Tuesday, 05 May 2020 10:16

Water quality – not just farming’s problem

Written by  Peter Burke
Water quality: not just an issue for farmers. Water quality: not just an issue for farmers.

A report by the Government is offering further evidence that New Zealand’s freshwater is being impacted not just by farming but equally by urban development, forestry and other human activities.

Our Freshwater 2020, by the Ministry for the Environment (MfE) and the Department of Statistics (DoS), highlights how climate change is set to make the issues faced by our freshwater environments even worse.  

The report’s authors say it builds on the information presented in previous reports but goes deeper on the issues affecting freshwater in NZ. This includes new insights on the health of freshwater ecosystems, heavy metals in urban streams, consented water takes and expected changes due to climate change.

The aim, say MfE and DoS, is to provide the evidence to enable an open and honest conversation about available options and to tell a national story, while recognising that significant regional variations exist. It notes that the data and science presented in the report is up-to-date and the best available, but that there is much more work needed to be done.

It does conclude that most rivers in farming areas are polluted, quoting studies at national, regional, and catchment scales showing that show the concentrations of nitrogen, phosphorus, sediment, and E. coli in rivers all increase as the area of farmland upstream increases.  It says farm animals are a source of freshwater pollutants such as dissolved nitrogen, phosphorus, and pathogens and that fertiliser and animal dung and urine are important sources of phosphorus.

It notes that dairy cattle numbers have increased by 70% in NZ since 1994 and that farming has intensified with higher stock numbers per hectare in many regions.

But the report also notes that most of the rivers in catchments in the urban land-cover class are polluted with nutrients and suspended sediment, and many are polluted with pathogens and heavy metals.  And it points to a problem with aging infrastructure in urban areas, which is leading to pollution.

Farmer reaction

DairyNZ says the report highlights NZ’s environmental challenges and where everyone can play a part. 

Strategy and investment leader for environment, Dr David Burger, says dairy farmers are committed to protecting the environment and taking action on-farm to support that.

“Our dairy sector is on the journey to improve and protect water quality outcomes and our farmers have been working toward this for over a decade. We are continuing to do more every year. The Freshwater 2020 report does draw some key themes together for urban, farming and forestry, and shows us that all land use has an impact on our freshwater,” he says. 

But Burger says the report’s approach compares current water quality with native forest waterway condition and DairyNZ believes it is therefore somewhat misleading.

“We know that all development has an impact on water quality but it is unrealistic to compare this to native forest state. An estimated 95% of total river length in pastoral catchments exceeded one or more guideline values, simply because they are being compared to a very high native forest standard. 

“Interestingly, more than 50% of native waterways also failed to meet this criteria. This sets the benchmark very high for catchments with modified land use,” he says.

Federated Farmers says the data and findings in the report provide powerful backing for the case for greater investment in water storage. 

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