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

Abstract

The groundwater resources have always been explored for its utilization in domestic and agriculture purposes. In this study, Winder area in Balochistan which is along the coast of Offshore Indus Basin has been explored using electrical resistivity method for deeper understanding of hydrogeological and hydrogeophysical conditions. Schlumberger electrode arrays have been used to acquire vertical electrical sounding data for 23 different sites in this area. The field data were calibrated with theoretical curves during processing using software with graphical interface. The true resistivities, depths, thicknesses, aquifer attributes, soil type and groundwater quality has been extracted from the processed data. Pseudo-sections and geo-electrical lithology sections have been generated for lateral distribution of hydrogeological settings. Furthermore, Dar-zarrouk parameters calculations have been made and 3D surfaces generated at 30m and 60 m depth for transverse resistance (T), longitudinal conductance (S) and anisotropy (λ) plotted for resistivity distribution and coastal salinity intrusion analysis. The soundings results depict five layers mainly composed of silty sand, sandy clay, sand, and sandy gravel and the depth ranges from 0-110m. The interpretation illustrates that freshwater unconfined aquifer are present in the quaternary sand and sandy gravel deposits. The water table is at shallow depth along the river and deeper in northeast and away from Winder river. The resistivity ranges 29-1091 Ωm in layer-3 interpreted as saturated zone. The approximate range of water table is 19-30 m. The higher value of T greater than 10000 shows fresh water and low value 8200 for salinity intrusion in southwest toward sea.