Due to toxic algae, Masterton District Council has closed Henley Lake for recreational purposes. PHOTOS/TOM TAYLOR
Lake closed to rowers, swimmers, and canines
Masterton District Council has again closed Henley Lake for recreational purposes after tests showed high concentrations of toxic algae in its water.
The council issued a public health warning after finding high levels of cyanobacteria, also called blue-green algae.
Henley Lake was frequently closed in summer, having previously been closed in January 2019 and January 2020 by the council.
Masterton District Council [MDC] regulatory services manager Steven May said the green space around the lake – popular with walkers – was still safe to use. However, he said people should stick to the paths and stay away from the water’s edge.
“People should avoid all contact with water in Henley Lake – in particular children, pregnant women, and the elderly,” May said.
Cyanobacteria also posed a high risk for dogs, which should be kept out of the water and away from the lake.
“Anyone who believes their dog may have eaten algae or ingested water should contact their vet immediately,” May said.
A dog owner at Henley Lake on Monday said he had heard a warning about the toxic algae on the radio and was keeping his dog on a short leash to avoid it coming into contact with the water.
However, he said he had seen other dogs running about off-lead.
“We smelled it as we came in,” he said of the toxic algae.
“It’s just the water levels and the heat.”
The warning came after a similar toxic algae alert for Masterton’s Fourth Street Lake in November.
Most rivers and lakes in New Zealand contained cyanobacteria, but in warm temperatures, prolonged periods of sunshine, and low water flow, the algae could grow to very high levels.
Exposure to the toxic algae could cause skin rashes, nausea, and tingling or numbness around the mouth or tips of fingers. Pregnant women, children, and the elderly were more likely to be affected.
MDC monitored cyanobacteria weekly at Henley Lake during the summer and frequently closed the lake for recreational use, including rowing, dragon boating, and miniature boats.
The water in Henley Lake came from the Ruamahanga River. However, no water flowed into the lake when the river dropped below a certain level.
According to the Greater Wellington Regional Council [GWRC], toxic algae blooms generally lasted until heavy rain flushed them out.
GWRC said a piece of toxic algae the size of a 50-cent coin was enough to kill a dog.
GWRC did not monitor lakes in the Wellington region, saying river swimming spots were more popular.
However, it said that if the water in a lake had a “pea soup appearance”, it could contain toxic algae.
In rivers, people could look for black, green, or brown slime on rocks or brown or black “mats” as signs of the algae.
According to Land Air Water Aotearoa [LAWA], all monitored swimming spots in the Wellington region were currently safe for swimming. However, the Makakahi River at Eketahuna Motor Camp was currently deemed unsuitable for swimming after a sample was taken on January 4.
LAWA advised people not to swim for two to three days after heavy or prolonged rain, even at sites that generally had good water quality, because the rain could flush contaminants from land into waterways.