An evaluation of the relative importance of the effects of climate change and groundwater extraction on seawater intrusion in coastal aquifers in Atlantic CanadaUne évaluation de l’importance relative des effets du changement climatique et du prélèvement d’eau souterraine sur l’intrusion d’eau marine dans les aquifères côtiers du Canada atlantiqueUna evaluación de la importancia relativa de los efectos del cambio climático y de la extracción de agua subterránea sobre la intrusión de agua de mar en acuíferos costeros en Atlantic CanadaUma avaliação da importância relativa dos efeitos das alterações climáticas e da extração de água subterrânea sobre a intrusão salina em aquíferos costeiros do Canadá atlântico

To investigate the relative importance of projected sea-level rise, climate change effects on recharge, and groundwater extraction on seawater intrusion in important coastal aquifers in Atlantic Canada, a three-dimensional numerical model of density-dependent groundwater flow coupled with solute transport was developed for the Richibucto region of New Brunswick. The model was used, with an efficient 2k factorial design approach, to perform simulations for the period 2011–2100. The results of the factorial analyses indicate that the relative importance of the three factors investigated varies depending on the model location considered. The effect of declining recharge is most significant at shallow to intermediate depths along the freshwater–seawater transition zone, while the effect of increasing pumping rates dominates at a location relatively close to the well field. The effect of sea-level rise is shown to be significant only at the much deeper inland toe of the transition zone. The spatial variation in importance is related to how different model boundary conditions influence freshwater flow at the different locations within the model domain. This investigation indicates that sea-level rise has the least significant effect (of the three factors considered) on future seawater intrusion in sandstone aquifers in the Richibucto region.