The Tarawera River is in the Bay of Plenty Region in the North Island of New Zealand.
It flows from Lake Tarawera, northeastwards across the northern flanks of the active volcano Mount Tarawera, and past the town of Kawerau before turning north, reaching the Bay of Plenty west of Edgecumbe. The Tarawera Falls are located in the upper reaches of the Tarawera River.
Geology
The Tarawera River drains the north-eastern aspect of the Taupō Rift with its river mouth west of Matatā. The river commences at the north-east arm of Lake Tarawera with a mean outflow of , from effectively a watershed of the Ōkataina Caldera, with its risk of volcanic activity disrupting river flow. At this normal or less flow the river disappears underground into caves in the rhyolite lava flow just before the Tarawera Falls. It usually emerges about halfway up the full falls drop, Kaharoa eruption.
The Tasman Pulp and Paper Mill, now owned by Norske Skog, has been discharging waste into the river since 1955. Local residents have erected signposts labelling the river as the "Black Drain" since the 1990s.
The dark colour is due to the presence of pollution from farms, sewage and stormwater but it is predominantly from pulp and paper mill effluent. As of 1997, pulp and paper mills were discharging over 160 million litres of industrial waste into the river per day. By 2006, the oxygen levels in the river had reached a level where fish could survive, however the water colour was still dark. Since 1998 the colour and light penetration (euphotic depth) have improved in the lower section of the river due to less pollution from the Tasman Mill. In 2010, local iwi took a case to the High Court to shorten the 25 year water discharge permits issued under the Resource Management Act but the appeal was rejected.