Canterbury DHB’s Community and Public Health unit has lifted its algal bloom health warning issued for the
Selwyn/Waikirikiri River at Glentunnel. This was issued on 18 November 2020.
Recent cyanobacteria surveys of the Selwyn/Waikirikiri River at Glentunnel has shown the cover of potentially toxic
algae (benthic cyanobacteria) at the site has reduced and is now below levels that are of concern to public health.
Canterbury Medical Officer of Health Dr Cheryl Brunton says Environment Canterbury’s monitoring of the
Selwyn/Waikirikiri River at Glentunnel has finished for this season and will resume next summer when there is increased
likelihood of cyanobacteria growth.
A warning remains in place for ongoing algal blooms for:The Selwyn/Waikirikiri River at Coes Ford
Monitoring by Environmental Canterbury will continue until the warning can be lifted for this site.Facts about cyanobateria: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.
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Canterbury District Health Board
Canterbury District Health Board (CDHB) is a Christchurch, New Zealand based hospital and healthcare provider for the
Canterbury region of New Zealand. Our region extends from Kekerengu in the North, to Rangitata in the South and Arthurs
Pass in the West and comprises the six Territorial Local Authorities of Kaikoura, Hurunui, Waimakariri, Christchurch
City, Selwyn and Ashburton.
We collaborate with other health and disability organisations, stakeholders and our community to decide what health and
disability services are needed and how to best use the funding we receive from Government to improve, promote and
protect the health, wellbeing and independence of our population.
At the Canterbury DHB, our vision is to improve the health and wellbeing of people living in Canterbury.