Impacts of RSLR on the Tavoliere delle Puglie Coastal Area (southern Italy)

This study focuses on the geo-hydrological characterization of the coastal zone of Tavoliere delle Puglie (Apulia region, Italy), one of the widest coastal plains in southern Italy. Nowadays, the area, mostly devoted to agricultural purposes, is subjected to several natural and anthropogenic stresses, such as sea-level rise and consequent shoreline modifications, groundwater pumping from shallow and deep aquifers, and land subsidence, strongly enhanced by human activity. Recent investigations have been conducted to assess the impact of relative sea level rise along coastal sectors over the next few decades by considering multidisciplinary data. These include IPCC sea-level rise projections for different climate scenarios (SSP1-2.6 and SSP5-8.5); coastal topography from airborne and terrestrial LiDAR data, vertical land movement rates obtained from the analysis of InSAR and GNSS data, and shoreline displacement derived from the analysis of multiple sources. According to the results of such analyses, under the worst-case scenario (SSP5-8.5), the local sea-level rise will reach values of 0.39 ± 0.12 m, 1.23 ± 0.31 m, 2.07 ± 0.56 m with a land surface of 50.5 km², 118.7 km², and 147.7 km² potentially submerged in 2050, 2100, and 2150, respectively. Regarding the hydrogeological characterization of local coastal aquifers, recent studies have highlighted that groundwater overexploitation has led to a significant decline in piezometric levels, reducing the natural hydraulic barrier of groundwater that prevents the intrusion of saline water from the sea. By using a combination of models, i.e. independent soil water balance and a groundwater flow model, the hydrogeological balance and related groundwater budget have been assessed for three different pumping scenarios: FullIWR (full irrigation water requirement), IWR under CDI (irrigation water requirement under controlled deficit irrigation) and ActIWR (current irrigation water demand). About 300 borehole stratigraphies allowed to build the groundwater conceptual model, while the distribution of the hydrogeological parameters of the aquifer has been estimated by means of a variety of geostatistical tools. The modelling results suggest that both groundwater discharge and storage decrease in time due to i) reduction of effective infiltration, ii) increase in water demand for agricultural practices, iii) changes in rain regime, and iv) increase in evapotranspiration rate.

The ingression of marine water compromises groundwater quality, reducing the underground freshwater resources, making it unsuitable for human and agricultural purposes and posing a risk to regional water security.  The vulnerability due to this phenomenon is exacerbated by Relative Sea-Level Rise (RSLR), which further increases the pressure gradient driving saltwater into coastal aquifers, moving inland the coastline. Therefore, further investigations will focus on modeling the salinization of the aquifers due to the seawater intrusion as a consequence of RSLR. This will provide a comprehensive understanding of groundwater flow dynamics for supporting the integrated management of the coastal areas in response to ongoing climate change and defining tailored land-use practices for the sustainable exploitation of groundwater resources.