Look out for toxic algae, it's here

  • Published Date 01 Feb 2019

Hot weather and low rainfall have combined to increase the risk of toxic algae throughout the greater Wellington region, with some rivers now over the limit for safe swimming.

People are strongly advised not to swim in the Hutt River between Moonshine Bridge and Fairway Drive Bridge, or in the Pakuratahi River from SH2 to its confluence with the Hutt River in Kaitoke Regional Park.

Children should be kept away from water in these sites and dogs should be kept on a lead.

While currently below "no swim" trigger levels, toxic algae cover is also rising in Wairarapa at Greater Wellington's Waipoua, Waingawa and Ruamahanga river monitoring sites in Wairarapa, and in the Otaki and Waikanae rivers in Kapiti.

"No detached mats of toxic algae have yet been seen at any of our monitored sites. However this could change rapidly especially during warm weather, so we are urging people to be careful near all waterways throughout the region," says Dr Mark Heath, Senior Environmental Scientist at Greater Wellington.

Given the rapid growth of toxic algae, and its potential change in coverage between weekly monitoring points, people are also urged to know what it looks like. They should check out information signs around popular swimming holes and visit Greater Wellington's Is it Safe to Swim? website and Facebook page for more information about, and images of, toxic algae.

Current toxic algae status – monitored 29 - 31 January 2019

Kāpiti Coast: The Otaki and Waikanae Rivers both remain below guideline levels at approximately 5% cover, however, KCDC monitoring officers have noticed a significant increase in toxic algae coverage and it has become concentrated in some areas (approximately 15% cover).  

Hutt River: Toxic algae exceed the 20% cover guideline level at the Silverstream Bridge site. All other monitoring sites were below guideline levels.

Ruamahanga: Toxic algae cover is at approximately 10% cover at our Waipoua and Waingawa monitoring sites, while toxic algae at Ruamahanga River sites are at approximately 5% cover.

Pakuratahi River: The Pakuratahi River at Kaitoke Forest Park has a significant toxic algal bloom (20% cover).

Waipapa Stream: The Waipapa Stream near Red Rocks on Wellington’s South Coast also has a significant bloom.

Updated April 28, 2022 at 10:43 AM

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