The Cataract Dam is a heritage-listed dam in Cataract (formerly Appin), New South Wales, Australia, provides water to the Macarthur and Illawarra regions, the Wollondilly Shire, and metropolitan Sydney. It is one of four dams and weirs in the catchment of the Upper Nepean Scheme. 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. The dam was listed on the NSW State Heritage Register on 18 November 1999. Structural details A gravity dam with an unlined side spillway extending from the left abutment, it is tall; long; and it holds of water. Cataract Dam was the first dam built in the Upper Nepean Scheme. It was also first dam in Australia to use pre-cast moulded concrete blocks for the upstream face of the dam. The downstream face is of mass poured basalt concrete, with a basalt facing. A readily accessible source of suitable rock was located at Sherbrooke, situated near the top of Bulli Pass. To transport the basalt from the quarry to the dam construction site, a gauge steam tramway, long, was constructed. The dam is built of cyclopean masonry, composed of sandstone blocks weighing from . These were quarried at the site and bedded in cement mortar. The vertical joints were filled with basalt or sandstone concrete. The upstream face consisted of basalt concrete moulded blocks set in a cement mortar. The downstream face was of basalt concrete, thick in the lower section and thick in the upper section. There were two lines of diameter pipes which passed through the dam and discharged water into the Nepean River. The flow is controlled by a Larner Johnson needle valve. The dam wall was given a decorative finish. The upstream parapet was castellated with sandstone blocks while the top of the downstream wall was corbelled in concrete. In approximately the midsection of the dam stands the valve house. This is finished in quarried sandstone blocks with ashlar coursing. It features a steeply pitched slate-covered pipped roof topped with finials and gables at either side. Dam construction began in 1902 and was completed in 1907, and the spillway was widened in 1915. E. M. de Burgh was the supervising engineer for the project from 1904. History The Upper Nepean Scheme was commenced in 1880 after it was realised that the Botany Swamps