Our Fresh Water Crisis

So what’s wrong with our waterways? Dr Mike Joy, lecturer at Massey University, explains.

Our waterways are in dire straits

Recent statistics about our waterways are not good news. 44% of all monitored lakes are polluted beyond the point of eutrophication, and 62% of our lowland rivers have more pathogens than are safe to swim in. The stats are even worse for lowland lakes in farmland – a whopping 84% are so polluted they become eutrophic. In fact many of our waterways are so bad that even our native fish have disappeared. It’s not the clean green image we associate with New Zealand is it? And without significant intervention now, it’s only going to get worse.

What streams should be like

Before humans arrived in New Zealand, a majority of our lowland waterways were heavily shaded by forests. Streams and rivers were cool, slowly meandering, stony-bottomed and supported an abundance of life. Great for drinking from, harvesting from and swimming in…

What went wrong?

Over the last several hundred years, a large proportion of lowland forest has been cleared for

farming, forestry, horticulture and, of course, human habitation. Loss of vegetation and modification by us humans has many negative impacts on streams and rivers:

• Loss of shade to the water body – warm water carries less oxygen, which freshwater species need to survive
• Loss of structural habitat for aquatic fish and invertebrates – no tree roots, benches and shelves for refuge
• Stream bank erosion – stony stream bottoms (fish habitat) silt up
• Dams, weirs and floodgates – loss of access to native fish that migrate during their lifecycles

On top of that, intensive farming and other industrial practices have also contributed to the problem:

• Increased leaching of nitrates and phosphates contribute to algal blooms in waterways
• Algal blooms can be toxic to humans and animals
• Algal blooms lead to oxygen depletion and smelly, slimy, waterways
• Lack of oxygen spells death to our native freshwater species
• The presence of animals in or near waterways leads to faecal bacteria which are also bad for human health.

And it doesn’t stop there. The silt and contaminants course straight to our beaches and harbours, impacting the marine environment – especially shellfish, fish stocks and seaweeds.

Riparian planting – a solution worth investing in

Riparian restoration (replanting the banks of streams, rivers, lakes and wetlands) is a valuable

tool for improving water quality and enhancing freshwater biodiversity. While it is not the one magic bullet that will fix all the problems it is a great start. Local councils, farmers and community groups around New Zealand have already made a start replanting rural and urban waterways.

Riparian planting has the following benefits:

• Reduce erosion and sedimentation by trapping sediment before it enters the stream

• Filters phosphorus and industrial contaminants before they enter the stream
• Buffer the impacts of floods by acting as sponges to hold excess water
• Provide cool shaded habitat and food for native species
• Sequester carbon.

The health of our waterways affects all New Zealanders, so we all need to be part of the solution. Because if we don’t do something now, who will?

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