Swimming in the Seine

In less than 365 days, the Olympic Games will begin in Paris. One of the biggest challenges for the city is to make the Seine swimmable for the competition – and afterwards for the citizens. You can find an update on this here.

The Olympic triathlon dress rehearsal for Paris 2024 took place a week ago. The participants were supposed to compete in the swimming part of the event in the Seine. However, the dress rehearsal literally fell through: contaminated water due to a defective wastewater valve and dead rats led to health risks, which is why the triathlon became a duathlon without swimming. During practice, some athletes experienced gastrointestinal complaints and E. coli bacteria were discovered.

Rio de Janeiro faced a similar problem at the 2016 Olympic Games, when contaminated water in the sailing area led to canceled competitions. Water samples are usually taken before a triathlon, as is the case in Paris, although it is not always clear where in the water the samples are taken.

Nevertheless, the city of Paris aims to hold open water competitions of the Olympic Games in the Seine in 2024. Although swimming in the river has been banned since 1923, the idea of swimming in the middle of the French capital is appealing. When the Olympic Games were held in Paris in 1900, it was still possible to swim in the Seine. At the second event in 1924, swimming had to take place indoors. In addition to Olympic competitions, the Seine is to be opened to the public for swimming in some places from 2025.

Like every major river in a city, the Seine in Paris is a popular recreational area. The city has already invested 1.4 billion euros in the greater Paris area to open up the Seine. This requires thousands of households and hundreds of houseboats to be connected to the sewage system. It is also necessary to build and modernize sewage treatment plants. Catch basins are planned for the Summer Olympics in order to guarantee the water quality of the river even when it rains. This is because wastewater from the overloaded sewage system can overflow into the river during heavy rainfall.

Currently, the water quality of the Seine is heavily dependent on the weather. The new infrastructure should guarantee good quality regardless of the weather.

One of the three places where it should be possible to swim in the Seine in future, even without an Olympic qualification, is not far from the Eiffel Tower. Another site is a water sports center that is already used for leisure activities on the Seine. And according to Paris Mayor Anne Hidalgo, the third site is also to be centrally located. All the water areas concerned are to be separated by buoys and accessible via a footbridge. Areas for changing and showering are also planned.

For several years now, swimming in the Seine has been possible in a floating outdoor pool. However, this consists of a separate pool that is anchored in the water. Accordingly, chlorinated water is currently used instead of river water. Jacques Chirac, president from 1995 to 2007, promised Parisians that they would soon be able to swim in the Seine again.

Now, 102 years after the ban on swimming, the three planned bathing areas, a legacy of the Summer Olympics, are set to fulfill this promise. The water quality was already poor in 1923. There was also concern about the increasing boat traffic, which could be dangerous for swimmers. So far, Paris’ investments have been largely successful and the water is safe for swimming 90 percent of the time, according to the city. Regular tests should guarantee this in the future.

In view of the consequences of climate change and predictions of increasingly hot summers, a swimmable Seine will not only make the French capital more attractive, but also more climate-resilient. Because when the summer weather reaches 40°C, or perhaps even 50°C from 2050, cooling off will be worth its weight in gold.

Despite the failed triathlon attempts in August 2023, Paris is on the right track as far as the water quality of the Seine is concerned. Samples taken on 6 June and 19 July showed values that were suitable for swimming according to World Health Organization guidelines. Due to heavy rainfall in August 2023, the water quality has recently dropped again.

The city plans to continue testing regularly and implement appropriate measures to clean up the Seine. Since the early summer of 2023, there have been two water treatment plants on the Seine and the Marne. And a new storage basin called Austerlitz can store over 50,000 cubic meters of water. So if it rains heavily shortly before next year’s Summer Games, wastewater can be fed into the sewage system and treatment plants via the storage basin instead of polluting the Seine.

There will also be alternative dates for the competitions in the water, just in case. Depending on the water quality, it should be possible to hold competitions at a later date if necessary. This shows that the city of Paris is not yet entirely sure about the water quality in 2024.

By the way: An overview of the 2024 Olympic Games in Paris, including urban planning changes, can be found here.