Ground Water Quality Assessment of Orangi Town, Karachi, Pakistan: The Largest Slum Area of South Asia

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department of geology, university of Karachi

Abstract

This study focuses on assessing the hydrogeochemical characteristics of groundwater of Orangi Town situated in the western district of Karachi and determining its quality through the Water Quality Index (WQI) method. To achieve this objective, a total of 20 groundwater samples were collected from different sites in Orangi Town. Sampling depth varied from 12 to 350 ft, and the age of wells spanned between 1-15 years. The groundwater quality revealed significant variations in various physicochemical parameters, presenting ranges as temperature (25.1-26.5 °C), pH (5.67-7.29), EC (1953.12-23125 μS/cm), TDS (1250-14800 ppm), turbidity (0.00-5.00 NTU), hardness (800-7800 mg/L), Mg2+ (6.1-1530 mg/L), Ca2+ (88-933 mg/L), K+ (11-46 mg/L), Na+ (300-3398 mg/L), SO42- (78-3293 mg/L), HCO3- (200-580 mg/L), NO3- (1.21-31.98 mg/L), Cl- (70-10779 mg/L). The results, compared with World Health Organization (WHO) and U.S. Environmental Protection Agency (EPA) standards, revealed that except pH, all physicochemical parameters are exceeding the corresponding limits for drinking purposes. The calculated Water Quality Index (WQI) value (206.83) provides clear evidence that the groundwater in Orangi Town is unfit for drinking purpose. The Piper diagram illustrates that the dominant hadrochemical facies include chloride-type water, mixed calcium-magnesium-chloride, and sodium chloride types indicating that diverse sources are influencing groundwater chemistry.

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