significant work of engineering in its day.

It continues to play an important role as the major source of supply for the Wollongong, Port Kembla and surrounding towns and areas.

The other residential buildings associated with the dam are relatively modern replacements for the original set of houses, but are representative of their type.

The design and technologies used in the construction of the dam are representative of methods developed by the Public Works Department of NSW at the time.

The design and construction of Avon Dam was undertaken by the Water Supply and Sewerage Branch of the NSW Public Works Department.

The buildings and grounds have some associations with past identities of the board, which was until comparatively recently one of the major government departments in NSW in regard to its economic and political influence.

The architectural detailing of the superstructures evokes a romanticised vision of the "Ancient Near East" at a time when many Australians had first hand experience of the area through military service, and through knowledge of archaeological finds reported in the popular press.

Upstream of the dam wall this setting is characterised by the broad expanse of the pool of water bordered by the crests of the valley sides.

The topography, at times of high water level, imparts a picturesque scene when viewed from selective vantage points above and on the dam wall.

The landscaping of its lower picnic grounds exhibit a high level of design awareness through its planning, evolution and association with the Botanic Gardens on the original layout and selection of species.

[1] The practice of ongoing maintenance of the wall after completion through resident staff and workshop facilities is representative of procedures undertaken at other dams and weirs constructed in NSW.