Possible pollution incident as Belfast river water turns red

The river in Derriaghy Glen, which runs to the River Lagan, had turned red on Saturday

Concerns have been raised about a possible pollution incident in a waterway in West Belfast after the water in a river turned red.

The river that runs through Derriaghy Glen in Dunmurry turned a red/pink colour on Saturday, July 26, causing concern among local residents and park users who were worried that the water may have been polluted.

Videos and pictures of the water show it being a pink/red colour and it is understood that the water had turned this colour before entering the park. The waterway is understood to run beside the site of the former DeLorean factory.

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It has also been alleged the water in the river turned a bright blue colour the previous week.

Speaking to Belfast Live, one local resident said: “I was out for a walk on Saturday evening and was going through the park when I saw the colour of the water and couldn’t quite believe it. It was like a pink or red colour that I though looked more like Ribena than actual water.

“Anytime that I have been in the park before the water quality always looks quite good and you see herons and other wildlife there a lot, so I was quite worried that it may have been polluted.

“I reported the issue to the Environment Agency when I got home and went back to the park a few hours later to see if the water was still the same colour, which it was.

“I hope that something was done to address the issue and thankfully the following day the water looked like it was back to its normal colour.”

The Northern Ireland Environment Agency attended the area shortly after receiving a report of a discolouration in the waterway and said that it tracked this as far upstream as it could.

It has said while there is no indication of any long term impact on the waterway, it is investigating the incident which could result in enforcement action.

A DAERA spokesperson said: “At 1920hrs on Saturday 26 July 2025, NIEA received a water pollution report indicating a red discolouration to the Derriaghy River, Belfast. A NIEA Water Quality Inspector was tasked to the incident, carrying out an investigation at 2040hrs.

“Further to the investigation, a red discolouration was confirmed in the waterway where it flows through Derriaghy Glen. This discolouration was tracked upstream as far as possible that evening. There was no indication of significant or longer-term impact on the Derriaghy River or its fishery. A line of enquiry is being pursued currently and, as enforcement action may result from this investigation, NIEA is unable to provide further details at this time.”

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