International water pollution conference in Rotorua

NIWA Media Release 19 September 2011

International water pollution conference kicks off in Rotorua

Freshwater experts from around the world kicked off a five-day international conference on diffuse pollution in Rotorua this morning.

Unlike point-source pollution, diffuse pollution refers to pollution from widespread activities with no single discrete source, such as runoff from agricultural practices, pesticides, and urban areas. Diffuse pollution is the biggest source of pollution in New Zealand waterways.

The 15th International Water Association’s Diffuse Pollution Specialist Conference (DIPCON) draws together scientists, engineers, economists, and resource managers from 28 countries, to share, and discuss, the latest developments in diffuse water pollution management.

Opening the conference this morning, Parliamentary Commissioner for the Environment, Dr Jan Wright told delegates different environmental issues capture the public and media’s attention at different times.

“Now it’s water quality’s time. Water quality has become a major issue in New Zealand in recent years.”

Dr Wright also said water quality science is complex and not widely understood.
“Changes that really improve water quality must be built on understanding and communicating that complexity. You are here to develop that understanding.”

One of New Zealand’s main sources of diffuse pollution is runoff from farming.
NIWA Principal Scientist Dr Bob Wilcock has just completed a ten-year study looking at mitigation measures to decrease the impacts of dairying runoff, and gave a presentation on his results at the DIPCON conference today.

Since the 1990s dairying has intensified significantly in New Zealand. In the early 1990s there were around 2.5 million dairy cows on New Zealand farmland – now there are around 4.5 million. This has resulted in increased levels of nitrogen (N), phosphorus (P), sediment, and faecal matter in New Zealand lakes, rivers, and tributaries.

Dr Wilcock’s study looked at how mitigation measures, such as fencing to keep stock out of waterways, riparian planting, and using effluent for irrigation, have reduced pollution levels in waterways.

Five catchments, ranging in size from 6 km² to 40 km², in Waikato, South Taranaki, Canterbury, and Southland were monitored for ten years, and a fifth catchment on the West Coast for six years.

“There have been dramatic improvements in areas where farmers have put fences up to exclude stock from streams, converted from pond discharge to irrigation back on to the land, and planted along the river banks. With these measures, there have been major improvements in water clarity, suspended solids, particulate phosphorus, and E. coli levels, “Dr Wilcock said.

“However, nitrogen and dissolved phosphorus levels remain high in nearly all sites monitored. What this tells us is that measures to improve nitrogen and phosphorus levels must be long-term. Progress may be slow, but incrementally, over decades, we will continue to see improvements. Ideally, this study would continue for another 10 years.”

“Around 75 percent of nitrogen and phosphorus runoff in New Zealand rivers originates from modified, mostly pastoral, land use. Although our waterways are generally in better condition than those overseas, we do have a recognised pollution problem in them, and we need to solve it,” says NIWA Chief Scientist, Freshwater, Dr Clive Howard-Williams.

“Water pollution is a now a global issue. Bringing the best freshwater minds together in one room at this conference gives us great insight into how other countries are grappling with the same pollution issues. It will be beneficial for New Zealand and the rest of the world.”

The DIPCON conference is being held at the Energy Events Centre in Rotorua from 18 to 23 September 2011. For the conference programme, and other information, go to: www.dipcon2011.org

Media are welcome to attend any of the sessions.

For a copy of Dr Jan Wright’s speech go to: http://www.pce.parliament.nz/

ENDS

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