Black, 'stinking' wastewater dumped near Waikato wetland - and it's totally legal

Tuesday, 21 March 2023

Agricultural and industrial run-off have caused a botulism outbreak that has killed thousands of birds at Whangamarino Wetland near Te Kauwhata and Meremere.

Shocking photos show black, “stinking” wastewater being discharged close to an internationally important wetland where a disease outbreak has killed thousands of birds.

But the pollution is entirely legal - permitted under resource consents that allow water to be pumped off farmland on the floodplain and into the swamp to protect pasture.

Fish & Game – whose staff have picked up thousands of dead birds to prevent further spread of avian botulism – have called for urgent action on how Waikato’s waterways are managed.

Waikato Regional Council said the discharge is not typical and reflects the significant rains that fell during January’s Auckland Anniversary weekend.

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‘Stinking’ water discharged into the Maramarua River, in February 2023. The waterway feeds into the Whangamarino Wetlands, where thousands of birds have died in an avian botulism outbreak.

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Large populations of Whangamarino’s birds have fallen sick with avian botulism, dying a gruesome death after they have lost the ability to walk and use their wings.

The Whangamarino Wetland near Te Kauwhata and Meremere is considered internationally significant under a global convention.

The paralysis eventually robs them of the ability to hold up their heads, and they drown in the mosaic of swamps, fens, bogs and open water between Meremere and Te Kauwhata.

After this summer’s heavy rainfall, the scheme’s pump stations kicked into action, draining water from the flood plain into waterways.

The photos supplied to Stuff show a large screw pump – known as the Motukaraka station – discharging into the Maramarua River which flows into the wetlands, on February 4.

“It literally stunk and there was effluent smell and froth and scum in the water pumped in at this point,” the photographer, a volunteer who was collecting corpses, said.

Hunters, volunteers and Fish & Game staff have been left distressed by the sheer number of dead wildlife.

”Over the next three weeks we saw the black water slowly make its way upstream [and] with it a tide of dead birds, eels and carp.”

The volunteer saw hundreds of carcasses, including grey kotuku (heron), native teal, cormorants, and swans.

The blackwater mixes with the Maramarua River, already coloured brown from floods in late January.

He knew of the collection of at least two corpses of Australasian bittern (matuku). The wetland is home to the largest population of the species in the world. The Department of Conservation said it has had no reports of deaths of the endangered bird.

The pollution is known as a blackwater event, when organic matter such as sticks, leaves, grass, crops and stock excrement are washed off the floodplain and into rivers and creeks.

But in areas where there is intense dairy farming, elevated levels of nitrogen and phosphorous are present in the soil from agricultural fertilisers.

Fish & Game staff are horrified at the number of dead birds, killed in an avian botulism outbreak at the Whangamarino wetlands.

The water appears black due to the release of dissolved carbon compounds, as the organic matter decays.

But the rising levels of dissolved carbon also changes the chemical balance of the water, depleting the oxygen that is essential for aquatic organisms to breathe underwater.

A volunteer picks up one of the wetlands’ dead birds in a desperate attempt to slow the avian botulism outbreak.

As the pools become stagnant, this creates the perfect breeding conditions for bacteria which produces a botulism toxin deadly to birds but harmless to humans.

Heavily polluted Lake Waikare, which locals call ‘Fanta Lake’ because of its toxic orange colour, is also artificially drained into the wetlands.

Flood protection was built in the 1960s after a major flood in 1958.

“The water coming into the wetlands is bringing a massive organic load and is poor in terms of water quality and low in oxygen,” said David Klee ofAuckland/Waikato’s Fish & Game Council.

“There's a multitude of issues occurring and Whangamarino is a complex system. But in general, it is going to take a major shift or realignment in how we view wetlands, and it's going to take some really strong policy direction from politicians, who set policy and rules.”

The wetlands are usually an oasis for rare wildlife. It is home to the largest population of Australasian bittern, or matuku, in the world.

On Sunday, the organisation’s chief executive Corina Jordan launched a stinging attack on the regional council, pointing to “long-term systemic failures in freshwater policies and a lack of implementation that has caused severe degradation in our freshwater ecosystems.”

Jordan, who is a freshwater ecologist, said the council needs to take a hard look at how the system is managed and limit discharges into the waterways.

Lake Waikare’s waters are toxic orange, thick and turbid. Cyanobacteria – or blue-green algae – which can produce dangerous toxins, thrives there.

Greg Ryan, the regional council’s integrated catchment director, said the photos showed water from the Kopuera canal being pumped over a stopbank and into the Maramarua River.

The discharge has a resource consent, he confirmed. “Conditions require the water quality of the Maramarua River to be monitored to inform future review or re-consenting processes.”

The flood infrastructure was put in place in the 1960s – after a 100-year-flood in 1958 flood event to protect urban and rural areas from flooding, Ryan said.

He stressed that it was a complex hydrological system, and that is exacerbated by the presence of flood protection and land drainage infrastructure.

Catchment development and farming practices were among factors that caused the deterioration of water quality and environmental health.

“Today, with regards to any type of development, there is a much greater focus on ensuring there is a sustainable balance of outcomes, so environmental outcomes are considered as well as economic ones.”

The pollution was “unusual” and created by extreme weather events in the region over the summer, he said. Monitoring showed low oxygen levels up (less than 10%) upstream of the pumping site in mid-January to the end of February.

“The rains received in the Northern Waikato area were up to 200mm over a 24-hour period.

Across the region, flooding resulted in significantly higher flows and levels of contaminants in waterways, which impacted a number of water bodies – whether they had flood protection or drainage assets or not.”

Some farmers are also frustrated with the council. A landowner on the shores of Lake Waikare said that in 20 years, she has never been contacted about its water quality or control of agriculture intensification.

“We have planted, retired paddocks, stocked very lightly and not used fertilisers,” she said. “By doing so, we have reaped the benefits of allowing nature to regenerate our land with the increase of plant, tree and grass growth, worms and much better soil than when we came.

“We just so wish Lake Waikare and Whangamarino swamp could have the same privilege.”

The farmer, who wished to remain anonymous, said emails asking for advice and support go unanswered.

“My voice goes unheard. Numerous times I have been ignored by the regional council asking for their support - for growing plants, to talk to someone about floating plant islands, ideas about the storm water creek that runs through our property.

“Inevitably, I never get a reply. Even when I follow up, I still don’t get a reply. It's very frustrating.”

She pointed to a lowering of Waikare’s water level, as part of flood control measures, and the discharge of waterwater, which contained non-compliant levels of phosphorus, nitrogen and E.coli, for three years.

“To control the lake’s level and drain the excess into beautiful Whangamarino like a soak hole has been utterly disastrous over 60 years,” she said. “There are a lot of landowners in this area who care very much about the land and water quality and who have watched as the only action taken is planning to make plans.”