New Plymouth’s hydro-electric scheme still operates as TrustPower’s (2023, now known as Mercury) Mangorei Power Station alongside the Waiwhakaiho River near Burgess Park. The complex has been added to a number of times over the years since its beginnings in 1906 as a combined water and electricity supply. It’s one of New Zealand’s oldest operating stations albeit much-evolved from its simple beginnings.
The first scheme was merely a 1200-metre water supply piped directly from the Waiwhakaiho River to the generating station. The water supply, of course, suffered in times of low summer flow, so a storage dam was built on the Mangamahoe Stream in 1914. A new intake was also constructed a little further up the Waiwakaiho River and a 420-metre open water race led to the dam. This second intake proved nearly impossible to maintain as it frequently became blocked with boulders, gravel and timber which then had to be removed by hand. The first dam on the Mangamahoe Stream was washed out in 1917 and replaced by the surviving, but now unused, low-head dam a few metres downstream.
The 1914 & 1918 dams may be accessed from the present power station intake at the northern end of Lake Mangamahoe and via a short 1.5 km walk across the 1931 dam and through the forest tracks to the lower Mangamahoe Stream before it joins the Waiwhakaiho River.
Access across the 1918 dam is restricted for safety reasons.
The present concrete-cored earth dam now operating, was built in 1931 to form Lake Mangamahoe and its water, taken from the Waiwhakaiho River and the Mangamahoe Stream, is conveyed through tunnel and penstocks to the power station.
The Alchemy of the Engineer: Taranaki Hydro-electricity, Ron Lambert (2015)