Paris 2024 Olympic Games Triathlon - Update Water Quality

World Triathlon wants to share a report made public on July 4, 2024 by the City of Paris regarding water quality at the Seine river. Please note that the Triathlon and Para triathlon venue and swim course are located at Pont Alexandre III.

Seine Water Quality

The four points monitored daily and presented in this Seine water quality bulletin provide a precise indication of the microbiological quality of the water along the entire stretch of the river in Paris. They are located at the following sites:

Bercy (right bank);
Bras Marie;
Pont Alexandre-III – Olympic Site;
Bras de Grenelle;

For each of these points, daily samples have been taken since early June and analyzed by the Eau de Paris laboratory. Two bacteria (Escherichia coli and intestinal enterococci) are being tested for.

During the period from June 24 to July 2, 2024, the results for each of the monitored points were as follows:


E. Coli (concentration level in CFU / 100ml)

Enterococcus (concentration level in CFU/100ml)

In spite of a rather significant water flow, the Seine water quality has improved over the period, and the results are consistent with the thresholds as determined by the European directive over six days (from 24 to 29 June, 1 and 2 July for almost all sampling sites)

This positive evolution is due to the return of sunshine and warmer temperatures, and to the works carried out as part of the Seine Water Quality Improvement Plan.

Water quality degraded on Sunday 30 June as a consequence of rainfall on Saturday 30 June over the Île de France catchment, before improving again the following day..

In more detail:
- The Seine water flow remains high and significantly higher than usually observed in the summer season (four to six times the usual summer flow).
- It decreased slowly over the week, dropping from 605m3 /s to 407m3 /s before increasing again.
- The hydrological context is unfavourable on Sunday 30 June because of strong thunderstorms and heavy rains upstream of Paris that have impacted the Seine and Marne rivers. In total, 24mm of rain have fallen down the whole of the Île de France catchment over the weekend.
- The degraded quality observed on 30 June on the four sampling sites, with a lower incidence downstream of Paris than upstream, is due to the rain fallen upstream.
- The water quality results drop beneath swimmability threshold again on the following day, 1 July.
- The increase of E. coli rates at the level of the Pont Marie site on Thursday 27 June may be related to occasional local pollution that has had no impact downstream.

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