Waiau River's 'unmitigated environmental disaster'

Friday, 11 January 2019

It's a jetboat ride in paradise - as long as you don't touch the water.

Tourists taking a trip on Wairaurahiri Jet, a scenic ride on Southland's Waiau River, are warned not to touch the water after benthic cyanobacteria was found in the river just before Christmas.

The algal bloom is harmful to people and animals if swallowed or through contact with skin. 

Jetboat company operator Joyce Kolk, who operates Wairaurahiri Jet, lays the blame for the algal bloom with Meridian Energy, one of the country's biggest power generators.

It's a claim Meridian rejects.

'They have taken the water from Lake Manapōuri and are using it to generate electricity for the smelter at Tiwai Point, instead of letting it flow down the river,' Kolk said.

In December, Prime Minister Jacinda Ardern opened a fourth potline at the smelter, and Kolk says Meridian are taking more water from the lake at the head of the river to generate electricity to run it, leading to a reduced flow in the Waiau.

'This is an unmitigated environmental disaster. The cause is obvious and so is the cure, but corporate greed and very cunning lawyers have left this community, province and country with a disgusting toxic ditch from what once was New Zealand's second largest, crystal clean river.

'Meridian needs to be forced by the State to let more fresh clean water from Lake Manapouri to flow back down the Waiau.'   

After advising the public of the algal bloom, which was located downstream at Tuatapere in December, Environment Southland emailed Kolk to say it was safe to continue jet boat tours, as long as her staff and customers avoided contact with the water, and didn't ingest or inhale it and avoided skin contact.

Cyanobacteria has been found in several Southland rivers in the past, but Environment Southland's director of science and information Graham Sevicke-Jones said this is the first time it's been found in the Waiau.

'To the best of our knowledge, there has not been a cyanobacteria bloom in the Waiau River before.'

Several factors can contribute to the growth of toxic algae, such as high levels of nutrients or sediment run-off into waterways, a sudden increase in temperature, and low flows.

'Toxic algae or benthic cyanobacteria can arise from stable low flows in a waterway, so it is possible that this was a contributing factor to the bloom which we are seeing in the Waiau River.'

Sevicke-Jones said monitoring showed that Meridian had not breached their consented minimum flow conditions around the time of the toxic algae alert.

He said cyanobacteria was generally always present, however it was when it formed a bloom and started to produce toxins that it became a problem.

In December, the council warned people experiencing health symptoms after contact with contaminated water to visit a doctor immediately.

'If you are concerned that any animals have consumed toxic algae or contaminated water, they should be taken to a vet immediately.'

It said benthic cyanobacteria can be recognised at rivers and streams as a green/brown slime on rocks, or dark brown/black mats at the water's edge. 

Meridian says the increase in consumption from the opening of the fourth potline at Tiwai has not impacted on how it has operated the Manapouri power station, and the resource consents drive the amount of water that flows down the Waiau.

'We always ensure that we put the minimum flow down the Waiau to maintain river health,' a Meridian spokesperson said.

The power generator says it is aware of the toxic algae alert issued by Environment Southland and is compliant with its flow requirements

'During late November and early December flows in the river have been variable and included significant flows. Power generation has not been affected by the toxic algae alert.'

Meridian operates the Manapouri Hydro Power Scheme and uses water from lakes Te Anau and Manapouri to power the hydro station at West Arm on the western side of Lake Manapouri. The water used in the station is discharged via tailraces to Deep Cove in Doubtful Sound. 

Guardians of Lakes Manapōuri, Monowai and Te Anau chairman Darryl Sycamore disagrees this is the first time the toxic bloom has been found in the Waiau River.

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'It is my understanding Phormidium will always be present in the catchment. The Mararoa, a significant Waiau tributary under 'normal flows' often has Phormidium present in its lower reaches during summer.'