Holistic analysis of Ganga basin water quality: a statistical approach with WQI, HMCI, HMQI and HRI indices

The Ganga river, one of the largest and most culturally significant rivers in India, supports millions of people living along its banks. However, extensive use and untreated wastewater discharge have led to significant contamination. This study utilizes land use and land cover (LULC) analysis, along with regular water sampling from 2021 to 2222, to assess variations in physical, chemical, and biological characteristics and evaluate health risks posed by heavy metals across eight monitoring sites in the Ganga and Yamuna rivers, Prayagraj, India. Results were compared with drinking water standards established by the Bureau of Indian Standards (BIS) and the World Health Organization (WHO). The Water Quality Index (WQI) indicated substantial water quality degradation at sites S2 (Ganga) and S8 (Yamuna). Although heavy metal levels (Cu, Fe, Cd, Pb, Mn, Cr) fluctuated across sites, Pb and Cd frequently exceeded permissible limits. Health Risk Assessment (HRI) findings pointed to potential health risks at sites S4 (Ganga) and S8 (Yamuna) due to elevated Pb and Cd levels. The Heavy Metal Contamination Index (HMCI) ranged from 733.78 to 981.33, classifying all samples as highly polluted, with Heavy Metal Quality Index (HMQI) values also indicating high risk, especially at sites S4 and S8. Further analysis using principal component analysis (PCA) and cluster analysis highlighted correlations among water quality parameters, while Pearson's correlation matrix and heat maps indicated positive relationships for DO, pH, alkalinity, and SO₄, with most heavy metals (except Zn and Mg) showing strong inter-correlations. These findings underline the urgent need for pollution control measures to safeguard public health in the region.