Paris honoured for the historic return of swimming in the Seine after more than a century
Paris has received the first Environmental Award from the World Aquatics Foundation for its long-term Seine restoration project and the reopening of the river to public swimming after a ban introduced in 1923. The World Aquatics Foundation formally presented the award to the City of Paris at a ceremony held at the Bras-Marie bathing site, one of three developed and supervised swimming locations in the heart of the French capital. The award was presented by World Aquatics President Husain Al Musallam and Foundation President Dale Neuburger, in the presence of European Aquatics President António Silva, while the City of Paris was represented by Deputy Mayor Antoine Guillou, responsible for the Seine and canals. The organisation highlighted the Paris project as an example of the long-term legacy of major sporting events, because investments launched and accelerated ahead of the 2024 Olympic and Paralympic Games did not end with the final competition. After several decades of infrastructure and environmental works, the river has become a space for sport, recreation and summer cooling in a densely built-up urban area.
World Aquatics announced on 5 June 2026, World Environment Day, that the inaugural edition of the award would be shared by the City of Paris and the Republic of Azerbaijan. The award is intended for practical and measurable projects that contribute to environmental protection, water sustainability and the preservation of aquatic ecosystems. Each recipient receives support of 25,000 US dollars, and the Paris share of the funds, according to a subsequent announcement by the World Aquatics Foundation, will be directed to the "1, 2, 3… Nagez !" programme. The programme is carried out in cooperation with six Paris swimming clubs and offers free swimming lessons to children and adults during school holidays. In this way, the award is linked not only to the ecological restoration of the river but also to access to swimming, water safety and the social use of a space that for decades had been practically separated from the everyday lives of residents and visitors.
From the 1923 ban to three public bathing sites in central Paris
Swimming in the Seine was once a common part of city life, but it was banned in 1923 because of deteriorating water quality and safety concerns. The return of swimmers is not the result of a single project or a single Olympic investment, but of decades of improvements to the sewerage system, wastewater treatment and the reduction of direct discharges into the river. Nevertheless, the bid and preparations for Paris 2024 gave the project a clear deadline and a strong political and financial boost. According to the French Ministry for Ecological Transition and the City of Paris, the Water Quality and Swimming Plan encompassed a broad system of works on the Seine and Marne, with the aim of reducing bacteriological pollution, enabling Olympic competitions in the river and creating permanent public swimming sites after the Games. The City of Paris states that the state, local authorities, public agencies and other partners invested around 1.4 billion euros in the overall plan.
In its announcement about the presentation of the award, World Aquatics describes the project more broadly and cites more than 1.6 billion euros in investments related to improving water quality, modernising infrastructure and restoring the river ecosystem. These two figures are not necessarily directly comparable because they refer to differently defined scopes of investment, so the official French estimate of around 1.4 billion euros remains the key reference for the Plan baignade itself. Its implementation involved the City of Paris, the French state, Agence de l’eau Seine-Normandie, the interdepartmental sewerage authority for the Paris agglomeration SIAAP, local authorities in the metropolitan area, waterway managers and other public partners. The objective was not merely to meet the requirements for several days of sporting competition in 2024, but to permanently reduce the quantity of wastewater and stormwater that can end up in the river during heavy rainfall. It is precisely this long-term infrastructure that forms the basis of today’s supervised swimming system.
The three official bathing sites in Paris were first opened to the public on 5 July 2025 at Bras-Marie, Grenelle and Quai de Bercy. The City of Paris states that almost 100,000 people swam there during the first season, and interest was high enough for the operation of two locations to be extended into September. In the 2026 season, all three bathing sites reopened, with free access and clearly prescribed safety rules. Bras-Marie is located in the historic city centre, Grenelle alongside the western section of the central Seine, and Bercy farther east, with each location featuring a physically delimited area for swimmers and organised supervision. Outside the official zones, swimming in the river remains prohibited, primarily because of river traffic, currents and changing hydrological conditions.
