This theme presents the index of water health along the banks of the St. Lawrence River. It makes it possible to determine if the sites present risks to human health and if they are suitable for swimming. These data are the result of an exploratory monitoring program that aims to raise awareness among the population and local actors about the possible reopening of bathing sites that have good potential. This program also makes it possible to highlight any improvement in bacteriological quality resulting from the reduction of wastewater overflows during rainy weather or resulting from the installation of disinfection equipment.**This third party metadata element was translated using an automated translation tool (Amazon Translate).**

This dataset presents the physicochemical and bacteriological evolution of water in rivers in southern Quebec and the St. Lawrence River. The 10-year (2015-2024) temporal trends on the rivers and in the river present the evolution of the ambient concentrations of physicochemical and bacteriological parameters, while the 20-year (2004-2023) time trends on the rivers present the evolution of loads and concentrations adjusted for the flows of physicochemical and bacteriological parameters. *Note that the temporal trends in total phosphorus have been invalidated due to an underestimation of concentrations caused by analytical biases that affect the majority of the data targeted for calculations. Therefore, they are not broadcast.**This third party metadata element was translated using an automated translation tool (Amazon Translate).**