Image of Forty Foot – Photo credit: Oscar Meagher
Dublin swimmers are advised to take caution after periods of heavy rainfall as there is an increased risk of contaminated seawater.
By Oscar Meagher
As Dublin continues to face poor weather conditions, swimmers have been warned to take precautions before returning to the sea.
Ireland’s bathing season runs from June 1st to September 15th. During this period, local authorities monitor swimming areas for the presence of harmful bacteria.
These conditions are largely unsupervised during the remaining months.
“Heavy rainfall is one of the key factors in water quality contamination,” said Wim Meijer, Professor of Microbiology in UCD School of Biomolecular and Biomedical Science.
“Treatment plants and sewers can’t contain the increased volume of wastewater during periods of extreme weather. That excess ends up bypassing the complete treatment process,” he said.
“When sewers overflow, that water will need somewhere to go. It may flow back through the toilet, or it will wash onto our beaches.”
Swimming in this contaminated water can lead to infection, skin rashes, dysentery and may even result in diarrhoea and vomiting in extreme cases.
“I would advise swimmers to wait at least 48 hours to swim after periods of heavy rainfall – particularly in areas where sewage may pose a risk,” added Professor Meijer.
Image of Blackrock Baths – Photo credit: Oscar Meagher
Bathing areas are tested for the presence of two bacterial markers, E. coli and Intestinal Enterococci. They are often resident within the intestines of humans and animals.
Waste from dogs and sea birds is one of the key factors in water pollution.
“Dogs account for 30% of water contamination,” said Professor Meijer.
“Even a small amount is enough to contaminate water in an area the size of a tennis court. This can result in temporary bathing prohibition notices being issued by local authorities.”
Image of Sandycove beach – Photo credit: Oscar Meagher
Frank Kelly is a member of The Gollymocky Whalers, a local swimming group that began as a result of the Covid pandemic.
“I’ve been swimming at Sandycove ever since the plague started six years ago. I go swimming three or four times a week,” he said.
Kelly is one of many taking part in the ‘Freezbrury’ challenge – which involves submerging yourself in the icy cold water for one minute every day throughout February. Every day, another minute is added.
“It was 17 minutes today, and we’re hoping to get up to almost half an hour by the end of the month,” he added.
“I know to steer clear of the sea after lots of heavy rain. Thankfully, Sandycove is well protected, but I’m worried about some of the other beaches,” said Kelly.
One young swimmer at Seapoint Beach, who did not wish to be named, also expressed uncertainty regarding water quality.
“I only started swimming recently as a sort of New Year’s resolution. There’s still a lot of things I’m unfamiliar with,” she said.
“I was advised not to swim after it’s been raining. I haven’t really gone much because of the terrible weather we’ve been having for the last month.”
Image of Seapoint Beach – Photo Credit: Oscar Meagher
While water quality is generally monitored exclusively from June to September, out-of-season sampling is voluntarily reported by local authorities.
“I would advise swimmers to regularly check sites like Beaches.ie for information regarding water quality,” said Professor Meijer.
Dublin City Council monitors bathing water quality at three designated locations: Dollymount Strand, Half Moon and Sandymount Strand.
The DLR website regularly publishes findings from water quality samples.
Recent findings from February 4th in areas like Dún Laoghaire Baths and the Forty Foot were categorized as “excellent”, while labelling others like Blackrock Baths as “poor”.
The Bathing Season will continue on June 1st.
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