River warnings

What is benthic cyanobacteria?

Benthic cyanobacteria attaches to river beds, and can detach and float freely. Its appearance depends on species - Phormidium looks like a thick and velvety black or brown mat and has a musty, earthy smell, while Nostoc forms small globular mats.

Routine monitoring for potentially toxic benthic cyanobacteria is carried out at a number of river sites that are popular for recreation throughout Canterbury.

Popular rivers and streams used for recreation are currently being monitored around Canterbury for blooms of potentially toxic benthic cyanobacteria.

Popular bathing sites with moderate-high cyanobacteria cover now have warnings in place.  However, sites with low cover of cyanobacteria can rapidly increase at anytime and river users should keep vigilant. For what to keep an eye out for and more information visit Cyanobacteria warnings or read our brochure

See below sites for health warnings... 

Waihi River at Wilson Street footbridge, Geraldine

15th January 2020
 

Monitoring has identified moderate cover of potentially toxic cyanobacteria algae in the Waihi River at Wilson Street footbridge, Geraldine. Community and Public Health have issued a health warning and signage will be erected at that site. 

There are also other access points along the Waihi River that may have cyanobacteria present and people are advised to check for the presence of cyanobacteria and avoid contact.

Warnings remain in place at:

  • Waihao River at Bradshaws Bridge
  • Opihi River at SH1
  • Opihi River at Waipopo Huts
  • Opihi River at Salesyard Bridge

Opihi River at Salesyard Bridge

15th January 2020
 

Monitoring has identified moderate cover of potentially toxic cyanobacteria algae in the Opihi River at Salesyard Bridge.

Community and Public Health have therefore issued a health warning and signage will be erected at that site.

Canterbury Medical Officer of Health Dr Alistair Humphrey says the algal mats can produce toxins harmful to humans and animals.

“Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips,” Dr Humphrey says.  “If you experience any of these symptoms, visit your doctor immediately, also let your doctor know if you’ve had contact with dark brown/black algal mats or water in this area.”

 Once monitoring indicates that these rivers are safe, the signs will be removed.  Humans and animals, particularly dogs, should avoid these areas until the health warning has been lifted.

Opihi River at Waipopo Huts

8th January 2020
 

Monitoring has identified moderate cover of potentially toxic cyanobacteria algae in the Opihi River at Waipopo Huts. Community and Public Health have therefore issued a health warning and signage will be erected at that site. Once monitoring indicates that these rivers are safe, the signs will be removed.

There are also other access points along the Opihi River that may have cyanobacteria present and people are advised to check for the presence of cyanobacteria and avoid contact.
Warnings remain in place at:

  • Waihao River at Bradshaws Bridge
  • Opihi River at SH1
  • Opihi River at Salesyard Bridge 

Humans and animals, particularly dogs, should avoid these areas until the health warning has been lifted.

Ashley/Rakahuri River at the Rangiora-Loburn Bridge

6th January 2020
 

The Community and Public Health division of Canterbury DHB has issued a health warning for the Ashley/Rakahuri River at the Rangiora-Loburn Bridge (also called the Cones Road Bridge) after identifying potentially toxic blue-green algae (benthic cyanobacteria) in this area.

People and animals, particularly dogs, should avoid the area of the Ashley/Rakahuri River at the Rangiora-Loburn Bridge until the health warning has been lifted. There are also other access points along the Ashley River that may have cyanobacteria present, and people are advised to check for the presence of cyanobacteria and avoid contact.

Canterbury Medical Officer of Health Dr Alistair Humphrey says the algae look like dark brown to black mats and can produce toxins harmful to people and animals.

“Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips,” Dr Humphrey says.

“If you experience any of these symptoms, visit your doctor immediately, and also let your doctor know if you’ve had contact with dark brown/black algal mats or water in this area.”

Reticulated town water supplies are currently safe, but no one should drink water from the river at any time.  Pets that show signs of illness after coming into contact with algal mats should be taken to a vet immediately.

Waihao River at Bradshaw’s Bridge

26 November 2019
 

Monitoring has identified moderate cover of potentially toxic cyanobacteria algae in the Waihao River at Bradshaw’s Bridge. Community and Public Health have therefore issued a health warning and signage will be erected at that site. Once monitoring indicates that these rivers are safe, the signs will be removed.

Humans and animals, particularly dogs, should avoid these areas until the health warning has been lifted.

There may also be other access points along the Waihao River that have potentially toxic cyanobacteria present and people are advised to check before entering the water and avoid contact.

Selwyn River at Glentunnel (immediately below Swimming Hole)

27th December 2019
 

The Community and Public Health division of the Canterbury District Health Board has issued a health warning after potentially toxic blue-green algae (benthic cyanobacteria) were found in Selwyn River at Glentunnel (immediately downstream of Glentunnel Camping Ground Swimming Hole).

People and animals, particularly dogs, should avoid the area directly below the swimming hole of the Selwyn River at Glentunnel until the health warning has been lifted.

There are also other access points along the Selwyn River that may have cyanobacteria present and people are advised to check for the presence of cyanobacteria and avoid contact.

Opihi River at SH1

28th November 2019
 

Monitoring has identified moderate cover of potentially toxic cyanobacteria algae in the Opihi River at SH1. Community and Public Health have therefore issued a health warning and signage will be erected at that site. Once monitoring indicates that these rivers are safe, the signs will be removed.  

There are also other access points along the Opihi River that may have cyanobacteria present and people are advised to check for the presence of cyanobacteria and avoid contact.

Warnings remain in place at: Waihao River at Bradshaw’s Bridge. Humans and animals, particularly dogs, should avoid these areas until the health warning has been lifted.