Infrastructure beneath the city was crucial for a cleaner river
One of the most important interventions was the large underground Austerlitz basin in Paris’s 13th arrondissement. The City of Paris states that the reservoir has a capacity of around 50,000 cubic metres, approximately equivalent to twenty Olympic-size swimming pools, and is used to temporarily retain a mixture of stormwater and wastewater during heavy rainfall. Instead of excess water from the sewerage system being discharged directly into the Seine, the basin retains it and then gradually returns it to the system so that it can pass through treatment facilities. Austerlitz alone cost around 90 million euros, according to data from the City of Paris, and it is only one part of a much broader network of works. Other large collectors and stormwater treatment facilities were also built as part of the plan, upstream treatment plants were modernised, and special attention was paid to incorrect building connections and wastewater from boats and floating structures.
Such interventions are particularly important because water quality in urban rivers is extremely sensitive to heavy rainfall. When a large amount of rain enters the sewerage system over a short period, it can exceed its capacity and increase the risk of untreated water overflowing into the river. It was precisely this problem that led to the cancellation of the Paris Marathon Swimming World Cup race in 2023, when World Aquatics concluded after above-average rainfall that the water quality did not meet the standards required to protect athletes’ health. That event demonstrated how technically demanding the project is and why the mere visual cleanliness of the river is not sufficient for a decision on swimming. Safety depends on microbiological analyses, flow, weather conditions and the functioning of the entire sewerage system upstream from the locations where people enter the water.
Olympic races were the test, public swimming the long-term goal
During the Paris 2024 Olympic Games, the Seine became one of the most striking sporting stages in the heart of the city. Marathon swimming races were held in the river, and it was also used for triathlon competitions, while the river itself played a central role in the opening ceremony. Water quality was then subject to daily monitoring and intense international interest, particularly after periods of rain and postponements of certain training sessions and competition decisions. For the organisers and the city administration, however, the Olympic programme was a transitional phase towards a goal that was intended to become visible only a year later: regular summer swimming for residents and visitors. The International Olympic Committee presented the opening of the three bathing sites in 2025 as one example of the lasting legacy of the Games, emphasising that the sporting event served as a catalyst for an infrastructure project that, under different circumstances, could have taken considerably longer.
The return of public swimming therefore has a broader significance than the symbolic "return to the river". During periods of intense summer heat, the developed zones provide residents and visitors with additional space for cooling off, recreation and physical activity without the construction of new indoor facilities. In its explanation of the award, World Aquatics particularly highlights the combination of supervised zones, daily water monitoring and urban infrastructure that increases access to cooling locations during high temperatures. Such an approach is becoming more important in European cities adapting to increasingly frequent heatwaves, but at the same time it requires constant risk management because a natural river is not a swimming pool with stable and fully controlled conditions. The Paris model is therefore not based on the claim that the Seine is always suitable for swimming, but on a system in which bathing sites open only when current data and conditions allow it.
Water quality is checked every day
In August 2026, the City of Paris announced that during the season water samples are taken daily to verify whether they meet official health criteria. Laboratory analyses focus primarily on the bacteria Escherichia coli and intestinal enterococci, two microbiological indicators used to assess the suitability of water for bathing. The results are combined with real-time measurements, field observations, data on possible sources of pollution, weather forecasts and the state of the river flow. The city states that the speed or volume of the flow is also monitored because an excessively high flow can itself pose a danger to swimmers, even when microbiological indicators are not problematic. This multi-layered monitoring system makes it possible to temporarily close bathing sites when rain, storms or other conditions increase the risk.
Regulatory supervision is also carried out by the regional health agency Agence régionale de santé, and the criteria are based on the European framework for the management of bathing water quality. This means that decisions on opening are not based on occasional symbolic measurements, but on repeated analyses and predefined thresholds. For visitors, the practical consequence is simple: the fact that swimming has returned to the Seine does not mean that it is permitted everywhere and at all times. For each official location, the city publishes information on whether it is open or closed, while safety rules include lifeguard supervision, restriction of swimming areas and coordination with river navigation. In this way, the return of swimming is treated as a permanent public service that depends on operational management, rather than merely as a one-off achievement.
