Development of a groundwater quality index for seawater intrusion in coastal aquifers

Coastal aquifers are increasingly threatened by seawater intrusion due to increased urbanization, groundwater exploitation, and global sea-level rise. Pattern diagrams, which constitute the outcome of several hydro-geochemical processes, have traditionally been used to characterize vulnerability to seawater intrusion. However, the formats of such diagrams do not facilitate the geospatial analysis of groundwater quality, thus limiting the ability of spatio-temporal mapping and monitoring. This raises the need to transform the information from current pattern diagrams into a format that can be readily used under a GIS framework to define vulnerable areas prone to seawater intrusion. In this study, a groundwater quality index specific to seawater intrusion (GQISWI) was developed for the purpose of aggregating data into a comprehensible format that allows spatial analysis. The index was evaluated with data from various coastal regions worldwide and then applied at a pilot karstic aquifer along the eastern coast of the Mediterranean Sea.