12 Rivers That Came Back to Life, Like the Seine, Where Swimming Was Banned for 100 Years

Four hydroelectric dams on the Klamath River, which runs from southern Oregon into California, came down in 2023 and 2024. NOAA called it the world’s largest dam removal effort, reconnecting 420 miles of salmon habitat for the first time since 1918.

The salmon didn’t wait long. On Oct. 16, 2024, Oregon biologists found a fall-run Chinook salmon in a tributary above the former J.C. Boyle Dam, the first sea-run fish to reach the Klamath Basin in Oregon since 1912.

Swimming in the Seine was banned in 1923 because of pollution. On July 5, 2025, Paris opened three public swimming spots in the river: one near the Eiffel Tower, one close to Notre-Dame and one in eastern Paris.

They were free, with lifeguards, for anyone aged 10 or 14 and up, depending on the site. A few dozen swimmers were waiting when they opened at 8 a.m. More than €1.4 billion, about $1.6 billion, had gone into cleaning the river before the 2024 Olympics.

In 1969, a fire on the oil-slicked Cuyahoga River in Cleveland made it a symbol of polluted American water, and NPR has called it the poster child for the Clean Water Act.

The EPA tracks the river’s problems one by one, and five of the nine on its list are now officially gone. Restrictions on eating fish were lifted in January 2019, fish tumors were crossed off in August 2023 and beach closings in September 2024. Two old dams were taken out in July 2020 to help fish move upstream.

Seoul started covering the Cheonggyecheon stream with concrete in 1958, and from 1969 an elevated highway opened in stages right on top of it. For decades, traffic ran over the old stream bed.

In 2003, Seoul began tearing the highway down, and in 2005 the stream reopened as a 3.6-mile corridor of water and walking paths. Between 2003 and 2008, the number of fish species there rose from 4 to 25, and bird species from 6 to 36. The air along it is up to about 10°F cooler than on a road a few blocks away, and about 64,000 people visit every day.

The Bronx River is New York City’s only freshwater river, and for decades it was badly polluted. In 2007, beavers returned to it for the first time in more than 200 years.

In June 2026, a motion-activated camera photographed a North American river otter foraging in the river, the first documented there since the early 1900s, according to the Wildlife Conservation Society. One otter doesn’t prove that a family lives there, but otters need clean water and plenty of fish.

Two dams built on the Elwha River in Washington state in the early 1900s blocked salmon and trout for about a century. Their removal, the largest in U.S. history at the time, began on Sept. 17, 2011. The Elwha Dam was gone about six months later, and the Glines Canyon Dam followed in 2014.

By 2014, the river was running through the old bed of Lake Aldwell, the reservoir behind the Elwha Dam, and NASA satellite images showed it carrying off sediment that had been trapped behind the dams for decades.

Heavy pollution meant the Thames estuary was deemed incapable of sustaining aquatic life in the 1950s. It has recovered a great deal since.

In 2013, a Zoological Society of London survey counted 708 seals in the estuary, about 500 harbor seals and 200 of the larger gray seals. People have reported seals as far up the river as Richmond, by the London Eye and at Canary Wharf.

Official swim events in the Chicago River ended in 1926, and for decades the river was a dumping ground for industrial pollution and sewage.

On Sept. 21, 2025, hundreds of swimmers took part in the first official Chicago River Swim in nearly 100 years, and organizers planned a second race for September 2026 with 500 more spots. Downtown, floating wetlands now host beavers, muskrats and snapping turtles, and a 1910 dam was removed in 2018 so fish can travel upstream.

The Mersey in northwest England was once famous for its salmon, but after the Industrial Revolution it became infamous for pollution. People used to say there were no fish in the estuary at all.

In 2003, BBC News reported that the river was clean enough to support fish for the first time since the Industrial Revolution, after nearly 20 years of clean-up. The year before, the Environment Agency had caught 26 salmon in a fish trap at Woolston Weir and put them back. Anglers were also catching brown trout, sea trout and lamprey.

Raw sewage made the Willamette River in Portland, Oregon, unsafe, and it was closed for swimming in 1924. In 2012, the river officially became swimmable again.

Now people in Portland swim and float in it every summer, and an annual inner-tube parade called the Big Float has drawn thousands of people onto the water.

The Rhine runs from the Swiss Alps through Germany and the Netherlands to the North Sea.

According to the International Commission for the Protection of the Rhine, salmon have been migrating up the river from the North Sea since 1990, and since 1994 they have reproduced naturally in the Sieg, a tributary in Germany. New fish passes at weirs now let salmon and sea trout reach the Upper Rhine and spawn in streams in Alsace and the Black Forest.

A year after the last dam came down, 28 teenage tribal representatives set out to paddle the entire Klamath River. In July 2025 they finished a 30-day, roughly 310-mile journey from the headwaters in the Cascades to the Pacific, the first people to kayak the whole river in more than a century.

On the way, they ran rapids that had been hidden under the reservoirs for decades, including more than 2.5 miles of class IV whitewater.