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Published: 2004-04-19 00:00:00

A 15-year study into trends in river water quality throughout the Waikato Region shows that the quality of water in rural streams and rivers is declining.

While the study showed that the overall quality of water in the Waikato River has improved over the period, it also revealed that some indicators of water quality in rural streams and rivers had worsened.

The report – “Trends in River Water Quality in the Waikato Region 1987 – 2002” – has just been released by Environment Waikato. It shows the shifts in a number of indicators of water quality during the period at 10 sites along the length of the Waikato River and 100 sites on other rivers and streams throughout the Waikato Region.

The report’s author, water scientist Bill Vant, says that a number of the indicators showed improvements while others had deteriorated over the 15-year period.

“Overall the quality of water in the Waikato River has improved because we have been able to identify and tackle major sources of water contamination.” he says.

“However, the quality of water in some of the Region’s other rivers and streams has deteriorated in a number of important indicators including decreases in water pH and increases in nitrogen and phosphorus levels.”

Mr Vant says that water quality indicators reflect what is happening on the land.

“In several cases these adverse changes reflect increased intensification of land use in rural areas. However there are changes in other water quality indicators where it is less easy to identify the causes. Some of the environmental reasons for the changes are not well understood and need to be investigated at a national level.”

Mr Vant said there were also some positive indicators in rural areas, such as improved water clarity and a reduction in ammonia levels.

“We believe some of these improving trends are due to some positive changes in farming practices, particularly the trend towards spray irrigation of effluent on land.”

Environment Waikato Chief Executive Harry Wilson says the report is extremely important because it provides a long-term picture of water quality trends in the Region.

“The people of the Region have already told us that they regard water quality as the single most important environmental issue for them. It shows that we can work to control identified sources of contamination and improve water quality indicators as we have seen in the Waikato River.”

“However it also demonstrates the difficulty we face as a community in managing non-point sources of contamination.”


Mr Wilson says Environment Waikato’s 2004 Long-Term Council Community Plan says that, given the difficulty in controlling non-point sources of contamination, it is unlikely there can be any rapid improvement in water quality in the short term.

“We know that a very significant number of farmers have made concerted efforts to reduce the adverse effects of farming on water quality by fencing off streams and diverting effluent to land-based disposal.”

However, Mr Wilson says these measures will only address part of the problem.

“More intensive stocking rates inevitably have an adverse impact on groundwater quality which eventually reaches the Region’s rivers and streams – that’s a fact of life. As long as we accept such intensive farming practices there will be an impact on water quality in our rivers, streams and lakes,” he says.

Mr Wilson says that Environment Waikato has distributed the report widely and will work with those affected and the community to identify options.

Find out more by downloading our free technical report, 'Trends in the River Water Quality in the Waikato Region, 1987 - 2002', available in PDF format.