Benmore Dam
| Benmore Dam | |
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 Location of Benmore Dam in New Zealand
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| Location | Canterbury Region, New Zealand |
| Coordinates | 44°33′50.92″S 170°11′49.92″E / 44.5641444°S 170.1972000°ECoordinates: 44°33′50.92″S 170°11′49.92″E / 44.5641444°S 170.1972000°E |
| Construction cost | $62 million |
| Dam and spillways | |
| Type of dam | Earth-filled dam |
| Impounds | Waitaki River |
| Height | 110 m (360 ft) |
| Length | 823 m (2,700 ft) |
| Width (crest) | 10.6 m (35 ft) |
| Width (base) | 490 m (1,610 ft) |
| Dam volume | 28 million tonnes |
| Spillway capacity | 3,400 km3 (820 cu mi) |
| Reservoir | |
| Creates | Lake Benmore |
| Total capacity | 1.25 km3 (1,010,000 acre·ft) |
| Surface area | 75 km2 (29 sq mi) |
| Maximum water depth | 102 m (335 ft) |
| Power station | |
| Operator(s) | Meridian Energy |
| Commission date | 1965 |
| Hydraulic head | 92 m (302 ft) |
| Turbines | 6 x 93 MW (125,000 hp) |
| Installed capacity | 540 MW (720,000 hp) |
| Annual generation | 2,215 GWh (7,970 TJ) |
Benmore Dam is the largest dam within the Waitaki power scheme, located in the Canterbury Region of New Zealand's South Island. There are eight other power stations in the Waitaki Power Scheme.
The dam is the largest earth-filled water-retaining structure in New Zealand. Its core is low permeability clay material, supported by two massive shoulders of river gravel. Lake Benmore has a volume of 1.25 billion cubic metres, about 1.5 times as much water as Wellington Harbour. The dam's spillway can cope with 3,400 cubic metres of water per second, about 10 times the mean river flow.
With a generating capacity of 540 megawatts (720,000 hp), Benmore Power Station is the second largest hydro station in New Zealand behind Manapouri, and the largest dam in the country.
The $62 million construction of the dam and hydroelectric station began in 1958. It was commissioned in 1965, and officially opened by Prime Minister Sir Keith Holyoake on 15 May that year. It was built for the New Zealand Electricity Department; since 1999 it has been owned and operated by Meridian Energy.
From 2008 to 2010 the six turbines are being refurbished at a cost of $67 million. This will enable a 6% reduction in water use for the same generation capacity, increasing annual generation by 70 GWh (250 TJ). New switchboards and an upgrade to the switchyard are also planned.
Benmore is the South Island terminus of the HVDC Inter-Island link between the North and South Islands of New Zealand. The HVDC converter stations are on the west side of the tailrace, and convert 220 kV AC power to ±350 kV DC for the 610 km (380 mi) journey to the North Island converter station at the Haywards in Lower Hutt.
Otematata is the small town that supports the dam, although with advances in technology the staffing needed to maintain the dam is drastically smaller. Due to this the town is now a small holiday community, with only around 200 permanent residents. The dam is about 8 kilometres (5.0 mi) up the valley from the township.
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Wikipedia