Power to the People


Early in the 20th century Marlborough, like the rest of the top of the South, was isolated from the national grid and the lack of bulk electricity was handicapping development in the province. Blenheim's street lights1 were run on gas, while Picton had a diesel plant as early as 1917 and Havelock had a power plant driven by a Pelton water wheel.

Waihopai Power Scheme 

The Marlborough Electric Power Board (MEPB), which was established in 1923, borrowed £300,000 to build a hydroelectric  power scheme on the Waihopai River  to meet the electricity needs of the region. The Waihopai Power Scheme was commissioned 2 on April 6, 1927 and, for the first time, electric lights shone in the streets of Blenheim.  By February 1928, there were 1451 consumers in Blenheim and Seddon and the load was 400 kilowatts (KW).

The Waihopai powerhouse situated above the Waihopai River. Photo courtesy Marlborough Lines Ltd
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The Waihopai Power Scheme consisted of a 36 metre concrete arch dam, 120 metre long concrete lined tunnel, 96 metre long steel penstock, a large powerhouse and a 40 km transmission line to Blenheim. It was capable of generating up to 1000 kW of electricity.

For many years the station was run by a team of three on-site operators but in the early 1980s, the control system and switch gear were automated and the station run from Blenheim.

In the early years the dam created a lake of more than 28 hectares but it rapidly filled with silt and debris. A crane and grab and 600mm siphon were mounted on the dam to keep the plant clear for the first six decades. Modifications were carried out in 1990 - a hole was cut into the dam and a sluice gate which automatically flushes out the debris was installed.  The contractors had some difficulty cutting the concrete and were surprised at the strong condition of the 68 year old dam.

Murphy's Road Diesel StationThe Murphy’s Road diesel station. Photo courtesy Wayne Stronach.
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Murphy's Road Diesel Station

In the 1930s, two diesel engines, designed for use as auxiliary engines3 in large passenger ships, were installed to meet the province's increasing demands for electricity.  The engines are: a Davey Paxman, a 630hp six-cylinder unit capable of producing 430kW and a Harland and Wolff, a 1300hp plant with a 900kW output.  Between 1936 and 1952 the diesel generators, along with the Waihopai Scheme, provided all of Marlborough's electricity needs. They are housed in the Murphy's Road Diesel Station.

In 1952 Marlborough was connected to the Cobb Power Scheme, which reduced the need for the diesel plant.  After Marlborough was connected to the National Grid in 1956, the Power Board unsuccessfully tried to sell the generators. The Murphy's Road diesel generators were finally decommissioned in January 1992 only to be fired up six months later to help Marlborough cope with a nationwide power crisis.   They are still located at the Murphy's Road Diesel Station in Springlands, Blenheim.

The opening of the branch power scheme by (l-r) Prime Minister Robert Muldoon, board chairman Lester Munro, and board CE Ken Forrest. Photo courtesy Marlborough Lines Ltd.
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The Branch Power Scheme
Cutting through the Waihopai dam to install the sluice gate. Photo courtesy Marlborough Lines Ltd
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The Branch Power Scheme was opened in April 1984 by Prime Minister, Sir Robert Muldoon, who commended MEPB for taking advantage of a Government loan aimed at developing small hydro schemes throughout the country.

The project which cost $24.5 million produced on average 54,000,000 kWh (kilowatt-hours) per year of electricity. The run of river scheme sees water stored in Lake Argyle, passing through turbines in the Argyle and Wairau powerhouses before being discharged into the Wairau River.  Electricity generated is then transmitted to Blenheim over TransPower's Argyle-Blenheim transmission line.

Plans for a community irrigation scheme for Wairau Valley farmers using tailrace waters from the dam unfortunately had to be abandoned due to prohibitive costs. A board investigation showed four or five powerhouses would be required at a cost of $82 million to make the scheme feasible.

Marlborough electricity consumers had reason to be grateful for more than pocketbook benefits from The Branch.  The scheme gave MEPB considerable versatility during power shortages and outages and in the negotiation of power prices from the national grid.

Lake Argyle and the Argyle powerhouse at the Branch power scheme. Photo courtesy Marlborough Lines Ltd
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The Waihopai and Branch Power Schemes were sold to Trust Power in 1999, following the 1998 Electricity Industry Reform Act. By the 1990s, the combined generation of the two schemes was up to 13,500kW, which supplied up to 26% of the region's electricity needs.

Government Restructuring

The Energy Companies Act 1992 required the MEPB to become a commercial power company with a responsibility to operate as a successful business. In 1992, the board became Marlborough Electric - one of 35 integrated electricity businesses around New Zealand and one of a small number of electricity companies to operate its own generation business.

The 1998 Electricity Industry Reform Act  required that all electricity companies split into either the lines (network) business or the supply business (generating and/or selling electricity) by 1 April 1999. Marlborough Electric's generation and retail businesses were sold to TrustPower and from April 1999 the company became Marlborough Lines and now focuses on the operation and maintenance of the province's lines network.4

2008 (updated 2022)

Sources used in this story

  1. Humphris, A. (2010) Streets and lighting - Street lighting. In Te Ara - the Encyclopedia of New Zealand
  2. Power for Blenheim (1927, July 9) Auckland Star, p.11 http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&d=AS19270709.2.88
  3. The Marlborough Electric Power Board has acquired an interesting diesel-driven alternator set, which... [truncated] (1937, June 14) Evening Post [image], p.17
  4. Marlborough Lines, retrieved March 2022: 

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Further sources - Power to the People




  • Stephens, J. (2008) From a Power Board to a Company: Marlborough Electric 1983 to 1993 [unpublished manuscript]
  • Personal Communication, Wayne Stronach, Marlborough Lines engineering manager, 15 August 2012

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