'Hard yards' to repair water quality

Last updated 09:30 22/03/2014

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Water is one of a country's most important assets so managing it should be high on the priority list. Sven Herselman takes a look at how the rivers in Marlborough stack up and what is being done to look after them.

The first time I met Marlborough District Council senior environmental scientist Peter Hamill was at a fishing club meeting where he was speaking about the water quality in our rivers.

I thought it quite brave of him to step into a room of staunch freshwater fisherman - many of whom regard the rivers as their second home - to speak openly about what he and his team are doing to keep the water in good condition.

The report he was talking about, the 2013 state of the environment surface water quality monitoring report, is no secret and is freely available online, but it was clear that few people at the meeting had looked at it.

Typical of such reports, it is long and technical, but down on page 47 it lays bare the top 10 of Marlborough rivers taking into account water samples from 2010-12. Peter left this bit toward the end of the evening as a sort of crescendo to his talk, but I would prefer to go there first.

Top of the crop is the upper Wairau River followed by the little Wakamarina River, while the middle and lower sections of the Awatere River sit in second last and last position, respectively.

The poor old Awatere holds the bottom spots only because of high turbidity [muddiness] levels. More damming is Mill Creek, which sits 31st out of 34 because of its worryingly high nitrogen levels.

"Turbidity is more of a natural occurrence. For example the lower Waihopai [River] scores low because of turbidity from a big slip way up river that has nothing to do with human activity.

"Nitrogen levels, on the other hand, are a direct result of human activity," Peter says.

He makes no excuses that people are almost always to blame when the health of a river goes backwards. When humans settle in an area the quality of the rivers is generally affected - no two ways about it.

Farming, stormwater runoff and even dumping lawn clippings or the unwanted contents of a fish tank into rivers can have terrible and lasting effects.

The river weed in the Taylor River is the perfect example, Peter says. Both species found in the river, egeria and lagarosiphon, are invasive and almost certainly came from people dumping unwanted fish and weed from their fish tanks.

The invasive weeds have taken over and no native river weed remains in the Taylor.

Last week Peter was out with a colleague fishing out more than a dozen goldfish that had been dumped in the Taylor. The fish are not the big part of the problem, but the aquatic weed as well as any foreign diseases in the fish tank water are of great concern.

"It could have been just one person who dumped weed in the river years ago. Because of that, council spends over $100,000 a year controlling the weed. All we can do is manage it because the chemicals needed to totally getting rid of it are far too harsh," Peter says.

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It's the old story of trying to control one evil with a lesser, as the aquatic herbicide Diquat has become the weed control measure of choice in New Zealand. Speak to trout fisherman and some environmentalists and they will usually voice strong opposition to the herbicide being used.

Again Peter is candid on the point. It comes down to economics, he says. Removing the weed by hand alone is simply too expensive.

"No one wants to have to use poison, but we have to use the tools we have to control the situation. If the weed was left to grow it would choke the river and have wide-ranging effects on the water table, stormwater runoff and the effects of flooding."

Managing what has already gone wrong is just one part of the job for Peter and his team. Gathering data by taking monthly water samples is where it all begins.

Since 2012 they have used a new method to analyse and present their findings, taking their cue from Canadians and their "water quality index". The Marlborough team went one step further, going on to look at what the causes of unfavourable results are, which the Canadian model doesn't do. The model is used by less than half of councils in New Zealand.

Action can be taken based on the results of these studies. In the case of the Taylor, it's not just the weed that is a problem. The river ranks near the bottom of the table are somewhere in the "marginal" water quality range, and its closeness to Blenheim means it is highest on the priority list.

"We are busy with the Taylor River characterisation study, where we are trying to track the sources of things like the high levels of inorganic nitrogen in the river. It means testing up the river and into the tributaries and their catchments," Peter says.

The results are due out in July.

Prevention is better than cure and getting into the schools to teach children about what effects they can have on rivers is a big part of that.

Kids can be great for keeping an eye on the river, especially in summer when the waterways become popular to escape the heat.

In Nelson a group of school children were responsible for finding a mosquitofish in a river. The invasive species had never been seen in the top of the South Island.

Work with farmers is another big part of what councils around the country are doing to keep the rivers and streams clean. In Marlborough there has been more than a decade of work, particularly with the farmers in the Rai Valley area.

It has been a long process, but there has been movement. Peter recalls the first time the council broached the issue at an A&P show in the area in 1998. Most farmers were resistant, but have since got behind the project.

Big business such as Fonterra are also being won over, making preventative measures part of their milk contracts with farmers. As a result the Rai River looks to be on the mend - it sits at 11th spot in the report table and has shown a pleasing decrease in the nitrogen levels from 2010 to 2012.

With rivers, nothing happens quickly and the source of quality problems can reach back up to 50 years.

"With the Taylor River we just don't know what the cause is yet. It could be from farming practices way before the viticulture industry started in Marlborough," Peter says.

Compared with the rest of the world New Zealand rivers are in decent shape, but you can never rest on your laurels.

Back in my home country of South Africa, a frightening number of the rivers are absolutely squalid. A small stream near my old home is so bad you wouldn't step in it, let alone let children play near it.

Unfortunately humans seem to mess rivers up, but we can work to fix them, too.

- The Marlborough Express

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