Integrated geophysical and hydrochemical assessment of groundwater in Samaro Tehsil, District Umerkot, Sindh, Pakistan

Abstract

Groundwater is the primary source of drinking and irrigation water in the semi-arid region of Samaro Tehsil, District Umerkot, Sindh, Pakistan. However, the detailed information on aquifer geometry and groundwater quality has remained limited. In this study, the first integrated assessment combining Vertical Electrical Sounding (VES) and hydrochemical analysis to assess the subsurface aquifers and evaluate groundwater quality for drinking and irrigation purposes. Twelve VES surveys were conducted using the Terrameter SAS-4000 and subsurface resistivity models were interpreted using IPI2Win software. Groundwater samples collected from the corresponding boreholes were analyzed for major physicochemical parameters and irrigation suitability indices. The integrated interpretation showed distinct vertical salinity gradients with freshwater aquifers (10–30 Ωm) on top of brackish (3–8 Ωm) and saline (3 Ωm) layers at a depth of 20–30 m. Hydrochemical results showed that several groundwater samples exceeded WHO drinking water standards for TDS, sodium, magnesium, chloride, and electrical conductivity, whereas irrigation indices (SAR, KI, Na%, and MH) indicated potential long-term risks of soil salinization and reduced agricultural productivity. The combination of geophysical interpretations and hydrochemical assessment demonstrated the effective characterization of aquifer. This research provided the valuable information for groundwater resource management, sustainable irrigation planning, and future groundwater monitoring in the Lower Indus Basin.