Water  |  23 Sep 2025

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Canterbury Regional Council (Environment Canterbury) has developed a predictive model that will give swimmers and other harbour users real-time information about water quality at popular sites around Whakaraupō Lyttelton and Akaroa harbours.

Currently being tested for release this summer, the model addresses long-standing community concerns about the long-term grades and sites being considered unsuitable for swimming all season. Swimmers and other water users will be able to see hourly water quality predictions, rather than using a season-long warning.

The model will provide water quality information which is updated hourly on LAWA's 'Can I swim here?' website.

"We know there's been frustration in the past with the reliance on long-term grades for these sites, and we've been listening," says Dr Elaine Moriarty, Environment Canterbury's Acting Chief Scientist.

"This new approach means people can make informed decisions about when it's safe to swim based on current conditions. We anticipate that the model will be ready for use for the swimming season this summer,” she says.

The predictive model uses real-time environmental data including rainfall, wind direction and strength, and tidal information, combined with historical water quality data, to predict current water quality conditions.

Similar models are already operating successfully in Auckland, Northland and Wellington.

More testing, not less

Dr Moriarty emphasises that the model doesn't replace physical water sampling.

"We’ll actually be doing more testing than before. Weekly sampling continues, plus additional wet weather sampling and resampling when needed," she says. "The model uses all this data to give us the most accurate picture possible."

Cautious approach for launch

Environment Canterbury is taking a gradual approach for the system's first summer. Two harbour sites - Cass Bay and Governors Bay Sandy Beach - will not be included to start with, because more data is needed optimise performance at these locations.

"We're being careful to make sure the model works reliably," Dr Moriarty says. "We're working to gather more data so we can include these sites as soon as possible."

The model is particularly good news for popular swimming sites like Corsair Bay, which has had long-term warnings in place.

"Instead of blanket 'unsafe' warnings that might last for days or even the whole summer, people will now get information that responds to changing conditions," she says. "This means they'll be able to swim at their favourite bays more often, especially when conditions improve quickly after rain."

The real-time water quality predictions will be available this summer on LAWA's 'Can I swim here?' website at lawa.org.nz/swim.

Find out more about how the new predictive model works on the Environment Canterbury website.