More water warnings for the Waikato River

Thursday, 25 January 2024

Lake Arapuni on the Waikato River is the latest water body to have a health warning placed on it.

Recreational river users have been asked to stay out of the water at two more locations along the Waikato River after tests found a rise in the concentration of cyanobacteria in lakes Arapuni and Whangape.

Waikato Te Whatu Ora Medical Officer of Health Dr Elizabeth Becker said health warnings had been issued for both lakes while warnings remained in place for lakes Rotoroa (Hamilton Lake), Ngā Roto, Hakanoa, Waikare, Kainui, and Rotokauri.

Becker said a precautionary health warning was issued for Lake Arapuni based on scientific observation and monitoring of water quality, which suggested a recent rise in the concentration of cyanobacteria.

Scum produced by blue-green algal blooms are a tell-tale sign of cyanobacteria in the water and should be avoided.

A full public health warning was issued for Lake Whangape which has seen a dramatic rise cyanobacteria volumes.

She said all of the lakes mentioned should not be used for any activity that involved skin contact with the affected water.

“Swallowing water from lakes affected by blooms should also be avoided.

“If people still choose to use the lakes when warnings are in place, or any other lake where there are visible changes to water colour, they should shower and change their clothing as soon as possible afterwards, even if no symptoms are noticeable,” she said.

Cyanobacteria can release toxins which can trigger asthma and hayfever symptoms, and can cause skin rashes, stomach upsets, and in some cases neurological effects such as tingling around the mouth, headaches, breathing difficulties and visual problems.

These symptoms may not appear until some time after contact with the affected water.

Becker said scums were a particular risk because they contain a high level of toxins.

“If contact with scum does occur, skin should be rinsed clean and clothing changed as soon as possible. This warning is particularly important for children.

“Dog owners should prevent their dogs from drinking or swimming in the water, as dogs are particularly sensitive to cyanobacteria.”

A South Waikato District Council spokesperson said staff alerted the Waikato Regional Council (WRC) to a possible cyanobacteria outbreak in Lake Arapuni after locals spotted signs of blue-green algae in the river at Jones’ Landing late last week.

“The WRC are in the process of installing warning signs for blue-green algae at additional locations along the Waikato River this week, including at Jones’ Landing.

“They've also let us know with more hot, dry weather forecast by MetService, more cyanobacteria blooms are possible in rivers and lakes.

“As a general rule of thumb, if the water smells or is bright green like pea soup, it’s better to stay out,” the spokesperson said.

Waikato Te Whatu Ora Public Health Unit said anyone developing health problems after exposure to water in any of the district’s lakes should contact them by calling (07) 838 2569.