This story is part of a special series that explores the global water crisis. For more clean water news, photos, and information, visit National Geographic's Freshwater website.
The fly-fisher standing in the clear-flowing river could be from the movie A River Runs Through It: Even his Western-style hat is like the one Brad Pitt's character wore in the U.S. film.
Except this isn’t Montana (see map). Instead of pines and mountains, the backdrop is a busy high street, with red double-decker buses, betting shops, and kebab houses. This river, the Wandle, runs through the middle of London.
A similar scene unfolds in central Stockholm. Outside the Swedish Royal Palace, an angler carrying his heavily bent rod weaves between tourists and waterside hot dog sellers. He straddles the wrought iron railings, goes down a ladder, and later emerges with a large, silver trout.
Across Europe, fish are returning to city waterways thanks to major cleanup efforts in recent decades. And with them, a rare species of recreationist: the urban angler.
Atlantic salmon and sea trout (sea run brown trout)—migratory fish that are extremely sensitive to pollution—are among 67 fish species now found in the Rhine, which passes through 17 major European cities, according to a 2009 survey by the International Commission for the Protection of the Rhine.
"As far as fish are concerned, the species composition is almost complete today," the report said.
Between 1870 and 1950, the Rhine's annual salmon catch plummeted from 280,000 tons to zero. But in 1990, salmon reappeared, and two years later, the fish began breeding, according to the Rhine-protection group.
And in 2009, scientists announced that salmon had returned to Paris—a lucky angler even managed to catch one. About a thousand salmon that had migrated up the River Seine were recorded in the French capital, which had been devoid of the species for nearly two decades.
River Wandle Goes from Sewer to Success
The River Wandle, which snakes through central London, may best illustrate the story of Europe's reviving urban waterways.
Once one of England's finest trout streams, its fans included Battle of Trafalgar hero Lord Nelson, who—despite the loss of an arm and the sight in one eye—would fish there on shore leave during his ultimately victorious campaign against Napoleon’s fleets.
But the Wandle began to decline with the industrial revolution—an 11-mile (18-kilometer) stretch of river supported more than 90 water mills, which made everything from snuff to silk to gunpowder. Inundated with toxic chemicals and raw sewage, the Wandle was officially designated an open sewer in the 1960s.
Yet after serious cleanup efforts by government, water companies and conservation groups, the river today is teeming with life. Fly-fishers can once again be seen casting for its fabled brown trout, said local angler Theo Pike, chair of the environmental nonprofit Wandle Trust. (Watch a video of trout spawning.)
These inner-city trout originally came from tiny fry introduced to the river as part of a local school project. But in the past few winters, Pike said, the fish started spawning in the river. "It's like New Zealand out there," he added, referring to that country's trout-rich waters.
In March, during a sample survey, Pike and a colleague discovered the first wild-born Wandle trout fry in in more than 80 years. "That one little fry was the first definite proof of success," he said.
The reason behind this success—vastly improved water quality—is due to both a collapse of extensive industry and improved sewage-treatment technology in recent decades, Pike noted.
River Thames Also Improving
The Wandle empties into the River Thames, which is now considered one of the world's cleanest metropolitan tideways—boasting seals, dolphins, and about 120 fish species. (Also see: "Rare Seahorses Found in River Thames.")
But between 1860 and 1960—like the Wandle—the Thames was reduced to sewer status. Deprived of oxygen due to feces-feasting bacteria, the river's London reaches formed an impassable barrier to salmon and other fish, said Neil Dunlop, of the United Kingdom’s Environment Agency.
But the city's main sewage-treatment facilities were enlarged and improved, Dunlop said—"that's the major reason why the tideway has been cleaned up."
In Stockholm, modern water-purification plants put in place in the 1970s prepared the city's waters for the reintroduction of migratory sea trout.
And in 1996, the Aquaria Water Museum capitalized on Stockholm's revitalized waters to create a unique visitor attraction. Each autumn, sea trout migrating from the Baltic Sea literally swim into the museum—via an artificial stream—where visitors can observe them in a glass-fronted pool.
Their offspring—raised in a hatchery from eggs and sperm harmlessly taken from the returning trout, and then released as juveniles—will also find their back to the museum as adults because of their powerful instinct to breed where they grew up, said museum curator David Mårding.
The largest trout to return so far weighed in at a whopping 24.6 pounds (11.2 kilograms), Mårding said.
While the urban renaissance of trout and salmon is in large part due to regional environmental actions, the trend also reflects tougher European Union legislation, said Peter Kristensen, inland water project manager for the European Environment Agency.
For instance, the 1991 Urban Waste Water Treatment Directive requires all settlements with populations of more than 10,000 that discharge wastewater into environmentally sensitive areas to meet the highest collection and treatment standards.
Upstream Battles Remain
Kristensen admitted, however, that some member states are more proactive than others in obeying the directive. The Senne (Zenne) River, which flows through the Belgian—and ironically, E.U.—capital Brussels, is "still one of the most polluted rivers in Europe," Kristensen said.
Elsewhere, more work is needed. London has a $3.6 billion (£2.5 billion) "super sewer" in the pipeline that would prevent untreated sewage from periodically spilling into the Thames during rainstorms.
On the Rhine, the river-protection group said its goal of 7,000 to 21,000 migrating salmon by 2020 will require further action in the form of weirs and dams to remove barriers to their upstream passage.
Still, the signs of recovery are promising—especially for Europe's growing ranks of urban anglers.