Seawater intrusion in karst aquifers: A critical review of factors, methods, and mitigation actions

Hitherto, seawater intrusion (SWI) in karst aquifers has too often been interpreted through porous-media simplifications, with karst typology treated as a secondary caveat rather than a governing structural control biasing both investigative design and model inference. This review foregrounds karst architecture and organizes SWI drivers into (i) primary controls that set hydraulic-head balance and density stratification and (ii) co-drivers that modulate responses in space and time. Synthesized evidence shows that the degree and spatial organization of karstification decisively govern intrusion pathways, matrix–conduit exchange, and mixing dynamics, establishing karst development as a primary control on SWI mechanisms. Methods are structured into investigative and predictive domains. Investigative approaches couple hydrochemical and isotopic tracers with hydrogeophysical imaging to constrain intrusion geometry and depth dependence; persistent challenges include separating paleo- from modern intrusion and resolving depth-stratified processes, but multi-method integration can materially reduce ambiguity. Predictive tools chiefly comprise vulnerability assessments and variable-density numerical modeling, yet are constrained by weak typology-aware transferability, inadequate uncertainty quantification, and limited integration of heterogeneous data motivating data model fusion to shift practice from diagnosis to anticipatory management. Management is staged: under incipient intrusion, prioritize head maintenance through managed aquifer recharge and optimized abstraction; as salinization advances, deploy hydraulic barriers and where vertical control is feasible Fresh-Keeper configurations, recognizing reduced effectiveness in conduit-dominated systems. Subsurface cutoff walls/dams can still retard wedge migration when designed to local stratigraphy and tidal forcing. Overall, this synthesis provides decision-ready guidance from regional screening to site-specific intervention design.