The Mangawhero River is in the North Island of New Zealand.
Map of Mangawhero River, Mangamahu, New Zealand
It drains the south-western slopes of Mount Ruapehu, passes though Ohakune before discharging into the Whangaehu River to the south-west of Mangamahu.
On 8 September 1979 up to 17,000 litres (4,500 US gal) of heating oil were spilt into the river from the Turoa ski field.
References
Mangawhero River Wikipedia(Text) CC BY-SA