Manapōuri is a hydro power station located in Fiordland National Park, South Island, New Zealand.
It has seven 122 megawatt generating units, and an operating maximum station output of 800 megawatts. Manapōuri generates enough electricity each year for about 619,000 average New Zealand homes.
Manapōuri is the largest hydro power station in New Zealand, and is located on the edge of Lake Manapōuri’s West Arm in the Fiordland National Park, which has UNESCO World Heritage status as part of Te Wāhipounamu.
The hydro power station is located underground, with the station’s generating units housed in a cavern excavated from rock 200 metres below the surface of Lake Manapōuri.
The original construction of the Manapōuri hydro station was a huge engineering achievement. The project took 1,800 workers eight years to complete in extremely harsh conditions. The project involved constructing the power station 200 metres below a granite mountain in an underground cavern.
Several access and service tunnels were built. The 10-kilometre tailrace tunnel was excavated to take the water that flows out of the station into Deep Cove in Doubtful Sound. All this was completed using drill and blast excavation methods to carve through the hard Fiordland rock.
The first power was generated in September 1969, with the installation of two generating units. The station became fully operational in 1972 when the seventh and final generating unit was commissioned.
In 1998, work began on the second tailrace tunnel. An additional outlet for the station was drilled, allowing it to generate to its full rated capacity.
In 2002, the second tailrace tunnel was completed. It runs parallel to the original 1970s tunnel and allows the station to achieve a maximum continuous rating (MCR) of 850 megawatts, although resource consent conditions limit generation to 800 megawatts.
- 1964 Construction begins
- 1972 Manapōuri fully operational
- 2002 Second tailrace tunnel completed
The Manapōuri project is regarded as the birthplace of New Zealand’s environmental consciousness.
The original plans for the power station were developed in the 1960s and proposed raising the level of Lake Manapōuri by up to 30 metres. But Lake Manapōuri’s famed wooded islands would have disappeared, and the fragile shoreline beech forest would have been left to rot in the water.
An increasing number of New Zealanders realised the extent of the environmental impact, and protest became widespread and passionate. In 1972 the Government confirmed that the lake level would not be raised. In February 1973 the Government created the Guardians of Lakes Manapōuri, Monowai and Te Anau to oversee management of the lake levels.
The Guardians are still active today. Meridian also supports the habitat restoration work of the Waiau Fisheries and Wildlife Habitat Enhancement Trust in the Waiau Valley catchment.