An analytical methodology to estimate the changes in fresh groundwater resources with sea-level rise and coastal erosion in strip-island unconfined aquifers: illustration with Savary Island, Canada

Abstract

Closed-form analytical solutions for assessing the consequences of climate change on fresh groundwater oceanic island lenses have been developed by hydrogeologists during the last decade. Based on existing equations, this study focuses on the case of strip oceanic islands when three combined effects of climate change are observed to affect the freshwater lens volume and its groundwater resource renewal: sea-level rise, erosion, and change in groundwater recharge rates. New equations, integrating these combined effects of climate change on fresh groundwater resources are provided. These equations are solved by a novel methodology based on a Dupuit-Forchheimer groundwater flow model that allows for determination of the hydrogeological parameters included in the equations. The approach is illustrated with the strip island of Savary, which is located along the Pacific Coast of Canada in the province of British Columbia. This example illustrates, on the one hand, the volume depletion of the island freshwater lens and, on the other hand, the decrease of the renewal rate of groundwater. The proposed approach can be applied to any strip islands worldwide to assess the cumulative effects of sea-level rise and shore erosion on groundwater resources, depending on the predicted climate change scenarios. The results can then help decision-makers to anticipate the effects of climate change on the groundwater availability in strip oceanic islands and plan future groundwater use accordingly.