Seawater intrusion (SWI) has emerged as a significant global environmental challenge, particularly in coastal areas, representing the most prevalent form of groundwater pollution. Given the vital role of groundwater as a freshwater resource, especially in arid areas, effective management of these resources is imperative. GALDIT, an index-based method, incorporates six crucial parameters that exert substantial influence on seawater intrusion (SWI). These parameters, namely Groundwater occurrence (G), Aquifer hydraulic conductivity (A), depth to groundwater Level above sea (L), Distance from the shore (D), Impact of existing seawater intrusion (I), and aquifer thickness (T), are mapped using ArcGIS in six layers, each assigned specific ranges, rates, and weights according to the GALDIT approach. This study focuses on mapping the vulnerability of the Shabestar Plain aquifer using GALDIT for the years 2003, 2013, and 2021, enabling a comparison of vulnerability over time. In 2021, only 9% of the aquifer exhibited low vulnerability, while 64% had medium vulnerability, 18% had high vulnerability, and 9% had very high vulnerability. The findings indicate a decline in aquifer levels and an increased vulnerability, particularly within the moderate range and higher, which has seen an approximate 2% increase from 2003 to 2021. These findings offer valuable information that can be utilized to identify areas of vulnerability and make informed decisions regarding resource management.