Assessing Groundwater Quality for Drinking and Irrigation Using Hydrochemical and Multivariate Techniques in Coastal Thatta, Sindh, Pakistan

The study assesses water quality in coastal district Thatta, Sindh, Pakistan, a region severely impacted by salinity and seawater intrusion, which threaten groundwater resources and public health. Multivariate indices, including the Water Quality Index (WQI) and Irrigation Water Quality Index (IWQI), were applied to assess water suitability for drinking and irrigation purposes. WQI values ranged from 33.6 to 256.5, indicated that None of the samples qualified as “Excellent,” while 20.0% were rated “Good,” 31.7% “Poor,” 16.7% “Very Poor,” and 31.7% “Unsuitable for drinking.” IWQI indicated 36.7% of samples under High Restriction (HR) and 20% under Severe Restriction (SR) for irrigation use. Permeability Index (PI) averaged 65.52 meq/L, indicating good irrigation quality, while Kelly’s Index (KI) and Magnesium Adsorption Ratio (MAR) confirmed brackish water impacts. Soluble Sodium Percentage (SSP) exceeded safe limits in 46.7% of samples, threatening soil structure, as did Cl/ $${\text{HCO}}_{3}^{ - }$$ ratios, indicating chloride dominance. Correlations highlighted salinity’s dominance, with EC linked strongly to TDS (r = 0.992) and chloride (r = 0.984). Sodium-related indices (Na%, SSP) flagged risks to soil permeability, while 70% of samples exhibited negative Chloroalkaline Index (CAI) values, suggesting harmful ion exchange in soils. The findings highlight the critical need for strategic water management interventions to address salinity challenges, protect agricultural productivity, and enhance community health in this highly vulnerable coastal region.