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 affects water quality and can make us sick.

Bacteria that can make us sick with stomach upsets enters our waterways via human and animal waste. This can be from sewage, septic tank discharge, farming run-off, industrial pollution and boats.

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 and 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 to 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 8 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


Harmful bacteria: what we test for

Escherichia coli or E.coli – This is the bacteria we look for in freshwater as it is easy to measure.  It stays alive in freshwater for four to six weeks and that tells us that there has been recent contamination from human or animal waste.  Although it is not possible to tell if the E. coli came from humans or animals, this doesn't matter: all E. coli can make us sick.  Since multiplying or increasing in freshwater is rare, E. coli can give good indication of how much waste is getting into the water.

Faecal Coliforms
– These bacteria live in the digestive tracts of humans and animals. Outside of the body they are relatively short lived, although they can multiply in freshwater which can lead to high levels that can make us sick.

E. coli and faecal coliforms don't survive well in salty water, so we look for Enterococci to see if a marine area like a beach or estuary is contaminated. Enterococci are typically only found in human faeces, however can also enter water from natural decomposition of animals and plants.
Read our media release here
Please remember that our water quality testing only covers these bacteria, not metals, other toxicants or viruses.

Toxic algae

Environment Southland currently has toxic algae alerts for the following locations. You can also see our alerts for toxic algae here on our map. We advise caution in these areas, especially with dogs and young children, and avoid contact with water or any slime or dry slime mats.

  • There are no toxic algae alerts in Southland at present.

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.

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: 20 Jun 2018 11:47am