Glacier-fed Lake Wanaka can look clean and idyllic, but the
algae growing in its depths is frustrating many Wanaka
residents, as the resort's water supply is drawn from the
192sq km lake. Photo by Matthew Haggart.
A non-toxic, naturally occurring algae has been plaguing
Wanaka residents for several years but attempts by the
Queenstown Lakes District Council to reduce or eliminate it
The very fine algae seems not to affect older houses and
appliances, where, unfiltered, it passes straight through the
In those situations, the tasteless algae is not visible in a
glass of water.
But in newly built or renovated homes fitted with modern
appliances with fine mesh filters, the algae can soon
accumulate and become an unsightly brown mush in shower heads
and basin plug holes.
The weather and lake conditions are believed to be factors
behind variations in build-up from one summer to the next.
More nutrients in the lake, possibly through climate change,
has been suggested as an explanation for algae bloom.
The council spent $66,000 replacing coarse intake screens
with finer mesh screens in 2009 and more intake work will
The replacement mesh screens appear not to have made a
difference to affected householders.
The water mains were flushed last summer, but the algae just
built up again.
Tests have concluded the algae is not toxic and there are no
water quality issues.
The tests identified 13 different types of algae in Lake
Wanaka, so the council is analysing which ones are the
culprits and what the best solutions could be.
Deep-water sampling took place in May to determine when the
algae occurs, its type and structure and the depth and
temperature at which it grows.
The tests showed the algae is present in both deep and
shallow water all year round.
It was not clear whether the deep water algae was actually
growing there or was dead and had sunk; more testing is to
take place this summer.
Meanwhile, a chorus of complaints to the media and plumbers
from those worst affected has continued, but the council had
only recorded 17 complaints over four years by May.
That low number surprised Wanaka councillors and sparked a
meeting with plumbers to learn more about the extent of the
All along, council officers and Wanaka Community Board
chairman Lyal Cocks have encouraged householders to manage
the situation until a solution can be found.
The council says people noticing reduced water pressure in
their homes should clean their filters or get a plumber to do
it for them.
Primary filters could also be installed near the toby (meter
tap) at the property boundary, with plumbing costs likely to
be several hundred dollars.
An information flyer has also been prepared, and is available
from the council offices, explaining the problem and giving
advice on how to deal with filters.
Council officers say a detailed filtration system at the cost
of "several millions" may be the only answer.
Water operations manager Martin Ellis said earlier this year
most of the Wanaka community would have to indicate through
community consultation that was what they wanted.
Once such a system was installed, there would be ongoing
It might be more cost effective for the council to help on a
case-by-case basis, Mr Ellis suggested.