Skip to content

Is it Safe to Swim?

Is it Safe to Swim?

During summer, Wellington’s regional, city and district councils monitor the quality of water at popular beaches and rivers each week. Toxic algae, which can be dangerous for dogs, is also monitored at river sites.

Our water quality in the region is usually very good, but there are a few things to keep in mind before you dunk your head under. Especially if you’re a dog!


Water quality alerts

Check our interactive alert map for the latest water quality and toxic algae information.

If you notice a problem with water quality then you can report it to us on 0800 496 734.

Wait for two days after heavy rain before you swim again

Water quality in our rivers and at our beaches is generally pretty good over the summer, except after heavy rain.

Heavy rain flushes contaminants from urban and rural land into waterways and we advise you not to swim for at least two days after heavy or prolonged rain – even if a site generally has good water quality.

Find out more about water quality

Toxic Algae

Toxic algae is only an issue if you eat. It is still safe to swim when it is present.

In summer, the Hutt River regularly has high levels of toxic algae.

The algae forms leathery looking mats on rocks in the riverbed, ranging from blackish/brown to dark green in colour. These mats can come loose and wash up on the edge of the rivers, or floating in shallow water. As they dry out they turn light brown or white and produce a strong musty smell.

Deadly for dogs

Dogs love the musty smell and may try to eat the mats if they get the chance. The algae produces a powerful neurotoxin, and in extreme cases, dogs can die within 30 minutes after the first signs of poisoning. 

The best thing you can do to keep your dog safe is:

  • to know what toxic algae looks like and avoid it. 
  • Check our monitoring information for a heads up where algae may be at dangerous levels - if in doubt keep your dog on a lead.
  • Henley Lake in Masterton often has high levels of toxic algae - we recommend you don't let your dog swim in or drink from this lake.

If you think your dog may have eaten algae, take it to a vet immediately.

This video shows you what to look out for:


Toxic algal mat growing on the river bed

Toxic algal mats washed up on the river's edge

National water quality information

If you are travelling outside of the Greater Wellington region you can find national water quality information on LAWA. LAWA is a key resource for measuring the current state of New Zealand's waterways and shows longer-term trends, information and data.