Seawater intrusions for coastal aquifers are increasingly dominated by anthropogenic drivers in the Southern Mediterranean Basin

Study Region: Coastal aquifers at river outlets in North Africa are facing rapid degradation due to increasing aridity. Of particular interest is how these degradations extend to vulnerable lagoonal systems in semi-arid areas that are suffering from recent, accentuated climate fluctuations. Among these, the Medjerda River and Ghar El Melh Lagoon exhibit notable hydroclimate complexity, which is representative of several lagoonal systems in the southern Mediterranean Basin that remain poorly quantified. Study Focus: To address this deficiency, we utilize GALDIT-AHP statistical methods to assess the susceptibility of coastal aquifers to seawater intrusion under decadal hydroclimatic fluctuations from 1985 to 2023. GALDIT combines aquifer hydraulic conductivity, groundwater levels, proximity to the coastline, seawater intrusion, and aquifer thickness with piezometric data and historical records spanning 1997–2022, encompassing hydrogeological, hydrological, and geospatial parameters during wet and dry seasons. New Hydrological Insights for the Region: Our results indicate that aquifer vulnerability in these lagoonal systems is primarily governed by anthropogenic extraction, rather than the river basin’s seasonal hydraulic conditions. The correlation between GALDIT-AHP vulnerability index and seawater intrusion is well established. Vulnerability is most pronounced during the dry season, with hotspots concentrated along lagoon coastlines and in highly urbanized areas. Our findings underscore the need to reinforce sustainable groundwater management practices in the lagoonal systems of the southern Mediterranean Basin, thereby mitigating the growing and potentially irreversible seawater intrusion associated with increasing hydroclimatic fluctuations in coastal watersheds.