The Seine River, a defining feature of Paris, has long captivated visitors. A key question now is its water quality: Is the Seine clean enough for swimming? This inquiry stems from recent efforts to transform the river’s ecological state. Understanding its current condition involves examining its journey through significant improvements and ongoing environmental health commitments.
The Seine’s Journey to Cleaner Waters
For over a century, swimming in the Seine River was prohibited since 1923 due to high levels of pollution. Historically, the river suffered from extensive contamination, receiving untreated urban and industrial sewage, leading to low oxygen levels and high concentrations of ammonia, nitrites, and fecal bacteria. By 1970, about 60% of urban sewage was directly discharged into the river, reducing fish species to only three.
Significant improvements began in the early 2000s, driven by regulatory measures like the European Water Framework Directive. These efforts led to reductions in organic carbon, phosphorus, and ammonium, decreasing algal blooms. Fish species near Paris rebounded from three to 32 by the early 2020s, including Atlantic salmon. Daily monitoring analyzes indicators like Escherichia coli (E. coli) and intestinal enterococci, signaling sewage pollution. While water quality improved, heavy rainfall can still overwhelm the system, causing temporary bacterial spikes.
Key Initiatives Driving Improvement
The Seine River’s water quality transformation results from substantial investments and targeted projects. A €1.4 billion ($1.5 to $1.6 billion) cleanup program, known as the “Swimming Plan,” was launched in 2018 to make the river safe for public use. This investment included upgrading wastewater treatment facilities. For instance, the Seine Aval wastewater treatment plant, Europe’s largest, has undergone modernization, including the installation of biofiltration and membrane filtration processes, and a new biogas production unit. These upgrades allow the plant to treat wastewater from six million residents daily, ensuring efficient pollutant removal.
Addressing stormwater runoff was another central focus. Paris constructed the Austerlitz water storage basin, a subterranean reservoir with a capacity of 50,000 cubic meters, equivalent to 20 Olympic swimming pools. This basin collects excess wastewater and stormwater during heavy rains, preventing untreated discharges into the river by gradually releasing it into the sewer system for treatment. Efforts also connected over 20,000 homes and 170 boats that previously discharged directly into the Seine to the sewer system. These infrastructure improvements, combined with continuous monitoring, aim to reduce bacterial contamination.
Public Access and Future Milestones
The improved water quality has paved the way for public swimming in the Seine. For the first time in over a century, public swimming has been permitted since early July 2025. Three designated bathing sites have opened in central Paris: one near the Eiffel Tower (Bras de Grenelle), another near Notre Dame Cathedral (Bras Marie), and a third in Bercy. These sites are equipped with amenities such as changing rooms, showers, and lifeguard supervision. Daily water quality tests are conducted and communicated via a flag system.
The cleanup efforts were accelerated by the river’s role as a venue for the 2024 Paris Olympics. While Olympic events faced some postponements due to temporary water quality issues after heavy rainfall, the competitions ultimately proceeded, demonstrating the river’s capacity to meet safety standards. Beyond these three initial sites, plans include opening 14 additional bathing spots along the Seine and Marne rivers. These milestones signify a significant environmental achievement and a renewed connection between Parisians and their iconic waterway, aiming for sustained public access to a cleaner Seine.