Accessing the Differential Suitability of Ganga River Water for Drinking, Irrigation, and Industrial Use: A First-Time Report Based on Index Analysis and Unsupervised Machine Learning, Highlighting the Need for Region-Specific Water Management Approaches

One-third of India’s population depends on the Ganga River (also known as Ganges), facing progressive degradation due to industrial effluents, rapid urbanization, and agricultural runoff. From Gaumukh (a glacier) to Gangasagar (a delta), this study offers a spatial assessment of the suitability of Ganga water quality for drinking, irrigation, and industrial use across 26 sites. Sector-specific suitability was measured using the Langelier saturation index (LSI), sodium adsorption ratio (SAR), and National Sanitation Foundation Water Quality Index (NSF-WQI). Between the Upper Ganga Stretch (UGS) and the Lower Ganga Stretch (LGS), the quality of Ganga water decreased, with only 15% meeting safe drinking standards, 38.5% being moderately suitable, and 46.2% being unsuitable as per NSFWQI values. While 38% of total water samples were found only moderately suitable for irrigation purpose as per SAR values. Risks to industrial operations (LSI values) were identified that 30.8% of the sites were severely corrosive, while 69.2% of the sites were slightly corrosive. Principal component analysis (PCA) and hierarchical clustering (HC) further defined distinct usability zones and key pollution drivers, underscoring the need for spatially adaptive and sector-specific water management strategies.