MEDIA RELEASE

Volcanic rock may improve lake’s water quality

For immediate release: Friday 7 September 2007

Lake Okaro will take a further step towards achieving its water quality goals this month.

During September the lake will have a layer of treated zeolite applied. Zeolite is a volcanic rock. It is ground to the size of sand and will sink to the bottom of the lake, forming a layer that will absorb phosphorus and nitrogen. The zeolite is sourced locally.

The step is one of the actions set in the Lake Okaro Action Plan which was signed off by the Rotorua Lakes Strategy Group in 2006 after a public consultation process. It sets in place the key steps to restore water quality within the lake.

Other actions already completed as a result of the action plan are the construction of a wetland, streams in the catchment being fenced off and riparian areas planted in native vegetation.

Andy Bruere, Lakes Project Manager at Environment Bay of Plenty says it’s great to see a local product being used to address water quality problems in the lake.

“Close monitoring will take place to determine the success of this work and we’re hopeful that we’ll be able to use this method in other Rotorua lakes to help improve water quality.”

Dr Chris Hickey, Research Scientist at National Institute of Water and Atmospheric Research (NIWA) says that the treatment is non-toxic and very effective at binding the nutrients.

“We’ve done tests using organisms and fish that live in the sediment and lake. We are continuing monitoring after the application to check the effect on fish populations and their health, as well as the effect on the lake water and sediment chemistry.”

Dr Hickey says that understanding how the treated zeolite can be best used for lake restoration will help manage nutrients and subsequent algal blooms and deoxygenation in other lakes.

The studies are a collaborative undertaking between Environment Bay of Plenty, University of Waikato, NIWA and Scion.

The lake will be closed to recreational use while the zeolite is applied to the lake bed – from September 10 to 14. For more information please visit www.envbop.govt.nz.

ENDS

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