The death of Lake Horowhenua has been on the radar for decades.

It divides a community, figuratively and literally, as it creates a watery border between a town and countryside.

From a distance it resembles a picture perfect postcard, but up close the reality is very different.

Two hours north of Wellington, surrounded by rich alluvial plains and next to Levin, Lake Horowhenua is one of New Zealand's most polluted lakes.

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Its catchment is tiny and so are the streams and drains flowing into it. Despite being small, they include the country's second and fourth most polluted waterways, Arawhata Stream and Patiki Stream.

The poor quality stems from a combination of problems, including 25 years of sewage discharge from Levin, which ended in 1987.

A warning sign urges visitors to prevent further invasive weeds being introduced into Lake Horowhenua. Photo / Alexander Robertson
A warning sign urges visitors to prevent further invasive weeds being introduced into Lake Horowhenua. Photo / Alexander Robertson

Increasing nutrient and sediment loads come from surrounding farms and market gardens.

The clearance of coastal forest, draining of swamps, intensification of surrounding land use and urban expansion have also contributed.

The lake used to teem with fish and other seafood, which fed local iwi Muaūpoko who lived in the coastal forest that surrounded the water in pre-European times.

Weeds cover the lake in spring, before rotting and causing toxic algae bloom each summer.

Sediment swirls around the banks of Lake Horowhenua. Credit / Alexander Robertson
Sediment swirls around the banks of Lake Horowhenua. Credit / Alexander Robertson

Swimming is discouraged year-round, and in summer, boating and kayaking are discouraged. Niwa freshwater scientist Max Gibbs shocked the district council in 2012 when he said the water was toxic enough to be lethal if swallowed by a small child.

A report card earlier this year put the lake at a 6.7, on a measure of 1-7 (seven being the worst). It looked at water clarity, chlorophyll content, phosphorus and nitrogen content.

But despite funding from local and national government, the clean-up is a long process slowed by lengthy court battles, objections from locals, fights over the lake's ownership and a few bureaucratic messes.

Resident Christine Moriarty is fighting to restore the health of the lake. She is frustrated at what she believes is a lack of action - or not the right action - from Horizons Regional Council, whose job it is to do something about it.

Horowhenua resident Christine Moriarity says a sediment trap system is taking focus away from the source of the lake contamination. Photo / Alexander Robertson
Horowhenua resident Christine Moriarity says a sediment trap system is taking focus away from the source of the lake contamination. Photo / Alexander Robertson

The council manages a vast swathe of the greater Manawatū-Whanganui region, including the land, air and waterways.

"The buck stops with the regional council," says Moriarty. "The regional council is not only not listening, but they have taken sides against us who are trying to get them to do the right thing. And now we are the bad guys.

"I'm always an optimistic person and I believe it's going to come right but it's going to take intervention by the Government to make some decisions about what farming practices happen in the country. We either fix it or we change the name to Lake Horror-whenua. It's a horror ride for the lake owners. Any other European land owner would be up in arms."

She highlighted some of the major causes of pollution, including stormwater runoff from nearby subdivisions and a drain within Levin's industrial area.

Opinions differ on the cause and solutions for pollution in Lake Horowhenua.

Horizons have made improvements around the lake, such as a $230,000 sediment trap, but Moriarty says it failed to address the source of contaminants.

"The sediment trap that the council has put at the south end of the lake is basically an ambulance at the bottom of the cliff.

"A stream starts as a spring and, in less than 2km, it becomes the second filthiest in the country. That should make it the easiest to clean," says Moriarty.

"Most streams are miles and miles long and you don't know where [the pollution] is coming in.

The Horizons Regional Council sediment trap was installed at a cost of $230,000. Photo / Alexander Robertson
The Horizons Regional Council sediment trap was installed at a cost of $230,000. Photo / Alexander Robertson

"It is just common sense that if you are going to clean the water, you clean it before it comes into the waterways."

The lake is owned by the descendants of a small group of the Muaūpoko tribe, who set up the Lake Horowhenua Trust in 2013 to administer it.

