The Porter Brook underwent the lurid transformation yesterday, Thursday, July 22, as the footage shared by Tonia Lucas shows.
Despite initial concerns about a big pollution spill, thankfully it turned out there was nothing sinister behind the dramatic colour change.
It is believed to have been caused by a green dye pumped into the drains in an attempt to locate a blockage.
Speaking this afternoon, a spokesperson for the Environment Agency said: “The Environment Agency investigated discolouration in the Porter Brook in Sheffield on Thursday 22nd July.
“The green discolouration is thought to be from fluorescein tracing dye used in drainage systems, which is not harmful to aquatic life and does not present a risk to the environment.
“If you are aware of pollution to our rivers and watercourses, please call the Environment Agency immediately on 0800 80 70 60.”