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The Underground Manapouri Power Station:

This is the largest hydro electric power plant in New Zealand:

Fiordland map It is housed underground in the Fiordland National Park in a cavern carved from rock almost 200 metres below the West Arm of Lake Manapouri. Unlike other hydro power stations, Manapouri does not have a high dam. It uses the natural 183 metre height difference between Lake Manapouri and the sea at Deep Cove in Doubtful Sound to generate electricity.


Over a hundred years ago, enormous potential was recognised for power generation using the water from the beautiful black Lakes, Manapouri & Te Anau. During the 1950s this potential was studied in detail. The discovery of Bauxite in Queensland, Australia led to growing interest in the idea of developing a cheap and reliable source of power for the process of Aluminium smelting. The N.Z. government at that time proceeded with discussions with Comalco. In 1960 it was announced that an agreement had been made between the Government and Comalco, giving the company a long-term, fixed contract for electricity until 2021. The project to build the Underground Power Station to supply electricity to the Aluminium Smelter to be built at Bluff got started in 1963. It took 1800 men 8 years to build, working 24 hours a day. 

How the Manapouri Power Station works:

Water enters the Manapouri Power Station through intake gates and down large pipes, vertically, which are called Manapouri Power Station modelPenstocks to drive the turbines. (photo beside - Click for enlargement) The water spins the turbines, which turns the Rotor, a part of the Generator. The Generator is made up of a spinning set of Magnets (rotor) inside a stationary set of Windings (stator) and this action creates electricity. The water then goes through the Draft Tubes and out the two Tailrace tunnels to Deep Cove in Doubtful Sound.

Destination Queenstown logoView of Underground Power Station Underground Power Station generators


The construction involved four separate projects:

  1. The tailrace tunnel from Deep Cove through the mountains to the power house in West Arm (10kms long) - (In 2002, the second tailrace was completed)

  2. The Power Station was built.

  3. Linking the two sites of construction is the Wilmot Pass road. This opened in 1965.

  4. The transmission lines sent across the country from West Arm to Bluff (160kms long).

Access to the underground Power Station is via a 2.1km long tunnel. (Yellow tube in model at left & below) It is 9 metres wide and was built to take the largest piece of machinery in the original building of the plant. Trucks had to reverse down the tunnel when delivering the machine parts - this sometimes took up to 7 hours. Today, Real Journey's tour coaches, as part of the Doubtful Sound experience drive down here to allow visitors to view the plant, (click images above to enlarge) turn around at the bottom and drive out again.
Schematic of the Underground Power Station

This is a highly recommended tour : It is part of the day tour to Doubtful Sound. For further details, Email: