Groundwater and salinization risk: tapping works and management experience in the Mediterranean Area

The progressive population growth in coastal areas constitutes a huge worldwide problem, particularly relevant for coastal aquifers of the Mediterranean basin.

The increasing use of groundwater and the effect of seawater intrusion makes the study of coastal aquifers extremely relevant.

There are various measures, practices, and actions throughout the world for managing groundwater when this natural resource is subject to salinization risk.

This research focused on the seawater intrusion, classifies the different practical solutions protecting the groundwater through salinization mitigation and/or groundwater salinity improvements along the Mediterranean Area.

The literature review was based on 300 papers, which are mainly international journal articles (76%). The rest includes conference papers (11.8%), reports and theses (7%), and books or chapters of a book (25%).

Three main schematic groundwater management approaches can be distinguished for the use of groundwater resources at risk of salinization.

The engineering approaches pursue locally the discharge increase avoiding or controlling the salinity increase.

The most recent experiences of tapping submarine springs were realized using underground concrete dams, tools shaped like a parachute or tulip, or a fiberglass telescopic tube-bell, especially in the case of karstic aquifers.

The current widespread form of the engineering approach is to address the issue of groundwater exploitation by wells.

More complex solutions use subhorizontal designs. Subhorizontal tapping schemes were realized using tunneling and/or boring in combination with wide-diameter wells or shafts.

These works include horizontal drains or radial tunnels bored inside the saturated aquifer, shafts excavated down to the sea level with radial galleries or drains realized together with weirs to improve the regulation of the discharge rate and of salinization. Application of these solutions in areas where a thin fresh groundwater lens floats on the saline groundwater, as in the case of narrow and highly permeable islands, can yield high discharges, thus causing a very low drawdown over very wide areas. These solutions were successfully applied in Malta Islands.

The discharge management approach encompasses at least an entire coastal aquifer and defines rules concerning groundwater utilization and well discharge.

A multi-methodological approach based on monitoring networks, spatiotemporal analysis of groundwater quality changes, and multiparameter well logging is described in Apulian karstic coastal aquifers (Italy). The core is the definition of the salinity threshold value between pure fresh groundwater and saline groundwater mixture. The basic tools were defined to be simple and cost-effective to be applicable to the widest range of situations.

The water and land management approach should be applied on a regional scale. The main choice for this approach is pursuing water-saving measures and water demand adaptation. A multiple-users and multiple-resources-water supply system model was implemented to evaluate the effectiveness of the increasing maximum capacity of the surface reservoir and managed aquifer recharge in Apulia, a semi-arid region of Southern Italy.