Dogs in Water - ECan banner image

Can I swim here? Check the water quality before you get in

Each summer, from November to March, Environment Canterbury (ECan) monitors more than 100 of Canterbury’s popular swimming sites weekly to check for water quality issues that can be harmful to people and pets, especially dogs.

Within the Mackenzie District there are a number of swim spots to cool off during summer, though it is important to be aware of water quality issues and how to stay informed.

Weekly monitoring accessed via LAWA

ECan monitors water quality at popular lake, river and beach locations each week so up-to-date information is available and you can make decisions about where is good to swim to avoid becoming ill.


It’s easy to find water quality for any monitored swim site in Aotearoa on the Land Air Water Aotearoa (LAWA) website, under the ‘Can I swim here?’ section. Water quality can change, so it’s important to check first, before heading out.

ECan further monitors for E. coli and cyanobacteria (toxic algae) at freshwater (lakes and rivers) sites, and enterococci bacteria at coastal sites.

If the results show the water at a site has changed and may be unsuitable for recreation, Canterbury District Health Board or South Canterbury District Health Board will issue a health warning for that site and it will be listed on Ecan's ‘Health Warnings’ page and the LAWA website.

If a site is generally unsuitable for swimming, permanent signage should be erected at the site.

Know what to look for

Cyanobacteria is a naturally occurring blue-green algae with the potential to bloom and may produce toxins that can harm people and can kill pets.

Blooms form when cyanobacteria grow quickly, usually due to changes in environmental conditions such as warmer temperatures, sunlight, high levels of nutrients, or stable river flows.

In rivers, cyanobacteria (called benthic cyanobacteria) grow on the bottom of riverbeds. It appears as thick dark brown or black mats that have a slimy or velvety texture and a strong musty smell. These mats can detach and gather at the rivers edge.

Cyanobacteria In lakes, ponds and lagoons, cyanobacteria (called planktonic cyanobacteria) are suspended in the water. Water can look cloudy, discoloured, or like it has small globules in it. Some planktonic cyanobacteria may not have obvious visual traits.

Algae - ECan

Tips to stay safe this summer

  1. Check water quality information before swimming on the Land Air Water Aotearoa (LAWA) website.
  2. Avoid swimming for 48 hours after heavy rain or prolonged rainfall.
  3. Follow any warning signs.
  4. Know how to look out for cyanobacteria (toxic algae) and if in doubt, keep out.
  5. Avoid eating fish and shellfish taken from areas where health warnings are in place. Boiling food and water does not remove the toxins from cyanobacteria.
  6. Stay away from potential contamination sites - pipes, culverts, and flocks of birds.

Further Information