Punahau pilgrimage

I visit one of New Zealand’s most polluted lakes (10 minute read)

I’m alone in the park, and it’s an unsettling feeling. I take in the closed-up clubrooms of a boating club, the overflowing rubbish bins, and the metal skeleton which is the roof of a derelict building. There’s an empty playground edged by a concrete block wall, on which is painted a giant, white swastika. Someone has dumped a heap of black plastic rubbish bags, a half dozen at least, just below.

A light rain falls. I pick my way past puddles, plastic food wrappers and broken glass until I can see what I’ve come to see – the waters of Punahau, or Lake Horowhenua. As far as I can tell, this park is the only place where there is public access to the lake, so I'm here on a cold afternoon in July, with only the birds for company.

This shallow lake, on the outskirts of Levin¹, has the unhappy distinction of being one of the most polluted in the country. During the summer, nutrient pollution in the lake – an excess of nitrate and phosphate – caused a bloom of toxic algae. The bloom of toxic algae sucked all the oxygen from the water. The lack of oxygen killed eels and other fish. The combination of low oxygen and decaying fish encouraged the growth of botulism bacteria, which killed many birds. The local iwi, Muaūpoko, who have been battling to restore the lake, placed a rahui² on it – the environment was just too toxic for people to be using the lake. The same thing happened last year, too, and it will probably happen again. The only reason it isn’t happening now is that it’s mid-winter, and cooler temperatures reduce growth of the algae.

I read about the state of Punahau back in February, and it was one of the reasons I contacted Susie Wood, from the Cawthron Institute, to discuss her research on cyanobacteria. After that interview, I realised that New Zealand’s waterways were in a far worse condition than I’d previously thought. The more I read, the worse things looked. But Punahau still stood out. It was in a dire state, thanks to Levin’s sewage and runoff from farms, market gardens and industry. Something about its story lodged in my head. I kept coming back to it in my mind. Eventually, on a day when I’d managed to get a little ahead on my weekend’s work, I decided to drive north and see it.

As I stand on the shore of the lake, I hear an engine and turn to see a silver car drive into the park. It pulls off the road and onto a side track by the derelict building, coming to a stop behind some trees. Nobody gets out. I keep an eye on it for a while, wondering who else has decided to come to this desolate park on a miserable winter day. But I have no interest in finding out.

Punahau hasn’t always been like this. It was once surrounded by wetland and forest with huge kahikatea and pukatea trees. The streams flowing in were clear. The lake was an important source of food for Muaūpoko, providing eels, kōura (freshwater crayfish), flounder, kākahi (freshwater mussel) and watercress. But it was, and still is, so much more - it is described as “the heart of Muaūpoko”.

By 1924, though, Punahau was in trouble. Hundreds of eels died off – a wool scourer using toxic chemicals on the lakeshore was blamed. In subsequent decades there were further eel deaths, as the lake became more and more polluted. Levin’s treated, and sometimes raw, sewage was piped into the lake, over the objections of Muaūpoko. Toxic algal blooms, a consequence of nutrient pollution, began.

As I learned about Punahau’s history, I realised that it isn’t just a lake, not to Muaūpoko. It is their lake, both a source of physical sustenance and a place resonating with centuries of history. The loss of Punahau isn’t about a change in ownership and the actions of the colonial government in the 19th century. It is a far more recent loss, still continuing today as the lake’s condition becomes worse and worse.

Although sewage no longer flows into Punahau, the pollution has not stopped. On my way to the park, I saw a stream running beside the road, so I stopped to take a look. It was wide, a couple of metres across in places, and it looked deep, although that was just a guess, because the water was opaque. It wasn’t the typical yellow-brown which comes from clay sediment, but an ominous shade of dark brownish-grey. The stream flowed steadily out of a pipe, well over a metre across, through a grille and across some paddocks towards the lake.

Image credit: Melanie Newfield

I couldn’t tell exactly what was in it just by looking at it, but there was a clue growing on the stream’s banks. There, I saw a plant named water celery, an introduced species which is common on the banks of drains and streams. There’s nothing unusual about water celery in itself, but I’ve never seen it grow so big or such a dark shade of green. The remarkably lush water celery tells me that this water is high in nutrients such as nitrate and phosphate.

Apart from water celery, there’s nothing on the banks of this stream but grass. At first I don’t notice, but then it occurs to me that it’s simply flowing through a paddock, unfenced, offering access to any livestock which might be grazing there. I suppose with such a polluted stream, a few cows may not make much difference, but it feels like the final insult to a much-abused waterway.

From the shore of the lake, though, there’s little sign of its dire condition. The water isn’t exactly clear, but it’s better than the water flowing into it – clear enough that I can see a few drink cans in the shallows. I sniff, but there’s no smell. There are no dead birds or fish on the shore. In fact, I can see dozens of birds, apparently thriving. There are noisy red-billed gulls, squabbling over the rubbish from the overflowing bins. There’s a big flock of geese and a few black swans³. There are little shags, diving for food then reappearing.

