Application of 2D electrical resistivity tomography to recognize groundwater salinity sources relevant to the Messinian salinity crisis, Kert aquifer, NE of Morocco

Abstract

Groundwater salinization poses a growing threat to water security and sustainable development in arid regions, particularly in northeastern Morocco. In the Kert Basin, increasing salinity levels compromise groundwater quality, especially in the southern and eastern areas, where total dissolved solids (TDS) exceed 12,000 mg/L. This study employs 2D electrical resistivity tomography (ERT) to characterize subsurface salinity patterns and investigate the geological and hydrological processes influencing salinization. A total of 20 resistivity profiles were acquired across the basin, with 12 selected for detailed analysis. The results reveal a clear spatial correlation between electrical resistivity and measured groundwater salinity. Low resistivity zones (< 20 Ωm) are associated with highly mineralized waters and Miocene marls, particularly in the east and south, whereas higher resistivity values (> 100 Ωm) in the northwest correspond to fresher water conditions (TDS < 600 mg/L). The study identifies two major sources of salinity: (1) the dissolution of evaporite minerals within the Miocene marls and (2) possible infiltration from the Kert River, which shows elevated electrical conductivity (3828 µS/cm) during seasonal flow. These findings align with previous hydrochemical and isotopic studies and underscore the value of ERT as a non-invasive method for delineating saline and fresh groundwater zones. By enhancing the understanding of subsurface salinization processes, this research contributes to the sustainable management of water resources in the context of climate-induced aridity and historical geological events such as the Messinian Salinity Crisis.