Assessing Aquifer Vulnerability to Seawater Intrusion : Application of the GALDIT-Index to the Emilia-Romagna Coastline.

Saltwater intrusion (SWI) in coastal aquifers due to excessive groundwater withdrawals (for civil, agricultural and industrial purposes) has become a major concern affecting a large number of coastal aquifers worldwide. This trend is expected to grow in the very near future due to the expected sea-level rise (SLR) associated with the human-induced climate change. In this context, the following research proposes an assessment of the vulnerability of the Emilia-Romagna coastline (Italy) to SWI under present conditions. This assessment is conducted through the use of the GALDIT-Index, an indicator-based model which is made of 6 parameters that are presumed to control the phenomenon of SWI (Groundwater occurrence, Aquifer hydraulic conductivity, Level of groundwater above the mean sea-level, Distance from the shore, Impact of existing status of SWI, Thickness of the aquifer). The thematic maps of the 6 factors were prepared in a GIS environment. They were given appropriate ratings and weightages and were overlaid in order to produce two vulnerability maps, one for the surface phreatic aquifer and one for the underlying confined one. The results are relatively similar between those two maps and show that the coastline is highly vulnerable over a width of a few kilometres. The coastal plain, on the other hand, is characterized by a moderate vulnerability that tends to be reduced when moving landwards toward higher topography. Those vulnerability maps can generally be used as a tool for management of the coastal groundwater resources.