More information on Southland bathing water monitoring

The main human health risk associated with bathing is the risk posed by disease-causing micro-organisms (such as viruses, bacteria and protozoa). Increases in these pathogens result from human or animal faecal matter finding its way into water. The major sources are sewage, industrial discharges, and runoff from agricultural land. In some areas water quality is also affected by septic tanks and discharges from boats.

Environment Southland regularly monitors marine bathing and freshwater bathing sites during summer (December to March). The bathing water quality is assessed according to concentrations of indicator bacteria: these do no cause disease themselves, but signal the potential presence of disease-causing pathogens. A high concentration of the indicator bacteria means that it is more likely that disease-causing organisms are present, therefore a potentially higher health risk. However, it does not mean that anyone swimming in the water at that time will actually be affected. Councils do not measure the pathogens directly because the technology to do this cost-effectively or reliably is not available.

The indicator used depends if it is a freshwater or marine site. In freshwater the council measures levels of bacterium known as Escherichia coli ( E. coli ), whereas it measures enterococci bacteria at marine sites.

Southland's recreational bathing microbiological water quality is assessed and reported according to national guidelines set by the Ministry for the Environment and Ministry of Health ? these guidelines can be accessed on the Ministry for the Environment website.

Environment Southland prepares a monitoring plan for ?Recreational Bathing and Shellfish Gathering Waters in Southland', in collaboration with Public Health South, Southland District Council and Invercargill City Council. The monitoring results automatically go to the health authorities (Public Health South, and the territorial authorities) who are responsible for informing the public of health risks associated with contaminated bathing and shellfish growing waters.

How do I know if it is safe to swim?

The national guidelines for microbiological water quality categorise recreational bathing sites into a three different ?modes' (green, amber, red) according to the results of indicator bacteria counts. This ?traffic light' approach helps inform the public on whether the water quality of a site is suitable for swimming and other water-based recreational activity.

For more information on health risk associated poor recreational water quality contact the health authorities on the contacts list

When am I most at risk?

Under certain conditions there is a greater risk of getting sick in the course of recreational water-based activities.

Swimmers can reduce their risk to illness by:

• swimming away from stormwater outlets;
• swimming away from streams and areas with possible runoff from intensive agriculture ,
• by not swimming during and for up to two days after heavy rainfall.

There is potentially a greater risk to those with weakened immunity, such as the very young, and the elderly.