Russel Norman

Water pollution and debunking the Yale study

by Russel Norman

The Government is once again under attack for its lack of effective action to clean up waterways. The Cawthron Institute released a report stating that the Government’s National Policy Statement on Freshwater Management combined with the subsidies for new irrigation, and hence new cows and pollution, will mean our rivers won’t be cleaned up in the near future, if ever.

The report and the the response of freshwater scientists are worth a look.

The report was commissioned by Fish and Game which led Nick Smith to attack Fish and Game (yawn) more than really getting into the substance of the report. In a nice irony, Nick is a trustee of the Cawthron Institute.

In defending the Government, Nick Smith was forced to go back to a report produced by Yale University which claims that NZ does really well on water quality – 2nd best in the world. It is the same report that John Key has been repeatedly referring to in order to defend the diabolical state of our rivers when BBC Hardtalk and us have asked him about it.

So it’s worth putting on the public record the views of Professor David Hamilton – Professor of Lakes Management at Waikato University and President of the New Zealand Freshwater Sciences Society. Prof Hamilton wrote this release but I’m not sure it ever went out publicly and he passed it on to me at my request – I tabled this statement in the House today with his permission.

It debunks the Yale study: the Yale study is based on data more than a decade old; it lumps NZ in with the rest of the Pacific; and Yale refuse to release their data set so other scientists can’t check their work. The fact that Key and Smith keep using it is a sign of their desperation.

Media Statement: International Water Quality Study Lacks Relevance

The Yale Water Quality Performance Index that ranked New Zealand second only to Iceland, with a score of 99.2, is inaccurate and badly outdated say researchers from Waikato University.

The 2010 Yale and Columbia University study ranked countries according to their environmental performance.  But Professor David Hamilton, Chair in Lakes at Waikato University, is disappointed with selection of data used to characterise New Zealand’s water quality.

“We have not only been lumped together with other Pacific Island nations in the NZ Water Quality Index but the data set used for the study is more than 10 years old” says Hamilton.

He added that “recent scientific reports show evidence of increasing nutrient levels in large numbers of the 77 streams and 134 lakes that effectively comprise a national water quality monitoring network”. NIWA maintains the river monitoring network and the Ministry for the Environment holds the lake data set.

Hamilton says that “in view of recent water quality trends and the intensification of land use that is driving many of these trends, the widely reported Yale Water Quality Performance Index for NZ should be disregarded.  We used the most up to date data from the 134 lakes to examine NZ’s performance against the metrics used for the Water Quality Performance Index and obtained a ranking for NZ of only 66.7%”.

Jon Abell, a Ph.D. student at Waikato University, compared water quality in the 134 NZ lakes against that of more than 1500? lakes across the globe in a paper recently published in the international scientific journal Ecosystems. He says that the rating of 66.7% for NZ is much more in line with where his study placed nutrient levels in NZ lakes compared with lakes internationally.  A follow-up paper found that high production pasture had the greatest effect on lake nutrient levels in the 134 lakes.

Hamilton indicates that Abell’s research has been very important in placing NZ into the international context.  “Many of our lakes have naturally very low levels of nitrogen but we also noted that the most polluted lakes had levels that surpassed even the most polluted of lakes internationally.  His study has also emphasised the need for controlling both nitrogen and phosphorus inputs to waterways because these two nutrients are extremely closely related even though most of the phosphorus comes through sediment erosion from overland flow and most of the nitrogen comes indirectly from leaching into groundwaters”.

Published in Environment & Resource Management by Russel Norman on Tue, August 2nd, 2011   

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