Swimmers and dog owners are being advised to avoid areas of the Hutt River after high levels of toxic algae were identified in the waterway.
Greater Wellington Council says algae, including detached algal mats, had been identified at two monitoring sites along the river.
“Monitoring data at the Hutt River at Silverstream Bridgelaunch, and Hutt River upstream of Silverstream bridgelaunch returned red alert levels of toxic algae. This means there are high levels of cyanobacteria present rendering the site unsuitable for swimming and it should be avoided,” said Greater Wellington Marine and Freshwater Team Leader, Dr Evan Harrison.
He said toxic algae presented a significant health risk as swallowing water containing the bacteria can make people very sick, with pieces as small as a 50c coin enough to kill dogs.

The presence of detached algal mats carries increased risk as the algae has broken off rocks and can wash up on the river’s edge where dogs, who love the smell and taste, can easily spot it. Young children should also be watched closely if in the area to ensure they do not come into contact with toxic algae.
Greater Wellington monitors a large proportion of freshwater and coastal sites around the region, publishing updated safe swimming data weekly on the LAWA website.
“There are plenty of spots we monitor, and a suitable swimming location may be just a stone’s throw away. Excluding Silverstream, there are four further locations we monitor in Upper Hutt.”
“As Summer rolls on, people taking the plunge with or without their four-legged friends should continue to check online before hoping into the water and be aware of what toxic algae looks like,” said Dr Harrison.
Swimmers and dog owners are being advised to avoid areas of the Hutt River from the Moonshine Bridge down to just upstream of Taita Rock – but not including TaitaRock.