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:

The Baby Blacks - who won the tournament from 2008 to 2011 - ended England's two year hold on the trophy.
England went in front through Max Clark, who burst through, before New Zealand hit back through Vince Tavae-Aso to lead at half-time.
Akira Ioane went over from close range to extend their advantage, as Otere Black added four penalties.
England beat South Africa in the semi-finals, while New Zealand went through to the showpiece after thrashing France in the last-four.
The New Zealand juniors performed the haka before kick-off, but England started confidently, going ahead through Bath centre Clark.
After a slow start, New Zealand got back into the game as Tavae-Aso powered over for a narrow 11-10 half-time lead.
Ioane bundled himself over early in the second half, before being sent to the sin bin, and although Rory Jennings kicked four penalties for England, they relinquished their hold on the trophy.

Lewis Elliot, 19, predicted both teams would score in both halves of the Crawley v Carlisle, Hibernian v Aberdeen and Chelsea v Tottenham games.
The bet came in at odds of 6,858/1 when Eden Hazard scored for Chelsea in their FA Cup semi-final.
"I am absolutely delighted," said Mr Elliot. "I went crazy when Hazard scored."
The first two legs of his bet came in as Aberdeen reached the Scottish Cup final with a 3-2 win over Hibs.
Later, Crawley and Carlisle shared the spoils in a 3-3 draw in League Two.
Mr Elliot's win was confirmed at Wembley on Saturday evening, with Chelsea's Willian and Spurs' Harry Kane scoring in the first half of the two London sides' cup clash.
Dele Alli scored for Tottenham just after the break to leave Lewis requiring just one more Chelsea goal to land his bumper bet.
That goal came courtesy of Eden Hazard, who scored in the 75th minute to give the Blues the lead and send them on their way to the FA Cup final.

The Independent Monitoring Board report said between September 2013 and August 2014 less-experienced officers were supported by fewer senior officers.
Board chairman Nick Adams said he was concerned senior staff were leaving while cheaper employees are taken on.
The Ministry of Justice said new prison officers were being trained.
The spokesman said after receiving extensive training, they are mentored by an experienced staff member for at least a year.
The report said there were also "significantly fewer" officers on each wing to care for and manage prisoners.
It said the reduction of experienced supervising officers has had a "significant negative impact on the care and safety of prisoners".
Observations by board inspectors suggest the "incidence of bullying, low-level violence and disobedience by prisoners has increased".
Nick Adams, chairman of the monitoring board, said:  "There have been very large cuts to budgets available to the prison service.
"One way to reduce the cost is to pay off large numbers of experienced staff and employ younger people starting on lower salaries."
A scheme to tackle water pollution is to be extended.
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