Simulating the impact of climate change on the groundwater resources of the Magdalen Islands, Québec, Canada

Study region: This study is conducted in the Magdalen Islands (Québec, Canada), a smallarchipelago located in the Gulf of St. Lawrence.Study focus: This work was undertaken to support the design of a long-term groundwa-ter monitoring network and for the sustainable management of groundwater resources.This study relies mostly on the compilation of existing data, but additional field workhas also been carried out, allowing for the first time in the Magdalen Islands, directobservation of the depth and shape of the transition zone between freshwater and sea-water under natural conditions. Simulations were conducted along a 2D cross-sectionon Grande Entrée Island in order to assess the individual and combined impacts of sea-level rise, coastal erosion and decreased groundwater recharge on the position of thesaltwater–freshwater interface. The simulations were performed considering variable-density flow and solute transport under saturated-unsaturated conditions. The modelwas driven by observed and projected climate change scenarios to 2040 for the MagdalenIslands.New hydrological insights for the region: The simulation results show that among thethree impacts considered, the most important is sea-level rise, followed by decreasinggroundwater recharge and coastal erosion. When combined, these impacts cause thesaltwater–freshwater interface to migrate inland over a distance of 37 m and to rise by6.5 m near the coast to 3.1 m further inland, over a 28-year period.

Mots clés

Coastal aquifers, Seawater intrusion, Climate change,Magdalen Islandsa