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Upper Nepean Scheme

The Upper Nepean Scheme is a series of dams and weirs in the catchments of the Cataract, Cordeaux, Avon and Nepean rivers of New South Wales, Australia. The scheme includes four dams and two weirs, and a gravity-fed canal system that feeds into a large storage reservoir to provide water to the Macarthur and Illawarra regions, the Wollondilly Shire, and metropolitan Sydney. The four dams and associated infrastructure are individually listed on the New South Wales State Heritage Register.

History
By 1867, Sydney was outgrowing the water supply available from Botany Swamps and the Governor (Sir John Young) appointed a Commission to recommend a future water supply. In 1869, the Commission recommended the Upper Nepean Scheme. This comprised weirs on the Cataract and Nepean rivers, a storage reservoir at Prospect and of pipelines, tunnels, canals and aqueducts to bring water from the catchment area to Sydney. Work on the Scheme began in 1880 and was completed in 1888. This emergency work was dismantled as the main scheme was completed. As originally built, the Upper Nepean Scheme was capable of supporting an estimated population of 540,000. By 1902, Sydney had a population of 523,000 and was again in the grip of a severe drought. A Royal Commission appointed to report on Sydney's water supply recommended a dam on the Cataract River and construction commenced in the same year. Dams were subsequently built on each of the Cordeaux, Avon and Nepean rivers, with the last being completed in 1935. Each dam includes a public picnic area. In total, the four dams hold and can safely provide per day. The Scheme is now managed by the Sydney Catchment Authority. Further supplementary water supply is provided by a feed from the Shoalhaven Scheme through various pumps, pipes, cuts and diversions. ==Associated dams==
Associated dams
Cataract Dam The Cataract Dam is a heritage-listed gravity dam with an unlined side spillway extending from the left abutment. It is tall, long and holds of water. The core of the dam consists of large sandstone blocks, quarried onsite and cemented together. The downstream face is of mass poured basalt concrete, with a basalt facing. A readily accessible source of suitable rock was located some distance away at Sherbrooke, also known as Ferndale, 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. Dam construction began in 1902 and was completed in 1907, and the spillway was widened in 1915. Poet Banjo Paterson wrote a satirical ballad "The Dam that Keele Built" about the politics behind the construction of Cataract Dam. Cordeaux Dam The Cordeaux Dam is a heritage-listed arch dam across the Cordeaux River with an unlined side spillway on the left abutment. It is high, long and creates a reservoir which holds . Construction began in 1918 and was completed in 1926 at a cost of 945,000. The blue metal used in the construction of the dam was supplied from the Government Quarries at Kiama and brought by rail to Douglas Park. From here it was conveyed by aerial ropeway across the Nepean Gorge to an interchange on the eastern side where the material was transferred to a gauge steam tramway to a point adjacent to the dam site. Avon Dam The Avon Dam is a heritage-listed arch dam across the Avon River; it is tall, long and its reservoir holds . It has the largest capacity of all the dams in the Scheme. Construction of the heritage-listed dam wall began in 1921 and was completed in 1927 at a cost of 1,047,000. The dam construction and materials are the same as Cordeaux. Nepean Dam The Nepean Dam is a heritage-listed arch dam across the Nepean River; it is tall and long. Construction on the Dam began in 1926, construction was delayed for two years during the Depression, it was finally completed in 1935. The capacity is listed variously as . Railway sidings were established on the Main Southern railway line at a point between Bargo and Yerrinbool. Transport to the dam site was again by light railway, on this occasion of standard gauge. This avoided transhipment from the Government vehicles bringing materials from large commercial quarries, effectively making the line an extended privately owned siding. The line was long through gentle countryside. Trains were worked by a variety of locomotives, including a former Sydney Steam Tram Motor. Additionally, there was a system of narrow () gauge lines in use at the dam construction site. Additional work was carried out on the spillway between 1943 and 1947 to prevent scouring of the dam foundations. == Gallery ==
Gallery
Image:Cataract_at_capacity.jpg|Cataract reservoir at full capacity, discharging through spillway Image:Cataract_spillway.jpg|Detail of Cataract Dam spillway Image:Cataract_outlet_works.jpg|Outlet works at Cataract Dam Avon Dam plate.jpg|Avon Dam plate Nepean Dam plate.jpg|Nepean Dam plate ==See also==
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