Integrated statistical, hydrogeochemical and geospatial assessment of seasonal monsoon variations in groundwater quality of Landhi-Korangi area, Karachi, Sindh, Pakistan

Abstract

This study evaluates the groundwater quality in the Landhi-Korangi areas of Karachi, Pakistan, using an integrated approach combining statistical analysis, hydro-geochemical analysis, and geospatial techniques. Groundwater samples shows higher concentrations of parameters (TDS, Cl-, and SO42−) in pre-monsoon samples and higher concentrations of parameters (Na2+, hardness, TDS, and SO42−) in post-monsoon samples, both exceeding the WHO drinking water limits. Multivariate statistical techniques (PCA and correlation analysis) clearly reveal that groundwater chemistry is dominated by water-rock interaction involving dissolution of carbonate rocks and major ions (TDS, Ca2+, Mg2+, Cl−), with minor contributions from anthropogenic sources (industrial and sewage), while monsoonal recharge is dominated by dilution. Principal component analysis shows that pre-monsoon (81.97%) and post-monsoon (84.24%) variability is dominated by salinity and mineralization. Spatial analysis shows that, during the post-monsoon period, higher concentrations were observed in central and northwestern areas. In the post-monsoon period, these higher concentrations were shifted towards the central and eastern parts. Additionally, nitrate and sulfate levels were significantly elevated in the southeastern region. The hydrogeochemical analyses performed using the Piper, Gibbs, and Schoeller diagrams indicate that the groundwater in the Landhi-Korangi aquifer is dominated by the Na-Cl/SO4 type throughout the pre-monsoon and post-monsoon periods, suggesting salinization controlled by water-rock interaction and evaporation. Integrated spatial mapping and hydro-geochemical plots are used to evaluate the changes in groundwater interaction, hotspots, facies, ion distribution, and contamination.