Assessing the water quality of River Ganga in Varanasi, India, through WQI, NPI, and multivariate techniques: a comprehensive study

Abstract

The present research was conducted to study the water quality of the Ganga River in Varanasi. Water quality from nine different sampling points (S1–S9) from the River Ganga at Varanasi was examined for different water quality parameters, and multivariate statistical analyses were carried out. Subsequently, several indices, such as water quality index and Nemerow pollution index (NPI), were calculated. The results indicated that water in the Ganga River at Varanasi had high levels of coliform concentrations, altered pH, and elevated dissolved oxygen/biochemical oxygen demand and chemical oxygen demand values. The weighted arithmetic water quality index values revealed that sites S8, S9, and S2 were the most polluted and unfit for bathing and drinking. Most of the sampling sites have NPI values greater than 1 for several parameters, indicating high levels of pollution. The study revealed that the water quality is poor for bathing and drinking at most of the sites throughout the year. In addition, the upstream water quality assessment revealed that water quality was good compared with the heavily contaminated downstream region. This knowledge can be useful for environmentalists, policymakers, and water resource managers to develop strategic plans to preserve the cultural and aesthetic worth of the Ganga River in the future.