'Would You Jump Into Your Local River? Swimmable Cities May Be Within Reach as Once-Polluted Waterways Are Restored,' Smithsonian Magazine

March 11, 2026

Smithsonian Magazine: Efforts to improve the "swimmability" of urban areas are gaining global traction, from Paris to Chicago

When government officials, environmental leaders, entrepreneurs and researchers gathered in the Netherlands last summer for an important summit, the first order of business was cannonballs.

"We asked people to register, and then we said, 'Get in your bathers, we're going for a swim,'" says Matthew Sykes, co-founder of the global alliance Swimmable Cities, which hosted the event. "We had 200 people that didn't know each other jumping into the Rotterdam harbor in waves and basically turning into playful children."

For many people, leaping into a body of water on the edge of a major urban area might spark revulsion. But Swimmable Cities aims to get people to do just that. The group brings together stakeholders and experts from all over the world to share knowledge about making urban waterways clean enough to swim in. The Rotterdam gathering, which included representatives from more than 20 countries, was the organization's first summit.

Swimmable Cities reflects a wider global movement to improve water quality in urban rivers, which have long been dumping grounds for sewage and storm runoff, making them unsafe for humans and many animals. Its appeal is broad-the coalition, which began in 2023, spans governments, utilities, businesses, academics, swimmers, nonprofits and beyond, and it already represents 100 cities. Sykes says he hopes to bring that number to 300 by 2030.

Cleaning up city waterways would come with many benefits, including healthier ecosystems for plants and animals and reduced flooding. But while improving water quality looks a little different for every city around the world, the concept of "swimmability" is something anyone can relate to, says Gary Belan, senior director of clean water supply at the nonprofit American Rivers.

"The reason why we focus on swimmability is clean water is complicated," he says. "It's a lot of chemistry. There's a thousand different pollutants and a thousand different ways for it to get in the water. And people's eyes glaze over when I talk about the infrastructure and whatnot. When you talk about swimmability, it's something that people can easily grasp."

And swimmable waters, he argues, can bring a cascade of positive effects. "If you can make the river swimmable, then you're addressing a whole host of other clean water problems around the community."

What happened to our rivers?

For most of their histories, urban centers poured sewage into the nearest river, filling it with bacteria that can harm marine ecosystems and endanger swimmers. To combat this release of waste, 1972's Clean Water Act prohibited the discharge of pollution into U.S. waterways without proper treatment or permits, and the European Union's 2000 Water Framework Directive implemented monitoring rules and water quality standards that member states must meet.

Now, "a lot of people don't think twice about where their water goes after it leaves their houses," says Patrick Thomas, a public affairs specialist at the Metropolitan Water Reclamation District of Greater Chicago (MWRD). "It's all got to be treated and cleaned and eventually goes back to the environment."

But even with those legislative frameworks and wastewater treatment procedures in place, many urban rivers still see sewage pollution each year. An estimated 860 billion gallons of sewage overflows in the U.S. annually when sewer pipes burst, crack or flood-enough to fill more than 1.3 million Olympic-size swimming pools.

This pollution can inundate rivers with bacteria like E. coli and enterococci, which can cause a slew of health issues in people and prompt algae blooms, harming plants and animals.

On top of that, when it rains in cities, the stormwater runs along streets and buildings, picking up pollutants like the oil and gasoline that drip out of vehicles, before flowing into waterways. It also washes agricultural runoff-including manure, fertilizers and pesticides-into streams and lakes. And stormwater, which is often not regulated to the same degree as sewage, can also enter and flood sewer systems and wastewater treatment infrastructure.

Good water quality is essential to cities, says Belan. "Water-and clean water-is a fundamental reason for why we build communities where we build them," he says. But when enough sewage and stormwater enter urban waterways, the problem goes beyond the river. This can lead to flooding and infrastructure problems across cities when excess pollution and liquid aren't managed properly, he adds: "It's not just an ecosystem thing; it's a community health issue."

Efforts to improve river water quality are not new. Cities around the world have been working for decades to make their waterways safer. Stockholm, for example, opened its major river for swimming in 1991, after nearly 20 years of infrastructure work. But now, many more cities are reaching results that the public can see-and even dive into.

Finding paths to swimmable rivers

Prior to 1889, Chicago dumped its sewage into the Chicago River, which emptied into Lake Michigan, the city's drinking water source. To protect residents' health, the MWRD was tasked with reversing the flow of the river-engineering a solution that sent the polluted water in the opposite direction, where it ultimately became diluted as it headed down the Mississippi River. The utility built a network of canals, followed by treatment plants and improved sewer systems in the early 20th century to restore its local waterway.

This past fall, Chicago opened its river to swimmers for the first time in around a century.

Now, the organization continues to work on improving the river's health-it collects daily water quality data, treats 450 billion gallons of water annually and manages a 110-mile network of tunnels that capture sewage and stormwater before they can enter the river.

In September, Chicago held its first official public swim in roughly a century. Though the MWRD was not involved with organizing the event, Thomas says, the return of recreation to the river is a new achievement and consideration for a system that is "always going to be a work in progress."

