Canterbury District Health Board’s Community and Public Health unit has lifted its algal bloom health warning issued along the Selwyn/Waikirikiri River at Glentunnel. This was issued on 27 December 2019.

Recent cyanobacteria surveys of the Selwyn/Waikirkiri River at Glentunnel have shown the cover of potentially toxic algae (benthic cyanobacteria) in the river has decreased and is now below a threshold that was of concern to public health.

Canterbury District Health Board Medical Officer of Health Dr Cheryl Brunton says Environment Canterbury’s sampling of the Selwyn/Waikirkiri River at Glentunnel will continue to the end of this summer and then will resume next summer when there is increased likelihood of cyanobacteria growth.

The warning to remain out of the following waterway due to ongoing algal blooms is still in place:

• Selwyn/Waikirkiri River at Whitecliffs Domain and Whitecliffs Picnic Area

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).
• 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 information visit:

https://www.lawa.org.nz/explore-data/canterbury-region/

Or contact Community and Public Health on (03) 364 1777:

https://www.cph.co.nz/your-health/recreational-water/

For more information about Mahinga Kai:

https://www.cph.co.nz/wp-content/uploads/saf0112.pdf

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