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A source of irrigation water is needed to meet the demands of golf and residential uses at a new development on New Providence Island in the Bahamas.Therefore，a comprehensive hydrogeological investigation was conducted to study the feasibility of developing a raw water supply for a proposed reverse osmosis (R0) plant.The study included field investigations and the development of a three-dimensional variable-density SEAwAT model.The model was calibrated using salinity data collected from adjacent test wells and a man-made lake that may be utilized for withdrawal purposes.Pumpage from shallow wells constructed in close proximity to the lake was also considered.Atier calibration,the model was used to evaluate the long-term water quality changes that may occur in the source water due to different withdrawal scenarios.The results indicate the raw water total dissolved solids (TDS)concentration would increase quickly due to vertical igration of salt from below.However.the raw water salinity remains well below that of seawater and thus，treatment costs will be approximately 50％lower using the brackish-water source than standard seawater RO treatment costs.The results of model simulations indicate that there is no significant difference between well or lake withdrawals.