Grand Bahama Post-Hurricane Dorian: A Comparison of Fresh Water in Two Primary Wellfields

Freshwater lenses, a layer of fresh water that floats atop saline groundwater, are vulnerable sources of drinking water for small islands. The threats to freshwater lenses, and their recovery following catastrophic events, is not well documented. Due to storm surge and flooding during the Category 5 Hurricane Dorian in September 2019, the freshwater lenses of Grand Bahama were inundated with salt water, removing the freshwater source of drinking water for the island. This study builds on previous work to monitor the recovery of the freshwater lenses three years after the hurricane by assessing tidal lag, as well as stable isotopes in water (δ2H and δ18O), to understand the hydrologic characteristics of the FWL in Grand Bahama. Results from electrical conductivity revealed that the tidal lag, or the time it takes for the tidal effect to be observed in groundwater, was approximately 2.5 hours on average. Through stable isotope analysis of precipitation samples, we determined a local meteoric water line of δ2H = 8.2 * δ18O + 12.2, which is close to the global meteoric water line. Groundwater samples did not show evidence of significant evaporation from precipitation. These results serve as baseline data for additional monitoring and recovery efforts on Grand Bahama