Integrated Assessment of Groundwater Quality and Health Risks in Iran’s Bardsir Plain Using Water Quality Indices, TOPSIS, and CDI–HQ Analyses

This study provides a comprehensive, nine-year (\(\:2012\)–\(\:2020\)) assessment of groundwater quality in Iran's Bardsir Plain, analyzing 450 samples from 50 distinct wells. To evaluate the water's suitability for drinking, agricultural, and industrial applications, we employed three separate Water Quality Indices (WQI, DWQI, IWQI), resolving contradiction classifications through a Multi-Criteria Decision-Making (TOPSIS) framework. Further quantification of human health risks was achieved via Chronic Daily Intake (CDI) and Hazard Quotient (HQ) analyses. The findings reveal a generally favorable water profile, with WQI values spanning from 143.21 (excellent; Sorkhkan Well 40W) to 106.014 (poor; Abdollahabad Well 17W) and 94% of wells rated as "good" to "excellent." However, the TOPSIS analysis, which effectively reconciled inconsistencies between the DWQI and IWQI, identified Well 30W (Deh Babak; score: 0.998) as the most suitable overall and Well 17W (score: 0.215) as the least. Among the ions analyzed, a potential health risk emerged specifically from chloride, which exhibited a mean HQ of 4.03, thereby surpassing the safety threshold (HQ > 1). In contrast, other constituents, including calcium (Ca²⁺: 0.004), magnesium (Mg²⁺: 0.043), and sulfate (SO₄²⁻: 0.003 mg/L) were found to pose negligible hazards. Spatiol analysis delineated a clear pattern of escalating ion concentrations, particularly in the northern and northwestern sectors of the plain. The evidence thus points directly to anthropogenic pressures as the principal driver of water quality decline. In offering a replicable framework for semi-arid regions, this study underscores the critical need for targeted monitoring of chloride sources and advocates for the strategic implementation of artificial recharge systems in vulnerable zones to mitigate further deterioration.