"We're stepping into uncharted waters here, so to speak," he says.

Logistically, the process to this achievement will vary by city, says Belan. Making a river swimmable involves efforts on financial, political and cultural levels-beyond considerations around the science of water quality. Different urban areas often have different sources of funding for water treatment, and various types of water pollution are managed by separate entities.

In Milwaukee, Wisconsin, for example, a single regional wastewater authority manages sewage for 26 municipalities, Belan says, but each municipality manages stormwater individually. Bringing these localities together to capture and filter all sources of contaminated water presents bureaucratic and logistical challenges. Milwaukee joined Swimmable Cities' charter in 2025 and is working to clean all its waterways to the standard of swimmability.

The local relationship between a community and its rivers also looks different everywhere. "In the Southwest and on the West Coast, for example, rivers are smaller," Belan says. "They're dry a lot of the time. There might not necessarily be a culture in those places of enjoying the rivers as recreational amenities, whereas if you go to the Great Lakes, they're all about water and the rivers. So there's a cultural element to it as well."

Swimmable Cities is working with both New York and Melbourne, Australia, on their rivers' swimmability, and the cities' respective hemispheres are not their only major difference. In New York, the city is building a manmade pool in the East River that's designed to filter the river's water and educate swimmers about environmental issues. In Melbourne, officials are prioritizing the environmental health of its major river, but they're also using legislation informed by Indigenous practices, which recognize the river as a living entity with rights in the region.

Sykes says these different approaches highlight that "each story is different, but you run into very similar themes." The makeup, history and priorities of each city inform how it brings recreation back to its rivers, he adds. But getting cities to work together and share knowledge shifts "what has felt like a very lonely journey to a much more collaborative one," he says, "and what felt like impossible tasks to being much more possible and inspiring and fun."

Paris' swimmability efforts made international headlines in 2024 as the city opened the waters of the Seine-where swimming had been banned since 1923-to Olympic athletes. The work to improve the river's water quality started in 2016, following the city's 2015 bid to host the Olympics. Using other cities' infrastructure as models, Paris' $1.5 billion project added new pipes, tanks and pumps to control runoff from heavy rains and worked with large-scale and household polluters to prevent wastewater discharge, says Mathilde Théry, an environmental consultant for the city. After Paris welcomed swimmers to its waters, the mayors of London and Rome also announced plans to open their urban waterways for recreation.

"We were inspired by other cities, and we hope to inspire other ones," Théry says.

These cleaning efforts continued after the Olympics. A year later, Paris opened the Seine to the public, allowing people to dive in at designated swimming spots that were subject to regular testing to ensure bacteria levels met European standards for recreation.

"The main challenge was to convince people to come," Théry says. Because of pollution, rivers in major cities "have a bad reputation," she adds. "We have to change this image and construct some places where [people] want to go and have a good time and be happy and refresh when it's hot outside."

Keeping the swimmability movement afloat

Growing up in rural West Virginia, Belan spent most of his childhood swimming or playing in nearby rivers. When he moved to Washington, D.C. as an adult, he recalls, he was surprised that most kids he met did not even consider that type of recreation an option.

"My interaction with rivers was completely different from the kids in this community, and I wanted to know, 'How do we change that?'" Belan says. "I wanted to make sure these kids had the same experience I did. And they shouldn't have to travel two hours to the country to do that. They should be able to go in their backyard."

Washington's Potomac River now has a network of advocacy groups, scientists and community members that monitor water quality, litigate against polluters and increase public awareness of issues affecting rivers. In January, though, an upstream sewer valve in Maryland burst, spilling more than 240 million gallons of raw sewage into the Potomac-a swimmability setback, to say the least. The event ranks among the largest sewage discharges in the country's history.

The Potomac Riverkeeper Network, which joined the Swimmable Cities charter in 2024, has been monitoring water quality and spreading awareness about the pollution since a Washington, D.C. resident initially noticed the leak, says Betsy Nicholas, the organization's president.

"We're really pushing for meaningful restoration that goes well beyond just cleaning up the site of the rupture and repairing the pipes but actually considers the ecological impacts and the recreational and commercial impacts of the river," she says. "There's also this big stigma that's going to sit out there; people are calling it the 'poop-tomac.'"

Though the city has now lifted the ban on river recreation, Nicholas says there's more work to be done. Swimming is still prohibited in the D.C. sections of the Potomac without a permit, something the Riverkeeper Network hopes to change by 2030. Nicholas says the sewage spill puts "a big question mark in the middle of that but could also be an opportunity."

"There's a few things this is going to highlight," she says. "One is that the biggest issue overall to swimming in our urban waterways is failing infrastructure, and that's the story in all cities. We can't have those high bacteria levels without it being unsafe, and the bacteria is always coming from leaky, broken, aging sewage pipes."

Without major investment, this type of situation is a risk for cities all over the United States and the world, Nicholas says, but the disaster could serve as a catalyst for solutions at the government level.

"Perhaps this can be a moment to recognize that this needs to be a priority," she says.

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