Beaches and water quality

The water quality of natural sources such as beaches and rivers can vary greatly. Watching for signs of poor quality – water that is discoloured, murky or smells unpleasant – will help you decide when it is safe to go in. By paying attention to a few noticeable signs, you can keep yourself safer.

People with weaker immune systems, including young children and older adults, face a greater risk of swimming-related illness and should take particular care.

Staying safe in the water#

A few simple habits reduce your risk:

• Use nearby toilet facilities and take children on regular toilet breaks.
• Stay out of the water if you have diarrhoea or are vomiting.
• If you have an open wound or infection, avoid swimming.
• Avoid warm, slow-moving or stagnant water.
• Do not swim if you see sick or dead marine life in or near the water.
• If you are boating, dispose of all waste hygienically.

If you are uncertain, or you notice any signs of poor water quality, do not swim.

What pollutes natural water#

Microbiological pollution is made up of harmful microorganisms called pathogens, such as bacteria and viruses. These can contaminate both water and sand. They reach the water through sources such as sewage, including malfunctioning septic tanks, spills and animal droppings.

If you swim in or swallow polluted water, you may become ill – most commonly with gastroenteritis (gastro), a short-term illness. Symptoms can include:

• fever
• vomiting
• diarrhoea
• stomach pain
• nausea
• headache

Eye and upper respiratory infections can also occur.

Stormwater runoff#

Stormwater runoff is rain that does not soak into the ground but runs across the surface into the drainage system. From there it can flow untreated into natural water sources, including bays, rivers and lakes. Stormwater runoff can carry:

• chemical pollutants – such as fertilisers, detergents and fuel
• litter – such as cigarette butts, cans, food wrappers and plastic bags
• natural pollutants – such as leaves and animal waste

After heavy rain (more than 10 mm), natural swimming spots can be more polluted from stormwater runoff. In general, it is best to avoid swimming in coastal waters for one day after heavy rain, and in rivers and estuaries for three days after heavy rain.

Avoid stormwater drains#

To stay safe, pay attention to advisory signage about rain impacts and avoid swimming near stormwater drains. A sewerage system is built to handle only a certain volume of flow; very heavy rain can exceed that capacity and is considered an extreme storm event.

When this happens, sewage may be discharged at designated overflow points, which are located at less sensitive spots in the system.

To be safe, avoid swimming anywhere with a stormwater drain. If water is actively flowing from a nearby drain, find somewhere else to swim.

Water quality monitoring and forecasts#

Many regions monitor water quality at fixed sites and track trends over time, measuring changes in nutrient levels, algae composition, oxygen conditions, toxicants and water clarity. Some also issue short-term water quality forecasts for popular swimming sites during the warmer months, often updated more than once a day.

Forecasts are commonly grouped into categories such as:

• good – fit for swimming
• fair – often issued after rainfall
• poor – avoid all contact with the water

Other alerts may be issued at any time of year, such as warnings about algal blooms (blue-green algae).

Check signage at your local beach, and look for water quality information published by your local environmental or public health authority before you swim.

Key points#

• Assess the water before swimming; avoid water that is discoloured, murky or smells unpleasant.
• Children, older adults and people with weaker immune systems should take extra care.
• Do not swim with diarrhoea, vomiting, or an open wound.
• Avoid swimming for about one day after heavy rain in coastal waters, and three days in rivers and estuaries.
• Stay away from stormwater drains and check local water quality advice.