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Chichester Dam
Chichester Dam - panoramio.jpg
Chichester Dam
Country Australia
Location Dungog, New South Wales
Coordinates 32°13′54″S 151°41′04″E / 32.23167°S 151.68444°E / -32.23167; 151.68444Coordinates: 32°13′54″S 151°41′04″E / 32.23167°S 151.68444°E / -32.23167; 151.68444
Purpose Water supply
Status Operational
Construction began 1917
Opening date 1926
Construction cost 1,049,000
Owner(s) Hunter Water Corporation
Dam and spillways
Type of dam Gravity dam
Impounds Chichester River, Wangat River
Height 43 m (141 ft)
Length 254 m (833 ft)
Dam volume 18.4 ML (650×10^3 cu ft)
Spillway capacity 3,300 m3/s (120,000 cu ft/s)
Reservoir
Creates Lake Chichester
Total capacity 21,500 ML (760×10^6 cu ft)
Catchment area 197 km2 (76 sq mi)
Surface area 1.8 km2 (0.69 sq mi)
Maximum length 4.22 km (2.62 mi)
Maximum width 580 m (1,900 ft)
Normal elevation 156.2 m (512 ft) AHD
Power station
Operator(s) Delta Electricity
Commission date November 2001 (2001-11)
Type Conventional
Turbines 1
Installed capacity 110 kW (150 hp)
Annual generation 0.4 GWh (1.4 TJ)

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

Commenced in 1917 and completed in 1926, the Chichester Dam is a minor dam on the Chichester River, a tributary of the Williams River, approximately 21.6 km (13.4 mi) north of Dungog. The dam contributes about thirty-five percent of the lower Hunter region's water supply.

The dam wall is 43 m (141 ft) high and is 254 m (833 ft) long and was constructed using a cyclopean system of interlocking concrete blocks and large boulders with a volume of 91 m3 (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 ML (760×10^6 cu ft) of water at 156.2 m (512 ft) AHD. The spillway is capable of discharging 3,300 m3/s (120,000 cu ft/s). The surface area of the reservoir is 1.8 km2 (0.69 sq mi) and the catchment area, largely located within the Barrington Tops National Park, is 197 km2 (76 sq mi). The dam is connected to reservoirs in Maitland, Cessnock and Newcastle by an 80 km (50 mi) long gravitation main.

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. The Act appropriated 1,049,000 as the estimated cost of construction of the dam, with additional funds set aside for land resumption.

In 1965 the spillway was lowered by 2.75 m (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.

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. Completed in 2001 and operated by Delta Electricity, the mini-power station generates up to 110 kW (150 hp) of electricity at times of peak flow; with an average annual generation of 0.4 GWh (1.4 TJ).

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