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Minister launches giant wetland project

Thursday, 28 July 2011 8:00 a.m.

Minister for the Environment Dr Nick Smith launched a 3000 square metre floating wetland in Lake Rotoehu today as part of the Rotorua Lakes restoration programme.  

The massive floating wetland - an artificial island constructed of recycled soft drink bottles and planted with native plants - is designed to remove nitrogen from lake waters. Nitrogen is one of the key nutrients causing deteriorating lake water quality.

The wetland has been funded 50 percent by the Crown through the Deed of Funding to clean up the four priority Rotorua lakes, Rotorua, Rotoehu, Rotoiti and Ōkāreka. It is part of the Rotorua lakes restoration programme which is an initiative of the three partners - Bay of Plenty Regional Council, Rotorua District Council and Te Arawa Lakes Trust.

The giant wetland covers 2800 square metres, and is covered by a resource consent held jointly by the Regional Council and Te Arawa Lakes Trust. It is built from 364,000 recycled bottles and planted in native wetland species eco-sourced from the local Rotorua area. It is anchored in place by 10 screw anchors so that it can be moved if there are any changes in the lake's water level.

Regional Council Chairman John Cronin said the launch signalled that the partners were making significant progress in cleaning up the lakes.

"This 800 hectare lake has become a very useful melting pot for testing lake restoration techniques that could be applied to other larger lakes in the programme. Weed harvesting has already removed up to 3500 tonnes of weed each year. This achieves the reduction in lake nutrients required to restore the lake, even before land use changes come into play," he said.

Other smaller projects had also been tried on the lake, including bio-treatment in Otautu bay and de-nitrification of an in-flowing stream on the Tautara Matawhaura Māori Land Trust farm.

"Some of these trials have been initiated as a result of input from the community. The Regional Council recognises the value of the support we have had from local iwi, who are the main land owners around the lake.

"They have contributed to restoration ideas, providing land and access to sites so that we can undertake these actions, and they have changed their land use practices to meet the targets set for sustainable loads reaching the lake," Mr Cronin said.

"These projects now coming to fruition mark the culmination of more than 10 years' work, when at the outset this outcome may have been difficult to imagine."

Mr Cronin said another project was planned for later this year was de-stratification to prevent oxygen loss in the lake's bottom waters over summer and autumn.

"This will augment the actions already undertaken, and has the potential to accelerate the restoration process at Rotoehu. It is also an opportunity to test this restoration technique as a possible action we can take in other lakes," he said.

Rotorua Mayor and Rotorua Te Arawa Lakes Strategy Group Chairman Kevin Winters said it  was very pleasing to see that a device designed to help clean up lake waters could also fit so well into the environment and enhance the beauty of Rotorua's lakes while doing its work.

"I'm sure that future generations of residents and the many visitors to our region will appreciate this and other work being carried out to improve water quality in our lakes," he said. 

The Minister also visited the Waitangi Soda Springs phosphorous locking plant which is designed to remove 750 kilos of phosphorous each year from one of the main inflowing streams by dosing it with alum. He also saw the nitrogen plant at Tikitere.

Dr Nick Smith 2011 lowres