Geophysical Modeling and Hydrostratigraphic Study for Assessment of Groundwater Sustainability in Southern Part of Thal Doab, Punjab, Pakistan

ABSTRACT Groundwater resources across the country are swiftly heading towards depletion and quality deterioration. This study extensively examines the geological and hydrostratigraphic complexities in Thal Doab area, Punjab, Pakistan offering valuable insights into its subsurface lithology and groundwater quality. Data from twenty five (25) Vertical Electrical Soundings (VES) using Schlumberger electrode configuration were carefully analyzed, and calibration of resistivity models was performed by comparing them to lithological borehole logs to ensure their accuracy. The study establishes a fundamental connection between subsurface lithology and resistivity values, revealing four to six geo-electric sub-layers comprising the intermixing of clay, silt, sand, gravel, and kankar inclusions. These layers exhibit resistivity ranging from very low (<20 Ω-m) to very high (>230 Ω-m) at various depths. 2D/3D aquifer models identify the higher resistivity areas with promising good-quality groundwater primarily within sand, gravel, and kankar layers, while lower resistivity values indicate marginally suitable or saline/brackish groundwater within fine sediments like clays/silts. Groundwater quality improves significantly at depths below 75 m, suggesting sustainable water extraction potential. However, caution is advised while drawing water from depths below 50 m due to the presence of saline or brackish water, posing challenges due to limited recharge potential. The study emphasizes the importance of Indus and Chenab rivers, canal systems, and precipitation in the processes that recharge groundwater.