Beach Water Quality Monitoring
Beach Water Quality Monitoring
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We monitor recreational water quality at Emily Bay and Slaughter Bay to assess the level of faecal pollution which occurs when contaminated stormwater flows into the ocean.
Anticipated rainfall forecasts can also be used to predict the likelihood of bacterial contamination at our beaches.
As a general precaution, swimming at Emily Bay and Slaughter Bay should be avoided after heavy rainfall or for as long as stormwater is present. The most obvious signs of stormwater pollution are water discolouration as well as debris in the water and on the tide line.
Signs of stormwater pollution
The main signs of stormwater pollution are water discolouration and debris in the water and on the tide line. There is a stormwater outlet in the west end of Emily Bay and swimming should be avoided whenever the sand plug is open.
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Discoloured water in Emily bay after heavy rain |
Emily Bay Outlet |
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Stormwater running into Emily Bay |
Stormwater running into Emily Bay |
When samples are collected?
Samples are collected every week. If faecal contamination is detected, samples are collected daily until bacteria levels drop.
What do we test for?
We test water samples for a bacteria called enterococci. Enterococci is found in the intestines of warm blooded animals and excreted in faeces and rarely present in unpolluted waters.
Studies have shown a strong relationship between elevated levels of enterococci and illness rates in swimmers. It’s important to note that, when swimming in water where enterococci is detected, this bacteria may not be the cause of illness. However, its presence means there are possibly pathogens present (in human and/or animals faeces), which do cause illness.
Indicator organisms are used to test for sewage pollution because:
• they are easily detectable by simple laboratory tests
• they are generally not present in unpolluted waters
• results are available relatively quickly (24h).
The National Health and Medical Research Council (2008) Guidelines for Managing Risks in Recreational Waters recommend enterococci as the single preferred indicator organism for the detection of faecal pollution.
How do we interpret the results of the tests?
The table below shows how the enterococci results are interpreted.
| Enterococci reading (MPN/100ml) | Description |
| <41 | Good |
| 41-200 | Fair |
| 201-500 | Poor |
| >500 | Bad |
What happens when contamination is detected?
When test results indicate faecal contamination, the sampling site is immediately retested and a public health warning is issued via our website and Facebook page