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 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) Look out for local signage and monitor relevant websites for up-to-date warnings and water quality information. These include:
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.