Freshwater lenses on small islands are vulnerable to many climate change related stressors, which can act over relatively long time periods, on the order of decades (e.g. sea level rise, changes in recharge), or short time periods, such as days (storm surge overwash). This study evaluates response of the freshwater lens on a small low-lying island to various stressors. To account for the varying temporal and spatial scales of the stressors, two different density-dependent flow and solute transport codes are used: SEAWAT and HydroGeoSphere. The study site is Andros Island in the Bahamas, which is characteristic of other low-lying carbonate islands in the Caribbean and South Pacific regions. In addition to projected sea level rise and reduced recharge under future climate change, Andros Island experienced a storm surge overwash event during Hurricane Francis in 2004, which contaminated the main wellfield. Simulations of reduced recharge result in up to 19% loss of freshwater lens volume, while sea level rise contributes up to 5% volume loss. The lens responds relatively quickly to these stressors, within 0.5 to 3 years. Simulations of the storm surge overwash indicate that the freshwater lens recovers over time; however, prompt remedial action can restore the lens to potable concentrations up to one month sooner.
Holding, S., & Allen, D. M. (2015). From days to decades: Numerical modelling of freshwater lens response to climate change stressors on small low-lying islands. Hydrology and Earth System Sciences, 19(2), 933–949. https://doi.org/10.5194/hess-19-933-2015