It joined four parties in 2013 to form the Lake Horowhenua Accord which includes the Lake Horowhenua Domain Board, Horowhenua District Council, Horizons Regional Council, and the Department of Conservation.

Government has given the accord partners $2.36 million and the lake accord partners have contributed $1.7m. The money has gone towards sediment traps, a weed harvester, thousands of trees and kilometres of stream-lake fencing. An estimated $7m will be spent in the first decade of the accord programmes.

But the lake owners are divided and its trust recently reached an impasse with legal challenges and disagreement over who governed it.

Former Lake Horowhenua Trust spokesman Matthew Sword says the Muaūpoko iwi feel it has taken too long to tackle the pollution in the waterway. Photo / Alexander Robertson
Former Lake Horowhenua Trust spokesman Matthew Sword says the Muaūpoko iwi feel it has taken too long to tackle the pollution in the waterway. Photo / Alexander Robertson

"There are always going to be people who, no matter what you do, are not satisfied and you can kind of understand that," says Matthew Sword, former trust spokesman.

"But at the end of the day, we have a mission here and we are supported by our people to push forward on that mission and not really make any excuses for why we might hold back on undertaking those really important interventions."

While the lake owners wait for that legal process, the lake has been the subject of other extensive legal action over the years around the best course of action to improve it.

Horizons was granted consents to use a sediment trap, fish pass and weed harvester in 2015. Appeals by a group of trusts to the Environment and High Courts failed.

Lake Horowhenua, with the Levin township at top right. Photo / Alexander Robertson
Lake Horowhenua, with the Levin township at top right. Photo / Alexander Robertson

In a separate case in 2016, the Environment Court made declarations on the way that Horizons needed to consider applications for intensive land use consents.

The result was that market growers could not apply for land use consents unless they met nitrogen leaching numbers in the council's One Plan.

But a the council's strategy and regulation group manager, Dr Nic Peet, says it is "largely impossible" for growers to meet the nitrogen leaching numbers and continue to run viable horticulture operations.

Some market growers are now operating without land use consents.

The council has begun a two-stage process of plan change. The first is under way and the second will go through a public process next year.

"In the meantime, Horizons continues to work with growers to improve environmental practice," Peet says. "Not having the consents is not a barrier to ongoing improvement."

Logan Brown is the freshwater and partnerships manager for the council and the man responsible for the sediment trap.

Freshwater manager for Horizons Regional Council Logan Brown says weed harvesting could make a noticeable difference to the pollution in Lake Horowhenua. Photo / Alexander Robertson
Freshwater manager for Horizons Regional Council Logan Brown says weed harvesting could make a noticeable difference to the pollution in Lake Horowhenua. Photo / Alexander Robertson

"There is a whole lot of work being done up-stream with farmers to reduce the amount of sediment loss that comes from land," he says.

"This [sediment trap] can be considered as a kind of end polishing type of thing."

The regional council wanted to use a weed harvester and use the weed, rich in nitrates and phosphates absorbed from the run-off into the lake, at nearby farms. But the harvester was stopped in its tracks by locals who objected.

"It is one we have been trying to get in place for the last two to three years and have had legal challenges," Brown says.

"When the weed harvesting is in place, it breaks a cycle that occurs within the lake. If we can do that weed harvesting, that toxic weed algae won't be there."

Tree-planting is another tool, but Brown knows the long-term solution is to stop pollution getting into the lake in the first place.

Ultimately, people could do more, he says, but it comes down to costs, budgets and regulations.

In the meantime, he urges critics to be patient and get involved.

Farmers at a crossroads. Consents for farm operations around Lake Horowhenua have been ruled unlawful by the Environment Court. Photo / Alexander Robertson
Farmers at a crossroads. Consents for farm operations around Lake Horowhenua have been ruled unlawful by the Environment Court. Photo / Alexander Robertson

"It is quite easy to be critical and not be involved in the processes," says Brown. "We have held, and still hold, numerous community planting days for people to get involved.

