The whirlpool on Llyn Padarn has caused unease at a lake popular with swimmers and paddlers
A large ‘whirlpool-like effect’ was photographed at the southern end of Llyn Padarn(Image: Dr Natasha Lucas)
A mysterious whirlpool that has been periodically appearing at one of Wales’ largest natural lakes has left onlookers “terrified”. The phenomenon, which measures approximately 30ft across, has caused unease at Llyn Padarn, a lake popular with swimmers and paddlers.
When it reappeared this week, accompanied by a drift of differently coloured water, immediate fears of a pollution incident arose in the nearby town of Llanberis, Gwynedd. With events scheduled for the weekend, word quickly spread about the need for extra caution.
However, Dŵr Cymru Welsh Water has ruled out waste water discharges as the cause, stating that all its local storm overflows were “operating as designed”. Natural Resources Wales, the environmental regulator, is keeping an eye on the situation but confirmed there have been no recent reports of pollution. Read the biggest stories in Wales first by signing up to our daily newsletter here.
One theory suggests that heavy rainfall earlier in the week could be responsible – potentially pushing extra volumes of water into Afon y Bala, which feeds into Llyn Padarn. This influx of water, along with material dislodged from surrounding mountains, could have created the “whirlpool-like effect” and stained the inflowing water.
Dr Natasha Lucas, an oceanographer and climate scientist at Bangor University, captured images of the disturbed water on Monday, September 1. She offered a simple explanation for the mechanics behind the phenomenon, reports North Wales Live.
“The flow coming down from the (Afon y Bala) channel is faster than the lake bank flow,” explained Dr Lucas, who is currently collaborating with the British Antarctic Survey on a study of ocean water mixing.
“This can be clearly seen in the dissipative pathways – how the whirlpool stretches out in the deeper waters while circulating back in the shallows.”
Water standards at Llyn Padarn have enhanced dramatically over the past decade following a £2m overhaul at Llanberis sewage treatment works and upgrades to the local sewer network.
Previously, local fishermen had threatened High Court judicial review proceedings over concerns that increasing nutrient concentrations and algal blooms were endangering Torgoch, an Arctic char found exclusively in Lake Padarn. An invasive plant species is now regarded as a greater danger.
This week’s whirlpool was short-lived – it quickly disappeared. Nevertheless, its emergence revived longstanding anxieties, with one local describing it as “disgusting”. One individual called it “terrifying”, stating, “Home of the Torgoch. Remember a time when the water was so clear.”
NRW explained the white “scum” observed on the whirlpool was likely foam created by the agitated water, potentially connected to wind patterns. Such foams, it noted, are typically caused by natural biological processes within the lake.
Four-year evaluations of the lake, through to 2024, discovered no oil or sewage waste in its bathing water. Minimal quantities of animal faeces were occasionally detected.
Far more frequent were small amounts of rubbish, a remnant of Padarn’s continuing appeal with tourists. Natural Resources Wales confirmed that the most recent bathing water sample taken at the lake’s Y Glyn (Lagoons) monitoring point on August 18 showed bacterial levels remained low and “within guideline parameters”.
This has remained consistent throughout the summer months. Earlier this year, as part of North Wales River Trust’s “Prosiect Torgoch”, students from Ysgol Waunfawr released more than 100 Torgoch into Llyn Padarn. Storm overflows surrounding the lake have discharged this week – however one on Afon y Bala has remained inactive since June.
A Dŵr Cymru spokesperson confirmed: “We do not have any outfalls directly near the whirlpool location. We have investigated the report as a precaution and all our assets in the wider area linked with Llyn Padarn are operating as designed.”
Overflows in Llyn Padarn can originate from its upstream neighbour, Llyn Peris, which forms part of the Dinorwig hydropower system. During periods of heavy rainfall, surplus water in Llyn Peris overflows into the Afon-y-Bala, which then drains down into Llyn Padarn.
NRW confirmed it was aware of the recent reports at the southern end of Llyn Padarn. A spokesperson stated: “We are monitoring the situation.
“We have liaised with Dŵr Cymru and its assets in the catchment are reported to be operating normally within environmental permit conditions. We would urge anyone who witnesses any signs of pollution to report it to us immediately via our incident hotline 03000 65 3000 or via our online incident form.”
