The pools above Gisborne's famous Rere rockslide has an overall high bacterial risk. Photo / Alan Gibson
Dozens of popular swimming spots in New Zealand are typically unsafe for a dip - prompting a warning for Kiwis to be vigilant this summer.
The Lawa (Land, Air, Water Aotearoa) website - an online tool that lets people check fresh monitoring results of hundreds of sites – shows many of our best-known spots are among those with unsafe or "caution" warnings.
Among those places which have long been plagued by high levels of bacteria are the pools at the top of Gisborne's famous Rere Rockslide, the Bay of Plenty's picturesque Kaiate Falls and 10 beach sites in Auckland.
Lawa – a partnership between regional councils, the Ministry for the Environment and the Cawthron Institute - regularly reports on sites' water quality sampling results, as well as their overall bacterial risk based on longer-term testing.
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It uses a traffic light system, with green indicating the site suitable for swimming and amber showing recreational water quality standards has been met but caution is advised for the very young, elderly, or people with compromised health.
Red means the water is not suitable for swimming, either because the risk of infection or exposure to potentially toxic algae is too high.
"Water quality changes, so over summer environmental officers from New Zealand's 16 regional and unitary councils regularly monitor popular swim spots," said water quality scientist Anna Madarasz – Smith, who leads Lawa's "Can I Swim Here" project.
"As we head towards the summer swim season, we're reminding people to wait two to three days after heavy rain before swimming outdoors.
"This applies to all sites; because even swim spots that usually have great water quality can be affected by pollutants in stormwater run-off.
"It's also important that swimmers check for potentially toxic algae at freshwater sites before they dive in."
She said swimmers could also do quick visuals checks of the water, to see if it was dirty or clear, or whether there were animals nearby.
Data from last summer showed monitored coastal spots were generally safer, being suitable for swimming 93 per cent of the time, and unsafe just 4 per cent of the season.
Freshwater sites - lakes and rivers - were suitable for swimming around 75 per cent of the time, with spots being either subject to a caution advisory, or unsuitable, 12 per cent and 13 per cent of the time respectively.
Beyond watched swimming sites, the wider picture was more concerning.
Recently-updated water quality data, measuring more than 1400 sites across New Zealand under nine indicators, showed the country's rivers were generally in a worrying state.
When measuring E. coli, around 45 per cent of sites had been either "likely" or "very likely" degrading, while at another 21 per cent of sites, results weren't clear.
While most strains of E. coli are harmless, some could make people sick, cause severe stomach cramps, diarrhoea and vomiting.
The picture for total nitrogen (TN) - a key nutrient linked to fertiliser, farm run-off and industrial waste that could fuel algae growth in rivers - were also dismal.
About half of river sites showed worsening trends, while there wasn't enough data at 17 per cent of sites to say either way.
Under another critical measure of a river's ecological health, called the Macroinvertebrate Community Index or MCI, only a quarter of sites were improving.
Previous reports have shown how levels of E. Coli were 22 times higher in waterways in towns and cities than in the relatively unspoiled waterways that flow through our native wilderness.
They were also nearly 10 times higher in the pastoral countryside that wraps around much of New Zealand's 180,000km of total river length.
A recent Colmar Brunton poll conducted for Fish & Game New Zealand showed that pollution of our rivers and lakes remains a top concern for Kiwis, with two-thirds expecting the Government to put rules and regulations in place to protect water quality.
Proposed Government measures would require farmers to have specific plans; effectively halt further dairy intensification; and force councils to give greater consideration of water health, with tougher rules on wastewater discharges and ensuring swimming spots were at higher standards over summer.
Waikato University's Professor Troy Baisden said any real changes that swimmers saw this summer wouldn't be the result of system-wide improvements, but water quality results being communicated better and faster.
"The hope would be that all of the interest we've had in freshwater lately as a result of discussion around the Government's action plan, will make improvements happen faster."
• NORTHLAND: Taipa Estuary boat ramp; Victoria River DOC reserve crossing; Waipapa River at Waihou Valley; Rawene Clendon Esplanade; Waimamaku River at Wekaweka Rd; Waipoua River swimming hole; Kerikeri River at Rainbow Falls and the Stone Store; Waitangi River at Spinnaker Pt; Matapouri Bay estuary at the northern bridge; Wellington's Bay; Hatea River at Whangarei Falls; Raumanga Stream at Raumanga Valley Park; Urquhart's Bay.
• AUCKLAND: Piha south and north lagoons; Fosters Bay; Laingholm Beach; Titirangi Beach; Wood Bay Beach; Green Bay Beach; Meola Reef; Cox's Bay; Wairau outlet.
• WAIKATO: Lake Kainui; Lake Ngaroto
• BAY OF PLENTY: Kaiate Stream at Kaiate Falls; Ngongotaha Stream at Railway Bridge; Utuhina Stream at Lake Rd; Lake Rotoehu at Kennedy Bay; Lake Rotoehu at Otautu Bay
• HAWKE'S BAY/GISBORNE: Tukituki River at Black Bridge, Puhokio Stream at Waimarama Beach Reserve
• WHANGANUI/MANAWATU: Whanganui River at Pipiriki; Hautapu River at Papakai Park; Ototoka Stream at Beach Rd; Mowhanau Stream footbridge; Ororua River at London's Ford and Fielding Rd bridge; Manawatu River at Ferry Reserve; Tokomaru River at Horseshoe Bend; Wairawarawa Stream at Waitarere Beach; Ohau River at Kirkcaldies Reserve.
• WELLINGTON: Te Horo Beach at Sea Rd; Waikanae River at Jim Cooke Park; Raumati Beach at Aotea Rd; Paekakariki Beach at Whareroa Rd; Hutt River at Maoribank Corner, Poets Park and Melling Bridge; Wainuiomata River at Richard Prouse Park.
• TASMAN/MARLBOROUGH: Pohara Beach Camp E; Maitai River at Collingwood St bridge and Girlies Hole; Wakapuaka River at Paremata Flats; Taylor River at Riverside Park
• CANTERBURY/WEST COAST: Hokitika Beach at Hokitika; Kaiapoi River boat ramp; Otukaikino Creek swimming hole; Avon River at Kerrs Beach; Heathcote River at Catherine St; Avon-Heathcoate Estuary at Humphreys Dr, South New Brighton Park and Penguin St; Lake Ellesmere lakeside domain; Ashburton River at SH1; Waihi River at Waihi Gorge; Opihi River at SH1 Bridge and Saleyards Bridge; Waihao River at Bradshaw Bridge.
• OTAGO/SOUTHLAND: Kakanui River at Clifton Falls Bridge; Taieri River at Waipiata and Outram; Waikaia River at Waikaia; Mataura River at Riversdale bridge and Gore; Oreti River at Winton Bridge and Wallacetown; Aparima River at Thornbury; Jacobs River Estuary at railway bridge east; New River Estuary at water ski club at Omaui.
• These sites have a red warning under overall bacterial risk. Weekly results may vary.
To check if the water is safe for swimming see: lawa.org.nz/explore-data/swimming/