(LONDON) — The River Thames winds 215 miles through England, carving out the curves and bends that define much of the geography, including London’s. For centuries, the river has been called “monster soup” and the “dirty old river.”
For thirty years, Lubos Grajciarik, known online as Urban Angler Lou, has stood on its banks with a fishing rod in hand.
“Originally, I came from Slovakia… and I have fished most of my life,” he told ABC News.
He has witnessed firsthand the river’s slow transformation, from Canary Wharf’s rise to the quieter stretches upstream at Richmond and at the weir Teddington Lock.
“Yes, there is improvement,” he said. “Water is still polluted. But it is significantly lower than in previous years.”
Further improvement, and the hope for an even cleaner future, now rests on a monumental infrastructure project beneath London: the £4.5 billion, or about $6 billion, Tideway Tunnel, also known as the “super sewer.” The 25-km tunnel — the largest upgrade to London’s sewers in 150 years — is, according to its designers, intended to intercept overflows and capture waste before it reaches the river.
Four of the tunnel’s 21 gates, which are valves that are designed to stop the waste before it enters the Thames, are operational, with more to open in the coming months.
“The newly completed Tideway Tunnel will reduce the volume of discharges entering the tidal Thames in a typical year by 95%,” said a spokesperson for Thames Water, the company responsible for London’s wastewater.
Optimism from those along the riverbank appears to be supported by science. For more than half a century, the City of London Corporation has collaborated with anglers and ecologists in a citizen science project to track fish populations.
Scientists estimate that more than 100 species now inhabit the Thames, a river once declared biologically dead. In 2024, volunteers caught 122 fish across five species — bass, flounder, eel, pouting and dab.
Grajciarik said his catches reflect that resurgence. “There is a mixture of both species,” he said. “Freshwater pike and perch coexist with occasional mullets, sea bus, sea route.” The Thames, where saltwater meets fresh, has become a rare brackish habitat — alive again, yet still fragile.
But beneath the river’s revival, a darker current still runs.
“In many ways, the Thames is a much healthier ecosystem than it was. Though there are other pressures, like pharmaceuticals, chemicals, [micro]plastics, in the sewage now, against heavy metals several decades ago,” said Dr. Alexander Lipp, an Earth and environmental scientist who created Sewage Map, a platform that tracks sewage overflows in real time.
“Only 6% of the rivers and streams in the Thames basin are classed as in ‘good ecological health’ by the Environment Agency,” a spokesperson for Thames21, an environmental charity working to revive rivers in the Thames Basin, told ABC News. “The primary culprit is physical modifications (straightening, deepening or even paving over rivers), followed by sewage pollution.”
Thames Water saw serious pollution incidents more than double in 2024 — to 33 from 14 a year earlier — according to the Environment Agency’s latest report, which was released before the new “super sewer” began opening. Out of nine water companies assessed, Thames Water alone earned a one-star rating, the lowest possible.
Officials at the Environment Agency — a government agency responsible to protect and improve the environment in the U.K. — attributed the decline in the rating to a mix of factors: unusually wet and stormy weather, years of underinvestment, poor infrastructure maintenance and more rigorous monitoring.
Thames Water said that “all discharges of untreated sewage are unacceptable” in a 2023 statement.
Addressing the low ratings, a company spokesperson said in an emailed response to ABC News, that “in 2024-25, Thames Water also made a record capital investment of £2.225 billion. We know we need to further improve for our customers, community, and the environment, which is why we have embarked on the largest ever investment programme, delivering the biggest upgrade to our network in 150 years.”
Yet those promises are shadowed by debt — nearly £17 billion, or about $22.3 billion, as of March 2025 — amid the growing pressure of climate change. The company said this month that its debt had grown to nearly £20 billion and that it was negotiating with its creditors.
“Any sewage discharged into the Thames negatively affects the river, increasing nutrient loading, bacteria, and plastic pollution,” the Thames21 spokesperson said.
“Climate change is something that’s going to make this worse,” Lipp said. He explained that London’s combined sewage system, where stormwater and wastewater share the same pipes, is easily overwhelmed by heavy rain. With more intense downpours expected, spills will likely become even more frequent.
Still, Lipp noted, “I would say that Thames is better than other companies when it comes to data transparency.”
The company says long-term recovery will take patience. “Transforming Thames is a major programme of work that will take time; it will take at least a decade to achieve the scale of change required,” a spokesperson said.
“I can see the people taking more responsibility for our waters,” said Grajciarik, the fisherman. He often reports oil from nearby boats or sewage spills to the U.K.’s Environment Agency’s hotline number.
But whether the massive investments and new infrastructure will be enough remains uncertain.
“Only time will tell,” Lipp said.
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