Hydrothermal Modeling of Groundwater–Surface Water Interactions Under an Evolving Climate

Groundwater–surface water interactions play a critical role in regulating river temperature and flow, particularly in northern regions affected by climate change. This study evaluates the influence of climate warming on groundwater discharge for two rivers in Quebec: the Sainte-Marguerite River, located in a humid continental zone without permafrost, and the Berard River, situated in a subpolar continental zone with discontinuous permafrost. Using two-dimensional hydrothermal modeling supported by field data, the analysis reveals that climate warming will increase groundwater seepage into both river systems. The effect is notably more pronounced in permafrost regions, where thawing accelerates subsurface flow. Model projections indicate that permafrost near the Berard River may vanish by 2040 under high-emission scenarios or by 2070 under low-emission scenarios. This transition is expected to result in more than a thirtyfold increase in groundwater discharge by the end of the century. These findings highlight the growing influence of groundwater in shaping river hydrology under changing climatic conditions and underscore the need to incorporate subsurface flow dynamics into future water resource management and habitat conservation strategies in northern environments.