Water quality forecast ratings

How we calculate Good, Fair and Poor ratings to forecast the overall water quality at our monitoring sites.

On this page

Check air and water quality to see water quality forecasts for beaches in Port Phillip Bay and the Yarra River.

Our beach water quality forecasts predict water quality conditions and the health risk to swimmers from stormwater pollution during and after rain. They're based on:

  • historical microbial water quality (indicating how susceptible a beach is to stormwater pollution)
  • observed and forecast rainfall (indicating recent or likely stormwater pollution)
  • light levels and cloud cover (this is because sunlight can cause microbes to die off in the water)
  • water quality sampling and monitoring results
  • pollution reports.

We may also consider:

  • water levels at rivers flowing into Port Phillip Bay
  • observations from samplers or the community.

To learn more about freshwater and marine water quality sampling and testing, visit How we monitor water quality.

Most of our beach sampling sites are located in front of lifesaving clubs, where people swim between the flags. Patrolled beaches display our water quality forecast signs.

For Yarra River forecasts, Kew, Healesville and Launching Place are always forecast as Poor. This is because of their background microbial water quality level. Check the healthy swimming advice when planning to swim in these sections of the river. Warrandyte may be forecast as Good, Fair or Poor.

There are 2 kinds of recreational water activity:

  • Primary-contact recreation is when you are in direct contact with the water. You can be fully immersed and could swallow water. This includes swimming, surfing, water skiing and diving.
  • Secondary-contact recreation is when you have direct contact with the water but are unlikely to swallow it. This includes paddling, wading, boating and fishing.

Our water quality forecasts are for primary-contact recreation. Secondary-contact recreation has less risk of illness, as you are less likely to ingest the water.

Our long-term water quality monitoring shows our microbial indicators rarely exceed secondary contact criteria.

The Beach and Yarra Watch season summary provides:

  • microbial sampling results for the summer season
  • analysis of the accuracy of water quality forecasting from our data.

Watch our videos to learn more about our water quality forecasts.

Water quality forecasts

Beach report - water quality forecasts
View transcript

Looking to escape the heat? Our beaches and rivers provide a cool escape. But is the water quality okay for swimming today?

It’s easy to check on your phone. Beach Report and Yarra Watch provide forecasts every day in summer for many beaches in Port Phillip Bay and locations along the Yarra River.

Water quality is rated as Good, Fair or Poor. Good means the water is probably safe for swimming. Fair means the water might be affected by pollution. So you might decide not to swim or avoid swimming at beaches with stormwater drain outlets. Poor means the water is probably not safe for swimming.

So, this summer, enjoy swimming. Just remember to always check the water quality at epa.vic.gov.au/summerwater.

Causes of water pollution

Beach report - causes of water pollution
View transcript

Our beaches and swimming spots are usually good for swimming but can sometimes become polluted. Why is that?

Stormwater run-off is the most common cause. During and after rainfall, water that falls around our roads washes things like chemicals, faeces and rubbish into our bays and rivers. Children, older people and those with weakened immune systems are most at risk of getting sick from polluted water.

So, before you enjoy our many great swimming spots this summer, remember to check the water quality from your phone. Simply visit epa.vic.gov.au/summerwater.

Water quality forecast ratings

We forecast water quality for 3 levels or ratings:

  • Good
  • Fair, or
  • Poor.

The forecast shows what the expected water quality is likely to be.

Our forecasts are conservative to:

  • protect human health
  • help people make informed decisions about swimming.

Follow our advice to avoid getting sick from poor water quality after rain.

We provide forecasts twice a day:

  • at 10 am for the morning forecast
  • at 3 pm for the afternoon and next-day forecast.

Morning forecast

The 10 am forecast predicts water quality between 10 am and 3 pm. It's updated on the map at 10 am.

Afternoon forecast

The afternoon forecast predicts water quality between 3 pm and 12 am. It's updated on the map at 3 pm.

Next-day forecast

The next-day forecast predicts water quality for the 24 hours from 12 am. It's published at 3 pm the previous day and updated on the map at 12 am.

Next-day forecasts reflect the most conservative rating of water quality for an entire day. If water quality is likely to be Fair or Poor at any time that day, this is what our next-day forecast shows.

For example, we might predict that water quality will be Good in the morning but turn Poor in the evening due to rain. In this case, our next-day forecast shows Poor for the entire day.

Forecast reasons

To see the reason for a forecast rating for a specific beach, click on its pin on the Check air and water quality map.

Good

Reason: Stormwater pollution is unlikely.

Advice: Your beach is suitable for swimming.

Fair

Reason 1: Recent or forecast rain means stormwater pollution is possible.

Advice: Your beach may not be suitable for swimming. Has it rained or is it forecast to rain? To see if there has been recent rain or when rain is due, check:

Check for pollution – for example, drains flowing, murky water, bad smell or rubbish on the water’s edge.

Reason 2: There may be a water quality alert for your beach.

Advice: Your beach may not be suitable for swimming. Check the forecast by clicking on the pin on the map, or look at our water quality alerts.

Poor

Reason 1: Recent or forecast rain means stormwater pollution is likely.

Reason 2: There may be a water quality alert for your beach.

Advice: Do not swim.

Healthy swimming advice

For healthy swimming:

  • Always check for signs of pollution before you swim.
  • Do not swim near stormwater drains.
  • Do not swim for 48 hours after rain.
  • Cover cuts and scratches with waterproof bandages.
  • Try not to swallow water.
  • Wash your skin with soap after touching the water, and shower after swimming.

Gastroenteritis and respiratory infections are common illnesses you can get from swimming in polluted water. Most at risk of getting sick are:

  • children
  • older people
  • people with vulnerable immune systems.

These people are also most at risk of getting more severe illnesses from water-borne pathogens – for example, central nervous system infections. See your doctor if you feel unwell or are worried after swimming.

Our forecasts are a starting point for decision-making. Water quality can be variable over large areas and over time.

Always check for signs of pollution before entering the water. You can use the following information to support your decision to swim.

Assess if your beach is likely to be sensitive to stormwater pollution:

  • Are there stormwater drains nearby?
  • Is it close to the mouth of a river or creek?
  • Are you going to be in the water close to the beach or further out in the bay?

Check the weather, especially if rain is forecast or if there's been rain in the last 48 hours:

Once at the beach, check for signs of pollution:

  • bad smell
  • flowing stormwater drains
  • murky or discoloured water
  • rubbish or other pollution in the water or on the water's edge.

To learn more about managing your health and water pollution, visit Water pollution.

Updated

Back to top