Silting from council bulldozing operations in the riverbed. Ruamahunga.
Ruamahunga, aka Sewermahunga. Gobs of fat and bagged rubbish floating past only adds to the river’s woes.
The Makakahi, north (downstream) from Eketahuna. A combination of very low flow, town discharges, agriculture and warming is turbid water. Surprisingly, in the riffles there are still small fish and other aquatic life.
Large dirty rivers are made up from many small sparkling streams. The sources of the Manawatu in the Ruahine Ranges are also home to small isolated populations of native galaxids (fish).
Another in our series about New Zealand … and its parallels to Tasmania, whether industrial farming or 1080 …
It is easy from just a simple travel map to tell where “dirty dairy” is ( TT HERE ); easier still from Google Earth. Any river with few or any towns and a vast hinterland of dairy farms will be a candidate. All the major Canterbury rivers, such as the Rakaia or the Ashley, fit the bill. But not all our waterways problems can be laid solely at the door of dirty dairy. Looking at three other river systems where other factors are at play …
The Manawatu is an interesting comparison. Not only is it often cited as one of New Zealand’s dirtiest rivers, research by the Cawthron Institute in Nelson showed it to be one of the dirtiest in the western world. In an item from the Dominion Post of 26/11/2009, it cites Dr Young of Cawthron claiming that a system measuring oxygen changes in water (un-defined) show the Manawatu has a reading of 107, nearly twice that of the next worse, a river near Berlin just below a sewage outfall, where the reading was 59. Dr Young cited leaching farm nutrient and treated town sewerage, with agricultural use, i.e. nitrogen run off, being most of it.
Looking to maps Google Earth, it is obvious that there is a lot of human settlement, hill country farming, some forestry and, in the valleys, long strips of pastoral farming (including dairy). There is just not the weight of dairy to support Dr Young’s claims. As well, there are many significant towns, and they cannot be ignored, this is where the authors of this review exhibit a bias. It starts with the description of the sewerage discharges; they are described as treated. In fact, the city of Palmerston North is operating a non-complying system on a temporary consent till 2020; it is the biggest urban discharge consent and for up to 46,600 cubic metres per day of only partially treated sewerage. Horowhenua District Council has also admitted dumping 5.1 million litres of “partially” treated sewerage into the Manawatu which they also admitted contained tampons, condoms and toilet paper!
Untreated storm-water is not even mentioned. It is all the rubbish from the roads and gutters, fuel spills, dead animals, garden rubbish in the drains, sometimes even raw sewerage from old combined connections. There will also be leachates from landfill rubbish sites – it’s everything.
In all, from the towns, Eketahuna, Pahiatua, Woodville, Dannevirke, Ashurst, Fielding, Shannon, Palmerston North and so on have a combined sewerage discharge consent of 75,600 cubic metres per day. To that, we can add industrial discharges from milk processor Fonterra, New Zealand Pharmaceuticals and Tui Breweries.
By claiming “sediment washing into the river from overgrazed farms or eroding countryside”, the authors ignore some of the bigger generators of silt. Forestry is certainly a major contributor, both in clearing the land for planting and at time of harvest. Another is cross blading and bulldozer work in the river bed. I’m not actually championing dairy farmers, but I think it is reasonable to say that there is a lot more involved in the Manawatu than agricultural runoff – aka “dirty dairy”.
The Cawthron report was presented to a panel holding hearings on Horizons Regional Council’s “One Plan”, a plan that sought to govern the amount of nitrogen in farm soils. From such a prestigious science institute, it would have an obvious impact on a panel of lay people.
Three years later in 2012, The Parliamentary Commissioner for the Environment (PCE) issued “The Water Quality in New Zealand Report”. This overturned the previous Cawthron findings, that the river was the most polluted of the Western World. The Manawatu Standard of 21/3/12 reported that the PCE found earlier report to be wrong. Dr Young of the Cawthron Institute said his earlier findings were taken out of context, he added only a tiny fraction of the worlds rivers had been tested using the method employed in a two year study that gave one unusually high result.
This report was welcomed by “stakeholders” (farmers?) who felt it was time to stop pointing the finger at them. Dr Young’s earlier assertion that it was “agricultural runoff, mainly nitrogen was the most of it” could no longer be relied upon as the culprit.
The Councils former regulatory manager was quoted as claiming there was no one single cause, but a combination of all users.
Unlike the first report, this report attributed the murky colour of the Manawatu and the high levels of phosphorous to the large amounts of sediment, which in turn came from eroding hill country further up the catchment. To an extent, that can be verified by Google earth, but it still ignores other issues such as land cleared for forestry, forestry itself and councils own bulldozer contractors in the river bed. Horizons Council chief executive Michael McCartney claims the councils “sustainable” land use programme has been in operation for several years. He claims we will start seeing a marked improvement thanks to hill country retirement and planting as reducing sediment which was one of the Manawatu River Accords action points. On checking the web site of the accord, (http://www.manawaturiver.co.nz/whats-happening/whats-happening) I find just about everything else that is being addressed including a formal launch on 11/3/16. It must be there somewhere? Words are cheap.
