Salinization in groundwater vulnerability: A review of GALDIT-Based methods

Groundwater quality is increasingly threatened by both natural and anthropogenic salinity, particularly in coastal aquifers where salinization represents one of the most critical challenges. In this context, a systematic review was proposed to critically analyze the most used parameters in overlay index methods for assessing groundwater vulnerability to salinity. The results highlight that the canonical GALDIT parameters remain the most widely applied, often complemented by newly introduced factors tailored to specific objectives and hydrogeological settings. Weight statistical analysis of the most frequently used parameters shows general consistency with the original GALDIT weighting scheme, although minor variations emerge during optimization. The proposed ranking system indicates that groundwater occurrence and the impact of existing seawater intrusion have relatively limited influence on vulnerability assessments, mainly due to constraints associated with their indicators. In contrast, distance from the coastline and groundwater head provide the most significant insights into salinity distribution and coastal aquifer vulnerability, despite some inherent limitations. Furthermore, additional parameters such as recharge effects, distance from surface water bodies (e.g., lagoons and rivers), distance from saline sources, and hydraulic gradient, show strong potential as flexible extensions for improving vulnerability mapping. This study highlights the strengths and weaknesses of GALDIT-like methodology and shows the way to improve their performance to ensure a better characterization and management of water resources in coastal aquifers all over the world.