HGS RESEARCH HIGHLIGHT – Vulnerability of the Saint-Charles drinking water source: portrait of the groundwater resources of the St-Charles River watershed and their links with surface water
Gatel, L., Tremblay, Y., Picard, A., N'da, BA, Frot, B., Therrien, R Cloutier, V., Barbecot, F. (June 25, 2024). Vulnerability of the Saint-Charles drinking water source: portrait of the groundwater resources of the St-Charles River watershed and their links with surface water. https://storymaps.arcgis.com/stories/179b86fca3cd4e828026660ad292cfe7
“In this model, water flows are modeled in two dimensions on the surface and in three dimensions in the subsurface environment. ”
Gatel, L., Tremblay, Y., Picard, A., N'da, BA, Frot, B., Therrien, R Cloutier, V., Barbecot, F. (June 25, 2024). Vulnerability of the Saint-Charles drinking water source: portrait of the groundwater resources of the St-Charles River watershed and their links with surface water. https://storymaps.arcgis.com/stories/179b86fca3cd4e828026660ad292cfe7
CLICK HERE TO VIEW THE ARCGIS STORY MAP.
We’re pleased to highlight this research effort, which focuses on understanding the vulnerability of the Saint-Charles River drinking water source and characterizing the groundwater resources that support it. Presented through a public-facing ArcGIS Story Map, this project delivers an accessible summary of a detailed hydrogeological study that integrates field measurements, geochemical analyses, and numerical modelling to evaluate the watershed’s current and future ability to provide safe, reliable drinking water for the City of Quebec and its surrounding municipalities.
The study area spans the 344 km² watershed upstream of the Château d’Eau intake on the Saint-Charles River, a critical source of drinking water for Quebec City and surrounding communities including Stoneham-et-Tewkesbury, Lac-Beauport, Saint-Gabriel-de-Valcartier, and the Wendake First Nation. With increasing urbanization and growing concerns over chloride contamination from road salts and reduced streamflow during low-flow periods, the study was initiated to better understand the linkages between groundwater and surface water and to assess potential vulnerabilities across seasons and hydroclimatic conditions.
To achieve this, researchers compiled and updated geological and hydrogeological data originally developed through the PACES-CMQ project. This update involved improving data resolution and precision at the watershed scale, while significantly expanding the scope to include surface water processes. The study applied a rigorous methodology that included new water quality and quantity monitoring installations, isotopic and geochemical characterization of groundwater and surface water, and the development of integrated conceptual and numerical models. These models were used to simulate the coupled dynamics of surface and subsurface flow, allowing researchers to explore transient behaviors of the hydrologic system and identify periods or zones of heightened vulnerability.
Of particular importance is the study’s alignment with Canada’s multi-barrier approach to drinking water protection, which emphasizes source-to-tap safeguards. By identifying key recharge areas, understanding baseflow contributions, and monitoring the impact of anthropogenic pressures, the research directly supports long-term water management and protection efforts in the Saint-Charles watershed. The integration of field data with a coupled surface–subsurface modelling platform, such as HydroGeoSphere (HGS), enabled the research team to simulate flow paths and groundwater residence times, helping to characterize the delay and distribution of recharge sources that ultimately feed the Saint-Charles River.
Using HGS, researchers constructed a digital model of the Château d’Eau water intake catchment, incorporating land use, geological features, and daily climate inputs at a spatially distributed scale. The model calculates water movement in two dimensions on the land surface and in three dimensions in the subsurface, solving the equations governing hydrological and hydrogeological processes. This comprehensive simulation framework allowed the team to assess how water flows through the watershed under different environmental and climatic scenarios—supporting their investigation into groundwater-surface water interactions and identifying areas of potential vulnerability in the drinking water supply.
Presented as a narrative map for broader accessibility, the Story Map distills complex scientific findings into a user-friendly format that allows residents, stakeholders, and policymakers to explore the spatial and hydrologic realities of their drinking water source. It emphasizes that while regional-scale modelling offers critical insights into water resource dynamics, local-scale issues still require site-specific studies for effective management and decision-making.
This work provides a foundational portrait of water resource vulnerability in Quebec City’s principal watershed and reinforces the role of integrated science and modelling in informing sustainable water management under changing land use and climate pressures.