The Manawatu is a river in two parts separated by the gorge. Above the gorge it splits into the northern and southern tributaries. There is still a significant urban burden from Eketahuna in the south to Dannevirke in the north and there has been a significant recent increase in agricultural activity including dairy. It is obvious to an observer that there has been a decline in water quality and the fishery in the last 20 years, but it is localised. The upper reaches of the Mangahao and Mangatainoka just below the forest park, look good, Fish populations have never been great in these upper waters due to less food about. The Mangatainoka descends into a broad valley of farmland where there was, 20 to 30 years ago, a great trout fishery that maintained tourism. The water is still clean, but the margins are now usually fenced and overgrown, access is difficult and there has been a dramatic decline in fish and other fauna. Last year, a friend and a very experienced angler walked the river from by Hamua to Nireaha over a couple of days. Due to the overgrown banks, he was forced to wade, sometimes up to his chest. He was surprised by the lack of fish, on one day, seeing none at all and as the water appeared reasonably clean, he could offer no logical explanation. He also commented on the lack of ducks, but that could be due to the lack of nesting sites amongst the blackberry and convolvulus that line the fenced off banks!
The eastern tributary of the Mangatainoka, the Makakahi looks good where it meets the main highway at the Anzac bridge, but north of Eketahuna, the water is discoloured – there are several possible causes – picking up silt where meanders bite into papa clay cliffs, Eketahuna town discharges and the areas of intensive dairy south of Ekatahuna. River flow is lower now than in the past, which suggests water extraction. Despite that, there is still a fishery, but nothing like 15 years ago.
Many years ago, probably the most famous of the Manawatu tributaries was the Makuri. Tisdall’s even named their top of the line fly rod after it. Where 20 or thirty years ago, there were tracks worn in the banks by overseas visitors and their guides as they fished the hallowed water; now the only tracks are made by the odd cattle beast. What made this river great was the limestone country it sprung from; its waters could support a rich insect fauna that supported both native fish and introduced trout. It is a river in sections, the first, the upper reaches through farmland, for the most part accessible, it then drops into a steep, turbulent and almost inaccessible gorge, the river there can be seen from the Pori road bridge. Below the gorge, the river is more settled, but in a narrow deeply cut bed. Access is difficult and wading conditions down in the bed are treacherous.
As the river is in two parts separated by a gorge, so to the water conditions vary. In terms of clarity, on the whole it is good, but above the gorge, there is, like the Mangatainoka by Nireaha, little life. Below the gorge it is better, but nothing like its former self. On this I have a theory. A possible cause of fish and fauna decline in many rivers are the sprays widely applied to the land to control grass grub and porina moth – insecticide Dimilin (diflubenzurin) for porina and for grass grub, Dew 600. This chemical is the organophosphate diazinon, a DDT substitute. There are proven poisonings of duck in New Zealand, but little else is known and as far as I’m aware, little or no testing is done for either of these insecticides. It is one of those things that as a nation, we don’t want to know about. Spread by air, the river would receive the same dose as the land as well as any runoff from the land. Not only would the fauna of the river be affected, but so too terrestrial insects like manuka beetle and brown beetle which are a significant part of a rivers food resources.
My theory is, that if the cause of decline is diflubenzurin and diazinon, the fact that the river is in better condition below the gorge than above could be as a result of dispersal of the more volatile (than water) contaminants in the tumbling waters of the gorge, where the river drops more than 100 metres in a kilometre or so. Until it is tested, we will never really know.
The Manawatu below the gorge flows through more intensively farmed land, and it is also in this part that urban discharge becomes the major issue. Observers have reported that although there have not been the big fish die-off as there have been in the past, fish are smaller in size and the numbers are low.
The Manawatu is far from one of the dirtiest of the western world. By the same token, it is far from the cleanest. Its problems are not simple single issues like dirty dairy but complex reactions to human activities over the whole of its catchment.
The largest catchment in the southern North Island is the Ruamahunga, it is also known as the Sewermahunga. It is sometimes described as one of the dirtiest rivers in the North Island. From its main headwaters in the Tararua Ranges to the west it flows out into a wide valley with farmlands and towns that is the major geographical feature of the Wairarapa. The two major western tributaries, the Waiohine and the Waingawa also rise in the southern end of the Tararua’s. Then there are lesser tributaries, some from large catchments in the dry eastern hill country. Many of those rivers carry sediment from the often clayey country they pass through as well as forestry.
Once out in the valley the Ruamahunga picks up the urban discharge of both large and small towns. By far the biggest, Masterton, until a year or two ago, operated on a grossly substandard consent It was the major polluter. Its new “land based” system still allows discharge into the river, via diffusers, though this is supposed to be much reduced. Sometimes water conditions indicate that there is significant failure of the Masterton sewerage system. All the other towns also discharge either into the Ruamahunga or its tributaries. Water take from the aquafers occurs over much of the valley, both for dairy and grape production. The rivers lower reaches are more intensively farmed, and there is both direct water take and agricultural/dairy run off.
