While still in early stages, suggestions from the group include aeration and dredging, feeding ducks on land or in another area rather than in the lake, removing plant matter, and sediment remediation such as treating the water with the chemical alum, which is used to purify water, or crab-shell extract.
Aeration can be achieved through the infusion of air into the bottom of the lake, lagoon or pond or by surface agitation to allow for oxygen exchange at the surface and the release of noxious gasses such as carbon dioxide, methane or hydrogen sulfide.
Kevin O'Shannessey, environmental advisor, Waikato Raupatu River Trust, said initially it was thought the issues could be resolved primarily by only using aerators but since realised the arsenic content from sprays used in the 1980s meant several issues would need to be addressed.
"When we realised there was arsenic in the bottom we realised it was more than just aerators that are needed. A blunt way [to get rid of it] would be to dredge the lake."
Mr Menkes said various options could be considered including removing plant material, which takes up the heavy metals and overload of nutrients causing the issues in the lake.
"One of the characteristics of this lake is it functions as a stormwater catchment. One theory would be to treat or process the stormwater as it comes in, so rather than have big pipes coming in from a roadway, vent it into some stream or creek where you have plants and soil, which could filter it. That would do a good job of [getting rid] of those nutrients like phosphorus and nitrate."
Mr O'Shannessey said there needs to be a long-term comprehensive plan for the lake.
"From our point of view, as long as there is a process and it is moving through and if it does take one or two generations everyone is still on the same page.
"The concern that we have is that councils, nothing has been achieved out of (the current plan). They're about to review it but of course we have a whole lot of new faces and new ideas instead of having a cohesive plan that carries over 20 years and every five years you go ok, 'what did we do in that five years, the next five year step is this'.
"What you get is each time they change their mind on how this should look, it is very easy for a group of councillors to say well you have no direction therefore you do not need the funding. The chances are if it is going in [the right] direction we could find the sponsorship for the shortfall."
Council's Parks and Open Spaces Unit has been monitoring and managing the algae issue for about five years, along with several other councils in the Waikato. Council will this year look to collaborate with experts to determine a solution to this problem.
In an effort to mitigate some of the algae-related issues, council has undertaken some work around the periphery of the lake, focussing on improvements to the quality of stormwater into the lake.
Their aim is to reduce the amount of nutrients and sediment going into the lake during stormwater events.
Addressing the algae issue is on council's agenda over the next 12 months.
Group members
David Menkes, MD PhD, medical academic and pharmacologist
Kevin O'Shannessey, environmental advisor, Waikato Raupatu River Trust
Tim Cox, PhD, water resources and water quality modeller
Michael Kahan, MB ChB FACOEM, occupational and environmental physician
Robin Janson, PhD, microbial ecologist/agricultural microbiologist
Anna Cox, PhD, project coordinator, Waikato Environment Centre
Rob Ebert, MB ChB, secretary, Hamilton Yacht Club
Alexander Gillespie, LLB LLM PhD, Professor of Law, University of Waikato
David Hamilton, PhD, Professor in Lake Restoration, University of Waikato
