People have been warned to stay away and also not let their dogs and livestock from swimming in the Ashley and Waipara Rivers as new survey as found high levels of toxic blue-green algae also called benthic cyanobacteria.

The Canterbury health authorities said that Humans and animals should stay away from Ashley River/ Rakahuri near State Highway 1 and the Waipara at Stringers Bridge till the time health warning is in place.

Alistair Humphrey, Canterbury Medical Officer of Health has said that algal mats might be able to produce toxins that are harmful to humans as well as animals. Coming in contact with these toxins may result in ‘skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips’, he warned.

Mr. Humphrey advised people to contact doctors immediately if such symptoms are experienced after coming in contact with the contaminated water and added that animals should be taken to vets for treatment if they get exposed to the water. He also warns against drinking even boiled water fro these rivers. Environment Canterbury has been monitoring the affected sites and will announce any changes in situation to the public.

The Blue-green algae occurs naturally in waterways throughout Otago and is more likely to be in summer months, explained John Threlfall, the Regional Council director of environmental information and science.

The time is suitable due to warm temperatures, more sunlight, and low, low stream force in rivers. The alga grows dark brown/black mats on rocks along the river, on water surface or on river banks.