The chairman of Northland’s biggest iwi is calling for urgent action to clean up a lake once regarded as the food basket of Ngāpuhi.

These days, Lake Ōmāpere, located between Kaikohe and Ōkaihau, is shallow, polluted and plagued by toxic algal blooms.

The largest lake in Northland has been the subject of protest and debate for decades.

Now, however, Wane Wharerau, chairman of Te Rūnanga-ā-Iwi-ō-Ngāpuhi, said the time for talking was over.

A new generation of leaders emerging across Te Tai Tokerau and a new council that reflected the Far North’s ethnic makeup — seven out of 11 elected members are Māori — offered “a great opportunity” to do things differently.

He called on Ngāpuhi and tangata te Tiriti [people of the Treaty] to work together to come up with a practical recovery plan to restore water quality, and the lake’s flora and fauna, as closely as possible to their original state.

Wharerau pledged to support the Lake Ōmāpere Trust, central and local government, and anyone else willing to help return the lake to health.

He also pledged the rūnanga’s support for any hapū leaders keen to get the clean-up moving.

Wharerau questioned why, despite years of protest, the problem had been allowed to “plod on” without resolution.

Just last month, locals had to spend days removing dead birds from the lake and surrounding area.

“Enough talking … Ngāpuhi are not here to whinge and whine. We want to get on with the work and correct the wrongs of the past. Everyone needs to take a proportion of responsibility for why the lake is in this condition,” he said.

“This is a challenge to the Far North District Council, the Northland Regional Council and Ngāpuhi to do our job.”

The lake’s woes began when the forest that once surrounded it was felled starting in the mid-1800s, allowing sediment to wash into the lake.

Originally said to be an almost uniform five metres deep, now the lake had a depth of just 1.5m.

In more recent times, the problems had been exacerbated by dairy farm effluent and the toxic algal blooms that occurred regularly as the water warmed up in summer.

The result was a “toxic soup” that drained into the Utakura River and then into Hokianga Harbour.

The lake once teemed with eels — a staple food for local hapū — as well as kēwai [freshwater mussels], fowl and invertebrates.

A political system that encouraged councils and Government to focus on the next election rather than long-term benefits to the community was part of the problem, Wharerau said.

The release of thousands of koi carp in the early 2000s, in a bid to control water weed, was an example of “economic and political failure”.

Cleaning up the lake would benefit everyone, he said.

“When the mauri [life force] of the lake is healthy, the spiritual wellbeing and mauri of Ngāpuhi will be healthy. If Ngāpuhi are vibrant and productive, then our wider communities will be happier.”

Far North Kahika [Mayor] Moko Tepania said his council was willing to work with Ngāpuhi to address the problem.

“Me mihi ka tika ki tō tātou heamana o Ngā Puhi! [We must thank our Ngāpuhi chairman!] It is hugely heartening to finally see this shared concern about the state of Lake Ōmāpere brought to attention. Far North District Council will be a willing participant in working together for solutions to restore the mauri and the mana of our lake,” he said.

Northland Regional Council (NRC) councillor Joe Carr, who represents the Far North constituency, believed the state of Lake Ōmāpere was one of the most significant environmental matters in Northland.

“There’s a huge amount of goodwill among all the stakeholders to prevent another ecological collapse of Lake Ōmāpere. NRC has to work together with the Lake Ōmāpere Trust and the farmers, including the Ōmāpere Rangihamama Trust,” Carr said.

“My view is we need to meet with no preconceived constraints or ideas, pool our information and work out what we must do to restore this lake. The council is very aware of the extent of the algal bloom pollution during a period of collapse. It extends right down to at least the Narrows in the Hokianga Harbour.”

NRC natural resources monitoring manager Jason Donaghy said the council had been working with Lake Ōmāpere Trust since April 2022 to formalise their relationship through a Memorandum of Understanding.

Details of the agreement had not been finalised, but the health of the lake was the focus.

Cleaning up the lake was important given its spiritual significance, but also because it was required by Te Mana o Te Wai, part of the Government’s National Policy Statement for Freshwater Management 2020.

More than a decade ago, a restoration project was started to improve the health of Lake Ōmāpere, Donaghy said.

From 2003 to 2010, more than $630,000 was spent and 10,000 “in kind” hours were contributed by multiple agencies and iwi.

“Council needs to consider the funding to support an ongoing project of this scale,” he said.

The council monitored the outflow of Lake Ōmāpere for cyanobacteria toxins caused by algal blooms.

When high levels were detected, the Lake Ōmāpere Trust, Te Whatu Ora – Te Tai Tokerau (formerly Northland District Health Board) and the regional and district councils activated a response plan.

In 2018, a severe algal bloom turned much of the 1200-hectare lake and the Utakura River a bright blue-green. The river was capped with thick foam and littered with dead eels.

Testing did not find cyanotoxins at that time but did find high levels of cyanobacteria and very low levels of oxygen, which had likely killed the eels.

The algal blooms that affect Lake Ōmāpere are caused by cyanobacteria, which thrive in warm water with excessive nutrients, usually from pollution or farm run-off.

When conditions are suitable, cyanobacteria can grow at an extraordinary rate and produce toxins dangerous to humans and animals.