Impacts of the Urban Wastewater Discharges on the Indus River Basin: Water Quality Assessment and GIS Pollution Mapping

This study assessed variations in water quality at the Indus River Basin (IRB) impacted by wastewater (WW) drains from five densely populated urban and industrial cities: Lahore, Faisalabad, Multan, Sukkur, and Hyderabad. Water samples from the barrages at upper and lower IRB, tributaries, and cities' WW drains were analyzed. GIS-based mapping was used to visualize the transport of pollution from the WW drains to the riverine bodies, identifying potential source cities and pathways of pollution. Employing sensitivity analysis through various models and validation matrices enhances the statistical reliability of hotspot mapping water quality variations. The riverine samples from the upper basin exhibited relatively good water quality with low COD and TOC levels. However, the COD levels at the Balloki and Panjnad barrages downstream of the Ravi and Chenab exceeded 160 mg/L. The analyzed WW drains in Lahore and Faisalabad discharged into the Ravi River and recorded high COD and TDS levels up to 600 and 4000 mg/L, respectively. Drains from the downstream Hyderabad region worsened contamination, with COD reaching 198 mg/L. Seasonal assessments revealed elevated pollutant concentrations during the dry season, with COD and TDS levels increasing by 1.68 and 1.58 times, respectively, compared to the wet season.