CLIMATE-DRIVEN SALTWATER INTRUSION DYNAMICS IN A CONFINED SMALL-ISLAND AQUIFER IN ATLANTIC CANADA

Many small island communities rely solely on groundwater, and climate change is projected to have significant impacts on these unique hydrological systems and their critical groundwater resources. Coastal aquifers may suffer salinization due to lateral SWI (e.g. sea-level rise, erosion, or recharge reduction), or by vertical salinization processes that follow seawater flooding (e.g. during coastal storms). In this study, we investigate the effects of climate change stressors on a small island (~1.5 km wide) off the northern coast of Prince Edward Island, Canada. The groundwater system consists of a series of (semi-)confined aquifers from which water is pumped to support the community (approximately 500 people). Field instrumentation and methods include piezometers, monitoring wells, time-domain EM geophysical mapping, and erosion monitoring. Numerical modeling with HydroGeoSphere was used to estimate flushing times and aquifer salinity distributions under different atmospheric and marine perturbations. Initial results suggest that the aquifer system that is pumped is relatively resilient to climate change due to the presence of confining layers and the associated upward flow that maintains the position of the freshwater-saltwater interface, which also prevents storm-surge infiltration from reaching appreciable depths where the wells are screened. The outcomes of this study will advance our understanding of how geologic conditions influence an aquifer’s response to various stressors, and will be useful for informing groundwater management in small island communities facing environment change.