Climate change risk assessment of a confined, small-island aquifer

ABSTRACT: Many small-island communities rely solely on groundwater, and climate change is projected to have significant impacts on these unique hydrological systems and their 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). We investigate the effects of climate change stressors on a small island off the northern coast of Prince Edward Island, Canada. The groundwater system consists of a confined aquifer from which water is pumped to support the community (approximately 500 people). Field instrumentation and methods include piezometers, monitoring wells, and time-domain EM geophysical mapping. Numerical modeling with HydroGeoSphere was used to simulate aquifer salinity distributions under different climate stressors. Results suggest that the aquifer system is relatively resilient to climate change due to the presence of confining layers and the associated upward flow that prevents storm-surge infiltration from reaching appreciable depths where the wells are screened, and high horizonal flows which prevent the saltwater-freshwater interface from moving far inland. The outcomes of this study will advance our understanding of how geologic conditions influence an aquifer's response to various stressors, and may help inform groundwater management in small island communities facing environment change.