A case study of the effects of climate change on seawater intrusion in coastal aquifers in New Brunswick, Canada
University of New Brunswick
To investigate the effects of climate change on seawater intrusion, a three-dimensional numerical model of density dependent groundwater flow coupled with solute transport was developed and applied to a coastal sandstone aquifer in New Brunswick, Canada. The model incorporated local topography, bathymetry of the surrounding tidal rivers and Northumberland Strait, stratigraphy from borehole and geophysical investigations, and well field characteristics. Based on predictions of climate change for the area, two scenarios for variations in groundwater recharge and sea level rise, and one for increased pumping, were applied in the model. Simulations were performed using various combinations of the scenarios to quantify the magnitude of the effects of these three factors. The maximum change in total dissolved solids at selected locations within the model during the period of 2011 to 2100 was used as the response in a 2³ factorial analysis. Results indicate that the relative importance of the three factors changes depending on the location within the aquifer. The effect of generally declining recharge was most significant at shallow to intermediate depths (i.e. less than 60 m below sea level), while the effect of increasing pumping rates was most important for a location relatively close to the well field. The effect of sea level rise was found to be significant only at the much deeper inland toe of the transition zone. This study suggests that sea level rise has the least significant effect (of the three factors considered) on future seawater intrusion in shallow to intermediate aquifers similar to the one investigated in this study. These results are supported by other recent studies that indicate the effect of sea level rise on seawater intrusion is negligible when freshwater flow in the aquifer is controlled by constant flux boundaries.