Northumbrian Water, which supplies water across the north-east of England, is expanding its cohort of water rangers.
It is recruiting new volunteers to walk by streams, becks, burns and bathing waters which are prone to pollution and report back on their condition.
The company's wastewater director, Richard Warneford, said the scheme had been "hugely successful"
"[It] has helped us to spot and deal with potential threats to the environment at the earliest possible opportunity on a number of occasions," he said.
New routes have been added in Northumberland, Tyneside, County Durham and Teesside.
The rangers are trained in environmental issues and what to look out for when monitoring watercourses.
The new routes are situated in:
A scheme to tackle water pollution is to be extended.