The population increase in Egypt and the supply limited fresh water resources of Egypt has driven the national policy in recent years to encourage investment in tourism, and establish touristic resorts in coastal areas. Desalination plants play a major role in closing the gap between supply and demand for the fresh water in coastal areas. An environmental friendly and cost effective design for the brine disposal system is essential. The aim of this research is to develop charts for designing and managing the injection and discharge wells in coastal areas, minimizing the impact on ground water. A numerical modelling study was carried to simulate the ground water extraction and brine disposal using Visual MODFLOW three-dimensional groundwater flow and contaminant transport modelling application. Eighty different scenarios were tested by varying the brine injection rate, spacing between production and injection wells, initial concentration of the aquifer, concentration of the injection well, type of soil and screen location. The model results revealed that the lateral extent of the salt plume is directly proportional to the rate of injection. Moreover, the injection well should be deeper than the discharge well for achieving the optimal design for the injection and discharge wells. Also, the salt plume lateral extension is directly proportion to the hydraulic conductivity of the soil.