By ANGELA GREGORY
OMAPERE - A Maori trust is considering lodging a Waitangi Tribunal claim to raise the level of a Northland lake in danger of self-destructing.
An algal bloom and weed growth are threatening the health of Lake Omapere, north of Kaikohe, and scientists fear it could turn into a large
toxic soup by the end of the year.
The chairman of the Lake Omapere Trust Board, Wallace Wihongi, believes the problem was created when the lake was partly drained after the First World War to provide farmland for returned servicemen.
The shallow waters in the remaining 1200ha waterway had prompted weed growth and the water quality deteriorated, he said.
In 1985, the lake became overrun with an introduced oxygen plant.
Scientists believe the weed congestion somehow led to an outbreak of algal bloom that created toxic water, killing fish and birdlife.
The pollution also travelled along the Utakura River to the upper Hokianga Harbour.
Last month, the Northland Regional Council warned that the water quality might collapse again after an outbreak of algae was discovered at the start of this year.
Mr Wihongi said his people had tried all they could to look after the Ngapuhi taonga (treasure), but the Crown had failed to meet its responsibilities.
About five years ago, the trust sought Department of Conservation approval to release grass carp into the lake to control the weeds.
The project had still not received the go-ahead, and the delays had added to the cost.
A $1.2 million application to the Environment Ministry's sustainable management fund recently failed.
Mr Wihongi said the trust considered that the Crown had created the problem and should fix it.
The trust would now look seriously at lodging a Waitangi Tribunal claim so it could raise the lake level about 3m back to its original depth.
That could swamp hundreds of hectares of farmland, he said.
"But we never gave up ownership of the original lakebed."
The trust would also consider seeking compensation for lost income.
It had previously sold the lake water to the former Kaikohe County Council, and the lake still provided some food for Maori.
"If the lake goes bad, a lot of eels will die."
Regional council monitoring officer Dwane Kokich said the algal bloom had been knocked back by the cooler weather.
"But my gut feeling is the lake will pack up when the weather warms up again."
Mr Kokich said the algae responsible for the present discoloration was Microcystis aeruginosa, the same species that dominated the bloom which devastated the lake in 1985 with similar levels of weed growth.
He said the lake could end up resembling a reeking green soup, and the polluted water might in turn harm river and harbour ecologies.
