Swimming in water with high levels of E. coli or other harmful bugs (faecal pathogens) can cause illness. These bacteria, viruses, and parasites from faecal sources can lead to stomach bugs, skin infections, and irritation of the eyes and ears. Vulnerable people, including young children, the elderly, and those with weakened immune systems, face a greater risk of getting sick.  

The number one rule for both monitored and unmonitored sites is to always follow the Swim Smart Checklist.

For monitored swim sites, you can check the LAWA website for: 

• Current warnings 
• Latest test results 
• Long-term water quality grades 

Think about potential sources of contamination near your swimming spot. Are there stormwater outlets, wastewater infrastructure, livestock, or flocks of birds nearby? If these are present, contamination after rainfall may be more likely. 

Avoid swimming near flocks of birds and don’t feed ducks at swimming spots. Large groups of birds can mean an increase in bacteria concentrations, making water unsuitable for swimming. 

Rain can wash contaminants like animal waste, sewage, and stormwater into rivers and lakes. This can temporarily raise bacteria levels, making the water unsafe. The 48-hour window allows bacteria and other harmful bugs to dilute and settle out, while sunlight and natural processes help reduce their levels, making the water safe again. 

ORC's Environmental Monitoring team collects weekly water quality samples at popular swim sites during summer. Samples are chilled and shipped to an accredited laboratory where they are analysed. 

At the lab, the water is warmed in special tubes for about 2 days. If E. coli is in the water, the tubes will change colour. This helps scientists figure out how many harmful bugs are in the water. 

Daily testing isn’t practical due to cost, logistics, and lab processing time. Weekly testing, combined with long-term data, provides reliable guidance for safe swimming. 

Note: most elevated results are associated with rainfall, which can temporarily increase bacteria levels. Water quality is likely to be safe again before a confirming test result is available, so the key thing to remember is to always avoid swimming for 48 hours after heavy rain. 

ORC tests more than 30 swim sites across Otago. Sites are selected based on popularity, known risks, and community feedback. You can view all monitored sites on the LAWA website.  

The risk estimates used to inform the national guidelines for recreational water quality come from studies that looked at how often people got sick after swimming in water with different levels of bacteria. 

If you feel unwell, contact your doctor or call Healthline on 0800 611 116. Watch for symptoms like diarrhoea, vomiting, or skin irritation. 

Most high bacteria results are short-lived and linked to rain. By the time results are available, the water may already be safe. 

Signs are however used when there’s a serious, ongoing risk to public health – like a major sewage spill. The need for signs is assessed on a case-by-case basis depending on the scale of the pollution event and degree of public health risk. 

Also, ORC run a dedicated public awareness campaign each year to educate the public about how to access information and make informed choices about where and when to swim. 

No – warnings usually apply to the specific swim site. Water quality can vary across a lake or river. 

ORC provides advice but does not enforce restrictions on public access to swimming sites, even when bacteria levels are high. People may choose to swim at these sites at their own risk, even when a warning is in place. 

The power to restrict access to a beach or river due to a public health risk (e.g., high bacteria levels) lies with the Medical Officer of Health, not the ORC or other local authorities, unless directed by the medical officer under the Health Act 1956. 

If high bacteria levels are associated with heavy rain, avoid swimming for at least 48 hours. 

Where there is an unexpectedly high result (i.e. no rain), a follow-up sample may be collected within the week to confirm there is no ongoing contamination occurring.  

The swim site’s status on LAWA will be updated once a follow-up sample returns a ‘suitable for swimming’ result. 

Remember, weekly tests only provide a snapshot of water quality at the time of the sample. 

Dogs and other pets can also get sick from swimming in contaminated water. They may drink the water or ingest bacteria while playing. If your dog shows signs of illness after swimming, contact your vet. 

Pet owners should also learn about the risks of toxic algae and know how to spot it. 

Generally, yes – as long as you avoid direct contact with the water. Wash hands and gear afterwards, especially if water splashes into your mouth or eyes. 

It’s best to avoid eating fish from contaminated water. If you do, clean and cook them thoroughly. Avoid raw or undercooked fish. 

These bacteria come from the gut of warm-blooded animals and indicate the presence of faecal contamination. They don’t always cause illness themselves, but they signal that harmful bugs like bacteria, viruses, or parasites may be present. 

In rivers and lakes, ORC tests for E. coli (Escherichia coli). It can survive for four to six weeks outside the body in freshwater, so it is a useful indicator of faecal contamination. 

At coastal sites Enterococci are the preferred indicator because they survive longer in salty water, whereas E. coli is more sensitive to salt and sunlight making it less reliable in coastal waters. 

• Animal droppings 
• Farm runoff 
• Wastewater overflows 
• Stormwater after rain 

No – human waste usually poses a higher health risk than animal waste, but all sources can carry harmful bugs.

ORC monitors water quality, investigates pollution sources, and works with landowners and councils to reduce contamination.