Combined geo-electrical and hydro-chemical methods to detect salt-water intrusion A case study from southwest Saudi Arabia

Purpose - Salt-water intrusion has always been a source of contamination in coastal aquifers that hinders sustainable groundwater development. Classical techniques to detect its occurrence are costly and time consuming. The application of combined geo-electrical and hydro-chemical methods is cheaper, executable in reasonable time, and successfully applied in mapping the interface between saline and fresh groundwater. The current study aims at detecting and delineating salt-water intrusion in the downstream part of Wadi Gizan in southwest Saudi Arabia using geo-electrical and hydro-chemical methods. Design/methodology/approach - The case study area is the downstream part of Wadi Gizan in southwestern Saudi Arabia. Geo-electrical data were obtained from field measurements using both Shlumberger and Wenner procedures. A number of 65 groundwater samples were collected and analysed for its total dissolved solids and major ionic composition. Findings - The results show variations in the resistivity of the water-bearing strata in the study area. Resistivity values decrease towards the Red Sea, and, in separate pockets. The total dissolved solids (TDS) and chloride distributions show the same pattern. Overlapping the areal distributions of the resistivity, TDS, and chloride concentration yield a map showing the limits of salt-water intrusion and up-coning pockets of saline water. Practical implications - Planners, decision makers and other interest groups can use these findings for a sustainable groundwater development in the study area, and, to safeguard the aquifer from further advancement of salt-water intrusion. Originality/value - The case study indicates the importance of applying combined geo-electrical and hydro-chemical methods for groundwater quality variations and especially in detecting and delineating the contact between saline and fresh groundwater in coastal aquifers.