Health Warning – Algal Bloom in Ashley and Waipara Rivers

Canterbury health authorities have issued a warning after water surveys of the Ashley and Waipara Rivers this week found high levels of potentially toxic blue-green algae (benthic cyanobacteria).

Humans and animals, particularly dogs, should avoid the Ashley River/ Rakahuri near State Highway 1 and the Waipara at Stringers Bridge until the health warnings have been lifted. 

Canterbury Medical Officer of Health Alistair Humphrey says the algal mats can produce toxins harmful to humans and animals.

“Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips. If you experience any of these symptoms after contact with contaminated water, visit your doctor immediately,” he says.

Drinking contaminated water, even boiled water, from these rivers should be avoided at all times, Dr Humphrey says.

Animals should be taken to a vet immediately if they come into contact with the contaminated rivers.

Environment Canterbury is monitoring the sites and the public will be advised of any changes in water quality.

Facts about cyanobateria:

• The algae occur naturally but can increase rapidly during warmer months. It grows as dark brown/black mats attached to rocks along the river, on the water surface, or on riverbanks. 
• It often has a strong musty smell and algal concentrations can vary quickly with changing environmental conditions.
• High river levels will remove the algal.
• If a health warning is in place avoid contact with the water.
• Although district or city councils may place warning signs, these may not be seen at the numerous river access points, hence the need for people/ dog-walkers to treat every low-flowing river cautiously.

For further information visit http://ecan.govt.nz/services/online-services/monitoring/swimming-water-quality/Pages/river-warnings.aspx

Or contact Community and Public Health on (03) 364 1777.