4 minute read
HOROWHENUA
RAUMATI • SUMMER 2022
Mangahao Power Station, exterior view of penstocks, 1924. Photograph by Albert Percy Godber. Ref APG-1738-1/2-G. Alexander Turnbull Library.
Few travellers heading through Horowhenua know about one of New Zealand’s largest and earliest engineering achievements located to the east of Shannon.
WORDS: David Watt IMAGES: Heritage New Zealand Pouhere Taonga and National Archives
The Mangahao Hydroelectric Power Station, Category 2 heritage listed, was the New Zealand Government’s first North Island power station. It was constructed as part of a national initiative providing a steady supply of electricity throughout the country, and was one of the last initiatives of Prime Minister William Massey who died shortly after its completion in November 1924. The power station and its penstocks are the most visually accessible extant components of the Mangahao scheme, which was an important precedent for what ultimately became the national power grid.
Most New Zealand hydro stations are built on rivers or supplied by natural lakes. The Mangahao makes use of small and remote rivers in the bush-clad Tararua Ranges. The Mangahao River, which flowed eastward into the Wairarapa, was dammed and its flow diverted via a tunnel into a reservoir which was formed by a dam on the westward flowing Tokomaru Stream. From there via another tunnel, the flow passed into a surge chamber and down a hill into dual penstocks to the power station located on the Mangore Stream.
Mangahao Power Station. Photo: Heritage New Zealand Pouhere Taonga
The tunnels and pipelines total 4.8 kilometres. Water storage in two reservoirs was an essential part of the scheme, necessitated by the variability of the Mangahao River flow. Noted mechanical engineer Frederick Templeton Manheim Kissel (1881-1962) oversaw the realisation of the Mangahao hydroelectric power scheme and was involved with the key early governmentsponsored projects for power generation. Survey work for the Mangahao hydroelectric power scheme started in 1915, but the realisation of Kissel’s plan would not begin until after the end of WWI. In April 1921, over 200 men were working in shifts tunnelling for the project. Two years later this number had increased to almost 900 men working eight-hour shifts over 24 hours a day. On 3 November 1924, when Prime Minister William Massey officially opened the power station, the day-long celebration was attended by numerous national and local officials.
An essential part of the national supply concept was the provision of a countrywide electric power transmission system, and Mangahao was to become the point of supply not only for Wellington, but also for Horowhenua, Taranaki, Hawkes Bay and the Wairarapa. The 110 kilovolt (KV) transmission lines from Mangahao to these areas were to prove to be the forerunner of New Zealand’s extensive transmission grid. The imposing concrete powerhouse is 84 metres long, by 25 metres wide, and over 16 metres high. The exterior style was typical for industrial architecture of the age with its largely utilitarian character and classical elements.
The powerhouse and its tailrace remain today largely intact to their period of original construction, which included the straightening of a bend in the Mangaore Stream in the vicinity of the powerhouse. There have been several seismic upgrades, including the replacement of a portion of the roof parapet and the 2015 construction of two transverse sheer walls.
Today the power station is jointly owned and operated by Todd Energy and King Country Energy. Visitors heading north through Horowhenua can turn right off State Highway 1 to view the exterior of the power station from Mangahao Road east of Shannon. n
This issue
1 HOROWHENUA The heritage secret in the heart of the Horowhenua
3 EDITORIAL Travel through time this summer
4 CANTERBURY A place of significant cultural heritage
6 CHRISTCHURCH A window into the world of heritage glass
8 HAWKE'S BAY Hakikino listed as a Wāhi Tapu Area
10 ŌTEPOTI DUNEDIN Ōtepoti Dunedin office creates tukutuku panel
12 RUSSELL/KORORĀREKA Pompallier Mission and Printery an ongoing inspiration for artist 14 HOKIANGA Pompallier, 20 years ‘home’ in Aotearoa
16 ŌHAEAWAI Preserving archaeology one tree at a time
18 STAFF PROFILE Pouārahi Māori Built Heritage Jasmine Hemi
20 EXHIBITION Wool bale stencil exhibition impresses
22 TOHU WHENUA Plenty of history education at Tohu Whenua heritagenewzealand heritage_nz @heritagenz
Editor: Adrienne Hannan Designer: Michael Steele
Published by Heritage New Zealand Pouhere Taonga, Heritage Quarterly keeps you up-to-date with heritage news from around New Zealand.
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All images credit Heritage New Zealand Pouhere Taonga unless otherwise stated.
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ISSN 2324-4267 (Print) ISSN 2324-4275 (Online).
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