The Canterbury Regional Council (Environment Canterbury) has released the annual water quality results following the 2024-25 summer season, which contribute to the long-term grades for each river, lake or beach site for the 2025-26 season.

The grades show that 77% of the region's monitored swimming sites are suitable for contact recreation (swimming and other water-based activities) – the same result as the previous season.

Each summer, starting in mid-November, Environment Canterbury monitors 52 popular freshwater sites and 47 coastal sites.

"Our teams are out weekly throughout the summer season collecting water samples and testing for faecal indicator bacteria to determine which sites are safe for everyone to enjoy," said Dr Elaine Moriarty, Environment Canterbury's Acting Chief Scientist.

"Canterbury has some fantastic swimming spots to cool off in over summer, and we're pleased that remains the case this season, with 77% of all monitored sites graded as suitable for contact recreation."

As the long-term grades, which summarise the last five years, are only updated after the end of each season, weekly water sampling provides a more up-to-date picture of water quality, which can be variable.

Look before you leap

"We recommend people use the LAWA’s 'Can I Swim Here?' website to check current water quality before swimming or engaging in water activities," Dr Moriarty advised.

Long-term and weekly grades, and toxic algae warnings, are available to view on the LAWA website.

Dr Moriarty also recommends avoiding swimming for 48 hours after rain, because rain can wash bacteria from roads, paddocks and other sources into the waterway.

"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," she said.

Positive results at coastal sites

Of Canterbury’s coastal sites (estuaries, harbours, and beaches), 85% were graded as suitable for contact recreation, with 100% of beaches on the open coast receiving 'very good', 'good', or 'fair' grades. This maintains the same high standard from the 2023-24 season.

"Across Canterbury, our beaches continue to perform exceptionally well, which is fantastic news for beachgoers," Dr Moriarty said.

Mixed results for freshwater sites

Freshwater sites showed more variable results, with 71% graded as suitable for contact recreation.

"Our lake sites consistently perform well, with 87% suitable for recreation this summer," Dr Moriarty explained. "However, river sites remain more challenging, particularly in the lower reaches of urban and agricultural catchments where elevated E. coli concentrations can occur."

For example, all sites on the Ashley River/Rakahuri, as well as the Hanmer River swimming area, Hurunui River at SH1, and the Selwyn River/Waikirikiri at Chamberlains Ford and Glentunnel are suitable for recreation. However, the Hurunui River at SH7, Waipara River at the Boys’ Brigade swimming hole, Waimakariri River between the highway bridges and at Thompsons Road, and the Selwyn River at Coes Ford remain poor this season and unsuitable for recreation.

“We will continue to work with local councils and the community to identify the sources of the contamination and improve water quality at these popular recreational sites,” said Dr Moriarty.

Public health warnings 

During the 2024-25 summer, 46 temporary public health warnings were issued across 34 sites, including 28 warnings for faecal contamination and 18 for toxic algae.

"These temporary warnings are a crucial part of keeping the public safe," Dr Moriarty said. "We monitor not just for bacteria but also conduct surveys for toxic algae at freshwater sites where blooms may pose health risks."

Toxic algae (also called cyanobacteria) is a naturally occurring algae with the potential to bloom, producing toxins that can harm or even kill dogs, people and other animals. Current warnings can be viewed online at ecan.govt.nz/health-warnings.

Investigating harbour contamination

Environment Canterbury continues its multi-year investigation into faecal contamination sources in Whakaraupō Lyttelton Harbour, working closely with Christchurch City Council and other partners.

"This season's investigations have identified several inflow points – streams and stormwater outfalls – that contribute to contamination, and we're working with our partners to address these sources,” Dr Moriarty explained.

Environment Canterbury is currently developing a predictive water quality model that will give swimmers and other harbour users real-time information about water quality at popular sites around Whakaraupō Lyttelton and Akaroa Harbours. We anticipate that the model will be ready for use for the swimming season this summer.

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