Ground water which is a renewable natural resource currently has an important role in providing clean water for various human needs. As a result of the increasing need for clean water that is in line with the increase in population has
caused excessive groundwater exploitation and one of the impacts is a decrease in groundwater level. A further consequence of this groundwater level decline is the occurrence of sea water intrusion (SWI) which damages the quality and quantity of groundwater in aquifers. The purpose of this study was to determine the influence of groundwater decline on sea water intrusion that occurred in Jeneponto Regency based on data obtained from the field and secondary data and then simulated in a numerical model. It was found that groundwater level decline gives the maximum effect in increasing the SWI on Binamu2 aquifer. Within 100 years after groundwater decline, SEAWAT numerical simulation estimated an increase in the value of SWI by 43% from the initial condition, which is 642 m in the Binamu2 aquifer, while for the Binamu1 aquifer, Arungkeke 1 and Arungkeke 2, the values were 559 m, 272 m, and 300 m, respectively. It can be seen that it takes quite a long time for seawater to intrude freshwater in the aquifer for each scenario of groundwater level decline. This is most likely due to the sufficiently thick aquifer conditions from each observation location that support the aquifer's ability to resist intrusion. In addition, the relatively small hydraulic conductivity value also helps to slow the occurrence of SWI so that it takes longer for sea water intrusion to reach steady-state conditions.