Lakes water quality improvements encouraging, says Winters

31 January 2013

A $200 million partnership programme to improve the water quality of Rotorua lakes is producing very encouraging results, says Rotorua Te Arawa Lakes Strategy Group chairman Kevin Winters.

Mr Winters and the strategy group oversee the Rotorua Te Arawa Lakes Protection and Restoration Programme which is a partnership of Rotorua District Council, Bay of Plenty Regional Council and Te Arawa Lakes Trust. It includes a $72 million funding contribution from the Ministry for the Environment for water quality initiatives on four priority lakes – Rotorua, Rotoiti, Rotoehu and Okareka.

Mr Winters said targets had been set with the communities of each of Rotorua’s lakes aimed at achieving water quality levels that would be acceptable to those communities. The targets are based on a water quality measure called the Trophic Level Index.

“Because many factors, such as climate, the amount of rain and lake levels, all play a part in affecting water quality, we need to look at the long-term trend of water quality in each lake to see how well we are doing,” says Mr Winters.

“But there have been some quite remarkable results in the last year and these are really promising signs for the future of our lakes.

“Lake Rotorua’s annual water quality, for example, is the best recorded since regular monitoring began in the 1990s. This has been achieved though expensive and short-term in-lake engineering options and favourable climate conditions. While this is great, it is not a long-term sustainable improvement and we need to reduce the amount of nutrients entering the lake from the catchment.”

“Lake Rotoiti water quality also continues to improve and there have been great improvements in Lake Rotoehu’s water quality with no recent health warnings needed.”

Mr Winters said the work being undertaken on Rotorua’s lakes had become known worldwide and the Rotorua programme was leading the way internationally in water quality management.

He said the programme was being supported by innovation, science and technology such as the construction of floating wetlands, the development of a number of wastewater sewerage schemes and a recent state-of-the-art upgrade of Rotorua‘s wastewater treatment plant.

Other measures underway include trialling of an aeration treatment process using giant air pumps to reduce the impacts of nutrients that settle on Lake Rotoehu’s lake bed, and a Tikitere pilot plant to test the performance of nitrogen removal from the Waiohewa Stream before it enters Lake Rotorua. Currently 30 tonnes of nitrogen enters the lake every year as a result of geothermal activity.

Initiatives in coming months would include the preparation of more lake action plans, developing rules and incentives for nitrogen reduction in the Lake Rotorua catchment, a trial of locally mined Zeolite as an alternative for removing nitrogen from geothermal sources, and testing a de-nitrification treatment wall for Lake Rerewhakaaitu.

“While it’s too soon to become complacent as there are still significant water quality issues with several lakes we can take some comfort in the early signs coming through indicating we’re gradually getting on top of the problem and genuine progress is being made. But there is much to yet to do if we are to achieve the results we want for our lakes.

“I am well aware that this is the most important issue for many Rotorua residents and we’re all committed to seeing it through to the best possible results for our communities and for future generations,” said Mr Winters.

SUMMARY OF PROGRESS RESULTS
• Lake Rotorua: Has recorded best water quality in decades, with a long-term trend of improvement.
• Lake Okareka: Long-term trend for water quality is stable. Recent initiatives will take time to produce water quality improvements.
• Lake Rotoehu: Great improvements in water quality. No health warnings issued in last three summer seasons.
• Lake Rotoiti: Water quality continuing to improve.
• Lake Rotoma: High lake water levels resulted in slight decline in water quality last year.
• Lake Tikitapu: All actions in the Action Plan completed but it will take time before results appear.
• Lake Rotokakahi: Water quality declining. Action plan will be developed.
• Lake Okaro: Water quality has fluctuated over last 10 years but has improved as a result of recent interventions.
• Lake Okataina: High Lake water levels last year increased run-off from rain resulting in increased nutrient levels. An action plan has now been prepared.
• Lake Tarawera: Water quality is declining and an increase in nutrients recorded last year.
• Lake Rotomahana: Long-term water trend has been declining since 2005. Monitoring underway to assess whether action plan required.
• Lake Rerewhakaaitu: A local sustainable farming project involving 25 farms to reduce the amount of nutrients entering the lake.

ENDS

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