Chichester Dam

Chichester Dam is a minor concrete gravity dam across the Chichester and Wangat rivers, upstream of Dungog, in the Hunter Region of New South Wales, Australia. The dam's main purpose is water supply for the Lower Hunter region. A mini hydro-electric power station operates at times of peak flow and is connected to the national grid. The impounded reservoir is Lake Chichester.

Location and features

The dam wall is 43 metres (141 ft) high, 254 metres (833 ft) long, and was constructed using a cyclopean system of interlocking concrete blocks and large boulders with a volume of 91 cubic metres (3,200 cu ft). The wall is anchored to the bedrock below it by 93 stressed tendons. At 100% capacity the dam wall holds back 21,500 megalitres (760×10^⁶ cu ft) of water at 156.2 metres (512 ft) Australian Height Datum. The spillway is capable of discharging 3,300 cubic metres per second (120,000 cu ft/s). The surface area of the reservoir is 1.8 square kilometres (0.69 sq mi) and the catchment area, largely located within the Barrington Tops National Park, is 197 square kilometres (76 sq mi). The dam is connected to reservoirs in Maitland, Cessnock and Newcastle by an 80-kilometre (50 mi) gravitation main.^[1][2]

History

Land for the water supply scheme was appropriated in the Gazette of 6 October 1916. To safeguard the purity of the water the populated part of the Wangat Valley, including the old goldmining town of Wangat, and the greater portion of the populated part of the Chichester Valley were resumed.^[3] The Act appropriated £A1,049,000 as the estimated cost of construction of the dam, with additional funds set aside for land resumption.^[4]

In 1965 the spillway was lowered by 2.75 metres (9 ft 0 in) to increase flood capacity. In 1985 the dam was post tensioned with cables and the spillway was relocated to the centre of the dam and returned to its original height. In 1995 the seepage potential was reduced under the northern abutment and in 2003 an improved drainage system for the dam's foundations was installed and the left parapet wall was raised to prevent overtopping in a major flood.^[1]

Power generation

Following a report by the Health Rivers Commission, in 1998 the Minister for Urban Affairs and Planning, Craig Knowles, announced that a small hydro-electric power station would be installed in the Chichester Dam in order to generate electricity, reduce greenhouse emissions and allow surplus power to be sold back to the grid.^[5] Completed in 2001 and operated by Delta Electricity, the mini-power station generates up to 110 kilowatts (150 hp) of electricity at times of peak flow; with an average annual generation of 0.4 gigawatt-hours (1.4 TJ).^[6]

See also

1. ^ ^{a b} "Chichester Dam". Hunter Water Corporation. Archived from the original on 27 January 2008. Retrieved 8 November 2007.
2. ^ "Register of Large Dams in Australia". Dams information. The Australian National Committee on Large Dams Incorporated. 2010. Archived from the original (Excel (requires download)) on 12 December 2013. Retrieved 22 April 2013.
3. ^ "Chichester Dam Approved". Hunter Water. 1916. Retrieved 14 April 2013.
4. ^ "Hunter Water Supply (Chichester Dam) Act" (PDF). NSW legislation. Government of New South Wales. 1916. Retrieved 14 April 2013.
5. ^ Knowles, Craig (2 June 1998). "Legislative Assembly – Chichester Dam Electricity Generation". Parliamentary Debates (Hansard). Parliament of New South Wales. Archived from the original on 22 June 2015. Retrieved 21 June 2015. Archived 22 June 2015 at the Wayback Machine
6. ^ "Chichester Dam Mini-Hydro". Case studies: Hydro. Clean Energy Council. 2013. Archived from the original on 29 March 2012. Retrieved 14 April 2013.