Health warning removed for algal bloom in the Selwyn/Waikirikiri River at Whitecliffs Domain and downstream of the Whitecliffs Domain near the picnic area

Canterbury District Health Board’s Community and Public Health unit has lifted its algal bloom health warnings issued along the Selwyn/WaikirikiriRiver at the Whitecliffs Domain and downstream of the Domain near the picnic area. The warnings were issued on 5 February and 21 January 2020.

Recent cyanobacteria surveys of the Selwyn/Waikirikiri River has shown the cover of potentially toxic algae (benthic cyanobacteria) in the river has decreased and are now below a level that is of concern to public health.

Canterbury District Health Board Medical Officer of Health Dr Cheryl Brunton says Environment Canterbury’s monitoring of the Selwyn River has now finished for the summer season and will resume next summer when there is increased likelihood of cyanobacteria growth. The public should therefore remain vigilant when accessing waterways and exercising dogs along rivers.

Warnings for the following waterways remain in place due to ongoing algal blooms:

• Ashley River from the Okuku River Confluence to SH1
• Lake Pegasus
• Lake Ellesmere

Facts about cyanobacteria in Rivers:

• 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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