Abstract
A comprehensive investigation has been conducted into the issue of seawater intrusion in the aquifer of the Mandalika Special Economic Zone (SEZ) on Lombok Island.Utilizing the RES2Dinv, Surfer13, and Rockwork software, data was processed in profiles and the time geoelectric resistivity survey method was implemented to monitor the velocity of seawater intrusion between 2021 and 2022.The findings of the study were segregated into three distinct transitional periods: a four-month transition from dry season to rainy season (Period I), a seven-month transition from dry season to intermediary conditions (Period II), and a year-long transition from dry season to dry season (Period III).The data revealed an expansion of the seawater intrusion zone from the south to the north at a depth range of 2 to 14 meters.This expansion was evidenced by a smaller volume of positive resistivity change in Period I compared to Period II.Moreover, a decrease in water content was observed in March 2022 measurements, leading to a less resistive, or more conductive, subsurface layer.In Period III, positive resistivity changes were solely identified in the western coastal area at a depth of 4 meters.Survey and measurement data indicated that seawater had infiltrated 12 coastal wells, with only wells 10 and 11 showing marginal mixing.This investigation underscores the escalating issue of seawater intrusion in the Mandalika SEZ aquifer, meriting urgent attention and mitigation strategies.