MEDIA RELEASE

Tuesday, January 13, 2015

Weed harvesting to remove toxic lake nutrients

Horizons Regional Council, along with its Lake Horowhenua Accord partners, have purchased a weed harvester to remove approximately 50 hectares of weed annually from Lake Horowhenua and improve water quality.

The Aquarius Systems Ltd weed harvester was purchased with the aid of funding from Central Government’s Fresh Start for Freshwater Clean-Up Fund as part of the Lake Horowhenua Accord.

Following two NIWA reports presented to Horizons, which identified weed harvesting as a key action to improve water quality, Council approved the purchase of a harvester in December. Dr Jon Roygard, freshwater and science manager, says a number of models were considered before Council decided upon the HM420 model which is the same as what Bay of Plenty Regional Council uses on its Rotorua lakes.

“Nutrients are currently a key issue for Lake Horowhenua. Lake weed absorbs nutrients as it grows and causes toxic conditions for fish and other lake life when it dies off in summer,” says Dr Roygard.

“Nutrients also lead to algae blooms that make the lake unsuitable for recreational use. As the lake weed has a considerable influence on the lake’s chemistry, harvesting the weed is an effective way of removing nutrients from the lake.”

Dr Roygard says from 2015, weed harvesting will take place on an annual basis and target the peak spring growth.

“As a starting point, Horizons will be aiming to harvest about 50 hectares of weed from the approximately 300 hectare lake. Thorough monitoring has been undertaken to determine the current water quality state and weed removal will be closely monitored, allowing the harvest programme to be refined as we go along.”

Horizons chairman Bruce Gordon says “improving the water quality of Lake Horowhenua has been a key focus for Horizons, the Lake owners and the Horowhenua community for a number of years now”.

“Weed harvesting has been identified in the Lake Horowhenua Accord Action Plan as a key action to improve water quality so we are really pleased to now have the equipment to do this. Operational costs to remove the weed will be discussed during the 2015-25 Long Term Plan process in April,” he says.

Horizons, along with the Lake Horowhenua Trust, Lake Horowhenua Domain Board, Horowhenua District Council and the Department of Conservation are part of the Lake Horowhenua Accord that sets a vision, objectives, key issues and management goals for the Lake. An Action Plan, which can be found atwww.horizons.govt.nz, has been put together by these partners to measure progress and weed harvesting is part of this.

ENDS

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