Auckland's mayor says it will take at least a decade to tackle the issues causing dozens of health warnings and no swim notices around the city's beaches.

Warnings have been issued at dozens of Auckland beaches due to concerns about wastewater overflow and poor water quality following today's torrential downpours.

An alert system on Auckland Council's Safeswim website warned wastewater overflow had been detected by sensors at all of the central beaches and said swimming was "not advised".

The warning was in place for Mission Bay Beach, Browns Bay, Castor Bay, Herne Bay, Mairangi Bay, Narrow Neck, Okahu Bay, Point England and St Mary's Bay.

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Phil Goff said there was a scheme in his 10-Year Plan to separate stormwater from wastewater and build a major new central wastewater interceptor. This would help prevent future wastewater overflows.

Goff told the Herald this afternoon more intensive housing and major weather events were putting pressure on the city's wastewater system.

"It's time, if we want to be a world-class city in the 21st century, actually to take real action to bring it to an end.

"A higher population, more frequent heavy rainfall events, will exacerbate this problem and make it worse."

He hoped Aucklanders would get behind a targeted rate for the city which would be used solely for the purpose of improving the city's water quality.

Tackling the issue of poor water quality would take a minimum of 10 years with the extra funding this rate would provide, but with current investment levels poor water quality could persist for 30 years.

Despite warnings of polluted beaches due to heavy rains, people still take to the ocean at Mission Bay. Photo / NZME
Despite warnings of polluted beaches due to heavy rains, people still take to the ocean at Mission Bay. Photo / NZME

More than a dozen further warnings had been issued about elevated health risks at beaches due to poor water quality.

A temporary no-swim warning was also in effect for these beaches.

More than 50 beaches were affected in total, ranging in location from Wenderholm Beach in the north down to Kawakawa Bay.

It wasn't the first time wastewater overflow had caused beaches around Auckland to close this year.

Late last month people were advised not to swim on Milford Beach after a burst sewage pipe spilt waste through local properties and down into the waterways.

Screengrab from the safeswim.org.nz website showing alerts across most beaches in the Auckland region advising people not to swim due to potential high-levels of pollutants. Photo / Supplied
Screengrab from the safeswim.org.nz website showing alerts across most beaches in the Auckland region advising people not to swim due to potential high-levels of pollutants. Photo / Supplied

Safeswim also issued a long-term no-swimming warning near the Wairau Creek outlet due to its "high risk".

And Auckland's popular Takapuna Beach was closed to swimmers at the start of January after pollution flowed into the water between the red and yellow flags.

Lifeguards shut the whole beach when a fault caused a stormwater drain to overflow.

A spokesman from Auckland Council told the Herald a warning was typically put in place following any major storm event due to the potential of water contamination.

Earlier this year Auckland Mayor Phil Goff committed to cleaning up the city's beaches and waterways, by separating stormwater from wastewater.

Mission Bay beach is deserted after health warnngs due to heavy rain. photo / NZME
Mission Bay beach is deserted after health warnngs due to heavy rain. photo / NZME

"We like to think of our environment as clean, green, 100 per cent pure and that's how we and New Zealand promote ourselves to the world," he said.

"Sadly, however, that is not the current reality and hasn't been for a very long time. When it rains, beaches around Auckland are not safe to swim in."

The scheme, laid out in Goff's 10 Year Plan, was expected to cost around $1 billion.