By TONY GEE
The Northland Regional Council is warning people not to swim or use water in Lake Omapere, north of Kaikohe.
Its public health warning, issued after advice from Northland Health, also applies to the lake's Utakura River outlet.
Regional council monitoring manager Tony Phipps said warm and calm weather this month
had increased the amount of potentially toxic blue green algae in the 1200ha lake.
The entire lake is dominated by blue-green algae, giving it a bright green, soupy appearance and a bad smell.
Mr Phipps said the lake's algae-rich water was flowing into and contaminating the upper reaches of the Utakura River.
The lake and river water was unfit for human and stock consumption, and people should avoid coming into contact with it.
Among possible health effects from the water were gastrointestinal illnesses and skin irritations.
Algal blooms of varying size were expected to continue in the lake until temperatures started to fall with the onset of autumn, Mr Phipps said.
Meanwhile, $135,000 from the Environment Ministry's Sustainable Management Fund is to go towards a $300,000 joint regional council-Lake Omapere Trust project that aims to restore the lake to good health.
Lake trustees and the council will use the money for a two-year lake restoration and management plan.
The work will include development of an aquatic weed management programme for pest plants such as oxygen weed, improving the lake's indigenous flora and fauna - native plants and freshwater mussels - and water quality monitoring.
Individual farm environment plans may be developed with local landowners to try to minimise farm nutrient run-off into the lake.
Lake Omapere has had algae and weed problems for 20 years.
In September, 2000, it contained about 5500 tonnes of oxygen weed which smothered the entire lake bed.
Weed levels were drastically reduced after more than 40,000 weed-eating grass carp were released into the lake, and surface algal blooms blocked life-giving sunlight needed by the deeper oxygen weed to survive.
Mr Phipps said Lake Omapere's algal contamination was part of a continuing problem affecting many other similar lakes around the country.
Herald Feature: Conservation and Environment
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