Station Infomation

The Manapouri Power Station is the largest hydro power station in New Zealand.
The underground station is owned and operated by Meridian Energy. It lies deep in a remote area of New Zealand’s South Island on the western arm of Lake Manapouri, in Fiordland National Park.

A significant proportion of the station’s power output is consumed by an aluminium smelter operated by New Zealand Aluminium Smelters Limited (NZAS) at Tiwai Point near Bluff, some 160 km to the south-east.


Soon after the power station began generating at full capacity in 1972, engineers confirmed a design problem. Greater than anticipated friction between the water and the tailrace tunnel walls meant reduced hydrodynamic head. For 30 years, until 2002, station operators risked flooding the powerhouse if they ran the station at an output greater than 585 MW, far short of the designed peak capacity of 700 MW. Construction of a second tailrace tunnel, 10 km long and 10 metres in diameter, finally solved the problem. The increased exit flow also increased the effective head, allowing the turbines to generate more power without using more water.


Early history

The first surveyors mapping out this corner of New Zealand noted the potential for hydro generation in the 178-metre drop from the lake to the Tasman Sea at Doubtful Sound. The idea of building a power station was first suggested in 1904, but the remoteness of the location and the scale of the engineering task made any project infeasible at the time.

In 1926, the New Zealand Sounds Hydro-Electric Concessions Company obtained water rights from the government to implement a scheme to use power from Manapouri to produce fertilizer and munitions. The idea was to use electricity to fix nitrogen from the atmosphere. The scheme did not proceed and the water rights lapsed.

In 1955 the modern history of Manapouri starts, when a geologist with Consolidated Zinc Proprietary Ltd identified a commercial deposit of bauxite in Australia on the west coast of Cape York Peninsula, near Weipa. It turned out to be the largest deposit of bauxite in the world yet discovered. In 1956 The Commonwealth Aluminium Corporation Pty Ltd, later known as Comalco, was formed to develop the bauxite deposits. The company started investigating sources of large quantities of cheap electricity needed to reduce the alumina recovered from the bauxite into aluminium. Comalco settled on Manapouri as that source of power and Bluff as the site of the smelter. The plan was to refine the bauxite to alumina in Queensland, ship the alumina to New Zealand for smelting into metal, then ship it away to market.

History Breakdown

1904 Potential for a hydro scheme first recognised by Mr P S Hay, of Public Works Department
1927 Public Works Department survey parties investigate the area
1947 Aluminium Co of Canada examines water resources
1954 Ministry of Works reports on various possible schemes
1955 Building restrictions on Crown Land within 100 feet (30m) of average water level of Lake Manapouri
1959 NZ Government invites Consolidated Zinc to consider hydro-electric potential of Lakes Manapouri and Te Anau
1960 Consolidated Zinc Prop. Ltd. granted rights to develop power from Manapouri/Te Anau lakes, Waiau and Mararoa rivers.
1960 Petition of 25,000 signatures against raising of Lake Manapouri
1960 Manapouri Development Validity Act enacted
1961 Bechtel Corporation’s investigations for Consolidated Zinc begin
1961 Power station site reached by vertical tunnel
Apr, 1962 Work and investigation suspended
Jan, 1963 Government to build power station
Feb, 1963 Bechtel instructed by Ministry of Works to start construction
July, 1963 Utah Construction and Mining Company and two local firms won contracts to construct the tailrace tunnel and Wilmot Pass road. Utah Construction also won the powerhouse contract.
Aug, 1963 Manapouri – Te Anau Development Act enacted
29 Aug, 1963 The Wanganella, a former passenger liner, was moored in Doubtful Sound to be used as a hostel for workers building the tailrace tunnel. During the 1930s she was a top-rated trans-Tasman passenger liner, with accommodation for 304 first-class passengers. She continued to serve as a hostel until December 1969.
Sept, 1963 Wilmot Pass Road commenced
4 Feb, 1964 First shot fired on Tailrace Tunnel
1 Nov, 1965 Wilmot Pass Road completed
1966 1963 Act amended to let Crown take more power from Manapouri for National Grid
June, 1966 Transmission Line started
July, 1966 Manapouri controlled level 610ft (185.9m) ASL 27.5 ft (8.4m) above natural mean level
1967 Pilot shoreline clearing carried out
Dec, 1967 powerhouse construction was completed
5:42am, 22 Oct, 1968 Tailrace Tunnel hole through
29 Aug, 1969 Work on Tailrace Tunnel completed
6 Sep, 1969 Tunnel filled with water
14 Sep, 1969 First power transmission
29 Sep, 1969 Second machine commissioned
16 Oct, 1969 Third machine commissioned
30 Oct, 1969 Fourth machine commissioned
17 Apr, 1970 Wanganella leaves Deep Cove for Hong Kong
Dec, 1970 Second petition of 264,900 signatures presented
Apr, 1971 First aluminium smelted at Tiwai Point
Aug/Sept, 1971 The remaining three generators were commissioned
Sept, 1971 Power Station complete
Feb, 1972 Te Anau Lake Control started
28 Apr, 1972 Transmission lines completed
July, 1972 Manapouri Lake control started
10 Feb, 1973 Guardians of the Lake established
Apr, 1974 Te Anau outlet into Waiau river diverted
Nov, 1975 Manapouri to be operated within natural levels
17 Sep, 1977 Guardians of the Lake Guidelines announced
22 Dec, 1977 Government endorses the Guardians’ guidelines
10 Dec, 1997 Second Tailrace Tunnel given go-ahead
9 Jun, 1997 First blast of construction at West Arm, construction work by a Dillingham Construction / Fletcher Construction / Ilbau joint venture
23 Sep, 1997 First blast of construction at Deep Cove
10 Apr, 1998 Tunnel Boring Machine (TBM) arrives at Deep Cove
12 Jun 1998
until 13 Mar, 2001
Work continues 24 hours a day, seven days a week
12 May, 2001 TBM demobilisation completed
5 May, 2002 Tunnel 2 fully operational
2002 – 2008 A $98 million mid-life refurbishment of the seven generating units begins, with the goal of raising their eventual output to 135 MVA (121.5 MW) each