Recreational water quality

​​​​We are lucky enough to have some wonderful spots in Southland to swim and gather shellfish. But we all need to be aware of the bacteria which affect water quality and can make us sick.

Southlanders have helped to identify popular recreational spots that Environment Southland monitors for the indicators of harmful bacteria. Our monitoring sites are located at:

  • 13 beaches
  • 7 rivers
  • 2 lakes
  • 8 shellfish gathering sites

Swimming sites

To find out if the water at swimming spots could make you sick, we test water for ‘indicator’ bacteria. Although they may not make you sick themselves, these bacteria tend to indicate the presence of other disease-causing pathogens (such as viruses and protozoa).

We don’t test for the pathogens themselves as this is expensive and generally takes a lot longer. The bacteria we are looking out for in freshwater are E. coli and faecal coliforms. At marine sites we are looking out for enterococci. You can find more on the harmful bacteria we test for here.

Environment  Southland uses two ways of assessing the water quality at popular swimming sites. These are:

  • Weekly monitoring of water quality over summer (the latest results are shown in our online map);
  • Incorporating long-term water data and other risks to give an overall Suitability for Recreation Grading.

During summer months (December through to the end of March) we update our results from monitoring at swimming spots every week. Use our map to find out the latest water quality results before you go swimming. Our SMART tips list all the things you need to think about when choosing a spot to swim.

Our monitoring shows that overall the best* freshwater swimming sites are:

  • Lake Manapouri at Frazers Beach
  • Lake Te Anau at Boat Harbour Beach

Our monitoring shows that overall the best* beach swimming sites are:

  • Awarua Bay at Tiwai pumphouse
  • Colac Bay at Colac Bay Road
  • Halfmoon Bay at Bathing Beach
  • Halfmoon Bay at Elgin Terrace
  • Kawakaputa Bay at Wakapatu Road
  • Monkey Island at Frentz Road
  • Oreti Beach at Dunns Road
  • Porpoise Bay at camping ground
  • Riverton Rocks at Mitchells Bay North

*These sites all fall into the category of "Very good" or "good" according to Suitability for Recreation Grading.

Shellfish gathering sites

We monitor the water quality at eight shellfish gathering sites around the region monthly throughout the whole year. In general we’ve found that shellfish gathering sites located near river mouths often have increased bacterial contamination. We recommend not gathering shellfish for at least five days after heavy rainfall. The bacteria we are looking out for at shellfish gathering sites are faecal coliforms.

Shellfish gathering site results are based on the previous year’s monthly water samples, in accordance with the national guidelines for shellfish gathering, and can be seen on our map here. Our SMART tips list all the things you need to think about when planning to be in the water.

Our monitoring shows that the site/s that pass national guidelines for shellfish gathering are:

  • Riverton Rocks at Mitchells Bay

The harmful bacteria we test for

In freshwater (rivers and lakes)  we test for Escherichia coli or E.coli. This is a group of bacteria are found in the gut of warm-blooded animals, including people. E.coli in fresh water can indicate the presence of pathogens (disease-causing organisms) from animal or human faeces. Too much E. coli means that the water is unsafe to drink or swim in and can cause gastrointestinal illness or infections of ears, eyes, nasal cavity, skin, and the upper respiratory tract. E.coli tells us if there has been recent contamination from human or animal waste.In salt water (beaches) we test for Enterococci. Like E.coli, these bacteria are found in the gut of warm-blooded animals, including people. E.coli doesn’t survive in salt water very well, which is why we look for Enterococci as an indicator of the presence of pathogens (disease-causing organisms) from animal or human faeces.Too much Enterococci means that the water is unsafe to swim in and can cause gastrointestinal illness or infections of ears, eyes, nasal cavity, skin, and the upper respiratory tract. In estuaries, which are a mix of freshwater and salt water, we test for both E.coli and Enterococci.In shellfish waters, which are also a mix of freshwater and salt water, we test for all Faecal coliforms (a name for all bacteria produced in the gut of warm-blooded animals including humans)- this includes E.coli and Enterococci. Faecal coliforms in shellfish waters can indicate the presence of pathogens (disease-causing organisms) from animal or human faeces which can be taken up by the filter-feeding shellfish, which store or “bio accumulate” the bacteria.

Testing is carried out so we can measure bacteria against National guidelines. Our water quality testing only covers these bacteria, not metals, other toxicants or viruses.​​

Toxic algae

Cyanobacteria, also known as toxic algae, are widespread in many lakes and rivers in New Zealand, particularly more so over the past decade. They are found across a range of water quality conditions, including relatively clean waters. Toxic algae blooms are more likely to occur over summer, and when rivers are low. The algae can produce toxins (called cyanotoxins) that are harmful to animals and humans when eaten, even licked, or when water containing the toxins is swallowed. Some people will have an allergic reaction to just touching the algae.

There are two types of cyanobacteria that form in Southland's waterways, benthic and planktonic. You are most likely to see the benthic type, which grown in rivers and streams. These algae form mats that detach from the riverbed and accumulate as scum along the river's edge. They also become exposed on the river's edge as the river level drops. Planktonic cyanobacteria (which you could also call floating or suspended algae) is different to that found in rivers. It tends to be hard to see as it forms little globules either suspended in the water, or floating on the surface making it harder to check for. This lake kind can also be invisible to the naked eye.

Children are at high risk of exposure or consumption, especially those who put things in their mouths when out and about. Dogs can be attracted to the musty smell of the toxic algae on riverbanks and in the water and can be poisoned from eating the slime or dried slime mats. Stock can wander into waterways with toxic algae and drink it, so you will need to arrange an alternative water source for them and keep them out of waterways. It is not safe to swim in rivers with toxic algae, and your wetsuit will not protect you.

 Please see our list of frequently asked questions here.

In this video, Dr Wood from Cawthron Institute talks about toxic algae in New Zealand rivers and what we need to look out for to keep ourselves safe.

Toxic algae (benthic cyanobacteria).jpg190215 Mataura Cyanobacteria-4.JPGBenthic cyanobacteria floating raft Hutt R at Silverstream 7 Jan 2008 01 CREDIT CAWTHRON INSTITUTE.jpg
Photo credit: Cawthron Institute

Benthic Cyano mat Makakahi at Hamua 11 December 2012 CREDIT HORIZONS.JPG
Photo credit: Horizons Regional Council


Environment Southland conducts monthly monitoring for toxic algae blooms across the region.

You can see our alerts for toxic algae here.
  • For further information on health risks: Public Health South, Medical Officer of Health,  (​03) 211 0900
  • For further information on environmental monitoring: ​Environment Southland 0800 76 88 45

For more information

Recreational Waters of Southland

This report summarises the results of Environment Southland's 2012/13 microbial monitoring programme, which monitors the public health risk from contact recreation at 11 marine beaches, 13 rivers and lakes, and 8 shellfish gathering sites in the region.

Download the report Recreational Waters of Southland

Recreational Bathing Survey 2015

This report includes the findings from a survey conducted across Southland over the summer of 2015. The survey's aim was to find where people undertake recreational activities, what activities are being carried out, what kai is being collected, what problems are being experienced, and whether the recreational bathing programme is delivering to the public needs.

Download the Recreational Bathing Survey 2015

Microbiological water quality guidelines for marine and freshwater recreational areas

View the guidelines on the Ministry for the Environment website
Page reviewed: 18 Apr 2019 10:57am