Despite the creation of multiple stormwater reservoirs, such as the Bassin d’Austerlitz, which collect rainwater and release it slowly when bad weather has passed, if enough rain is concentrated in a small enough time, not everything that falls from the sky can be captured. In such a situation, runoff water has to be released into the river, which increases bacteria levels.
“Weather variability due to climate change is a major problem and this will only make things more difficult,” said Dan Angelescu, chief executive of water monitoring startup Fluidion at a July 31 news conference at the company’s office in Alfortville, just outside Paris. The company makes remote water sampling devices that transmit their readings to a central base and has been working with Parisian authorities since 2016 providing water analysis at the Bassin de la Villette reservoir, a separate swimming site in northern Paris that is already open for public swimming.
“Unless new projects to harvest runoff are implemented in the coming years, the Seine’s suitability for bathing and the opening of recreational and sports areas are likely to depend on meteorological phenomena, with bathing bans after rainy days,” explains Loïs Mougin, a doctoral researcher in exercise and environmental physiology at Loughborough University’s School of Sport, Exercise and Health Sciences.
Even without an increase in extreme weather events, keeping the Seine clean enough to swim in normal weather conditions, such as summer rains, is a major challenge, says Jean-Marie Mouchel, a professor of hydrology at Sorbonne University. “There are also many non-exceptional weather events that have an impact on water quality. We need to make the system more efficient to improve water quality in the face of them.” Water quality data from last summer supports this point. The Seine was inaccessible for swimming about 30 percent of the time, but Paris was spared extreme rainfall a third of the time.
Experts say there is also a need to improve how water is monitored and what information is shared with the public and when. “It is essential that bacteriological data is published daily, along with information on the associated risks,” says Mougin. These include the possibility of gastrointestinal problems and eye and skin infections.
“Monitoring will be critical,” Angelescu says. “Having technology that can monitor the right risk, measure the actual risk posed by all the bacteria and provide results quickly will be extremely important.” Conventional monitoring methods, which were used to make decisions for the triathlon (and which did not involve Fluidon), involve taking samples from the river and sending them to a lab, a process that is much slower than real-time monitoring.
Separately, Fluidon has been testing its technology at the triathlon site near the Alexandre III bridge during the Games, focusing on the levels of E. coli bacteria, to show how a faster system involving in-situ processing could work in the river. He has been publishing his results in near real time on a open data siteand says its technology provides a more accurate and up-to-date picture of water conditions.