It was November 28, 1988. That day, Jacques Chirac, then mayor of Paris, made a promise that has remained famous. “In five years, we will be able to swim there again,” he announced when 5,000 pike were released into the Seine. “Chiche”, replies Brice Lalonde, Secretary of State for the Environment at the time. “I’ll come with towels and antibiotics,” he quips.
Two years later, Jacques Chirac confirms his promise during an interview on FR3, promising to “bathe in the Seine in front of witnesses” in 1993. He will do nothing. Thirty years after this episode, the question of the quality of water for swimming continues to fuel debate. Latest example: this Sunday, August 20. There will be no swimming in the Seine for the mixed relay triathlon test event for the Paris-2024 Olympics, the organizers announced.
The results of the analyzes of the water of the river do not offer “the guarantees necessary for the good performance of the swimming test”. The cause: the concentration of Escherichia Coli (E. coli) bacteria. “The laboratory sample had a slightly higher rate” than the level allowed by the regulations of World Triathlon, said the day before the sports deputy of the town hall of Paris, Pierre Rabadan, during a press point. “It was slightly above 1,000 (UFC per 100 ml)”, he further explained.
Storms, causing heavy rainfall in the event of waste water spilling into the river, are not the cause. “An investigation is underway to find the cause of this degradation but, to date, we have not yet found an explanation,” acknowledged Pierre Rabadan.
Less than a year from the Olympic deadline, this is the third test event affected by the quality of the river water in two weeks: at the beginning of August, the open water swimming event had been cancelled. The holding of swimming events in the Seine during the 2024 Olympic Games is therefore not completely guaranteed, as is the opening to swimming of three sites, in the 4th, 12th and 15th arrondissements, promised by the town hall to the summer of 2025.
The “Safe Ruhr” project
Let’s be reassured: the problem encountered with the Seine is not prohibitive. In Europe, it has indeed become possible to bathe in certain rivers or lakes for a few years after actions by the authorities. In Germany, for example, the “Safe Ruhr” research project made it possible to reopen the popular bathing site at Lake Baldeney, south of the city of Essen, in 2017. An industrial city, Essen has proven to be an innovative municipality from an environmental point of view, as specified by a bathing water management report of the European Environment Agency (EEA) dated 2020.
In the intensely industrialized Ruhr Valley, the river of the same name became increasingly polluted throughout the 20th century. Over time, its recreational use presented a health hazard. Due to chemical and microbiological risks, bathing was prohibited between 1971 and 2015. Following the installation of all levels of wastewater treatment in 2005 in Essen, the water quality of the Lac Baldeney, located on the Ruhr, has gradually improved.
The project combined extensive wastewater treatment with water quality monitoring, modeling the pathways by which bacteria and viruses enter the river, and developing an early warning system for pollution. short-term water, reports on The Conversation Tanja Radu, Lecturer in Water Engineering at Loughborough University.
In order for Lake Baldeney to be approved as an official bathing area, says the European Environment Agency, it was essential to have an early warning system for bathers, allowing the authorities to quickly prohibit the swimming on the site if necessary. This alert system is based on measured precipitation data. It is activated if the rain exceeds a certain threshold between the evaluation date and 2 days before. In this case, a web application issues an automatic warning message, and swimming is then temporarily prohibited on the site.
Amsterdam in pole position
Today, swimming in complete safety is also possible in certain European capitals: for example on the banks of the Danube in Vienna and Budapest, or on the river Spree in Berlin and in many places in Amsterdam. According to the report on bathing water management of the European Environment Agency, the cities with the highest number of bathing water points are Amsterdam (38), Stockholm (36), Berlin (33), Lugano (28), Geneva (25), Rotterdam (23) and Vienna (23).
Austria has very good quality waters: 96.9% of its bathing sites were judged to be of excellent quality in 2022, in second place behind Cyprus (99.2%), but ahead of Greece (96. 6%) and Croatia (95.6%), according to the report 2023 of the AEE.
In Vienna, about twenty places on the banks of the Danube are classified as excellent quality for swimming, as this interactive map from the EEA shows. The proportion of bathing waters of excellent quality reached 85.7% in the European Union in 2022, i.e. more than 18,500 controlled areas (compared to less than 4,000 in 1990).
Improving the water quality of Lake Varese
As in the German case cited above, the water quality of Lake Varese, in northern Italy, has deteriorated over a long period since the 1960s due to a significant proliferation of algae, often toxic, causing the death of fish.
Since the 1990s, however, a research program supported by the European Commission and the Italian Ministry of the Environment has restored the lake’s water quality. In 2000 and 2001, nutrients were removed directly from the lake through methods such as nutrient inactivation and dredging. Two of the lake’s three bathing sites are now of excellent quality. The last site remains of poor quality due to the discharge of insufficiently treated wastewater.
According to a survey by the Ifop institute published on July 1, 2021, the Seine is the least attractive French river for swimming: 70% of French people have a bad image of it. According to this study, only 12% of those questioned would have wanted to bathe in the Seine at the time, compared to 27% for the Loire, the most attractive river in this respect, ahead of the Garonne (25%), the Rhône (20% ) and the Rhine (19%).