Summer season monitoring
LAWA shows the best available water quality information to help you decide where to swim. For many sites there are two types of information available, the weekly sampling result and the overall bacterial risk.
Weekly sampling result
The combined weekly sampling result uses both E. coli and toxic algae data. It is a guide to the recent water quality at this site.
Overall bacterial risk
Overall bacterial risk is important to consider. Based on 3 years of data it is a guide to the general water quality at this site.
What do the icons mean?
Summer season monitoring history
E. coli sampling graphToxic Algae sampling graph
- Samples this season
- Samples from last 3 years
Keeping your dog safe and healthy this summer
A trip to the river is a lot of fun and knowing how to keep your dog safe means you are able to relax and enjoy the adventure even more. Potentially toxic algae can be harmful to dogs (and us) – this section shows you what to look for.
What to do
The best thing you can do to keep yourself, your kids and your dog safe is to know what potentially toxic algae looks like and avoid it.
If you are not sure, keep your dog on a lead at a stony river, and don’t let them in or near the water. Bring water from home for your dog so that they don’t need to drink out of the river.
What is potentially toxic algae?
Freshwater algae are naturally occurring in rivers and lakes in New Zealand, including waterways with good water quality. Most algae is harmless, if a bit slimy – but one group of algae, known scientifically as cyanobacteria, can be toxic. In rivers, this potentially toxic algae is called Phormidium. Most of the year it is present at low levels that are not much of a danger. But it can be a problem during the summer months, when low rainfall, warm temperatures and more sunlight create an environment where it can thrive. In parts of stony-based rivers it can form extensive mats which can be toxic to humans, dogs, livestock and wildlife.
Dogs are particularly susceptible to poisoning from toxic algae as they love to scavenge and play near water.
What to look for
In parts of stony based rivers toxic algae (also known as Phormidium) form soft, leathery-looking mats on rocks in the riverbed. These mats range in colour from blackish/brown to dark green (it's quite different from normal harmless green algae, which looks bright green and often forms long strings).
These mats can come loose and wash up on the edge of the rivers, or form ‘floating rafts’ in shallow areas. As they dry out they turn light brown or white and look like dried leaves or cowpats. They produce a strong musty smell, and this is when it poses the biggest risk to our dogs, as they love the smell and many dogs will try to eat it if they get the chance.
Council staff monitor for these mats in parts of rivers where these are known to form – often in shallow areas. Staff are not able to monitor all parts of rivers, so please learn what to look for and alert your regional or unitary council when you see algal mats so they can warn other people.
What if my dog has eaten potentially toxic algae?
If you suspect that your dog has eaten toxic algae, you should contact your vet as soon as possible. Signs a dog has been poisoned by toxic algae include lethargy, muscle tremors, fast breathing, twitching, paralysis and convulsions.
Find out more about potentially toxic algae here
Site suitable for these activities and has these facilities
Our lakes, rivers, and beaches are great natural playgrounds but they can be unpredictable. Be aware of other potential risks such as rips, strong currents, sudden drop offs, or underwater objects before jumping in. LAWA recommends that you avoid swimming for 2 - 3 days after heavy rainfall and follow the advice of any warning signs in place.