The restoration of the Seine has also brought visible ecological changes
The improvement in the river’s sanitary condition has been accompanied by the recovery of part of its biodiversity. The City of Paris states that around thirty fish species are now recorded in the Seine, whereas during the worst period of pollution in the 1970s only three common species were recorded in the Paris area. Joint materials from French public institutions from 2025 also report an increase from 14 species in 1990 to 36 species in more recent measurements, which is associated with lower pollutant loads and better oxygen conditions in the water. In January 2025, three species of freshwater mussels were also identified in the central section of the Seine, which the City of Paris describes as sensitive indicators of habitat quality. Such data do not mean that this is a fully restored natural ecosystem, but they do show that investments in sewerage and reductions in discharges have consequences that go beyond the possibility of recreational swimming. The ecological benefit is therefore one of the elements for which the World Aquatics Foundation singled out the project as relevant to the broader discussion on the sustainability of aquatic sports.
Paris shares the award with Azerbaijan
The other recipient of the inaugural Environmental Award is the Republic of Azerbaijan. The World Aquatics Foundation cited the country’s long-term state commitment to environmental protection and sustainability, including the management of natural resources and water systems, as the reason for selecting it among the first laureates. On 5 June 2026, Azerbaijan was also the official host of the global observance of World Environment Day under the leadership of the United Nations Environment Programme, UNEP, with a focus on climate action. On that occasion, UNEP highlighted the themes of climate change adaptation, the energy transition and challenges such as the declining level of the Caspian Sea. World Aquatics announced that Azerbaijan’s 25,000-dollar support would be formally presented during the Swimming World Cup in Baku in early October 2026.
The legacy of a major sporting event that remains after the spotlight fades
Discussions about the sustainability of the Olympic Games and other major competitions often raise the question of whether temporary sporting events justify large public investments. The Seine project does not provide a universal answer to that question, but it offers one of the clearest examples of infrastructure that remained in everyday use after the Games. The key works were not temporary stands or facilities intended only for competitors, but sewer collectors, reservoirs, treatment systems and connections that continue to reduce pollution regardless of the sporting calendar. The opening of the bathing sites in 2025 and their renewed use in 2026 transformed that infrastructure result into a publicly visible legacy. This is precisely why the World Aquatics Foundation highlights the Paris example as a model in which a sporting event can accelerate an ecological and social project larger than the competition itself.
Nevertheless, success continues to be measured season by season. The Seine remains a large urban river influenced by weather, traffic, upstream discharges and a complex drainage system, so the permanently "won" possibility of swimming depends on continuous maintenance and monitoring. In 2026, the City of Paris continues to publish daily water quality data, while the three official zones operate under a system that allows them to close whenever conditions require it. This approach may be the most important part of the project: the return of swimming is not presented as proof that all of the Seine’s problems have disappeared, but as the result of a system that has improved enough for the river, under supervision, to once again become part of public life. More than a century after the 1923 ban, it is precisely this change in the relationship between the city and its river that brought Paris the first environmental recognition from the World Aquatics Foundation.
Sources:
- World Aquatics Foundation – official announcement on the formal presentation of the Environmental Award to the City of Paris, the ceremony at Bras-Marie and the allocation of the 25,000-dollar support to the "1, 2, 3… Nagez !" programme (link)
- World Aquatics – announcement of the first award recipients, the recognition criteria and data on Paris and Azerbaijan (link)
- Ville de Paris – current information on swimming in the Seine in 2026, daily water quality analyses and microbiological monitoring (link)
- Ville de Paris – data on the Austerlitz basin, its cost of around 90 million euros and the overall swimming plan worth around 1.4 billion euros (link)
- French Ministry for Ecological Transition – description of the Water Quality and Swimming Plan, financing and infrastructure measures on the Seine and Marne (link)
- International Olympic Committee – overview of the reopening of the Seine for public swimming and the project’s long-term Olympic legacy (link)
- Ville de Paris – data on the return of fish species and other biodiversity indicators in the Seine (link)
- UNEP – official information on Azerbaijan as host of World Environment Day 2026 and the themes of climate action (link)