Popular Takapuna beach was unswimmable for five days in February after heavy rain caused water quality alerts across the region.

Human waste is the leading source of contamination at most of Auckland's most popular beaches, DNA test results show.

Results released by Auckland Council showed human waste was present in just over half of the 646 samples taken from sites including Browns Bay, Mission Bay, and Takapuna beach.

The data contradicts previous information from Watercare, which had labelled bird faeces as the main culprit of contamination.

LAINE MOGER/STUFF Human waste far outstrips that of any other animal for contaminating Auckland's swimming sites (file photo).

"Testing suggests that a significant proportion of the bacteria in the overflows can be traced back to avian waste, rather than human waste," the minutes of a Watercare Services Board meeting, dated March 27, stated.

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Auckland Council's Safeswim samples water at 84 beaches and eight freshwater locations around Auckland.

Where the water quality consistently falls short of national guidelines, DNA testing is then used to help source bacteria in the water as coming from farm, domestic or feral animals, humans or birds.

"The different sources pose different levels of public health risk," Safeswim programme manager Nick Vigar said.

"Knowing the source of the contamination helps to guide effective management. For example, contamination from dog sources would require a different management approach than [a] human source."

Second to human, results revealed avian faeces was the second most common with 198 samples. Dog faeces was detected in 129 samples and faeces from ruminant animals was detected in 41.

A total of 150 samples had no source reliably identified.

Doctor David Sinclair, a medical officer of health at Auckland Regional Public Health, said national guidelines were set around the exposure which would be likely to cause human illness, including gastroenteritis, respiratory illness, skin and eye infections.

Auckland's Takapuna beach – a popular spot for families and young children – could be considered the lightning rod for water quality monitoring.

Supplied Safeswim, launched last summer, aimed to shine a light on Auckland's water quality issues.

Test results from March and April detected human faeces contaminating the water at eight of 10 tested stormwater pipes.

The toilet block had since been repaired after its cracked pipes were identified as a source of the pollution.

The local community had also been approached to ensure private wastewater was not flooding or leaching into the main stormwater pipes.

Beach Series organiser Nick Carroll said Takapuna's water quality had improved a lot in a year. Last summer, poor water quality prompted the cancellation of several swim events.

Carroll said now there were two testing sites along the beach, where previously there had only been one.

"Issues are being fixed and there is a greater understanding of what is happening," Carroll said.

"That is only going to improve with the more funding Auckland Council provides."