Characterizing offshore freshened groundwater along the Maltese Islands through geophysical and geochemical data integration

The rising demand for potable water in densely populated coastal regions has recently promoted growing research interest in detecting offshore freshened groundwater (OFG) worldwide. Recent geophysical studies along the continental margins offshore Israel, New Zealand, Malta, and the United States of America provide some examples of integrating geophysical and borehole data to constrain the spatial extent of OFGs and estimate their pore-water salinity. However, occurrences of OFGs and the interaction between terrestrial, carbonate-hosted groundwater systems with seawater are understudied in many coastal regions by complicated seafloor morphology. In this study, we investigate whether OFG can exist offshore a semi-arid carbonate coastline along the Maltese Islands and explore the possibility of sustainably exploiting these reservoirs as an unconventional source of potable water to relieve freshwater scarcity. We present an integration of 2-D resistivity models derived from marine controlled source electromagnetic (CSEM) measurements with 2-D and 3-D seismic data, core samples, borehole data, and geochemical measurements. Electrical resistivity models identify localized resistive anomalies (> 10 ohm-m) offshore the northeastern coast of Gozo (the second-largest island in the Maltese archipelago). Furthermore, a resistive body is observed at ~ 300 m below sea level close to the coast of Gozo which extends northeastwards and disappears at ~ 8 km offshore. If the anomalous resistive body is associated with pore-water salinity variations or, alternatively, caused by lithological changes, will be discussed through an integrative geological model developed along each profile.&nbsp
The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)