Bathing Waters
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.
What is being done?
Environment Southland regularly monitors 13 marine bathing and six freshwater bathing sites during summer (December to March). The bathing water quality is assessed according to concentrations of indicator bacteria: these do not 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 is cost-effectively or unreliable.
The indicator used depends if it is a freshwater or marine site. In freshwater we measure levels of bacterium known as Escherichia coli (E. coli), whereas we measure enterococci bacteria at marine sites.
Southland's recreational bathing 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.
You can find out the latest results from our summer monitoring programme here.
Green/Surveillance
(minimal health risk) |
No single sample greater than 140 |
No single sample greater than 260 |
Amber/Alert
(health risk may have increased) |
One single sample between 141 and 280 |
One single sample between 261 and 550 |
Red/Action
(significant health risk) |
Two consecutive single samples greater than 280 |
One single sample greater than 550 |
For the weekly sampling results a traffic light approach is used to inform the public whether the water quality of a site is suitable for swimming and other water-based recreational activity.
Environment Southland uses two ways of assessing and advising the water quality risks to bathing. These are:
- by weekly monitoring of bathing water quality over summer (the latest results are shown in the map below);
- by incorporating long term water data and catchment use to give an overall Suitability for Recreation Grading.
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.
Suitability for Recreation Grades
As well as measuring bacteria levels, we allocate a grade to beaches according to the suitability of the water for recreation (Suitability for Recreation Grade, SFRG). The grades are based on faecal contamination risk factors within the catchment (e.g. intensive agricultural use in immediate catchment), and levels of indicator bacteria, based on data that has been collected over a number of years. This grade gives an overview on how safe it is to swim in a particular location. Beaches are graded as: Very Good, Good, Fair, Poor, Very Poor. The risk of becoming sick from swimming at a beach increases as the beach grading shifts from Very Good to Very Poor.
Environment Southland is the brand name of Southland Regional Council.