Hamilton lake users warned of increasing cyanobacterial levels

Warnings for Lake Rotoroa (Hamilton Lake) remain in place with more recent laboratory testing showing increasing levels of cyanobacteria. Photo / APN

Health warnings remain in place at Lake Rotoroa because of increasing levels of cyanobacteria.

A health warning was placed in late August 2023 at Lake Rotoroa (Hamilton Lake) and remains in place with recent laboratory testing showing levels of cyanobacteria were increasing.

The warning signs at the lake would continue to show the ‘alert’ warning until two consecutive samples showed the risk had decreased.

Lakes Hakanoa, Whangape, Waikare and Kainui also continued to have a cyanobacterial health warning in place.

Cyanobacteria levels are regularly monitored at Lakes Rotoroa, Kainui, Rotokauri, Ngā Roto, Puketirini, Waikare, Whangape, Hakanoa and Waahi.

Lake Kainui and Lakes Hakanoa, Whangape and Waikare also continue to have cyanobacterial health warnings in place. Photo / Outdoor Kid

Dr Richard Wall, Te Whatu Ora Medical Officer of Health for Waikato, said lakes should not be used for any recreational activity that involves contact with the affected water where cyanobacteria health warnings are in place.

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

“Scums are a particular risk because they contained a high level of toxins. If contact with scum does occur, the skin should be rinsed clean and clothing changed as soon as possible. This warning is particularly important for children.

“If people do come into contact with the lake when warnings are in place, or any other lake where there are visible changes to watercolour, they should shower and change their clothing as soon as possible afterwards, even if no symptoms are noticeable.”

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

Te Whatu Ora Public Health Unit for Waikato would like to be informed about health problems that developed after exposure to any of the Waikato lakes.

Phone Waikato Public Health Service: 07 838 2569.