Tarawera River

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 Template:Convert 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 Template:Convert,<ref name=Hodgkinson2005>Template:Cite journal</ref>Template:Rp 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.<ref name=Hodgkinson2005/>Template:Rp<ref name=TFT>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It usually emerges about halfway up the full falls drop,<ref name=TFT/> but can with recent rain fully occupy the drop. There have been two known major floods following the breakdown of temporary volcanic material dams at the lake outlet.<ref name=Hodgkinson2005/>

The first, and larger, followed the 1314 ± 12 CE<ref name=Villamor2022>Template:Cite journal</ref>Template:Rp Kaharoa eruption.<ref name=Hodgkinson2005/>Template:Rp The present river start is where the Tapahoro lava flow, created by the 5526 ± 145 BP<ref name=Villamor2022/>Template:Rp Whakatane eruption,<ref name=Hodgkinson2005/>Template:Rp runs into a 14,009 ± 155 BP<ref name=Villamor2022/> Pokohu lava flow. The Tarawera River flows across this in a Template:Convert wide channel.<ref name=Hodgkinson2005/>Template:Rp The 1314 eruption blocked the outlet with a temporary dam up to Template:Convert above present outlet levels, which was subsequently eroded with a great flood that created a Template:Convert wide, and almost Template:Convert deep valley spillway at the start of the river.<ref name=Hodgkinson2005/>Template:Rp It seems the river during this flood overflowed to the east draining for a time through the Awiti Ravine, and back into the Tarawera River flood plain by the present Waiaute Stream that drains the eastern slopes of Mount Tarawera.<ref name=Hodgkinson2005/>Template:Rp However it also evacuated Template:Convert downstream from the lake at the terminus of the Pokohu lava flow the amphitheatre of the Tarawera Falls.<ref name=Hodgkinson2005/>Template:Rp The flood deposited large boulders up to Template:Convert in diameter for Template:Convert below the falls and up to Template:Convert to Template:Convert below the falls.<ref name=Hodgkinson2005/>Template:Rp

The lake outlet was blocked again after the 1886 eruption of Mount Tarawera, and the lake level increased to a maximum of Template:Convert above its present level.<ref name=Hodgkinson2005/>Template:Rp This volcanic debris dam (the debris that blocked the outlet were not just from the eruption directly but included those washed down from a creek that runs into the lake by the outlet), first broke on 1 November 1904, with a main flood surge on 3 November 1904 which was assessed at a peak flow of Template:Convert.<ref name=Hodgkinson2005/>Template:Rp This flood resulted in the raising of the river bed (aggradation), and sedimentation problems to Template:Convert downstream of the lake.<ref name=Hodgkinson2005/>Template:Rp

History and environmental issues

Prior to the 1910s, the Rangitaiki River drained into the Tarawera River before entering the Bay of Plenty, west of the settlement of Matatā. In 1914, the Rangitaiki River was cut directly to the Bay of Plenty, with a similar effort undertaken in 1917 for the Tarawera River. This led to the former mouth of the river, traditionally known as Te Awa o te Atua, silting up and forming the Matatā Lagoon. The former mouth of the Rangitaiki River remains to the east of the mouth of the Tarawera River, creating the Old Rangitaiki Channel.<ref>Template:Cite report</ref><ref>Template:Cite report</ref>

The Tasman Pulp and Paper Mill, now owned by Norske Skog, has been discharging waste into the river since 1955.<ref name="rnz">Template:Cite news</ref> Local residents have erected signposts labelling the river as the "Black Drain" since the 1990s.<ref name="colour">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

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.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="colour"/>

In 2009, the mill gained permission to continue polluting the river for the next 25 years.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> 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.<ref name="rnz"/>

Gallery

• Upper Tarawera River.
  Upper Tarawera River.
• Tarawera Falls on a misty high flow day.
  Tarawera Falls on a misty high flow day.
• Easterly view across Tarawera River in its flood plain towards Putauaki.
  Easterly view across Tarawera River in its flood plain towards Putauaki.

External links

• Template:Commons category-inline