Integrated study of quaternary aquifer for hydrostratigraphy and groundwater quality assessment in central Thal Doab, Punjab, Pakistan

Abstract

The groundwater resources in different areas of Pakistan are heading towards depletion along with the deterioration of quality due to over-abstraction and urbanization. The main focus of this study is to map the current hydrostratigraphical and hydraulic conditions of the late Quaternary aquifers in the central part of Thal Doab of Punjab Plains. To achieve the target, a comprehensive approach was employed combining geophysical investigations using electrical resistivity surveys (ERS) and physiochemical analysis of groundwater specimens collected from the study area. Careful calibration of resistivity models was performed by comparing them with lithologs to ensure their accuracy. The current groundwater conditions were assessed through thirty vertical electrical soundings (VES) using the Schlumberger electrode configuration up to 300m of AB/2. The interpreted results revealed the presence of four to six geo-electric sublayers comprising the intermixing layers of clay, silt, sand, gravel, and kankar inclusions. These layers exhibited very low (<20 Ω-m) to very high (>230 Ω-m) resistivity zones at various depth intervals. The developed 2D/3D models of aquifer systems identify the promising areas of good/fresh quality groundwater in the regions characterized by medium to very high resistivity mainly within the sand with gravel layers. However, lower resistivity values indicate the presence of marginally suitable/fair and saline/brackish groundwater showing the existence of fine sediments such as clays/silts. Additionally, twenty groundwater samples were collected to assess various parameters including pH, TDS, arsenic, fluoride, iron, nitrate, and nitrite. The spatial distribution of these parameters was visualized using 2D maps. The suitability of the groundwater for drinking consumption was evaluated in accordance with WHO guidelines.