After a couple of days of rough weather and some heavy rain, beaches all around Wellington’s south coast and in the inner harbour have been slapped with an unsuitable for swimming status.
The problem isn’t confined to the capital. Many Auckland’s beaches are often unswimmable after rain, and Christchurch is looking at a plan to divert wastewater into the ocean outfall pipe as the council struggles to control a stench from fire-damaged treatment ponds at Bromley.
Nicola McCloy has put the work into discovering New Zealand’s best places to swim. She shares a handful of her favourite spots, from secluded sandy bays to urban lakes and saltwater pools.
What’s behind these advisories?
The Greater Wellington Regional Council tests water about once a week in the summer and every two weeks in the cooler months, says Edward Abraham, of Dragonfly Data Science, who is both an experienced oceanographer and a resident of Island Bay in Wellington. This testing has ramped up in frequency following last month’s Moa Point Wastewater Treatment Plant failure and shutdown.
“[The council] take water samples and they look for gut bacteria in the sea and if they find too much of that, then they might issue an advisory.”
The problem is that results can take days to come through so an advisory against swimming, especially immediately after heavy rainfall, is typically a prediction based on years of test results, says Abraham. Other city and regional areas, like Auckland and Christchurch, also lean on predictions so swimmers can be immediately notified if water is likely to be unsafe for swimming.
“Obviously, when you’re going swimming, …you want to know what it’s like right now.”
Auckland Council’s Safeswim did more than 6,000 water tests last year across 250 plus locations, says Dr Martin Neale, technical lead for Safeswim. A location gets tested about every two weeks, which is increased if there is an event such as a triathlon or a contamination issue. However, results take 48 hours.
“That’s why we use [prediction] models to help us fill in the gaps between the samples.”
Do I have to wait for an advisory before going in the water?
Use a little common sense, Abraham says. If you see water coming into an urban environment from, say, a stormwater drain, second-guess your decision to jump in.
“That fresh water is carrying all the grime and dirt off the street, and in addition, you might have cross over through the stormwater and the sewerage and getting problems coming in that way.”
It’s a tricky problem because the clarity of the water doesn’t indicate the amount of bacteria, says Neale.
“The one bit of advice in terms of visual of what you can do if you go to somewhere and you haven’t got any information is stay away from any stormwater discharges or stream discharges to the beach,” he says.
“Because if there is some contamination at the beach, it’s generally coming from one of those two things.”
Which websites should I check?
Land, Air, Water Aotearoa (LAWA) is a good place to start for nationwide advisories, Abraham says. This is where all the local councils feed their water testing results into, which LAWA bases its predictive model on.
“They upload their testing results, and they run these predictive models, and they’ve got a very simple traffic light system. They put up the red light if they think it’s going to be unsuitable for swimming.”
Swimmers can also check for regional-specific information, such as Auckland Council’s Safeswim website or a page on Christchurch Council’s website.
However, LAWA’s prediction model takes into account rainfall, but not other factors that can impact water quality like tides.
“LAWA are really focused on that urban run-off.”
In Wellington, sewage is being pumped 2 kilometres offshore, but weather and tide could impact swimming safety, he explains.
“If there’s a southerly that could blow back onto the coast, if the tide’s coming into harbour, it might take it towards those inner harbour beaches. That’s when you’d check Wellington water for its daily updates.”
If I swim in red status water, what’s the risk of getting sick?
If you swim when the official advice is not to, “there’s a 10 percent chance of getting sick from swimming in the sea, so it’s pretty high,” says Abraham.
Neale puts that risk lower at two percent. However, advisories are based on risk so nothing is guaranteed, and those with a weaker immune system will be at greater risk of getting sick, he says.
“It doesn’t mean that if you go swimming when a beach has a red or a black water quality warning, you will definitely get sick. It means that there’s a higher chance.
“And likewise, the other way around, you know, if it’s green, it doesn’t mean you will not get sick.”
Swimming in questionable water can give you a range of illnesses that often revolve around the intestines, such as cryptosporidium, which can result in a loss of appetite, fever, nausea and vomiting, according to the Ministry of Health website. Symptoms can last for two weeks or more.
E. coli is another waterborne illness that can leave you with diarrhoea (if there is blood present, go to your doctor) and severe stomach cramps, lasting between five and seven days. Giardia serves up similar symptoms and can be treated with antibiotics, according to the Ministry of Health website.
Swimmers can also pick up respiratory bugs, which typically have an incubation period of about ten days, says Neale.
“When I get a cough or cold, I blame my kids for bringing something home from school, but it may be that I’ve been swimming last weekend and I’ve picked up a bug from that.”
– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand