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Upper Nepean Scheme
Copied 31 March 2016

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 provides water to the Macarthur and Illawarra regions, the Wollondilly Shire, and metropolitan Sydney.

History
Busby's Bore Lachlan Swamp Paddington Reservoir Cooks River Dam informational page

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 63.25 mi of pipelines, tunnels, canals, aqueducts and pumping stations  to bring water from the 347 sqmi catchment area to Sydney. Work on the Scheme began in 1880 and was completed in 1888. The Scheme was a significant feat of engineering at the time of construction.

In June 1885 Sydney was in the grip of a severe drought and the Upper Nepean Scheme was incomplete. The Government accepted an offer from Hudson Brothers to bridge the gaps and deliver 3 e6impgal of water per day into Botany Swamps. This became known as Hudsons' Temporary Scheme and was turned on on 30 January 1886. This emergency work was dismantled as the main scheme was completed.

The scheme comprised the Upper Canal, the Reservoir, and the Lower Canal feeding into the Potts Hill Reservoir before continuing the feed of water into the Botany Swamps scheme with flow directed to (?) the (which) pond. The Lower Canal was thingy the aqueduct at Guildford, needed strengthening, bypassed by the water syphon.

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 483,600 ML and can safely provide 353 megalitres per day.

The Scheme is now managed by the Sydney Catchment Authority.

Weirs
Pheasants Nest weir

tunnel

Broughtons Pass

pumping house ? there is no pump ?!? it is all gravity

Upper Canal
http://www.environment.nsw.gov.au/heritageapp/ViewHeritageItemDetails.aspx?ID=5051481

Prospect Reservoir
see main article

Lower Canal
grade

Boothtown Aqueduct and Syphon

Guildford Pipe Head

Potts Hill Reservoir

Botany Swamps - into where ?

temporary scheme into airport ponds - canal and pipes into Crown Street ?

Cataract Dam
Cataract Dam is a straight dam with an unlined side spillway extending from the left abutment. It is 183 ft tall, 811 ft long and holds 97190 ML 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 core of the dam is large (2-4½ ton) 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, 8.8 km long, was constructed. Dam construction began in 1902 and was completed in 1907, and the spillway was widened in 1915. Ernest Macartney de Burgh was the supervising engineer for the project from 1904. Poet Banjo Paterson wrote a satirical ballad "The Dam that Keele Built" about the politics behind the construction of Cataract Dam.

Cordeaux Dam
Cordeaux Dam is a curved dam with an unlined side spillway on the left abutment. It is 191 ft high, 1327 ft long and holds 93,640 ML. Construction began in 1918 and was completed in 1926. The wall consists of large sandstone blocks, quarried onsite and cemented together, faced with a combination of bluestone and sandstone concrete. 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
Avon Dam is a curved dam; it is 237 ft tall, 732 ft long and holds 146700 ML. It has the largest capacity of all the dams in the Scheme. Construction began in 1921 and was completed in 1927. The dam construction and materials are the same as Cordeaux. All materials for construction were transported from Bargo railway station on a specially built road, all the other dams in the scheme used rail transport. There were some light tramways constructed at the dam site, however it would appear that no locomotives were employed; skips and other items being moved by winch, horse or manpower.

Nepean Dam
Nepean Dam is a curved dam; it is 269 ft tall and 709 ft 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 17898 e6impgal and  67730 ML.

Railway sidings were established on the Main Southern 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 4 km 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.