EVALUATION OF SEAWATER INTRUSION VULNERABILITY USING THE G-ALDLcR METHOD, CASE STUDY: KRUI, PESISIR BARAT, LAMPUNG

Abstract

Coastal areas play a crucial role in social, economic, and ecological activities, but are vulnerable to environmental degradation due to seawater intrusion, which occurs when seawater infiltrates inland aquifers as a result of hydraulic pressure imbalances between freshwater and saltwater. Excessive groundwater exploitation leads to a decline in the water table, which in turn opens up opportunities for seawater to enter the aquifer system, thereby reducing groundwater quality in several coastal areas. This condition has the potential to cause a clean water crisis that impacts public health and the sustainability of coastal ecosystems. The analysis was conducted using the G-ALDLcR method, a modification of the GALDIT method that incorporates land cover (Lc) and distance from the river mouth (R) parameters. Data were obtained through groundwater level measurements and hydrochemical analysis, including electrical conductivity (EC), salinity, and total dissolved solids (TDS), at ten observation points. The results show EC values of 43.10–814.00 µS/cm, salinity of 200–4000 ppm, and TDS of 24.2–391 mg/L, indicating the influence of intrusion at points near the coast. Based on spatial analysis using GIS, the study area is classified into three levels of seawater intrusion vulnerability: very high (19.10%), high (77.27%), and moderate (3.63%). The resulting vulnerability mapping serves as the foundation for implementing strategies to control groundwater utilization, conducting continuous environmental monitoring, and developing mitigation plans to prevent the escalating impacts of seawater intrusion on the sustainability of water resources and coastal ecosystems.