The Mangahao River is located in the

North Island The North Island, also officially named Te Ika-a-Māui, is one of the two main islands of New Zealand, separated from the larger but much less populous South Island by the Cook Strait. The island's area is , making it the world's 14th-largest ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. The headwaters are in the

Tararua Ranges The Tararua Range, often referred to as the Tararua Ranges or Tararua, is one of several mountain ranges in the North Island of New Zealand. The Tararua Range runs northeast–southwest for from near Palmerston North to the upper reaches of ...

. The river flows northeast feeds into the Manawatu River south of Woodville. There are two

dams A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, ...

on the river which tunnel water, via a third reservoir on the Tokomaru River, to the

Mangahao Power Station Mangahao Power Station is a hydroelectric power station near the town of Shannon, New Zealand. After being delayed by war, access road construction and foundation testing was started by late 1919 and the station opened in November 1924. It makes ...

located on the Mangaore Stream near Shannon.

Geology

Within the last 10,000 years the upper of the river has been captured at Kakariki from the Hukanui Stream, which feeds the

Mangatainoka River The Mangatainoka River flows in the Tararua District of New Zealand's North Island. Its water was considered so pure a brewery, now the well-known Tui Brewery, was established there. Its headwaters are on the eastern side of the Tararua Range to ...

. The

crush zone Crumple zones, crush zones, or crash zones are a structural safety feature used in vehicles, mainly in automobiles, to increase the time over which a change in velocity (and consequently momentum) occurs from the impact during a collision by ...

of the Wellington Fault probably assisted the capture. The capture has deepened the gorge cut into the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...

greywacke Greywacke or graywacke (German ''grauwacke'', signifying a grey, earthy rock) is a variety of sandstone generally characterized by its hardness, dark color, and poorly sorted angular grains of quartz, feldspar, and small rock fragments or lit ...

and

argillite :''"Argillite" may also refer to Argillite, Kentucky.'' Argillite () is a fine-grained sedimentary rock composed predominantly of indurated clay particles. Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts ...

of the Tararuas, which in places is over deep.

References

Rivers of Manawatū-Whanganui Rivers of New Zealand {{ManawatuWanganui-river-stub