The good, the bad and the ugly

6 December 2007

The Cascade Stream in Waitakere has finished top of the class for water quality according to a report commissioned by the Auckland Regional Council.

A close second is Ngakoroa Stream in Franklin, followed by Rodney’s Matakana River and West Hoe Stream. The Omaru Creek in Glen Innes had the worst water quality in the survey, just ahead of southern creeks Pakuranga and Otaki.

The report, which was completed by NIWA, was based on results from the Auckland Regional Council’s monitoring programme.

The rivers were rated on several things such as conductivity, faecal coliforms, nitrate, pH, suspended sediment, temperature and turbidity. The report is based on a decade of data collected from 25 sites across the region.

ARC’s Monitoring and Research group manager Grant Barnes says the report shows water quality in general is improving in the Auckland region.

“There are some encouraging regional trends – in the majority of our rivers, nutrients, suspended sediments and faecal bacteria indicators have decreased which is a positive sign since these are major contributors to poor water quality.

The downward trend in suspended sediments is particularly welcome as sediment affects not only the rivers, but ends up causing problems in region’s harbours, he says.

But while sediment levels are reducing in our streams, we still have the highest levels in the country, he says.

“The average visibility in Auckland streams was 0.6 metres, the next worst, but still nearly twice Auckland’s, in Waikato (1.1 m) with Nelson having the best water visibility (4.7 m). The trend shows that the region has made progress in reducing sediment sources, but there’s still a long way to go.”

Mr Barnes says the five sites that scored the worst in terms of water quality were all situated in the Tamaki catchment, which reflects the mainly urban and industrial land use in the area. Stormwater runoff in these areas transports pollutants to streams and estuaries, says Mr Barnes.

“Given that the close links between land use and water quality it’s not surprising that our region’s clearest and cleanest waterways are more likely to be in bush-clad areas.”

Mr Barnes says the report was important because it gave an accurate picture of the state of the region’s rivers and streams, could be used as a basis for council policy, and identified the major water quality issues facing the region and where there could be improvements.

ARC Environmental Management Chair Dianne Glenn says the overall message from the report is water quality in our streams is getting better but there is still room for improvement particularly when we compare our streams with the national standards.

ENDS

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