The past year has seen public anger over the pollution of rivers and streams.
According to environmental charity Earthwatch, people are increasingly taking pollution monitoring into their own hands.
John Pratt went fishing on the Evenlode which flows through the Cotswold Hills. Now he takes a chemistry set.
A resident of the area for 33 years, the river has become a part of his life.
So when the crystalline waters tasted like soup one summer, he was determined to act.
Some might join a protest or post pictures of polluted rivers on social media, but John has become a citizen scientist. He is one of many up and down the country hoping their data will help in the effort to clean up the rivers.
During the year, thousands of people took part in protests over sewage spills in rivers and on beaches from Essex to Edinburgh. And at the same time, there has been a boom in citizen scientists turning their attention to the health of the nation’s waterways.
The UK has seen a long tradition of public involvement in scientific research, including tracking the numbers of plants, birds and insects.
But as more people spend time in the water paddle boarding or wild swimming, there’s growing interest in sounding the alarm about pollution, from plastics to chemicals.
Earthwatch, which trains citizen scientists, says the number of community groups monitoring chemical pollutants has doubled in the last year alone. And on this stretch of the Evenlode, there are now more samples taken by citizen scientists than anyone else.
Earthwatch trains volunteers like John Pratt to test for nitrates and phosphates, chemicals found in fertilizers, wastewater and agricultural sludge.
These are naturally present in small amounts but in excess they can cause extensive algae blooms and kill fish and invertebrates.
The data John collected on the Evenlode helps scientists and regulators build a better picture of how pollution levels change over time.
“I’m just one of many citizen scientists concerned about the health of the river,” John explains, surveying this Area of Outstanding Natural Beauty near Charlbury.
“We hope that through dialogue and water agency action, Evenlode can be restored to the health it was before 2000.”
The Evenlode meanders to join the Thames through picture-perfect towns. Early 20th-century poet Hilaire Belloc wrote of the “lovely” Evenlode and how it tied its heart to English soil.
Yet today the river is plagued by pollution, causing weeds to grow, fish and insect numbers decline, and cloud cover much of the year. It’s not alone.
England’s rivers are “in disarray”, contaminated by “a chemical cocktail” of sewage, agricultural waste and pollution, according to a report by MPs from the Environmental Control Committee.
Monitoring regimes have been described as ‘outdated, underfunded and inadequate’.
Earthwatch’s Dr. Heather Moorhouse says citizen scientists can’t replace the job of regulators, but they can pressure polluters to clean up their act.
“Citizen science is filling an information gap and aiding our understanding of the water quality in our rivers,” he says.
“But this data needs to be used to account for polluters and to invest in improvements in the way our rivers are managed.”
The main problem for the Evenlode, like many rural rivers, is pollution from sewage and agricultural waste, says Dr. Izzy Bishop, Lecturer in Ecology at UCL London.
And the “big boom” in people collecting data through citizen science is helping to keep river pollution on the political agenda.
“The visibility and transparency of the data that is collected from the public is one of the big drivers for pushing this onto the political agenda,” he says.
As for John, he hopes that one day he will be able to relive his childhood memories.
“We all share childhood memories of the summer time of taking off our shoes and socks and paddling in creeks and rivers and being able to see our toes when we’re on our knees,” she says.
“It’s possible on some of our tributaries, it’s possible on some of the burns in Scotland, it’s possible on some of the streams in Wales, but in our poor river Evenlode it’s no longer possible.”
Follow Helen on Twitter @hbriggs.