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Health Warning Lifted For Algal Bloom In Pureora | Pareora River At SH1

Health New Zealand | Te Whatu Ora has lifted its algal bloom health warning issued for the Pureora | Pareora River at SH1. This was issued on 01/02/2024.

Recent cyanobacteria surveys of the Pureora/Pareora River at SH1 have shown that the Pureora | Pareora River flows are such that the riverbed at this site is dry and the potentially toxic algae (benthic cyanobacteria) in the river have dried out and are no longer harmful to humans or animals.

Dr Cheryl Brunton, Medical Officer of Health for the National Public Health Service, says Environment Canterbury’s monitoring of Pureora | Pareora River has finished for the season but will resume next summer when there is an increased likelihood of cyanobacteria growth.

Public health warnings in South Canterbury due to ongoing algal blooms are still in place for:

  • Hae Hae Te Moana River at Gorge
  • The entire Opihi River catchment
  • Temuka River at SH1 Bridge
  • Temuka River at Manse Bridge
  • Waihi River upstream of Wilson Bridge (Geraldine).

Facts about cyanobacteria

· Appears as dark brown/black mats attached to rocks along the riverbed

· A low cover of the algae can occur naturally but can increase rapidly during warmer months. Algal blooms are influenced by a combination of available nutrients in the water and sediments (such as nitrogen and phosphorus), a sustained period of low and stable flows, and favourable weather conditions (e.g., increased temperature, calm days)

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· It often has a strong musty smell and algal toxin concentrations can vary over short periods

· Although high river levels will remove the algal bloom, detached mats can accumulate along the shore and increase the risk of exposure to toxins

· 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:

Or contact Te Mana Ora | Community and Public Health on (03) 364 1777:

For more information about Mahinga Kai:

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