| 10 Jan 2023

Health Warning lifted for Algal Bloom in Waihao River at Bradshaws Bridge

Te Mana Ora | Community and Public Health has lifted its algal bloom health warning issued for the Waihao River at Bradshaws Bridge. This was issued on 16 November 2022.

Recent cyanobacteria surveys of the Waihao River at Bradshaws Bridge have shown the cover of potentially toxic algae (benthic cyanobacteria) in the river has reduced and is now below levels that are of concern to public health.

Dr Cheryl Brunton, Medical Officer of Health for Te Mana Ora, National Public Health Service Te Whatu Ora, says Environment Canterbury’s monitoring of Waihao River at Bradshaws Bridge will continue to the end of this summer and then will resume next summer when there is increased likelihood of cyanobacteria growth.

The warnings for the following waterway(s) due to ongoing algal blooms are still in place.

  • Waihao River at Gum Tree Road
  • Pareora River at Pareora Huts
  • Saltwater Creek at SH1.

Facts about cyanobacteria

  • Cyanobacteria occur naturally but can increase rapidly during warmer months.
  • Algal blooms are caused by a combination of nutrients in the water (such as nitrogen and phosphorus), and favourable weather conditions (e.g. increased temperature, calm days).
  • If the water is cloudy, discoloured, or has small globules suspended in it, avoid all contact.
  • Not all cyanobacterial blooms are visible to the naked eye and toxins can persist after the blooms disappear.
  • Cyanobacterial concentrations can change quickly with changing environmental conditions (e.g. wind). If a health warning is in place avoid contact with the water.
  • 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 details visit: https://www.lawa.org.nz/explore-data/canterbury-region/

Or contact Te Mana Ora on (03) 364 1777:


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For further information, contact:

Karen Berry
Communications Manager
Te Whatu Ora South Canterbury  
021 139 7442