Comparison of water quality between the Lake of Banyoles, Girona, Spain, and the River Seine, Paris, France, considering the bridges along the river where the Olympic Games took place: Evaluation of Suitability for Aquatic Sports Practice

The quality of water in recreational and sports environments plays a crucial role in ensuring the safety and health of participants. Aquatic sports, such as rowing and swimming, are becoming increasingly popular, but poor water quality can pose significant health risks. This study compares the water quality between two iconic locations: Lake Banyoles in Catalonia, a natural environment that has hosted numerous sports events since the 1992 Olympic Games, and the River Seine in Paris, an urban waterway that recently hosted the 2024 Olympic Games. Both locations present different challenges in water quality management due to their distinct environments. Banyoles has a lower population density and a rural setting, whereas the Seine flows through a densely populated city and experiences pollution from urban stormwater and wastewater discharges. Microbiological contamination, particularly from indicator bacteria such as Escherichia coli and enterococci, is used to assess water safety. These bacteria are widely recognized as markers of fecal contamination and indicators of potential health risks. This study analyzed microbiological parameters between 2014 and 2022, using samples from areas frequently used for recreational activities in both locations. The results show that Lake Banyoles consistently presented lower concentrations of Escherichia coli (1.70) and enterococci (1.58) compared to the River Seine, where concentrations were significantly higher, with values of 3.31 and 2.47, respectively. The analysis also highlighted greater variability in bacterial concentrations in the Seine, with higher peaks of contamination. Statistical tests confirmed significant differences between the two locations, with Escherichia coli levels consistently higher in Paris (p < 0.001) over the years. Temporal trends showed a slight improvement in water quality in Banyoles, particularly in Escherichia coli levels, whereas no significant improvement was observed in the Seine. The study highlights the importance of effective water management practices to minimize microbiological risks. It also underscores that urban environments like the Seine face persistent challenges, such as stormwater runoff and inadequate sewage systems, contributing to ongoing water contamination. These findings provide valuable insights for managing water quality in recreational areas, helping decision-makers prioritize health and safety measures to ensure sustainable aquatic sports practices.