Completed in 1907 under the supervision of Ernest Macartney de Burgh, the dam is currently owned by Water NSW, an agency of the Government of New South Wales.

At the time, Government House was in Parramatta and one of Macquarie's first intentions was to travel into the nearby country to discover the best land from which the colony could be provided with food.

It was already known that the most productive area for that purpose was the Hawkesbury River country, but these districts had proven precarious because of severe flooding which caused great losses in crops and stock.

The district became a great supplier of wheat, corn and barley, carried to Sydney by wagons pulled by teams of bullocks or horses.

In 1836 Rose built the huge stone windmill, one of the largest of its kind which gave great service for many years grinding wheat of the surrounding areas.

[8] The windmill is still standing; that is the four-storey tower which has long been converted to a water tank; but the top hammer and sails have long-since disappeared.

These and others such as Fairview, Blossom Lodge, Mount Carlon and the big poultry farm conducted by Ingham enterprises are all on the western side of the Appin Road.

[4] The seriousness of the position led the NSW Government, in March 1902, to appoint a Royal Commission to inquire into and report upon the Sydney water supply system.

[4] The Act authorising the construction of the dam was passed in 1902 and provided for a wall of 49 metres (160 ft) with a storage capacity of 83 gigalitres; 22 billion US gallons (83,000 ML).

The contract was for a dam 46 metres (150 ft) high from the natural flow of the river, which would store up to 97,340 gigalitres; 25,714 billion US gallons (21,411×10^9 imp gal).

[4] In December 2016 the state government gave approval for the controversial South 32 Dendrobium coal mine, in the Metropolitan Special Area, created to protect the waters of Cataract, Cordeaux, Avon and Nepean Reservoirs.

There it is diverted by another weir into Cataract Tunnel, 2 miles (3.2 km) long, (the first structure of the Upper Canal) by which it is conveyed to Prospect Reservoir.

It is built of ashlar sandstone masonry quarried on the site and features a verandah at the front with elaborate timber posts with curved quadrant brackets, a vertical slatted balustrade and pediment gable over the main entrance way.

There is a substantial brick house dating from the 1950s/60s located between the cottages and the Official Quarters, which is single-storied with a terracotta tiled hipped and gabled roof.

It is a simple bungalow form with timber casement and sash windows and has a separate garage with attached living quarters at the rear of the main building.

[4] The Official Quarters is a particularly fine example of a Federation Queen Anne Bungalow, with matching outbuildings and landscaped gardens and is associated with the accommodation of both the senior engineers of the Public Works Department and the Governor of NSW at the opening of the Dam.

[4] The Dam surrounds include remnants of its early 20th century gardens, evidence of a high level of landscape design awareness through its planning and detailing, and extensive areas of bushland.

Individual components of its remnant gardens, such as its main (upper level) grotto shelter and ornamental follies, are rare in NSW on account of their imaginative conception and quality of craftsmanship.

The extensive scale of the remnant area of public parklands is notable and that they continue to attract regular visitation since their opening indicates that the place is highly regarded.

The immediate environment around the dam wall - including the key engineering structures and associated architecture, the upstream body of water, the downstream gorge and surrounding vegetation - forms a localised cultural landscape of scenic distinction.

[4] The design and finishes of the crest house, albeit substantially reconstructed c.1953, parapet and abutments were undertaken by the Government's Architect Branch of the Department of Public Works, at the time under Walter Liberty Vernon.

There is a high level of design awareness in the planning of the grounds and the association with the Botanic Gardens in the layout and selection of species is of considerable note.

Downstream of the dam wall the setting is characterised by the steeper inclines that graduate into the gorge created by the river's flow over time.

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

[4] The adjoining hill of approach to the dam is laid-out with a plantation of Monterey Pines, which in juxtaposition with the paths, drives, culverts, steps and cottages impart a parklike setting.

[4] The hillside overlooking the dam was the site of the original construction village and retains steps and engravings cut within the rock outcrops dating from this era.

The lower valve house completed in 1907and extended in 1913 is a unique early example of its type and demonstrates the principal characteristics of the design of such structures.

These sites include a large curved masonry dam on a tributary of Cataract Creek of the Appin/Bulli Road, a potential stone quarry, the formation of a roadway adjacent to the road of access, powder magazines on Keele Island and on the adjoining west abutment of the dam wall, and fireplaces, horse yard drains and powder magazines on the abutment adjoining the spillway.

The screen tower (completed in 1907) is the earliest structure of its type constructed in NSW, and includes unique water intake system.

[4] The dam retains items of ironwork which are part of the original water delivery system, which are unique in NSW in regard to this date.