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.
The heritage secret in the heart of the Horowhenua 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
T
IMAGES: Heritage New Zealand Pouhere Taonga and National Archives
he 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.
RAUMATI • SUMMER 2022
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. Heritage Quarterly
1