In May 2004 the Environment Court ruled in favour of the Whanganui River Maori, reducing Genesis Energy's water right to the headwaters of the Whanganui from 35 years to ten, with no guaranteed right of renewal.
The disputed water flows through the Genesis Energy's Tongariro scheme and provides 20% of the water in the Waikato river, where it is used by ten power stations, including the country’s largest scheme – the 1000MW Huntly project.
Huntly thermal plant uses Waikato water for cooling. A reduced flow would result in a loss of power equivalent to that needed to supply every house in Wellington and Palmerston North. Both Genesis and Mighty River Power are scrutinising the 135-page court decision to decide whether to appeal.
The Tongariro scheme, opened in two stages in 1973 and 1983, diverts the headwaters of the Whanganui, Whangaehu and Moawhango rivers on the North Island central plateau via canals to the Rangipo and Tokaanu hydro stations. Total annual power production from the Tongariro scheme is about 1400GWh. The additional power from the nine Waikato hydro stations made possible by the Tongariro diversions is about 600GWh.
Whanganui Maori, who were never consulted about the scheme during its construction, went to the Environment Court objecting to the resource consents being extended another 35 years. In its decision, the court agreed with the Maoris that diversion of the water was a denigration of their values and beliefs.
