Surface-groundwater investigations to support ex-ante evaluations of water withdrawals

Effective groundwater management in coastal areas requires a detailed understanding of surface-water and groundwater interactions, particularly in alluvial plain affected by seawater intrusion. This study focuses on the Muravera alluvial plain, where both a phreatic and a partially confined aquifers are present. The research aims to refine the conceptual model of recharge sources and the hydrogeological balance by systematically integrating hydrogeological and hydrological data, supporting ex-ante evaluations of water withdrawals. This work was conducted under the collaboration agreement between the University of Cagliari (DSCG), the Sardinian Hydrographic District Agency (ADIS), and with the collaboration of the Regional Environmental Protection Agency (ARPAS). Between January and May 2024, extensive field campaigns were conducted, including piezometric surveys, geochemical analyses, and river-aquifer interaction assessments. The results reveal significant spatial variability in the hydrogeological properties of the phreatic aquifer, strongly influenced by prolonged drought conditions that have led to a decline in piezometric levels. This has activated previously undetected drainage axes, modifying local flow dynamics. The Flumendosa River alternates between recharge and drainage phases depending on location and hydraulic conditions. The partially confined aquifer remains less characterized due to limited data availability, requiring further investigation. This study provides a comprehensive dataset and interpretation framework to improve groundwater resource management, mitigate seawater intrusion risks, and optimize water use strategies in the region.