Dying lakes, our toxic heritage

Scientists have warned that some of the most beautiful and popular lakes including Lake Rotorua are threatened. Picture / Alan Gibson

The top scenic lakes in the central North Island need a "Herculean" effort over decades, not years, to save them from dying, says the country's environmental watchdog.

Scientists have been warning since the 1980s that some of New Zealand's most beautiful and popular lakes, around Rotorua, are threatened by human activities and byproducts such as farming and sewage.

Water quality has been declining for decades, and toxic algal blooms have become a perennial hazard in many of the lakes.

Now the Parliamentary Commissioner for the Environment, Dr Morgan Williams, has warned that the worst effects of pollution have yet to be seen, meaning long-term measures must be put in place urgently to make sure the lakes can be returned to a near-pristine state.

He said Institute of Geological and Nuclear Sciences research had shown it took many years for nutrient-enriched groundwater to move through the region's large volcanic aquifers, so the effect of intensive land-use had yet to reach the lakes.

That would see high, bloom-causing nitrogen concentrations increase significantly in the future.

It was therefore imperative work to save the lakes - already under way after reports issued in 2000 and 2004 highlighted the threat - be co-ordinated and involve as much of the community as possible, Dr Williams said.

"The challenge is enormous - firstly to halt current nutrient losses, secondly to mitigate the effects of past losses as they impact on the lakes, and thirdly to sustain and resource the long-term commitment. To turn back the nutrient tide we face some very tough land-use decisions."

The lakes are struggling due to the run-off of fertilisers from farms, discharges from septic tank soak fields from the region's many baches and urban runoff from Rotorua and other towns.

A Herald investigation three years ago, "Dying Lakes", showed many suffered from high levels of toxic algae and were in danger of dying unless millions of dollars were spent to fix the problem. Several Rotorua lakes and parts of Lake Taupo have sometimes been closed because of algal blooms.

Dr Williams recommended that a report card be developed to provide regular updates on water quality, land use and progress in restoring the lakes. "We are far from seeing the worst effects yet, so long-term structures to protect the lakes must be in place to see the job through."

His report, out today, reveals some dissatisfaction among interested parties, including concern the Government is not doing enough and the Ministry for the Environment is under-resourced. Groups are also worried about difficulties getting councils working together, scientists are spending too long writing research proposals and monitoring of water quality is inadequate.

Dr Williams did say major efforts were now being invested in the protection of the lakes, and an extensive range of projects had begun in the past three years.

To restore the lakes the commissioner recommends the following:

* Membership of the lakes joint strategy committee be expanded to increase community involvement in saving the lakes.

* A report card tracking progress improving water quality.

* The commissioner to consider investigations into research funding, integrated catchment management, and national lake management issues.

Several lakes now had action plans in place or under development, and Environment Bay of Plenty, the Rotorua District Council, the Ministry for the Environment and local iwi Te Arawa had all played parts in initiatives aimed at saving the lakes.

The report said some people felt because agriculture was an easily identifiable problem, farmers were an easy target and the first to be blamed.

Local Federated Farmers president Gifford McFadden felt that was "a fair enough thing to say".

However, farmers wanted to preserve the lakes and were actively involved in efforts to do so, Mr McFadden said. They wanted to see more funds devoted to scientific research into sustainable farming.

Rotorua Mayor Kevin Winters, who is chairman of the Rotorua Lakes Strategic Joint Committee, was pleased Dr Williams had called recent efforts to save the lakes "superb".

However, he echoed the prognosis of difficult times ahead.


The Problem

* Phosphorus and nitrogen, which produce toxic algal blooms, are leaching into the water of the Rotorua lakes.

* While the problems surrounding Rotorua are severe, lake water quality is a national issue. It is estimated that up to 40 per cent of NZ's 700 shallow lakes are high in algae and low in water clarity.