Source: Environment Canterbury Regional Council
Long-term grades and temporary warnings
Sites that have been given the long-term grade of ‘poor’ or ‘very poor’ are not recommended for swimming because there is an elevated risk of getting sick.
Weekly sampling and sanitary surveys over a five-year period highlight sites that have exceeded health guidelines for faecal contamination. This means swimming at this site at any time is considered a significant health risk and should be avoided. Sites that are not recommended for swimming are red on the LAWA website.
For swim spots that have been graded ‘fair’ or better, you still need to check that there aren’t any temporary warnings in place. If there is a ‘poor’ weekly testing result or toxic algae has been found, Te Whatu Ora will issue a health warning. This will be listed on the relevant health warnings pages and the LAWA website.
Dr Elaine Moriarty, our surface water science manager, explains that water quality can change from week-to-week or even day-to-day.
“It’s best to check the LAWA website for up-to-date information each time you head out,” she said.
We continue to monitor sites graded ‘poor’ or ‘very poor’ for future grading, but health authorities will not issue temporary health warnings for exceedances.
Coastal water quality results
This year’s grades for our coastal sites are similar to last year’s, with a few positive changes. Caroline Bay is now graded suitable for swimming at all monitored points of the beach. Akaroa Beach and Tikao Bay/Ōkoropeke in Banks Peninsula have also improved, moving from ‘poor’ to ‘fair’ and are now considered generally suitable for swimming.
The grades this year for Whakaraupō/Lyttleton Harbour remain the same as last year. Cass Bay/Motu-kauati-rahi, Church Bay/Kaioruru and Charteris Bay/Te Wharau at Paradise Beach are graded suitable for swimming. Corsair Bay/Motu-kauati-iti, Rāpaki Bay, Governors Bay, Diamond Harbour/Te Waipapa Beach and Purau Bay are graded unsuitable for swimming.
Following public feedback, our surface water team has been working hard to build a predictive water quality model for the bays in Whakaraupō/Lyttleton Harbour. It is hoped the model will give daily predictions of water quality at some of the bays. This takes time, as the data needs to be tested and analysed against real world conditions to ensure its predictions are accurate. Right now, the model is at the testing stage. We expect it to be ready for the 2026/2027 swimming season.
Pollution sources in Whakaraupō/Lyttelton Harbour
Last year, we undertook faecal source tracking in the Harbour to help find the sources causing the high enterococci results we have seen at times in many of the bays.
“We found markers of human wastewater at every bay we tested. Many also had dog, ruminant or avian markers.
“The presence of human wastewater increases the health risks of contact with the water as pathogens are more easily transmitted,” said Dr Moriarty.
Christchurch City Council has undertaken extensive work to look for sources of human wastewater in the Harbour and has reminded the public to check for any signs of breakages or leaks from the wastewater or stormwater network on their properties. Onsite wastewater management systems (septic tanks) could also be contributing to the problem, and we encourage all residents to properly service and regularly check their tanks for faults.
You can help reduce contamination by:
- Reporting any suspected sewerage leaks or wastewater overflows to Christchurch City Council on 0800 800 169
- Checking your septic tank or aerated wastewater treatment system:
– If it hasn’t been serviced for a while, contact a qualified contractor.
– Inspect your property, if there are wet spots or areas where you can see sewage, call a drainlayer for help. - Make sure downpipes from the roof are not directed into the wastewater system.
- Pick up dog poo on walking tracks, beaches and your section and put it in the bin — never leave it to wash into stormwater drains or waterways.
- Always use toilet facilities.
Freshwater water quality results
Long-term grades for our freshwater sites are fairly consistent with 2023 results with no sites changing from suitable to unsuitable for recreation based on long-term monitoring. However, Dr Moriarty explains that the news isn’t all good as we expect that toxic algae (or cyanobacteria) will be a problem again this year in many of our rivers and lakes.
“Hot, dry conditions, combined with low flows or water levels from an unusually dry autumn and winter will increase the likelihood of toxic algae blooms,” said Dr Moriarty.
“Learn what to look for and make sure you check for health warnings before getting in.”
Toxic algae naturally occur in waterways over summer. They can produce toxins which harm people and pets.
Find out what to look for to protect yourself, whānau and pets.
Benthic toxic algae on a riverbed
Planktonic toxic algae suspended in a lake
Avoid swimming after rain
Freshwater and marine swim sites can be affected by rainfall, especially those with ‘fair’ or ‘poor’ grades.
It’s important to avoid swimming for 48 hours after rain as there is an increased risk of faecal bacteria in our waterways. “Even if the water looks clear, it doesn’t always mean the water quality is good to swim,” said Dr Moriarty.
Sources of faecal bacteria can include animals (birds, dogs, livestock) or wastewater overflows into the stormwater network.
“For rivers, a handy guide is if you can’t see your toes when standing knee deep in water, then water quality is not good enough for swimming,” said Dr Moriarty
Check before you go swimming
Before you go, make sure you:
- check the water quality on LAWA
- avoid swimming for two days after heavy rain
- follow any warning signs
- know how to spot toxic algae and avoid it
- avoid eating shellfish from areas where health warnings are in place
- check for hazards.
If you have any doubts about the water quality, it’s best to be cautious and avoid the water.
