$2m price tag for weed harvesting

Thursday, 16 April 2015

Horowhenua ratepayers are each being asked to pay $10 a year towards the removal of weeds from Lake Horowhenua.

The proposal is part of Horizons Regional Council's draft Long Term Plan, currently out for consultation, and asks Horowhenua to cover the bulk of the cost of weed harvesting on the troubled waterway.

The operating cost of the work is projected to be $191,000 in the 2015/2016 financial year and $2.037 million over the 10-year life of the Long Term Plan.

Ratepayers in Horowhenua are being asked to pay 80 per cent of this each year, meaning a $10.22 annual contribution per ratepayer.

The remaining 20 per cent of the operating cost will be covered by ratepayers in the rest of the Manawatu/Whanganui region at a rate of $0.10 per $100,000 in capital value. This would equate to between $0.15 and $0.35 per ratepayer per year.

Horizons science manager Dr Jon Roygard told the council's environment committee this week the weed harvester had arrived in New Zealand.

The harvester was set to start working on the lake this summer.

 Horizons bought it in December for $250,000, part of its contribution to the $1.27 million Lake Horowhenua Clean Up Fund.

Former Horowhenua District councillor Anne Hunt has questioned the purchase of the harvester before any consultation on how to pay for its operation.

'It also reeks of pre-determination to buy equipment and then presume everybody will be happy to pay the exorbitant annual operating costs,' she wrote in her submission to the Long Term Plan.

She also questioned the effectiveness of the weed harvester in improving lake water quality.

'How can the owners of this privately-owned lake have any confidence that the weed harvester … will do anything more than mow a pathway for the rowers to follow for their recreational use of this lake?'

Weed removal was recommended for the lake in a 2011 report by Niwa scientist Dr Max Gibbs that formed the basis for the creation of the Lake Horowhenua Accord that administers the clean-up fund.

Gibbs calls the management of lake weed 'the key to restoring the water quality of Lake Horowhenua and its fishery'.

The weeds in the lake remove nitrogen from the lake in spring time, which it then releases when water flows into the lake are low.

This nitrogen promotes the algae growth that caused Gibbs to warn that water in the lake had the potential, at certain times, to be lethal to a child or dog.

Removing the weed when it is loaded with nitrogen was a method to quickly remove nutrients from the water, Gibbs says.

He wrote that weed harvester did not prevent weeds from regrowing and harvesting would need to be an ongoing management option, as opposed to spraying or releasing weed-eating fish such as carp into the lake.

Horizons is aiming to remove 50 hectares of weed from the 300-hectare lake each year. It will also consider using the weed harvester in other lakes around the region.