How safe are natural waterways?
What is a natural waterway?
A natural waterway is a natural water body such as a river, estuary, ocean, lake or reservoir.
Natural waterways can be polluted by a number of different ways such as bacteria or algae.
It is important to be aware of the health risks of natural waters as you are the best person to judge the safety of a swimming spot at a particular time.
What are the common health risks in natural waterways?
Two of the most common public health risks to water users are:
These are both more of a risk in river and estuarine systems, but they may still occur in coastal waters such as oceans.
Microbiological pollution
What is it?
It is often the things we can’t see that we need to be concerned about.
Microbiological pollution in water includes bacteria, viruses and protozoans, which are usually associated with human or animal faeces (poo).
Where does it come from?
Sources of microbiological pollution include:
- stormwater runoff
- sewage treatment plant malfunctions
- boating wastes
- malfunctioning septic tanks
- farming activities (cattle, sheep)
- faeces (poo) from domestic animals (dogs) and wild animals (birds)
- recreational population using the water for swimming.
What are the health risks?
Swimming and/or swallowing water that contains high levels of bacteria and other organisms can make you sick. Such illnesses can include:
| Microorganisms |
Some illnesses and symptoms
|
Bacteria (such as Salmonella)
|
Gastroenteritis (including diarrhoea and abdominal pain)
|
Viruses (such as hepatitis A)
|
Fever, gastroenteritis, diarrhoea, respiratory infections
|
Protozoa (such as Cryptosporidiosis)
|
Gastroenteritis (including diarrhoea and abdominal cramps, dysentery)
|
How do I know if the water is contaminated with bacteria and other organisms?
As you cannot see bacteria it is difficult to know if they are in the water unless the water is tested.
There are some basic rule that can be followed to reduce your risk of exposure to bacteria and other organisms.
- Avoid swimming after heavy rainfall (greater than 10 mm).
- Do not swim in water that looks discoloured, murky, or smells unpleasant.
- Look for posted warning signs and follow the advice on them.
- Avoid swallowing water or putting your head under water if you are unsure about its quality.
- Avoid swimming if you have an open wound or infection.
- Do not add to the risk; use appropriate toilet facilities.
- Take children on bathroom breaks regularly.
- Do not swim if you are feeling ill (diarrhoea or vomiting).
- Dispose of human waste (wee or poo) hygienically when boating.
- Avoid swimming in warm, slow moving, stagnant water.
Does anyone test water for bacteria?
During the swimming season (November to May) the Environmental Health Directorate of the Department of Health WA coordinates bacterial water quality monitoring. This monitoring is carried out in conjunction with local government authorities and some other agencies.
Monitoring is carried out at:
- popular swimming beaches along the metropolitan coastline
- Garden Island
- Rottnest Island
- the Swan River
- the Canning River
A number of other recreational lakes and reservoirs. A number of country local governments also monitor recreational waters which include quite a number of ocean, river, lakes, estuaries, inlets and reservoir sites.
Helpful tips to assist you in deciding where to swim
The tips below can help you make the right decision about where you should swim.
1. Check the weather
After heavy rainfall, rain can collects pollutants from our streets, gardens and farms. The rain and the pollutants then flush into our ocean and rivers through the stormwater systems. This can make the water unsafe for swimming, especially if you put your head under or swallow the water.
As a precaution people should avoid swimming:
- 1 day after heavy rainfall (more than 10 mm), in coastal waters.
- 3 days after heavy rainfall (more than 10 mm), in river/estuarine systems.
If there has been no recent heavy rain, then it is likely that the water is safe to swim in.
2. Look for signs of pollution
Some “tell-tale” signs of water pollution to look out for before entering the water include:
Discoloured water
|
Is the water an odd colour? Look for dirty, murky or coloured water, algal scums or oily films on the water’s surface. |
Unpleasant odours
|
Can you smell any unpleasant earthy or sewage odours?
|
| Flowing drains |
Can you see any drains actively flowing into the water
|
| Floating debris |
Are there any food wrappers, cigarette butts, general litter or excess leaves floating in the water?
|
Sick or dead fish
|
Can you see any dead or sluggish fish or crabs visible in the water? |
If you notice any of these “tell-tale” signs it is recommended that you find somewhere else to swim.
3. Avoid swimming next to stormwater drains
Stormwater runoff is one of the most common causes of water pollution. People should avoid swimming near stormwater drains, particularly during or after rainfall events.
4. Check for warning signs
Where pollution is detected in a water body (e.g. after a sewage spill or algal bloom) health warning signs may be installed to warn the public not to use the water. If you notice a health warning sign then follow the advice and do not go swimming.
Amoebic meningitis and water temperature (lakes, rivers and dams)
During generally summer, lakes, estuaries and dams can heat up. High water temperatures between 28°C to 40°C provide conditions suitable for the growth of amoeba Naegleria fowleri. This amoeba can cause the disease known as amoebic meningitis.
Amoebic meningitis can cause inflammation and eventual destruction (damage) of the brain and brain linings. It only occurs when water containing the amoebae goes up the nose.
Swimming and skiing in lakes and dams is not recommended when water temperatures are high due to the risk of contracting amoebic meningitis.
Seawater and estuaries are safe as the amoebae will not grow in water with more than 2 per cent salt content.
For more information refer to the amoebic meningitis factsheet.
Where to get help
Remember
- Avoid swimming after heavy rainfall (more than 10mm).
- Do not swim in water that looks discoloured, murky, or smells unpleasant.
- Look for posted warning signs and follow the advice on them.
- Avoid swallowing water or putting your head under water if you are unsure about its quality.
- Avoid swimming if you have an open wound or infection.
- Do not add to the risk. Use appropriate toilet facilities.
- Take children on bathroom breaks regularly.
- Do not swim if you are feeling ill (diarrhoea or vomiting).
- Dispose of human waste (wee or poo) hygienically when boating.
- Avoid swimming in warm, slow moving, stagnant water.
Acknowledgements
Environmental Health Water Unit
This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.