Ruamāhanga: The story of a river
Winding its way from the Tararua Range to Cook Strait, the Ruama¯hanga is one of New Zealand’s most beautiful rivers. Yet years of intensive farming and urban runoff have made it a place with a sometimes unenviable reputation. So how is it doing now? Jack
Mt Bruce
Long before it meanders its way through Wairarapa’s flat farmland and past the region’s five towns, the Ruama¯ hanga River begins in the mountains.
In the depths of the Tararua Range smaller streams trickle their way through the cold, green hills before coming together and emerging at Mt Bruce.
The river’s first public appearance, underneath State Highway 2, goes mostly unnoticed as cars and logging trucks rumble past overhead. Twenty-odd metres below it gently eases around a bend, flowing briskly but not powerfully, and flanked by an abundance of moss, ferns and birds.
Even from the bridge overhead it’s easy to make out a colourful array of stones on the riverbed. That it’s exceptionally clear is no real surprise, since it’s here that the river is at its most pure and unpolluted.
The Ruama¯ hanga is monitored regularly by Greater Wellington Regional Council along its 124km length, measuring nearly every aspect of its health: rainfall, nitrate levels, phosphorus, depth of clarity.
The first measuring point is north-east of the bridge, and the site’s exhaustive statistics confirm what is already clear to the naked eye. Here, with little to trouble it, it’s in the top 25 per cent of similar sites nationally for key markers such as water clarity, E coli rates, and nitrogen and phosphorus levels.
‘‘The Ruama¯ hanga generally has an excellent water quality in its headwaters,’’ senior environmental scientist Dr Mark Heath says.
‘‘That’s up around Mt Bruce, and the same is the case with the major tributaries that go into the Ruama¯ hanga out of the Tararuas. The Waingawa and the Waiohine have fairly good or excellent water quality.’’
That it begins so pristine is unsurprising, says freshwater ecologist and lecturer Dr Mike Joy. ‘‘It’s like all of our rivers,’’ he says. ‘‘It starts out really good, then gets worse as it goes downstream. When it comes out of the Tararuas it’s perfect, but by the time it gets to the bottom it’s not so good.’’
Masterton
The dampness that envelops Mt Bruce like a blanket, and never seems to leave, disappears after
just five minutes driving down State Highway 2. The forest canopy abruptly clears, and the terrain instead rolls out into flat, open farmland.
It’s here that the Ruama¯ hanga’s two biggest issues begin to emerge in the form of urban and rural pollution. ‘‘[The breakdown of polluters] is not something that we can absolutely pinpoint at the moment, but we know what the key pressures are,’’ Heath says.
‘‘They include urban discharges, current land use and intensive pastoral land use in particular. As the river moves through farmland, and passes through the towns of Masterton and Carterton, it picks up contaminants from the surrounding land. You have urban and rural runoff . . . so as we progress down the Ruama¯ hanga, the water quality progressively decreases.’’
The first town the Ruama¯ hanga flows past is Masterton, Wairarapa’s biggest town. It’s here that it encounters the first of the sewage treatment plants, which have been a major cause of the river’s woes in the past. It’s not hard to see where the river’s unkind nickname, the ‘‘Sewermahanga’’, comes from.
But according to Masterton District Council things are changing. About four years ago, the Homebush wastewater treatment plant upgrade was commissioned with the intention of drastically reducing sewage flow into the river.
Council assets and operations manager David Hopman points to the effect it’s had at the Cliffs, a popular summer swimming spot south of Masterton. According to current data, it’s low risk, with only a 0.1-1 per cent risk of illness.
‘‘[The Cliffs] was actually a caution site in 2014, the first year of the new plant,’’ Hopman says. ‘‘Since we’ve commissioned the plant – and we can’t take full credit for it because there’s been lots of other things going on as well – but since 2014 [water safety has] gone from critical right down to low risk. We actually have done a pretty good job there over the past three years.’’
Hopman says water quality is something the council has taken seriously. It recently adopted a
new wastewater strategy focused on increasing wastewater disposal to land, removing even more from the river.
