Assessment of groundwater quality in Bangalore rural district: a decadal analysis

Abstract This study presents a comprehensive decadal analysis (2015–2024) of groundwater quality in Bangalore Rural and Ramanagara districts, Karnataka, India, using the Water Quality Index (WQI) methodology. Six strategically selected monitoring sites spanning diverse hydrogeological and land-use conditions were analyzed to assess temporal and spatial variations in groundwater quality. The Weighted Arithmetic Index method was employed to calculate WQI values using key physicochemical parameters including pH, electrical conductivity (EC), total dissolved solids (TDS), nitrates, chlorides, and fluorides, following BIS 10500:2012 standards. Statistical analysis revealed significant deterioration trends across all monitoring sites (p < 0.05), with Mann–Kendall test confirming consistent year-over-year degradation patterns. Spatial heterogeneity analysis demonstrated significant differences between sites (F = 12.47, p < 0.001), indicating varying pollution sources and environmental pressures. Multiple regression analysis identified EC, TDS, and nitrates as primary WQI drivers (p < 0.001), suggesting combined impacts of natural mineral leaching and anthropogenic contamination from agricultural runoff and industrial effluents. Principal Component Analysis revealed distinct site clustering based on contamination levels, with high-risk sites (Aralalu, Shivagange 1) showing accelerated degradation patterns. ARIMA modeling and bootstrap projections indicate an 83 % probability that high-risk sites will reach “Unfit for drinking” classification (WQI > 100) by 2030. The findings underscore the urgent need for comprehensive water management interventions, pollution source control, and enhanced monitoring protocols to protect groundwater resources and public health in rapidly developing peri-urban regions.