Punahau with swans and cans (image credit: Melanie Newfield)

But it’s the swallows with their distinctive forked tails which catch my attention. There must be at least twenty of them, wheeling and dipping at the lake’s surface. I can’t remember seeing so many at once before and I stand watching, enjoying their energy.

Still, my ecologist’s eye knows that what I’m seeing is a shadow of what should be here. The gulls, swans, swallows and shags are all, technically, native species, but both the swans and the swallows are recent self-introductions from Australia and the gulls are a ubiquitous sight around coastal areas. I’m seeing the toughest of the tough, the strongest survivors.

There’s another clue in the water as well – no sign of aquatic plants. Healthy lakes have a rich growth of aquatic plants, which provide habitat for fish, clarify the water and stabilise the lake bed. In polluted water, murky with sediment and algae encouraged by excessive nutrients, there is not enough light for the plants, and they die. From this point, the lake is difficult to restore. It’s not simply a matter of replanting – the murky water means that the large plants struggle to survive.

I hear another engine, and a ute pulls up next to my car. As I stand watching, a man gets out, and then a boy. I relax a little. Seeing a family makes the place seem less bleak. I’m surprised, though, when they begin unloading fishing lines. What are they fishing for here? No doubt, the hardiest survivors again.

I head back to my car. I’ve seen what I came to see at Punahau, but I don’t go home just yet. The outflow of the lake is the Hōkio Stream. It runs out to the coast at Hōkio Beach, only a few kilometres away. I decide that I want to see it.

I’ve soon reached real rural New Zealand. There are none of the mansions characterising luxury lifestyle blocks in many areas close to Wellington. I see a few dairy farms, a couple of marae and the odd block of pines. On a hill, there’s a Hacienda-style house of the kind popular in the 1970s, painted in mint green. Everything looks a little run-down and damp.

The Hōkio Stream wanders along on its path to the sea. Sometimes it’s visible from the road, sometimes not. When I pass Levin’s landfill, the stream is close by. I don’t want to imagine what the landfill is leaching into Hōkio’s already polluted water.

Eventually, I pass a sign for Hokio Beach. There’s an old-school Kiwi bach⁴ settlement here, with asbestos-clad cottages and a couple of classic 1970s A-frames. Some of them look permanently occupied, others appear closed up and probably don’t see many visitors in the winter. I can see sand dunes, but no sign of the beach itself.

The stream passes along one side of the settlement and under a bridge. I park my car and get out to look. Standing on the bridge, I can see that some of the baches on the edge of the stream have their own bridges, taking them straight into the dunes without having to go on the road. I can’t say I’d like to have that particular stream running through my backyard.

The colour of the water is the same unpleasant grey-brown of the stream which flowed into the lake, and just as murky. There’s water celery growing on the edges, sprawling out into the flow of the stream. The only difference I can see is that this water celery is even larger than the plants I saw earlier. If it grows any larger, the plants on either side will meet in the middle and you won’t even be able to tell there’s a stream under it.

The road hasn’t ended yet, so I get back in my car and follow it through the dunes. Tall pampas grass grows either side and the road is rutted and pitted. I’m not entirely sure it was a good idea to drive down here, but there’s nowhere to turn, so I keep going. And then the view opens out.

In the late afternoon light, the lagoon of a polluted stream is transformed. It widens and winds back and forth across the sand, reflecting a golden light which makes me forget why I came here. I’ve stopped thinking about the tragedy of this lake and the loss it has been to the people, and the plants and animals, who once depended on it. I’m not wondering what is in the water which flows by, swift and silent.

Lagoon at the mouth of Hōkio stream (image credit: Melanie Newfield)

It’s windswept and desolate here, but it’s beautiful. Even back at my desk writing these words, I can feel chills running down my back. I look around me, at the piles of driftwood, the damp sand, the dunes covered with invasive pampas grass and gorse, as well as a few hardy natives like ngaio. In the distance, I can hear the rumble of west-coast waves on the shore.

I take a few photographs and watch the way the light changes as I change my angle of view. I want to remember this. I stand and I look around me, the smell of the sea and fresh air in my lungs. My hair blows around my face.

Finally, though, my thoughts come back to the stream. All of that toxicity passing beside me is bound for the ocean. What damage is it doing there? The ocean is so vast, but it doesn’t absorb all our waste without harm. The thought lodges in my brain, but it’s only there in the background.

I look around me at dunes which have been burned and are covered with gorse and pampas grass, water which is toxic, a coastline itself under threat from sea level rise, but what I observe is the resilience of nature. Flax and ngaio survive on the dunes, gulls ride the wind and swallows flit above the waters of Punahau. They may simply be the toughest survivors, but it’s good to know that we haven’t obliterated everything.

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1. For unfamiliar with the region, Levin is a town of just under 20,000 people, an hour north of Wellington.

2. For those outside New Zealand, iwi is the Māori tribal group and a rahui is a restriction on access

3. For those outside Australia and New Zealand – most of our swans here are black. They’re quite lovely birds. I didn’t get close enough with my camera so if you want to see what they look like here’s a link to a page about them.

4. For those outside New Zealand, a bach is a holiday home, traditionally a modest dwelling although as coastal property prices rise they are getting fancier and fancier.