High levels of toxic algae in Wairarapa and Hutt Valley rivers

Red alert level warnings are in place for several rivers in the Wairarapa and Te Awa Kairangi Hutt River due to widespread toxic algae.  

People are advised not to swim or let their dogs near the water at the following locations:

• The Ruamāhanga River from Double Bridges to Kokotau, including Te Ore Ore and The Cliffs.  
• The length of the Waipoua River, where some areas are up to 60% algae coverage.
• Te Awa Kairangi Hutt River and upstream of the Silverstream Bridge. 

Greater Wellington senior advisor Penny Fairbrother says the warm weather means toxic algae has “exploded” across the region.

“Toxic algae produces a neurotoxin which is harmful to humans and lethal for dogs if ingested,” says Penny. 

“We strongly advise that people avoid contact with water and keep all dogs and children away from the river’s edge. 

“Ingesting even a small amount of toxic algae, the size of a 50-cent coin, can be enough to kill a dog.” 

Toxic algae grows on rocks in the riverbed and forms leathery, dark green or black mats. The algae produces oxygen which lifts the algae off the rocks, forming detached mats that accumulate at the river’s edge.  

“These detached mats pose the greatest risk, particularly to young children who like to put things in their mouths, and dogs. As the algal mats dry out in the sun, many dogs seem to find the musty smell of the algae irresistible,” adds Penny. 

Dog owners who think their animals have swallowed toxic algae, or shows signs of lethargy, muscle tremors, fast breathing, paralysis or convulsions, should go to the nearest vet immediately. 

People who have been in contact with toxic algae and are feeling unwell, should see a doctor or ring Healthline on 0800 611 116.  

Greater Wellington is currently monitoring popular river swimming spots for toxic algae on a weekly basis.   

People are encouraged to visit the LAWA website for warnings and alerts before visiting their local river this summer:.

Learn more about toxic algae