Thursday, May 6, 2010

New Zealand - North Otago - Benmore Dam

Autumn in the Waitaki Valley with Benmore Dam in the background, North Otago, New Zealand.

Sent by adriennegarry from New Zealand.

This is from Wikipedia : Benmore Dam is the largest dam within the Waitaki power scheme on the borders of Otago and Canterbury regions in New Zealand's South Island. There are eight other power stations in the valley.

The dam is the largest earth-filled water-retaining structure in New Zealand. Its core is impermeable clay-like gravel, supported by two massive shoulders of river gravel. Lake Benmore has a volume of 12.5 million 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 MW, Benmore Power Station is the second largest hydro station in New Zealand.

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 5% reduction in water use for the same generation capacity, increasing annual generation by 70 GWh. New switchboards and an upgrade to the switchyard are also planned.

Benmore is the southern end of High Voltage Direct Current 500 MW (HVDC) link that joins the North and South Island electricity grids. There are two switchyards, one for AC transmission to the South Island and the other containing the static inverter plant for the HVDC link.

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 km up the valley from the township.

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