These rivers drain a 2,600-square-kilometre (1,000 sq mi) area including Ruapehu, Ngauruhoe, Tongariro and the western Kaimanawa Ranges.

From its inception to the current day tensions have existed between the need to generate electricity and cultural and environmental issues.

Plans to realise the potential of electricity generation in the central North Island volcanic plateau date back to the early years of the 20th century.

[1][2][3] In 1904 Hay's report to the government New Zealand Water-Powers identified a number of potential sites around the central plateau.

A dam could be built on the Poutu River feeding into Lake Rotoaira and the amount of power generated could be increased by adding water from Tongariro or Ngauruhoe.

While he identified the generation potential of the Whangaehu River, Hay noted that it was polluted by volcanic acids and chemicals making it unsuitable.

[4] Between the 1920s and 1950s a number of investigations on the potential of the volcanic plateau were undertaken by engineers, mostly in the Public Works Department.

[5]: 222 The scheme was built by the Ministry of Works and the project engineers were Warren Gibson and Bert Dekker.

[12] The tunnel was constructed by Downer and Associates between 1968 and 1973 and was beset with difficulties caused by water inflow and thermal activity.

[5]: 228 [12] The tunnel passes under State Highway 47 and through the saddle between Pihanga and Mount Tihia to penstocks dropping 180 metres (590 ft) to the Tokaanu Power Station.

[8] The aqueduct heads eastward, passing under the actual Whangaehu River, but not taking any water from it due to the fact it drains Mount Ruapehu's crater lake and is too acidic.

[5]: 226–227 [14] It was begun in 1969 but due to difficult tunnelling conditions, which included faultlines, rock falls and incoming water, it took 10 years to complete.

[5]: 232 Water from the Moawhango Tunnel and the Waihohonu Stream flows into the Rangipo Dam which is built on the Tongariro River.

[5]: 223 [8] After taking on more water from the Tongariro River (which now includes water from the eastern slopes of Ngauruhoe and Tongariro), the water is diverted through the 2.8-kilometre (1.7 mi) long concrete-lined Poutū Tunnel into the 5.6-kilometre (3.5 mi) long concrete-lined Poutū Canal which was constructed by the Ministry of Works and Development[5]: 222, 228 [12] The Canal, which is on average 4.3 metres (14 ft) deep,[8] travels under State Highway 1 and under State Highway 46 to the Poutū Dam.

The station was commissioned in 1983,[5]: 234 [8] and was built 63 metres (207 ft) underground beneath the Kaimanawa Forest Park, to minimise visual impact.

[18] Tokaanu Power Station is located on the Rotoaira Diversion of the scheme on the northern slopes of Mount Tihia.

[20]: 253  Desmond Bovey's book on the Tongariro National Park put it this way:Depending on your sensibilities, the scheme can be viewed as either a bold and ingenious feat of engineering, or alternatively as a high-handed grab of the headwaters of almost every river on the volcanic plateau.

[21]The Tongariro Power Scheme was conceived and commissioned at a time when Māori values were either not considered or dismissed.

[22]: 64 [20]: 248  The Ministry of Works met with Ngāti Tūwharetoa in 1955 to discuss land rights and fishing[5]: 223  but the other iwi with interests in the diversion of the Whanganui River and its headwaters were not consulted before or during construction.

[23] Genesis continues to meet with iwi and relevant fishery, recreational and environmental groups, and the Defence Force to mitigate the effects of the scheme on the environment.

[19]: 12 [5]: 225  He was supported by zoologist John Salmon who called for research into the long-term environmental effects of the scheme.

[26] Since 2011 Genesis has also partnered with the Department of Conservation on a blue duck/whio recovery programme which involves trapping predators on the Whakapapa, Wanganui and Mangatepopo rivers.

[29]: 4  As a result of construction work on access roads and near spawning streams on the Western Diversion the decline of fish stocks in the Lake was being reported in the late 1960s.

The iwi would not concede ownership and in a 1972 agreement the Crown was allowed control over the water for electricity generation but discharged from any compensation claims caused by environmental damage or adverse effects on the fishing.

[31] A 2015 Tribunal report acknowledged the harm that the Scheme had done not just to the Lake but to Ngāti Tūwharetoa's economic, social, cultural and spiritual well-being which included reduction in income from fishing licences.

[35] In 2010 Genesis and Ngāti Rangi formed a partnership to find ways to restore water flows in the rivers.

[38][39][40][41] The 2019 legislation created the framework called Te Waiū-o-Te-Ika which recognises the intrinsic connection between the awa and the iwi and hapū of the Whangaehu.

The following rivers have been monitored for clarity, temperature, acidity and oxygen levels: Tokiāhuru, Wāhianoa, Mākahikatoa, Tomowai and Whangaehu.

[45] When the project was approved in 1965 it was agreed that the Historic Places Trust (now Heritage New Zealand) would work with Ngāti Tūwharetoa to identify and protect sites on Lake Rotoaira and the Tongariro.

[47]: 4–13  A small settlement, dating from around the 1840s, was found at Opōtaka at the northern end of Lake Rotoaira and partial excavation of the site revealed several houses and a collection of traditional and European artefacts.