Beach Watch

Important points

Has there been heavy rain in the past two days?

Avoid swimming in the Derwent estuary for two days after heavy rain (> 10 mm rain over a 24 hour period) as beaches are likely to be polluted by stormwater. Check back regularly for the latest results.

For swimming event organisers and participants

• Avoid using sites with ‘Poor’ water quality classifications.
• Develop water quality contingency plans in the event of heavy rain or poor test results.
• Inform swimming event participants about water quality so that they can decide whether to swim.
• For more specific information or health advice contact the Department of Health by calling the Public Health Hotline on 1800 671 738, or your local council Environmental Health Officer.

What you can do?

• Pick up after your dog.
• Don’t feed the ducks and geese.
• Be aware of where and when you swim. Avoid swimming in the Derwent estuary for two days after heavy rain (>10 mm of rain over a 24 hour period) and don’t swim or allow children to play in or near stormwater outfalls (25 m on either side of outfall) or urban rivulets.

Further information

For sampling results for all sites, and further information about this program see the DEP’s latest Recreational Water Quality report.

Background to the program

Local councils, the Environmental Protection Authority and the Derwent Estuary Program collect water samples from 39 sites throughout the Derwent estuary each Tuesday from the start of December to the end of March.

All samples are analysed at the Public Health Laboratory (New Town) using the Enterolert method, which provides confirmed results within 24 hours of analysis. Results are typically reported between 24 and 48 hours after submission to the laboratory.

Sites are categorised as either Swimming Sites (Beach Watch) or Environmental Sites (Bay Watch):

• The Swimming Sites are in locations where a significant number of people swim or conduct other primary contact recreation.
• The Environmental Sites are not designated swimming sites, but are frequently used for secondary contact recreation, have been identified as potential sources of faecal contamination, or are sites associated with major swimming events, such as the Trans Derwent Swim.

Pathogens and health risks

Water contaminated by sewage and animal faeces may contain pathogenic micro-organisms (bacteria, viruses, protozoa) which pose a health hazard when the water is used for primary contact recreation, such as swimming. Infection may occur by swallowing, inhaling or by direct contact of contaminated water with ears, nasal passages, mucous membranes and cuts in the skin, which allow the pathogens to enter the body. The most common health conditions associated with primary contact recreation in contaminated water are gastrointestinal disorders, respiratory illnesses, eye, nose and throat infections and skin disorders.

Monitoring and guidelines

The Recreational Water Quality Guidelines for Tasmania were developed using the National Guidelines for Managing Risks in Recreational Water 2008. The Tasmanian guidelines adopt a three-tiered approach to classifying the long-term quality of a site based on available data. The tiers are:

• Good: rolling 5-year 95th Hazen percentile value of < 200 enterococci MPN (Most Probable Number) per 100 mL.
• Moderate (Fair): rolling 5-year 95th Hazen percentile value of 200–500 enterococci MPN per 100 mL.
• Poor: rolling 5-year 95th Hazen percentile value of > 500 enterococci MPN per 100 mL. In this case, water at these sites is considered to be a threat to public health in the event of primary contact recreation, and the particular local council is required to advise the general public and to erect warning signs to this effect.

In addition to long-term site classification, trigger levels have been set to manage public exposure to episodic or emerging water quality issues. If a sample exceeds 140 MPN per 100 mL, the relevant authority is required to re-sample, and if two consecutive samples return a result above 280 MPN per 100 mL, the swimming site must be closed and the public notified. The beach may only be re-opened for primary contact recreation following agreement between the Director of Public Health and Council’s Authorised Officer.

For further information see the Tasmanian Recreational Water Quality Guidelines and our national Guidelines for Managing Risks in Recreational Water.