Wadeable rivers nz e coli

The True Cost of Wadeable Rivers

Gareth MorganEnvironment

The water contamination scandal in Havelock North has had an untold cost on the people and economy of the region. Schools have been shut down and businesses have been at a stand still. While we don’t know the source of the problem yet, there are increasing signs it could have come from agriculture. Could this be linked to the quality of the water in our rivers, and what can we do about it?

The real question is whether we will learn from this mistake. Even if we take care of the bacterial risks to our drinking supplies, will we deal to the looming risk posed by increasing nitrogen levels?

Is this problem linked to agriculture?

Over the weekend the Havelock water scandal took another twist – tests reveal the contamination is likely to have come from cattle. On The Nation scientist Mike Joy pointed out that the risk of this sort of contamination happening elsewhere is increasing due to the intensification of agriculture. In fact, New Zealand already has the highest rate of waterborne diseases in the developed world. And on Morning Report today a scientist pointed out that the contaminated water could have come from the Tukutuki river.

This may come as a surprise to many people; the fact that rivers and lakes are linked to aquifers, and what happens in one can affect the other. How water moves between above ground and below ground flows is very complex, and in many parts of the country we don’t understand the interrelationships. In some places water moves very quickly, in others it is very slow. In areas where the water can move quickly, there is a possibility that bacteria contamination could survive long enough to infect a shallow aquifer.

The risk of this happening is increasing as we intensify land use. Firstly we taking water from shallow aquifers for agriculture and drinking supplies. When that water is taken, those aquifers will tend to get recharged from surface water. Secondly we are using that water to intensify land use; generally either through providing housing for humans or pasture for cows. In some areas the sewage from humans is a problem, but the scale of farming is a far greater risk; not only because of cow numbers but also the amount of sewage they produce (as this infographic shows).

While we don’t know if this is the cause of the issues in the Hawkes Bay, the intensification of farming around the country, particularly in Canterbury, has certainly increased the risk of problems. It is another clear example of where agriculture doesn’t foot the bill for all the costs they create, pushing them onto the rest of the economy.

Are there solutions?

Chlorinating water is the short-term solution, however there are moves a-foot which should reduce the risks of agricultural bacterial infection in our water supply. Longer-term improvements will be evident from the plan to keep livestock out of our waterways. The dairy industry has been working on this for some time, but other farmers are now coming on board and the plan is to have all livestock out of permanent waterways over a certain size by 2030. This is slow going, and won’t mean the small, ephemeral waterways are protected, but it is a good start. By planting all waterways we could also do a lot to make sure animal faeces are not washed into the rivers during heavy rainfall. Over time, these changes will reduce the risk of poo ending up in our water supply.

Fencing and planting won’t solve all the problems

 Sadly the one problem that is not solved by excluding livestock and planting rivers is nitrogen. Nitrogen is soluble in water, so ends up collecting in aquifers, rivers and lakes. Nitrogen needs to be at quite high levels to be toxic to humans, but at lower levels it can cause algal blooms and be harmful to the life in the water.

This problem is most noticeable in Canterbury, where water passes quickly through the stony soils. Environment Canterbury has already highlighted that it won’t meet its drinking water targets by 2040 because of the increased farming in the region; a clear sacrifice of human and environmental health for short term economic gain. The Canterbury District Health Board medical officer of health Alistair Humphrey has been raising these concerns for a long time.

Nitrogen is a much bigger problem than bacteria, and one that doesn’t have an easy solution. We can farm a bit more efficiently, but it really comes down to limiting the amount of livestock we have in a certain catchment. Either that or we need to be prepared to put up with the consequences in terms of poor water quality and poor human health. That is the hard question that we need to face up to as a nation.

Farming imposes costs on the rest of us. If we don’t get them to pay those costs, then society ends up paying in other ways. Just ask the good people of Havelock North.


The True Cost of Wadeable Rivers was last modified: August 22nd, 2016 by Gareth Morgan
About the Author

Gareth Morgan

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Gareth Morgan is a New Zealand economist and commentator on public policy who in previous lives has been in business as an economic consultant, funds manager, and professional company director. He is also a motorcycle adventurer and philanthropist. Gareth and his wife Joanne have a charitable foundation, the Morgan Foundation, which has three main stands of philanthropic endeavour – public interest research, conservation and social investment.