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Why this status?
Click here for detailed information on water quality monitoring
The scienceSummer 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 long-term grade.
Water quality test result
Current E. coli statusLast sampled 02 Dec 2024The weekly sampling result is a snapshot in time, and is a guide to the recent water quality at this site.
Long-term grade
Long-term E. coli grade5 year samplingLong-term grade is important to consider. Based on 5 years of data, it is a guide to the general water quality at this site.
Reminder
Heavy rain flushes contaminants from urban and rural land into waterways and we advise you not to swim for 2 – 3 days after heavy or prolonged rain – even at sites that generally have good water quality. Check that the water is clean and clear before taking a dip.
Toxic algae can rapidly bloom to harmful levels, and not all freshwater sites are monitored for toxic algae. Play it safe — if you can see toxic algal blooms in rivers or lakes, avoid contact or choose another site to swim.
Summer season monitoring history
- Samples this season
- Samples from last 5 years
E. coli sampling graph- View as graph
- View as donut
What do the monitoring results mean?
Suitable for swimming – The monitoring result met national water quality guidelines at the time of testing.Caution advised – The monitoring result for E. coli was slightly elevated at the time of testing. Water quality generally suitable for swimming, but young children, elderly or those with compromised health may be at increased risk of illness. For sites where toxic algae is routinely monitored, the monitoring result exceeded the surveillance criteria. Avoid contact where toxic algae is present.Unsuitable for swimming – The monitoring result did not meet the national guidelines at the time of testing. For sites where toxic algae is routinely monitored, the monitoring result exceeded the alert level criteria. Avoid contact with the water and with toxic algae along the edge of the water.Long-term grade information
Long-term grade based on five years of dataMinimum data points required 50 Highest E. coli per 100ml value {{riskData.maxValue | number:0}} Number of data points available {{riskData.dataPoints | number:0}} Lowest E. coli per 100ml value {{riskData.minValue | number:0}} Hazen 95th percentile result {{riskData.hazenResult}} Long-term grade {{riskData.rating}}What do the long-term grade icons mean?
Excellent – The estimated risk of Campylobacter infection has a <0.1% occurrence, 95% of the time.
95th percentile of E. coli / 100 mL is <= 130.Good – The estimated risk of Campylobacter infection has a 0.1 - 1% occurrence, 95% of the time.
95th percentile of E. coli / 100 mL is > 130 and <= 260.Fair – The estimated risk of Campylobacter infection has a 1 - 5% occurrence, 95% of the time.
95th percentile of E. coli / 100 mL is > 260 and <= 540.National bottom line: 95th percentile: 540Poor – The estimated risk of Campylobacter infection has a >5% occurrence, at least 5% of the time.
95th percentile of E. coli / 100 mL is > 540.Not available – There were not enough data to determine the long-term grade at this site.Learn more
See factsheets for more information.
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What about my dog?
Information about toxic algae
Dog ownersKeeping 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. Toxic algae can be harmful to dogs (and us) – this section shows you what to look for.
Toxic algae from Cawthron Institute on Vimeo.
What to do
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The best thing you can do to keep yourself, your kids and your dog safe is to know what toxic algae looks like and avoid it.
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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 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. 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.
Scientists do not yet understand when and why this algae turns toxic, so to be safe, always treat it as toxic.
Dogs are particularly susceptible to poisoning from toxic algae as they are often attracted to it's musty smell, and love to scavenge and play near water. Even a small amount (size of a 50 cent piece) can be harmful.
What to look for
In parts of stony based rivers toxic algae 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 at popular swim sites. Staff are not able to monitor all parts of rivers, so please learn what to look for to keep your dog safe. Dog deaths have been reported from sites where toxic algae have been present in small amounts, and at levels below the threshold for public health warnings at monitored swim sites. Please alert your regional or unitary council when you see algal mats so they can warn other people.
What if my dog has eaten 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 toxic algae here
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What's at this site?
Find out all recreational activities and facilities at this site
Activities & facilitiesSite 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.
Activities
Swimming
Canoeing/Kayaking
Boating
Facilities
Car parking
Wairau River
Blenheim Rowing Club
Last sampled 02 Dec 2024
Weekly result
Long-term grade
This site has a sloping grassy bank on one side and willow trees and paddocks on the other. Amenities include a boat launching ramp and the rowing club building. The site is very popular with fishermen, boaties, water sports enthusiasts and rowers. The banks are relatively steep making the site unsuitable for small children that cannot swim.
