Holistic Analysis of Ganga Basin Water Quality: A Statistical Approach with WQI, HMCI, HMQI,and HRI Indices

Abstract One of the biggest perpetual streams, the Ganga, preserves the cultural legacy of the Indian subcontinent while providing millions of people who live along its banks. As a result of its unlimited utilization, the rivers also get contaminated by untreated wastewater discharged from various sources. The current study assesses water samples at regular intervals for analyzing variations in physical, chemical, and biological characteristics and the potential health risk of heavy metals at 8 monitoring sites in the Ganga and Yamuna rivers, Prayagraj, India, during the years 2021–22. The outcomes were compared with the drinking water guidelines suggested by the Bureau of Indian Standards (BIS) and the World Health Organization (WHO). Water quality index findings showed that the water quality had significantly decreased in several areas, such as S2 in the Ganga region and S8 in the Yamuna region. Although the levels of heavy metals Cu, Fe, Cd, Pb, Mn, and Cr in rivers water varied from "low" to "high, Pb and Cd particularly were beyond the permissible limit. The analyzed findings of the Health Risk Assessment (HRI) show the same: Ganga Region at S4 and Yamuna Region at S-8 show health risks due to increased levels of Pb and Cd. Similarly, the Heavy Metal Contamination Index (HMCI) ranged from 733.78 to 981.33, which shows that all Ganga Rivers and Yamuna samples were graded as highly polluted, and the Heavy Metal Quality Index (HMQI) indicated almost identical patterns. Among all the samples collected from the study area, there is a warning level of HMQI > 1, especially Site 4 and Site 8, which show the most elevated values and high-risk factors for the local population if they utilize rivers water as their primary source of drinking water. Moreover, to find any possible correlations between the measured water quality indicators, a Pearson's correlation matrix was established, followed by a heat map that showed DO, pH, alkalinity, and SO4 are positively corelated at the same time, except Zn and Mg, all heavy metals are strongly corelated with each other.