Groundwater occurrence and quality in a hyper-arid desert: Insights from high-resolution electrical resistivity surveys in Tharparkar, Pakistan

Abstract The Tharparkar District in Pakistan is among the world’s most water-scarce regions, characterized by its hyper-arid climatic conditions and the absence of perennial surface water resources. Understanding the occurrence of groundwater potential and its quality is therefore critical, particularly in remote regions where hydrogeological information remains limited. This study characterized groundwater resources using 576 high-resolution electrical resistivity survey (ERS) probes up to a depth of 300 m, conducted from 2017 to 2020. Complementary hydrochemical investigations included laboratory analysis of 168 groundwater samples collected from dug wells and 672 soil samples up to a depth of 0.60 m. Results demonstrated that the water table lies at depths of 2–15 m (26% of the area), 16–30 m (23%), and 31–90 m (51%). Interpretation of ERS data revealed that approximately 10% of the groundwater resources, covering the southern parts of Diplo, Islamkot, and Nagarparkar Talukas, are suitable for drinking at a depth of 25 m, with around 3% classified as fresh and 7% as slightly saline. Groundwater salinity increases with depth, as 51% of the area shows high salinity at depths of 26–50 m and very high salinity at depths of 51–200 m. Arsenic and fluoride concentrations exceed permissible limits in 10 and 28% of the groundwater samples, respectively. These findings provide robust geophysical and hydrochemical evidence to guide targeted groundwater development, water quality mitigation strategies and inform policy interventions, aimed at enhancing water security and safeguarding the health of communities living in severely water-stressed desert regions.