Cataract Dam wall
|Location||Macarthur, New South Wales|
|Purpose||Potable water supply|
|Owner(s)||Sydney Catchment Authority|
|Dam and spillways|
|Type of dam||Gravity dam|
|Height||56 m (184 ft)|
|Length||247 m (810 ft)|
|Dam volume||112×103 m3 (4.0×106 cu ft)|
|Spillway capacity||1,550 m3/s (55,000 cu ft/s)|
|Total capacity||94,300 ML (2.07×1010 imp gal; 2.49×1010 US gal)|
|Catchment area||130 km2 (50 sq mi)|
|Surface area||8,500 ha (21,000 acres)|
Cataract Dam, one of four dams and weirs in the catchment of the Upper Nepean Scheme, in New South Wales, Australia, provides water to the Macarthur and Illawarra regions, the Wollondilly Shire, and metropolitan Sydney. Completed in 1907 under the supervision of Ernest Macartney de Burgh, the dam is currently managed by the Sydney Catchment Authority and is listed on the NSW State Heritage Register.
A straight dam with an unlined side spillway extending from the left abutment, it is 56 metres (184 ft) tall; 247 metres (810 ft) long; and it holds 94,300 megalitres (3,330×106 cu ft) 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 2 ft (610 mm) gauge steam tramway, 8.8 kilometres (5.5 mi) long, was constructed.
The dam is built of cyclopean masonry, composed of sandstone blocks weighing from 2 to 4.5 long tons (2.03 to 4.57 t; 2.24 to 5.04 short tons). 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, 1.8 metres (5 ft 11 in) thick in the lower section and 0.9 metres (2 ft 11 in) thick in the upper section. There were two lines of 122-centimetre (48 in) 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.
The Upper Nepean Scheme was commenced in 1880 after it was realised that the Botany Swamps scheme was insufficient to meet Sydney's water supply needs. The Nepean project consisted of the construction of a weir across the Nepean River to divert of the rivers Cataract, Cordeaux, Avon and Nepean, to the Prospect Reservoir.
The design and construction of Cataract Dam was undertaken by the Water Supply and Sewerage Branch and Harbour and Rivers Branch of the New South Wales Public Works Department. The construction of the dam necessitated the knowledge and experience of a number of engineers employed in the branches at the time including Cecil Darley (NSW Inspecting Engineer in London), Leslie Wade (Principal Engineer, Water Supply and Sewerage Branch), Henry Dare and Ernest M. de Burgh (Supervising Engineers). The successful completion of the dam and its continuation of use as a water supply dam are a lasting testament to the professional capabilities of the late Victorian/Edwardian era generation of engineers of the Public Works Department. The association of Thomas Keele with the initial dam proposal, and the subsequent problems associated with the cost and the ongoing Royal Commissions into the project was immortalised through Banjo Paterson's satirical ballad The Dam that Keele Built.
- "Register of Large Dams in Australia" (Excel (requires download)). Dams information. Australian National Committee on Large Dams. 2010. Retrieved 11 March 2014.
- Longworth, Jim (July 1993). "Construction Railways of the Upper Nepean Dams - Cataract Dam". Australian Railway Historical Society Bulletin: 163–174.
- "Cataract Dam". NSW State Heritage Register. Government of New South Wales: Office of Environment & Heritage. 5 September 2008. Retrieved 13 April 2012.
- Antill, J. M. (1981). "De Burgh, Ernest Macartney (1863 - 1929)". Australian Dictionary of Biography 8. Melbourne University Press. p. 266. Retrieved 22 April 2007.