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 formulated by Peter Hay, the Superintending Engineer of the Public Works Department, and Lemuel Morris Hancock, the Electrical Engineer and General Superintendent of the Transmission Department of the California Gas and Electric Company during their November 1903 inspection of Lakes Manapōuri and Te Anau. Each of the 1904 reports by Hay and Hancock noted the hydraulic potential of the lake systems, being so high above sea level, and while the rugged isolation of the region meant that it would be neither practical nor economic to generate power for domestic consumption, the engineers realised that the location and scale of the project made it uniquely suited to electro-industrial developments such as electro-chemical or electro-metallurgical production. In January 1926, a Wellington-based syndicate of ten businessmen headed by Joseph Orchiston and Arthur Leigh Hunt,
New Zealand Sounds Hydro-Electric Concessions Limited, was granted by the government via an Order in Council the rights to develop the waters which discharged into Deep Cove, Doubtful Sound, and the waters of Lake Manapōuri, to generate in total some . The company attempted to attract Australian, British and American finance to develop the project, which would have required the construction of a powerhouse and factory complex in Deep Cove, with accommodation for an estimated 2,000 workers and wharf facilities, with the complex producing atmospheric nitrogen in the form of fertiliser and munitions. Various attempts to finance the scheme were not successful, with the water rights lapsing and the company fading into obscurity by the 1950s. In 1955 the modern history of Manapōuri starts, when
Harry Evans, a New Zealand 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 Manapōuri 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.
Construction history • February 1963,
Bechtel Pacific Corporation won the design and supervision contract. • 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. • August 1963,
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. • February 1964, tailrace-tunnel construction began. • December 1967, powerhouse construction was completed. • October 1968, tunnel breakthrough. • 14 September 1969, the first water flowed through the power station. • September/October 1969, commissioning of the first four generators. • August/September 1971, the remaining three generators were commissioned. • 1972, the station was commissioned. It was then that engineers confirmed the limitations of peak capacity due to excess friction in the tailrace tunnel. • June 1997, construction work by a
Dillingham Construction /
Fletcher Construction /
Ilbau joint venture began on the second tailrace tunnel. • 1998, the Robbins
tunnel boring machine starts drilling at the
Deep Cove end of the tunnel. • 2001, tunnel breakthrough. • 2002, the second tunnel was commissioned. A $98 million mid-life refurbishment of the seven generator units begins, with the goal of raising their eventual output to 135 MVA (121.5 MW) each. By June 2006, four generating units had been upgraded, and the project was on schedule for completion in August 2007. By the end of 2007, all seven turbines had been upgraded. • 2014, three transformers were replaced following the discovery of an issue with the oil cooler on one of Manapōuri's seven transformers during maintenance in March. The first removed transformer was the largest pieces of hardware to leave the station since its completion. The three transformers were replaced with newly manufactured ones from Wilson Transformer Company (WTC), delivered via Wilmot Pass between December 2014 and February 2015. • 2018, the remaining four transformers were replaced with more from WTC. • 8 August 2023, the transformer for unit 1 was removed from service after monitoring detected elevated gas levels. The transformer for unit 6 also had a similar issue. Meridian initially planned to bring units 1 and 6 back on line on 29 September and 7 September respectively. • 2024 a replacement transformer from Wilson Transformer Company was supplied and installed at Manapouri. On 19 January 1960, the
Labour Government and Consolidated Zinc/Comalco signed a formal agreement for Consolidated Zinc to build both an aluminium smelter at Tiwai Point and a power station in Manapōuri. The agreement violated the National Parks Act, which provided for formal protection of the Park, and required subsequent legislation to validate the development. Consolidated Zinc/Comalco received exclusive rights to the waters of both Lakes Manapōuri and Te Anau for 99 years. Consolidated Zinc/Comalco planned to build dams that would raise Lake Manapōuri by , and merge the two lakes. The
Save Manapouri Campaign was born, marking the beginning of the modern New Zealand environmental movement. In 1963, Consolidated Zinc/Comalco decided it could not afford to build the power station. The New Zealand government took over. Electricity generated by the plant was sold to Consolidated Zinc/Comalco at under an arrangement designed to return the cost of building the power station to the government. In 1969, Consolidated Zinc's electric power rights were transferred to Comalco Power (NZ) Ltd, a subsidiary of the Australia-based
Comalco Industries Pty Ltd. In 1970, the
Save Manapouri Campaign organised a petition to Parliament opposing raising the water level of Lake Manapōuri. The petition attracted 264,907 signatures, equivalent to nearly 10 percent of New Zealand's population at the time. In 1972, New Zealand elected a new Labour government. In 1973, the Prime Minister,
Norman Kirk, honoured his party's election pledge not to raise the levels of the lakes. He created an independent body, the
Guardians of Lake Manapōuri, Monowai, and Te Anau, to oversee management of the lake levels. The original six
Guardians were all prominent leaders of the
Save Manapouri Campaign. In 1984, the
Labour Party returned to power in the
general election. The resulting period was tumultuous, with Labour's controversial ministers
Roger Douglas and
Richard Prebble driving
rogernomics, a rapid introduction of "
free market" reforms and
privatisation of government assets. Many suspected the Manapōuri Power station would be sold, and Comalco was the obvious buyer. In 1991, the
Save Manapouri Campaign was revived, with many of the same leaders and renamed
Power For Our Future. The Campaign opposed selling off the power station to ensure that Comalco did not rehabilitate its plans to raise Lake Manapouri's waters. The Campaign was successful. The government announced that Manapōuri would not be sold to Comalco. On 1 April 1999 - the 1998 reform of the New Zealand electricity sector took effect: the Electricity Corporation of New Zealand was broken up and Manapōuri was transferred to new state-owned generator
Meridian Energy. In 2002, the Government rejected an application of a business, Southland Water 2000, to bottle 40,000 cubic metres of water in 20 hours, twelve times a year, before the water from the power station is released into Doubtful Sound. In July 2020,
Rio Tinto announced it would be closing the
aluminium smelter in
Bluff in August 2021, triggering discussions on how to utilise the energy generated in Manapouri. In January 2021, Rio Tinto said they would keep the smelter open until December 2024. In May 2024, New Zealand Aluminium Smelters (NZAS) signed a 20-year electricity arrangement that guaranteed the future of the Tiwai Point aluminium smelter until at least 2044. NZAS, which owns and operates Tiwai Point, has signed contracts with electricity generators Meridian Energy, Contact Energy and Mercury NZ to set pricing for an aggregate of 572 megawatts (MW) of electricity to meet the smelter's full electricity needs. The agreements, which are subject to regulatory approvals and other conditions, are expected to commence in July 2024 and run until at least 2044. ==Specifications and statistics==