Review of Modeling Approaches at the Freshwater and Saltwater interface in Coastal Aquifers.

Around 40% of the world's population depends on coastal aquifers for freshwater supply but natural and anthropogenic drivers threaten groundwater availability. Of these drivers, saltwater intrusion (SWI) is one of the most critical and is increasingly affecting coastal areas worldwide. Interest in coastal aquifers has significantly increased, as demonstrated by the growing number of publications in which researchers describe various approaches to illuminate the importance of coastal aquifers, specifically with regard to SWI. The state of research and knowledge of the coastal SWI issue has been reviewed herein. The review includes a discussion of select geophysical and field methods and tools which can inform the numerical modeling of coastal aquifers. MODFLOW was identified as the most often used numerical modeling platform. Further, while many research sites, particularly in the United States, were identified where field studies and geophysical methods, mostly geoelectric ones, added important value to the numerical modeling of the SWI process in the coastal zone, in some regions of the world, data scarcity was identified as the main challenge. Overall, numerical modeling, combined with geophysical methods, is a valuable tool for studying SWI and managing coastal water resources. [ABSTRACT FROM AUTHOR]