Unraveling the influence of paleochannels in coastal environments vulnerable to saltwater intrusion: A synergistic approach of electrical resistivity tomography and groundwater modeling

Abstract

Paleochannels play a dual role in coastal aquifers, acting as groundwater reservoirs while also serving as preferential pathways for seawater intrusion. Understanding their influence on groundwater salinization is crucial for coastal water resource management. This study integrates geophysical, geochemical, and isotopic methods to delineate paleochannel morphology and assess its role in saltwater migration. A petrophysical conversion model was developed to transform electrical resistivity anomalies into total dissolved solids (TDS) distributions, enhancing subsurface characterization. Electrical resistivity tomography (ERT), borehole data, hydrochemical analysis, and stable isotope tracers (δ¹⁸O, δ²H) were combined to identify groundwater sources and flow dynamics. A numerical solute transport model incorporating these datasets was established to investigate the role of paleochannels in controlling groundwater salinity. Results indicate that paleochannels significantly influence groundwater salinity, with TDS concentrations following the trend: unconfined > semi-confined > confined aquifers. Groundwater within paleochannels is predominantly derived from precipitation, but excessive pumping accelerates seawater intrusion, whereas increased recharge mitigates its effects. The integration of geophysical anomalies with hydrochemical data effectively identifies paleochannel structures, particularly in shallow aquifers, providing a robust approach for assessing their vulnerability to seawater intrusion. The integration of geophysical anomalies with hydrochemical data effectively identifies paleochannel structures, particularly in shallow aquifers, providing a robust approach for assessing their vulnerability to seawater intrusion. This multi-source data framework offers an improved methodology for mapping paleochannel distribution and quantifying its role in coastal groundwater salinization, providing critical insights for water resource management and aquifer protection.