a half times as extensive as Cataract and three and a half times as extensive as Cordeaux. The Nepean Reservoir therefore fills more rapidly and, under normal conditions, is drawn upon more freely than the other reservoirs. Specifications of Nepean Dam: Total capacity: 17,898 million gallons (81,400 million litres). Years of construction: 1926–1935. Cost: £2,062,000 ($4,124,000). Crest level above sea level: . Amount of concrete in the wall: 300,218 cu yards (229,600 cu metres). Length of crest including pylons: . Length of spillway weir: . Width at crest: . Width at base: . Full supply level above sea level: . Greatest depth of water: . Area of lake: . Area of catchment: 123 sq miles (319km2). Average annual rainfall: . Average annual yield: 23,515 million gallons (106,993 million litres). Average annual evaporation: . The Nepean Dam continues to supply Sydney with water. It is discharged as required into the river bed below the dam and flows to Pheasant's Nest where it is diverted by a weir to the Nepean Tunnel, long, discharging into the Cataract Tunnel, long, emerging into the Upper Canal, by which it is conveyed to Prospect Reservoir. The Nepean Dam is now also cross-connected to the Avon Dam, which supplies the Wollongong area, to provide additional water supply to that district. If necessary, it can also receive additional water from the Shoalhaven Scheme. Water is supplied to the Picton and Bargo districts from Nepean Dam, with this water treated and filtered in the Nepean Water Filtration Plant, a treatment facility added to the dam to improve the water quality to this district, which is now supplied directly from Nepean Dam. The Nepean Dam includes within its area three brick residential staff cottages, two apparently dating from the 1960s and one from the 1980s, and two older weatherboard cottages, one of which, utilised by the Filtration Plant staff, is the original Resident Engineer's Cottage. Just north of the entrance to the Dam picnic area are the former Catchment workshops, a series of small corrugated iron and weatherboard utilitarian buildings which were formerly the central maintenance facility for the Upper Nepean Catchment area. They remain in use at a low scale by the Sydney Catchment Authority and include a weatherboard residential cottage similar to the second of the weatherboard residences at the Dam. The area of the former construction village for the Dam remains undeveloped and heavily overgrown, with