We want rivers and lakes that people can swim in – seems a simple enough request, doesn’t it? It’s not unreasonable that our kids and grandkids should be able to swim in lakes and rivers just like we have. However, 62 per cent of our monitored river sites are unsafe to swim in.

Before we can set about cleaning up our waterways, we need to know what makes them dirty in the first place. Unfortunately, there are a lot of things that can contribute to water pollution; sewerage, sedimentation, toxic chemicals, heavy metals, litter, hot weather, ducks and geese. But the major contributor to poor water quality that has emerged in the last ten years, as identified by the Parliamentary Commissioner for the Environment, is nutrient run-off from dairy farms. That’s why we campaigned hard to stop Landcorp from converting forests in the upper Waikato to dairy farms.

There are two nutrients to be concerned about; nitrogen and phosphorus.

Plants, such as the grass that cows eat, love nitrogen and use it to grow, but when that nitrogen is entering the soil from – let’s not beat about the bush – cow urine, it enters the soil in such a rush, the grass can’t get hold of it before it seeps away or is washed in water logged soils straight into rivers and streams.

So why’s that a problem? When nitrogen gets into a waterway, the plants in those waterways, which also love nitrogen to grow, get too excited! It’s like being fed a heap of sugar in one go. Weeds and algae gobble it up and can become a problem. Algal blooms can form, which are potentially toxic to humans and animals. Weeds can smother slower growing species that wildlife depend on.

Another problem with nitrogen is that it can cause waterways to become toxic for some of the small creatures who live in it while promoting the dominance of others. Around 75 per cent of our native fresh water fish are threatened with extinction – water pollution being one cause of their decline.

Too much nitrogen in the form of nitrate in the water supply has an effect on bottle fed babies depending on clean water for their only source of nutrition. ‘Blue baby syndrome’ is an easily treated but scary consequence of water pollution, and as the name would suggest, babies can turn blue as they struggle with the oxygen-carrying capacity in their blood.

Excessive phosphorus has some of the same effects as nitrogen, but different concentrations of nitrogen and phosphorus behave differently on plants and animals from each other.

So while nitrogen and phosphorus pollution can come from too much wees, another major factor in why some waterways are too dirty to swim in is all about poo.

Pathogens like e.coli live in the guts of many animals, and are carried in animal poos into waterways. E.coli poisoning can cause a pretty nasty tummy bug, as can other waterborne pathogens campylobacter and cryptosporidium. It’s unclear just how many people get sick from pathogens as a result of swimming, but at least 264 people became ill with intestinal diseases like these in 2014 who had swum in streams, rivers and beaches shortly before getting sick. The year before, the number was 349.

So you can see why we are so concerned about the density of cows on farms in our country, and why we would like to see different kinds of land use and more organic farming. We’d like to see fewer cows on existing dairy farms, waterways fenced off so cows can’t get into them, and planting on the edges of waterways – called riparian strips – that will take up some of the nutrients before they get to the water.

But more than that, we’d like the Government to see water as more than an economic resource to be exploited, we’d like the Government to set robust water quality standards that ensure waterways are clean and healthy enough for swimming, so we can all enjoy our rivers and lakes, now and into the future.

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