Lake health warnings

We monitor lake sites regularly over the summer to check for bacteria (faecal contamination) and toxic algae.

Each swim site is given a long-term grade prior to each summer monitoring season for suitability for swimming and recreation. The grade is based on the last five years of bacteria sampling. Sites that are not recommended for swimming because of their long-term grade are red on the Land Air Water Aotearoa (LAWA) website and signage should be in place at the site.

Temporary Health warnings are issued when a site was graded as good to swim but there is now an increased risk of cyanobacteria or faecal contamination. Advisory notes may be present but are not an official public health warning.

Toxic algae (cyanobacteria) can occur in any waterway, at any time, so it is important that you know what it looks like. Find out more about toxic algae and how you can protect yourself and your animals.

Faecal contamination poses a risk to health, it can cause gastrointestinal illnesses, respiratory diseases, and eye, ear, nose, throat and skin infections.

Find out more about our monitoring programme.

Temporary health warnings

Te Roto o Wairewa/Lake Forsyth

1 February 2024
 

Te Mana Ora | Community and Public Health has issued a health warning after toxic blue-green algae (planktonic cyanobacteria) was found in Te Roto o Wairewa/Lake Forsyth.

People should avoid the lake and animals, particularly dogs, should not be allowed near the water until the health warning has been lifted.

Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips. If you experience any of these symptoms visit your doctor immediately and please let your doctor know if you have had contact with the lake water.

No one should drink the water from the lake at any time. Boiling the water does not remove the toxin.

Animals that show signs of illness after coming into contact with algal mats or scums should be taken to a vet immediately.

Fish and shellfish can concentrate toxins and their consumption should be avoided. If fish are eaten, remove the gut and liver and wash in clean water.

We monitor the lake weekly during summer and the public will be advised of any changes in water quality that are of public health significance.

Lake Pegasus

5 January 2024
 

Te Mana Ora | Community and Public Health has issued a health warning after toxic blue-green algae (planktonic cyanobacteria) was found in Lake Pegasus.

People should avoid the lake and animals, particularly dogs, should not be allowed near the water until the health warning has been lifted.

The type of cyanobacteria that is currently present is Dolichospermum (formerly called Anabaena) which can be present as green globules floating in the water column or form surface scums or sheens.

Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips. If you experience any of these symptoms visit your doctor immediately and please let your doctor know if you have had contact with the lake water.

No one should drink the water from the lake at any time. Boiling the water does not remove the toxin.

Animals that show signs of illness after coming into contact with algal mats or scums should be taken to a vet immediately.

Fish and shellfish can concentrate toxins and their consumption should be avoided. If fish are eaten, remove the gut and liver and wash in clean water.

We monitor the lake weekly during summer and the public will be advised of any changes in water quality that are of public health significance.

Lake Hood (near Ashburton)

5 January 2024
 

Te Mana Ora | Community and Public Health has issued a health warning after toxic blue-green algae (planktonic cyanobacteria) was found in Lake Hood.

People should avoid the Lake and animals, particularly dogs, should not be allowed near the water until the health warning has been lifted.

The type of cyanobacteria that is currently present is Dolichospermum (formerly called Anabaena) which can be present as green globules floating in the water column or form surface scums or sheens.

Exposure may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips. If you experience any of these symptoms visit your doctor immediately and please let your doctor know if you have had contact with the lake water.

No one should drink the water from the lake at any time. Boiling the water does not remove the toxin.

Animals that show signs of illness after coming into contact with algal mats or scums should be taken to a vet immediately.

Fish and shellfish can concentrate toxins and their consumption should be avoided. If fish are eaten, remove the gut and liver and wash in clean water.

We monitor the lake weekly during summer and the public will be advised of any changes in water quality that are of public health significance.

Mata Kopae/St Anne’s Lagoon

07 July 2022
 

Long-term water testing indicates that potentially toxic cyanobacteria bloom periodically in Mata Kopae/St Anne’s Lagoon.

There is a permanent health warning advising people (and animals) to avoid contact with water at this lake.

Fish and shellfish can concentrate toxins and their consumption should be avoided. If fish are eaten, remove the gut and liver and wash in clean water. No one should drink the water from the lake at any time. Boiling the water does not remove the toxin.

Exposure to cyanobacteria toxin may cause skin rashes, nausea, stomach cramps, tingling and numbness around the mouth and fingertips. If you experience any of these symptoms visit your doctor immediately and please let your doctor know if you have had contact with the lake water.

Animals that show signs of illness after coming into contact with algal mats or scums should be taken to a vet immediately.

We continue to monitor the lake on a quarterly basis. Find more information about Mahinga Kai on the CPH.

Te Waihora/Lake Ellesmere

8 February 2022
 

Canterbury DHB’s Community and Public Health Unit has issued a health warning after potentially toxic blue-green algae (planktonic cyanobacteria) was found in Te Waihora (Lake Ellesmere).

People should avoid the Lake and animals, particularly dogs, should not be allowed near the water until the health warning has been lifted.

Fish and shellfish can concentrate toxins and their consumption should be avoided. If fish are eaten, remove the gut and liver and wash in clean water.

We continue to monitor the lake on a regular basis. Find more information about Mahinga Kai on the CPH.

Lake Rotorua (near Kaikōura)

Last updated 8 March 2019
 

Long-term water testing indicates that there is a regular bloom of the potentially toxic cyanobacteria Anabaena and/or Microcystis present.

There is a permanent health warning advising people to avoid contact with water at this lake.

We continue to monitor the lake on a regular basis.