Lake algae treatment options investigated
An algae present in Lake Wanaka for several years has been confirmed in Lake Wakatipu and has been reported in the
Queenstown water network since mid-2016. It has also recently been identified at low levels in Lake Hawea, although it
has not affected the Hawea water network.
Scientists have confirmed that the algae, Cyclotella bodanica (better known as lake snow) doesn’t present a health risk,
but it can cause a nuisance by blocking up water filters on commercial premises and residential appliances such as
dishwashers and washing machines.
Queenstown Lakes District Council is working with the Otago Regional Council and their scientific research partners to
learn more about the algae, what causes it, why it has affected Lake Wanaka and now Lakes Wakatipu and Hawea, and what
treatment options are available.
QLDC has also been looking into treatment options to reduce the effect the algae has on our water network. A decision
has yet to be made on treatment options, with the results of a trial of a filter system used at an intake in Wanaka
being evaluated to see if it is a feasible large scale treatment solution.
Other treatment options include installing in-line filters throughout the water networks that take water from Lakes
Wanaka and Wakatipu, moving from a lake intake to a bore water supply, or looking at expanding the filter system
trialled in Lake Wanaka.
The issue of algae in the water supply isn’t easily solved, explains QLDC Chief Engineer Ulrich Glasner. “While we would
prefer there to be no algae in our water supply, the fact of the matter is that it’s there and it is having an effect on
our network, both in Wanaka and Queenstown.”
Mayor Jim Boult agrees, but points out that good data is needed before committing to a treatment option. “We’re working
with the ORC to better understand the origins of the algae, but in the meantime we’re looking into all the available
choices to treat our network. There are potential solutions both in the short term and further down the track, but they
all involve a cost to ratepayers and as such we need detailed information to consider before we make any decisions.”
“Earlier this year the Minister for the Environment, Hon Nick Smith, announced the Freshwater Improvement Fund, a $100
million fund to support initiatives to clean up New Zealand’s fresh water. I’ve had initial discussions with the
Minister regarding this and he has indicated that water quality in our district’s lakes is high on his agenda, and
research into the issue of lake algae would be likely to qualify for investment using this fund.”
More information about how to identify if you have a problem related to lake algae, and a flyer ‘Managing algae in your
water supply’ are available at www.qldc.govt.nz/services/water-services/lake-algae/
ENDS