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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. 

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.


Toxic algae in the Hutt River:

Floating algae mats 

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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 you and 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. Even a 50 cent size piece of algae can be deadly to a dog. If you have been swimming in a river or lake and you feel unwell and have any of the following symptoms including nausea, vomiting, numbness, tingling, muscle twitches, shaking, weakness, breathing difficulties and potentially convulsions and loss of consciousness see your doctor. 

Toxic algal mat growing on the river bed

Toxic algal mats washed up on the river's edge

Wait for two days after heavy rain before you swim again

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


National water quality information


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.

Toxic Algae levels are high in the Hutt River, upstream of Silverstream bridge. We advise against swimming in that section of the river, and that you keep your dog on a leash if walking nearby. Birchville, Maoribank Corner, and Poets Park also have new growth, though at lower levels.