‘‘This is all sort of a new development,’’ he says. ‘‘The first step we’ve proposed involves us actually setting up a demonstration farm at Homebush where treated wastewater will be used. It’ll be . . . basically used like a farmer would, for growing different types of crops and different types of produce, as a way of demonstrating that treated wastewater can be used effectively for making money.’’
A bit further down from the Cliffs is the Gladstone Bridge monitoring station. Just outside Masterton, Gladstone is a farming community with no shops, a charming country pub, a highdecile school and a wheelwright’s shop.
Though the river flowing under the bridge is picturesque, the data captured there is less so. There’s an obvious decrease in water quality at the Gladstone Bridge monitoring station; while it’s not necessarily bad overall – as Heath points out, water quality has gone from an excellent state down to good – it’s still declining.
Nitrogen and phosphorous levels are in the worst 50 per cent of like sites nationally, if trending in the right direction. E coli levels are generally fine.
How much of this is because of farming is hard to pinpoint and, like the impact of farming on New Zealand’s waterways in general, it’s a contentious topic. While few deny farming has an impact on rivers, how bad that impact is and what the farming community is doing to ease its environmental footprint is subject to passionate debate.
Jamie Falloon, the provincial president of Federated Farmers’ Wairarapa branch, bristles when asked about farming’s role in polluting the Ruama¯ hanga.
He says singling out farmers is unfair, citing measures the community has taken, including heavy fencing of paddocks near rivers, floodbanks, and the current practice of discharging water to land instead of into rivers.
‘‘The myth of dairy cows as major polluters is not backed by the data,’’ he says. ‘‘In the past 28 years or so, we’ve seen water quality remaining stable, even with intensification, so it’s very disappointing to hear farmers being blamed for water quality issues.’’
Fencing off farms to prevent stock wandering into rivers is crucial, since animals can wreak environmental havoc if allowed to freely wander along riverbeds. Falloon says 97 per cent of waterways are now fenced, although Mike Joy says farmers could be doing more.
‘‘What [Federated Farmers] actually never tell you is the 97 per cent they classify as rivers are all the larger rivers,’’ Joy says.
‘‘What we know is that 75 per cent of the nutrients and the problems in our rivers come from the smaller streams that don’t meet [Federated Farmers] criteria and therefore don’t require to be fenced off.’’
Lake Wairarapa
Lake Wairarapa isn’t quite dead, but it’s not far off. Wairarapa’s largest lake is classed as supertrophic, the last stage before becoming extinct.
It wasn’t always this way. Until the 1960s, the Ruama¯ hanga flowed into Lake Wairarapa, but the Lower Valley Development Scheme, designed to protect surrounding farmlands from flooding, cut it off. For the lake, the results have been disastrous.
The point where the river steers away from the lake is called, for obvious reasons, the diversion. It’s easy to spot on a map, as the river’s curving, twisting route is suddenly straightened and forced through man-made stopbanks. Driving beside the river there’s little to see, the river’s protective banks shielding it from view.
It’s an odd area, isolated and eerie. The Geoffrey Blundell Barrage Gates, which control the the flow of the water from the lake into the Ruama¯ hanga, appear almost out of nowhere. Some barriers around the little building are rusted, and water at the foot of the gates is an ugly, murky yellow-green.
The point where the Ruama¯ hanga used to meet the lake was a sacred spot for Ma¯ ori. In his role as an environmental manager for Ngati Kahungunu, Ra Smith knows more about the river than most. He’s aware of not just its current health status, but also the role it has played for local Ma¯ ori, spiritually and physically.
‘‘We think of rivers as a character, and the character of the river holds the mauri, often called the life force,’’ he says.
‘‘On the opposite side from where the two rivers meet is the whare ko¯ hanga, a place like a maternity ward. When babies were born they would take the whenua [placenta] and be buried in the ground, and they would take the baby down into the river and make up a lullaby. It was no rockabye baby, it was eight verses of very intense lullaby about the blessing of the baby and its life expectancy.’’
Smith says the most important confluence was where the Ruama¯ hanga met Lake Wairarapa, a point that no longer exists.
Plans may be afoot for a revival, however. The idea of redirecting the Ruama¯ hanga back into Lake Wairarapa has been floated at a regional council meeting, and a feasibility study is being undertaken to see if such a rejoining would be possible and useful.
