Willow removal operation gets underway

9 February 2018

Cutting edge technology is about to be used in the fight to keep invasive aquatic weed Lagarosiphon out of Lake Wakatipu - literally.

On Sunday (11 February) divers working by hand - and also with underwater chainsaws, barges and other equipment - are scheduled to begin removing dead submerged willow trees from the Upper Kawarau River, which are a haven for the weed to grow and potentially spread into the lake. The work is projected to cost around $142,000.

"Thanks to funding from the Otago Regional Council, with support from Land Information New Zealand, the Queenstown Lakes District Council and the other members of the Lake Wakatipu Aquatic Weed Management Group, we are pleased that this critical piece of work in the fight against Lagarosiphon can now get underway," says LINZ Biosecurity Manager Dave Mole.

"The operation will be highly technical and challenging, and given it hasn’t been attempted before, it may need to be stopped due to its complexity and risk. But all going to plan, subject to safety considerations and river conditions, we are confident that the work can be completed within approximately two to three weeks.

"Removing the dead and submerged willows will also make it harder for the weed to hide and take hold, which helps us to keep the lake clear."

Otago Regional Council Director of Environmental Monitoring and Operations, Scott MacLean, strongly supported the project. The council had been extremely happy to collaborate with the other agencies, he said.

"We know that the issue of Lagarosiphon is high on the community’s priority list in terms of environmental management and it’s essential that we take all measures within our control to stop the spread of this weed."

The work is being carried out in the stretch of river between Kawarau Falls Bridge and Remarkables Park, with all water craft users reminded to take extreme care when near barges and divers.

Meanwhile, ongoing efforts to stop the spread of Lagarosiphon are making positive progress, with the weed not yet gaining a foothold in the lake - something all agencies are determined to keep up.

However, boaties and other lake users are still being encouraged to do their part to keep the lake weed-free by following the Check, Clean, Dry message, as agencies cannot do the job alone.

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