Study of the spatial and temporal variations in the vulnerability of water resources in the watershed of the St Charles River water intake (Quebec, QC)

The St. Charles River water intake supplies nearly 420,000 people with drinking water in Quebec City. Part of the river’s flow is taken and then treated before being distributed to the downstream residents. The management of the water resource is under threat in a context of climate change, with higher floods in the spring and more severe low water levels in the summer.

Previous studies have allowed us to propose a hydrogeological conceptual scheme and to draw up a first vulnerability map of the water resources in the catchment area of the water intake. Today, the transient nature of surface and underground flows must be investigated. The determination of the preferential recharge areas and periods, the distribution of the age of the groundwater and the average age of the water feeding the rivers are part of the project objectives, in connection with the study of the vulnerability of the resource.

Methodologies based on the study of isotopic tracers (¹⁸O-2H, ³H, ²²²Rn) and environmental tracers (CFCs, SF6, rare gases) will be implemented and combined with more classical hydrogeological approaches (flow measurements, determination of hydrodynamic parameters of aquifers etc.). This information will constitute a valuable tool for modeling surface and underground flows on the scale of the catchment area and will allow better management of the resource, making it possible to carry out management scenarios in a context of climate change.