The health of Lake Wanaka is continuing to improve and its
recreational opportunities are increasing, thanks to a
programme for controlling the aquatic weed lagarosiphon.
A recent lake inspection showed progress containing the weed
was well ahead of schedule.
Organised by the Lagarosiphon Management Committee, which was
formed in 2004, the inspection included representatives from
the Guardians of Lake Wanaka, Otago Regional Council,
Department of Conservation, Queenstown Lakes District
Council, Land Information New Zealand (Linz) and Niwa, which
provides scientific advice and input.
The committee developed a 10-year management plan - now in
its ninth year - to control the weed's spread and protect the
lake's native aquatic biodiversity, using a combination of
suction dredging, hand weeding and the herbicide diquat.
ORC environmental monitoring and operations director Jeff
Donaldson said the lagarosiphon containment line had now been
moved further south to extend from the southern tip of the
peninsula to the southern end of Bishops Bay, which
demonstrated the good results of the control programme to
''There's now improved access to parts of the lake, for
example at Paddock Bay and Bishops Bay, which were previously
restricted by dense weed beds. There's also been some
regrowth of native aquatic plants.
''It means the committee can direct weed control efforts on
to areas ... closer to Wanaka township.''
However, Guardians of Lake Wanaka's Peter Hook said
continuing control operations in Lake Wanaka was crucial.
''If lagarosiphon's left untreated or proper precautions
aren't taken when using the lake, it will tarnish the lake's
natural heritage values, limit access for future generations
and may result in spread to other New Zealand lakes such as
Lake Wakatipu, which is free of lagarosiphon.''
Also known as South African oxygen weed, lagarosiphon can
establish quickly in waterways if left untreated, choking the
waterway and smothering native aquatic plant communities. It
also poses safety problems for lake users by affecting
underwater visibility, creating a hazard for swimmers, water
skiing and fishermen.
The public can help stop the spread by visually checking
boats or other craft for weed fragments after lake use and
hosing down and drying all equipment such as water skis,
biscuits or fishing gear.