Abstract
Climate change has been directly linked to increased strength and frequency of natural disasters. Small islands in certain areas are prone to experience dramatic effects and suffer from dire damages due to these natural disasters. Two major phenomena associated with these natural disasters are saltwater intrusion enhanced by elevated sea levels and storm-induced salinization, both threatening the usability of freshwater lenses by contaminating groundwater with saline water. This study examines the effects of Hurricane Dorian, which hit Grand Bahama on September 2019, and contaminated the local freshwater resources, through the use of modeling techniques that study the aquifer before, during, and after the hurricane.The Grand Bahama groundwater model developed in this study is constructed using Visual MODLFOW Flex with the SEAWAT engine. The simulation runs through 82 years, from 1979 to 2060, and involves creating conceptual and numerical models for the Grand Bahama groundwater system simulating the Hurricane Dorian event in the process. Through multiple rounds of calibration, the model was optimized to obtain acceptable results consistent with in-situ observations of groundwater and salinity levels measured at various wells on the island.
In addition to modeling the lateral saltwater intrusion effects from the surrounding Atlantic Ocean, the numerical model simulated the hurricane induced salinization that resulted from flooding. The results show that the Grand Bahama groundwater lens is experiencing salinity concentrations well above the drinking water standards, which are expected to last about 20 years after Hurricane Dorian. At the end of 2039, the simulation predicts that the system will reach a salinity level of 200 ppm, which is considered a complete aquifer recovery. Variations in precipitation values caused by future climate change have an inversely proportional relationship with the recovery rate of the Grand Bahama groundwater system.