A woodland stream in Cardiff that turned into a bright blue colour was caused by a harmless dye used to check the drainage system, Natural Resources Wales has said.
The bright colour of the stream was spotted at Cefn Onn Park, just on the outskirts of Cardiff, and a video was shared by Twitter user David Kilner on Tuesday, January 11. David said in his Twitter post: “Can anyone explain this?
“In a woodland stream north of Cardiff today. I want to hope it's not bad but simply can't believe it…”
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A spokesperson from Natural Resources Wales told WalesOnline: “A local business was using harmless blue dye to check their drainage system for mis-connections."
Ecology professor at the University of Cardiff Steve Ormerod told WalesOnline: “Dye can be used for tracing work, where water is being traced either for hydrological measuring purposes to trace pathways, what operators will do is use a dye and they’ll put it in at a certain point they want to trace the exit from, and then wherever the dye comes out allows them to work out what the connections are between those two locations."
Noting how people can tell the difference between what can make water in rivers change colour, Mr Ormerod added: “I did share the images from colleagues from our chemistry department, and they thought that a dye was the most likely explanation for that colour. That would have been unlikely knowing the catchment that it would be pollution unless it was some inappropriate disposal of paint or something of that type, but even then it would be more cloudy.”
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