NZ's pure water 'gone forever'

JOHN HAWKINS/The Southland Times

FRESHWATER: Parliamentary commissioner for the environment Jan Wright says it is not realistic to return all our fresh water to a pristine state.

New Zealand's fresh water can never be as clean and pure as it once was, but action must be taken to improve the quality of rivers, lakes and wetlands, the parliamentary commissioner for the environment says.

In a new report for MPs on water quality, released today, commissioner Jan Wright says "clear, clean, cool streams, full of life" still flowed through forests in remote parts of the country.

"It is not realistic to return all our fresh water to this pristine state. But nor can we afford not to act."

Freshwater quality was the subject of high public concern and vigorous debate and one of the biggest environmental challenges facing New Zealand, Dr Wright said.

The report mentions a 2009 Dominion Post front page naming the Manawatu River "Our river of shame" and reporting that it was rated among the most polluted in the Western World by some criteria. Consequently, a case study in the report ruled it out as the most polluted, but confirmed "the Manawatu River is very unhealthy".

"Other indicators of river health such as nutrient concentrations, water clarity, faecal bacteria and stream invertebrates also indicate the poor status of the Manawatu River."

Dr Wright's report, which aims to support informed debate and decision-making, considers the historical context of land use changes and water-quality issues.

It highlights the three main pollutants affecting fresh water: water-borne diseases, sediment and excess nutrients like nitrogen and phosphorus.

Pathogens make people and animals sick, sediment makes water murky and stony riverbeds muddy, and excess nutrients such as nitrogen and phosphorus cause rampant weed growth, algal blooms and oxygen depletion.

There had been much progress in controlling pollutants that had entered water in recent years, she said.

Public concern about the state of New Zealand's rivers, lakes, streams, wetlands and estuaries had grown in the past decade and practices that were acceptable in the past would be inconceivable now.

However, there was still much that could be done.

Erosion-prone land in the hills could be planted with poplars that would develop extensive root systems to hold soil. The clearance of any remaining native vegetation in gullies should stop.

Bigger storage tanks should be built so town wastewater was not emptied into rivers when flows were low, or it could be sprayed on to land to fertilise forests.

Stock should be restricted from direct access to water, particularly cattle, and riparian strips of grass should be planted to limit phosphorus entering the water, Dr Wright said.