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Recreational Water

Swimming and collecting shellfish is safe in many of New Zealand’s estuaries, beaches, rivers and lakes, but it  is important to know when it is not safe, how to recognise signs of water contamination and to be aware of local warnings. This knowledge will minimize the risk of you and your family falling ill from contact with recreational water.

If you swim in or eat shellfish from contaminated water, you risk falling ill

The water quality at more than 80 popular coastal, river and lake recreation sites and shellfish beds in the region are surveyed and monitored by the Bay of Plenty Regional Council from October to March each year. National data is collected from all the local councils and is available on the Land, Air, Water, Aotearoa (LAWA) website. As monitoring only happens in specific places at certain times of the year, it is important for members of the public to know how to recognise signs of water contamination, so that we can keep our community safe together.

Recreational water and shellfish can be contaminated with toxins, viruses and bacteria:

·         Toxins are produced by toxic algae (also known as blue-green algae and cyanobacteria), which are naturally found in fresh water lakes and rivers, usually in low concentrations. However, when conditions are favourable, the algae can multiply quickly and form blooms, mats or surface scum.

·         Shellfish filter out algae from water as a food source, if the algae are toxic, these toxins can accumulate in the shellfish, making them poisonous to eat.

·         Faecal pathogens (such as viruses and bacteria) can contaminate recreational water. Human sewage and animal manure are the main sources of faecal contamination in NZ recreational waters.

Recommendations for safe use of recreational water:

1)       Do not swim in lakes/rivers/streams/estuaries in the 48 hours after heavy or prolonged rain

Why: Risk of contamination with animal faeces from rural or urban run-off + sewer overflows. Rainfall can wash livestock faecal matter from farmland into waterways.

Potential consequences: Bacterial contamination of water can lead to infections of the gastrointestinal tract (tummy bugs) and skin/eye/ear infections and breathing difficulties.


2)       Avoid contact with water if the river bed or rocks are covered in leathery mats of black/brown algae (figure 1) and do not eat shellfish from there

Why: This is a sign of potentially toxic algae

Potential consequences: Toxic algae are capable of producing toxins that are harmful to humans and animals, whether swallowed or exposed to skin. This can lead to fever, headaches, skin rashes, stomach cramps, tingling and numbness around the mouth or face, difficulty swallowing or breathing, dizziness, double vision, and in severe cases paralysis and respiratory failure (can be life threatening).


3)       Avoid contact with water that is murky or has a musty smell and do not eat shellfish from there

Why: This is a general sign of contaminated water; it could be toxic algae or bacterial contamination.

Potential consequences: The same as 1) and 2)


4)       Avoid swimming near or collecting shellfish where: Pipes/culverts run down to the waterway, sewage or storm water is discharged or there are a lot of houses nearby, farm animals are grazing nearby, there may be industrial pollution, boats may discharge sewage, or near wharves an marinas in general.

Why: These are high risk areas for faecal contamination of the water.

Potential consequences: The same as 1) and 2)


5)       Check the Toi Te Ora, your local council website and the LAWA website for up to date warnings and water quality information. Look out for local warning signage.

Why: The water quality can fluctuate over time, with temporary warnings being put in place

Potential consequences: It is not always possible to place signage at all parts of a river or lake that may be affected, so it is important to check online, in addition to using your own judgement.


Health risks

Toxic Algae

Toxic algae, also known as blue-green algae and cyanobacteria, are capable of producing toxins that are harmful to humans and animals, whether swallowed or exposed to skin during swimming, kayaking or water-skiing.

Symptoms include fever, headaches, dizziness, skin rashes, stomach cramps and aggravated hay fever and asthma and damage to the nervous system.

Download our fact sheet on Toxic Algae (blue-green algae / cyanobacteria)

Sewer Overflows

In built up areas such as Tauranga Harbour there is a possibility of sewage discharge from the reticulated sewage system.  This can lead to contaminated water.  Should this occur, the local authority would advise the public that an unplanned sewer overflow has occurred and remedy the affected area.

For more information about sewer overflows, contact your local council.

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