Groundwater Characterization and Salinity Intrusion Studies using Electrical Resistivity Survey (ERS)-Winder, Balochistan, Pakistan

Abstract

Groundwater resources have always been explored for domestic use, livestock, and agriculture activities. In this study, the Winder area has been explored using the electrical resistivity method for understanding hydrogeological conditions. The study area is located along the coast of Balochistan. Schlumberger electrode arrays have been used to acquire vertical electrical sounding (VES) data for 23 stations. The field data is calibrated with a theoretical curve matching technique using software (IPI2WIN). The true resistivity, depths, thicknesses, aquifer attributes, and soil type have been extracted from the processed data. Pseudo-sections and geo-electrical lithology sections have been generated for the lateral distribution of hydrogeological settings. Furthermore, Dar-Zarrouk parameter calculations have been made and 3D surfaces are generated at 30 m and 60 m depth for transverse resistance (T), longitudinal conductance (S), and anisotropy (λ). These parameters are plotted for resistivity distribution and coastal salinity intrusion analyses. The VES sounding results of 0-110 m depth depict five layers mainly composed of silty sand, sandy clay, sand, and sandy gravel. The interpretation illustrates that freshwater unconfined aquifers are present in the quaternary sand and sandy gravel deposits. The water table is at a shallow depth along the river and deeper in the northeast further from the Winder River. The resistivity ranges between 29-1091 Ω-m in layer-3, interpreted as the saturated zone. The approximate range of the water table is 19-40 m. A value of T greater than 10000 shows fresh water and values below 8200 indicate salinity intrusion in the southwest towards the sea.