This part of Wairarapa hasn’t been kind to the Ruama¯ hanga either. Although Featherston’s wastewater plant empties out just upstream of Lake Wairarapa, the wastewater plants of Martinborough, Greytown, Carterton and Masterton have all poured into it by the time it has flowed past Martinborough. It’s also encountered runoff from towns and a large number of farms.
The council monitors the river at Pukio, just south of Martinborough. Unsurprisingly, by this point its clarity has dropped significantly. It is in the worst 25 per cent of similar sites throughout the country with a visibility of just 1.1 metres (although, of course, this varies: it’s much better in February and March, and much worse in May and June). Turbidity, an index of cloudiness of water, is in the worst 50 per cent of like sites, and the same goes for nitrogen and phosphorous.
There were once plenty of natural resources to soak up nitrates and phosphorous, but changes in the river’s character have sapped its ability to fight back.
‘‘Right now we’re facing the challenge of nitrates in water,’’ Ra Smith says. ‘‘Something that was in the rivers and around rivers were wetlands, which would take out nitrates, and it seems like they do an OK job taking out phosphorous as well.
‘‘Both those two and sediments were all able to be taken care of by wetlands. But while our waterways once had a lot of wetland, now we have only 3 per cent left.
‘‘I understand the reason [for clearing them] about flooding and all those different things, but I wonder if there was a better way of working together and . . . finding a way to collaborate a little better. Our rivers are managed currently for flood protection, whereas I think there’s a wider management that should be operating.’’
The sea
The point where Lake Onoke opens out into Cook Strait is typical of Wairarapa’s southern coastline: long, isolated beaches, with winds whipping in from the sea and large, white clouds hovering overhead.
It’s a rugged area that feels like the end of the Earth, but it’s actually not quite as remote as it seems: the journey from the Ruama¯ hanga’s first public appearance at SH2 to where it flows into the ocean, via Lake Onoke, takes less than 90 minutes to drive.
Like Lake Wairarapa, Lake Onoke also suffers from poor water quality. According to some sources, the reason it’s in a bad state is because of polluted water fed into it by the Ruama¯ hanga.
There aren’t any regional council measuring posts as the river flows into Lake Onoke, with the last outpost further up past Martinborough. Given the trip it’s taken, the state of Lake Onoke, and measurements taken on lower points of the river, it’s clearly not in perfect health.
Is the river getting healthier? It depends on who you ask and how it’s measured. According to Mark Heath, over the past five years the river, the 29th longest in New Zealand, has basically stayed the same in terms of quality.
‘‘Our five to 10-year trends are showing that there has been no discernable change in water quality,’’ he says. ‘‘However, trends don’t necessarily reflect the state of water quality. So even though there is no trend . . . it still could be in a poor state and needing improvement.’’
Still, he says, efforts to help have been making a difference. ‘‘What I can say is that there’s been an absolute tidal wave of farming communities and urban communities within the Ruama¯ hanga who are actively trying to get out and monitor the river, to get out and do more to look after it.
‘‘A big part of that has been Federated Farmers, which has come up with a design for Wairarapa catchment communities – the actual subcatchments in the Ruama¯ hanga.’’
For Ra Smith, the river’s future is uncertain. Along with the current crop of issues it faces, there are others – most notably climate change – that pose hazards into the future.
‘‘In terms of conservation, I’m quite worried about the natural character of the river.
‘‘I would characterise the river as kind of an expressway for water, which is about how to get water away from places as quickly as possible . . . you can see the reasons why in terms of erosion and things like that, but there might be other solutions.
‘‘The future could be exciting, but there are challenges. The big challenge will be climate change. We will get water at a different rate, and while we get the same amount of water we’ll be getting it faster, so that a storm event that will bring water and if we’re in the same process of getting it out as soon as possible flooding would almost certainly occur.’’
Like Heath, Smith says the work done by various organisations is encouraging. Working with both the Masterton District Council and the Ruama¯ hanga Whaitua Committee, he sees people trying to help. ‘‘We are definitely looking at directions we might take in concrete ways,’’ he says. ‘‘It’s a good start for, perhaps, a better future for our water.’’