Much of both the river and its significant tributaries like the Waiohine have their beds regularly bulldozed and ripped, right from where they exit the gorges down to the lower reaches of the main river. All holes and pools are regularly filled with gravel “for flood control”. This initially results in major silting from the churned up river bed, and thereafter, in a river of shallow water running over sun-warmed beds the water will be depleted of oxygen. There will be with drifts of brown algae spreading from the shallow shores. In the shallow riffles, blue green toxic algae can be seen. Surprisingly there are still native galaxids (whitebait) coming in from the sea, but without monitoring, it is hard to determine how far up-river they get. A drift dive carried out by Wellington Fish and Game 3 or 4 years ago found roughly 2 trout per kilometre – a sure sign of a very sick waterway.
The Ruamahunga’s problems are not simple issues like dirty dairy or intensive agriculture: they are there, but so too is the loss of river margins and the consequent destruction of the river environment by bulldozing the bed. Urban discharge from both sewage and storm-water is still a major problem. In the smaller districts of Carterton and South Wairarapa there is no land based sewerage discharge at all and it is unlikely there will be as resources are directed to other priorities such as un-needed mega town halls for small populations. There are also plans for a major water storage scheme to permit widespread irrigation to the drier parts of the valley – that certainly won’t help.
The Waikato River
Although the Waikato has for generations been the heartland of New Zealand dairy, like the Manawatu, dairy is not the river’s only problem. As well, there are major differences between the alluvial soils of the southern rivers and the mainly volcanic soils of the Waikato region.
Forestry is a major industry up on the central plateaux and on much of the lighter pumice country, though even on the pumice country, former forestry land is being converted to dairy. From the forestry there is siltation, and from the dairy, on the light pumice lands, all the usual culprits of intensive dairy on light land – nitrogen, phosphates and hormones like oestrogen all migrating to the waterways. An in house report prepared for the Waikato Regional Council in April 2016 monitors what are seen as key indicators of soil health, ranging from soil compaction, phosphorous, nitrogen, carbon and density. Graphs indicate a slowly declining soil health over the period 2003 to 2014. The report is mute on the issue of heavy metals.
The geothermal activity of the central North Island are a source of heavy metal contaminants into the river, they include mercury, arsenic and boron, the major source is from the Wairakei geothermal power station, which releases into the river material that would otherwise have remained buried. Although much of this material is trapped in the hydro lakes further downstream, there are times when disturbances occur which allow mixing with the overlying water. It seems even renewable energy can have a price! The next major source of contaminants is the pulp and paper industry at Mareatai. Here there are further discharges of mercury as well as dioxins and other wastes. Further wastes from pulp and timber industry sources include persistent PCB’s which can remain in the river silt for generations. Cadmium from super phosphate is agricultures major contribution to heavy metals, and some sites in the Waikato are heavily contaminated.
Further downstream are the major towns of Hamilton and Cambridge with large urban populations and significant industrial areas. The Waipa River joins the Waikato at Ngaruawahia, bringing the further urban loadings of Te Kuiti, Otorohanga and Te Awamutu as well as the agricultural runoff from this widespread region. From whatever burden there is from agriculture, there is also leachate from open cast coal mining and waste heat, not only from the geothermal power stations, but also from the large Genesis thermal plant at Huntly.
There are many gaps in the analysis and effects of the Waikato’s water quality, but what can be assured is that it is high in cadmium, arsenic, PCB’s, mercury and DDT (a relic of an organo-chlorine use that has since been banned). Dairy is really only a problem on smaller tributaries.
Fish and food collection from the Waikato could expose people to harmful levels of toxins. With the river at only around 19m above sea level at Hamilton, it has almost 100km to run as a languid flow before it meets the ocean at Port Waikato where it finally discharges its toxic burden into the sea, in what is the habitat of the critically endangered Maui’s dolphin.
One of New Zealand’s longest river catchment’s includes some of the nation’s densest development. Its last 100 kilometres is by now an open drain for the central North Island, from that, water is taken off and treated to supply the city of Auckland – Bon appetite!
Bill Benfield comes from Christchurch, New Zealand. After a misspent youth fly fishing, exploring the mountains and rivers as well as travelling round the South Island, he settled down and studied architecture. After graduating, he left to see the world, ending up working in both Australia and the UK. On his return to New Zealand in 1974, he was alarmed at the pace of development that was occurring without any thought to the long-term planning or the consequences. He joined with others, and was involved with several major campaigns of the time, including the hearings on nuclear energy and the case brought against the Wellington City Council and the BNZ over the consents given for the BNZ tower. After setting up an architectural practice, Bill along with his wife Sue Delamare established a small vineyard and winery back in the mid 1980’s. In a time of flux in the industry, they set up using traditional French and Italian practices. Not only were the wines successful, but the winery was awarded a Ballance Farm Environment Award for sustainability in 2005. In the last 10 years, Bill has had more time to devote to environmental concerns, such as appearing at the ERMA hearings on the use of 1080 poison in 2007. He has also written the books, “The Third Wave” and “At War with Nature”, both published by Tross Publishing of Wellington.