"Those people who are quite critical of us, I'm yet to see one of them at those planting days."

While Horizons sorts out the bureaucratic mess, many farmers in the sensitive catchment zone are in limbo. They need assurances there is a long-term future in the region before investing in more anti-pollution schemes.

With no end to the delays and complications, some residents led by Moriarty lost patience with Horizons and wrote a letter to Environment Minister David Parker.

"The letter is asking for the Minister to remove the chief executive of the regional council and put in a commissioner," Moriarty says.

Many residents blame the market garden industry, which brings in more than $100m to the region and has been a primary source of employment for a century.

Woodhaven Gardens is the biggest market gardener in Horowhenua, employing up to 250 people. The business has already made changes including retiring land, establishing buffer zones and adding sediment traps throughout the farm.

Woodhaven Gardens co-owner Jay Clarke recognises a need for improvement in the agriculture sector. Photo / Alexander Robertson
Woodhaven Gardens co-owner Jay Clarke recognises a need for improvement in the agriculture sector. Photo / Alexander Robertson

"Is it in a place we'd like it to be? No." says Jay Clarke, one of the owners. "Do we see a need for improvement? Yes."

But Clarke points to the sensitive geography of the lake catchment.

"You have a lot of land area draining into waterways that don't have a high level of flow. And therefore the concentrations of pollution can go up quite high.

"That's very important for people to understand," Clarke says.

"We acknowledge we have an environmental impact and we contribute to the poor quality that we see in the Arawhata Stream."

Dr Mike Joy is an outspoken critic of intensive farming and its effect on waterways.

"It is just vandalism," he says.

Freshwater scientist Dr Mike Joy suspects industrial-scale farming around Lake Horowhenua has much to answer for. Photo / Alexander Robertson
Freshwater scientist Dr Mike Joy suspects industrial-scale farming around Lake Horowhenua has much to answer for. Photo / Alexander Robertson

"There's just hundreds of hectares of intensive horticulture, monocultures, worked up paddocks just constantly being ploughed up and turned over, heaps and heaps of nutrients and pesticides, very industrial-scale farming happening around here.

"The effects of that is, when there's a big rainfall event, all the sediment washes off into the drains. The sediment's rich in phosphorous.

"You've got nitrogen being put on to the land - it's flowing down through here. Plus those pesticides and things. The whole lot making its way into this lake." In the case of Lake Horowhenua, Joy also points to stormwater from nearby Levin.

"If any district or city council thinks it's acceptable to have stormwater run straight off into a body of water, then they are totally failing in their role," he said.

But he didn't simply blame the politicians.

"If they start fixing these things up and treating them properly, then there's a lot of money involved and then it's going to be rates increases and they'll get voted out.

"The system we have, once again, encourages ... living for now and leaving the problem for future generations."

Horizons Regional Council infrastructure manager Andrew Grant. Photo / Alexander Robertson
Horizons Regional Council infrastructure manager Andrew Grant. Photo / Alexander Robertson

The stormwater runoff in question is under the control of Horowhenua District Council, where new infrastructure manager Andrew Grant has been in the job for just two weeks.

"There is a problem and the council has acknowledged it," Grant says.

"We have allocated a large amount of money and the council has taken it on board."

Christine Moriarity wrote to Environment Minister David Parker, seeking government intervention over the pollution in Lake Horowhenua. Photo / Alexander Robertson
Christine Moriarity wrote to Environment Minister David Parker, seeking government intervention over the pollution in Lake Horowhenua. Photo / Alexander Robertson

Environment Minister David Parker says it is not a Government issue but he would make an exception in this instance.

"There's been a bit of a stalemate," Parker says.

"I asked the council and some of the critics of the council to meet in my office recently, to try and broker a way forward so that we resolve the underlying issues."

He has also appointed a planner and a lawyer to assist Horizons.

"It is their duty to do their job. Not all of these decisions can be taken at central government level, these are devolved councils and it is their responsibility to put things right."

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