Keep our drinking water clean

Future nitrate pollution threatens Christchurch’s drinking water

Environment Canterbury has now publicly notified Plan Change 7 (PC7), which includes implications for Christchurch’s drinking water. Intensive farming north of the Waimakariri is likely to contaminate the city supply with nitrate pollution over the next 50+ years, according to ECan models.

Plan Change 7 had already been open for what is called “Schedule One consultation” under the RMA, which included consultation with Christchurch City Council, Ngāi Tahu and other parties. Despite strong submissions from these bodies, the resulting plan’s across-zone implications remained unchanged. Even with on-farm mitigations, ECan’s modelling still anticipates nitrate pollution up to 3.8 mg/l in Christchurch’s drinking water in the coming 50+ years. While NZ’s current allowable limit of nitrates in our water is a whopping 11 mg/l, a recent Danish study involving 2.7 million participants has shown that more than 2.1 mg/l gives rise to a significant increase in bowel cancer.  There has rightly been widespread concern about this, along with calls for additional research into the Drinking Water Standard. I absolutely support such calls, and voted against the Waimakariri Zone Committee recommendations which formed the basis of Plan Change 7.

However, if you think these figures look bad, the situation is in fact even worse than it might seem.   Focussing on the drinking water standard alone fails to recognise the absolute imperative of a healthy ecosystem in delivering us clean drinking water. According to NZ’s few experts in the area of aquifer ecosystems and ecotoxicology, nitrate limits for ecosystem health are more than ten times lower than what we humans can tolerate.

New Zealand’s leading groundwater ecosystem scientist at NIWA, Graham Fenwick, suggests in his evidence to the Water Conservation Order hearing for Te Waikoropupu springs, a trigger value of 0.4–0.5 mg/l as a precautionary value to ensure ecosystem health. In his presentation to commissioners on behalf of Wellington Regional Council in 2018 he states:

Available research evidence empirically demonstrates that this standard, designed to protect human health, is inappropriate for ensuring the health of aquatic ecosystems and invertebrates under long-term exposure.”

Graham Fenwick, NIWA

Chris Hickey, NZ’s leading ecotoxicologist, recommends where long lag times apply (i.e. 8 years or more) a trigger value for management of 0.4–0.5 mg/l is appropriate. 

I believe this Plan Change, and this council, have failed to recognise that it is the ecological health of the aquifers that has provided Christchurch with clean drinking water for decades. This ecological health has given us the privilege of being one of the largest remaining cities in the world able to drink our water without treatment.

It is now of utmost importance that the public take the opportunity to have their say on this, and it’s my personal hope that the weight of public outcry and expert evidence will be able to change this plan. The plan does not go far enough; we need a true “precautionary approach” in protecting the ecological health of Christchurch’s aquifers and the privilege of the uncontaminated drinking water supply we have today.

Younger and future generations will be facing much greater challenges in the form of climate disruption and all the social, cultural, environmental and economic issues associated with such disruption. The least we can do is provide them a safe, ecologically functional water supply.”

Lan Pham and Axel Wilke

Luckily, the Plan Change implications are not all negative. One particularly positive part is the provisions relating to the identification of endangered native fish habitat and associated new restrictions on activities to enable their protection. Personally, I am extremely proud of the current ECan council for taking a lead on this. It was the quirkiness and general awesomeness of NZ’s native fish that first captured my interest in water and resource management issues. This has therefore been an area I have consistently been advocating for at ECan. It’s fantastic to see that this council’s elevation of biodiversity to our highest strategic priority alongside water is resulting in these kinds of statutory changes. I don’t doubt this will greatly aid in the protection of the very cool, yet often overlooked critters that make Canterbury unique. So yes, there are many positive aspects to PC7, but the glaring issue of the future nitrate implications for our city’s drinking water is one which needs your voice, calling for much tighter limits on nitrate pollution.

The Press has covered some of Lan’s concerns about Plan Change 7. The options for making a submission are outlined on the ECan website. For more updates, ‘like’ Lan and Axel’s Facebook pages. Or contact us directly.

Nitrate pollution is crossing underneath the Waimakariri River towards Christchurch

5 thoughts on “Keep our drinking water clean”

  1. Also it is already known that cows health suffers from too much nitrate levels in paddocks.

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