Dual-index framework for groundwater potability assessment in Bangalore’s Peenya industrial area: a comparative evaluation using conventional and entropy-weighted water quality indices

In the rapidly urbanising Peenya Industrial Area of Bangalore, groundwater sustains diverse industrial, domestic, and irrigation demands, but faces quality degradation from geogenic and anthropogenic sources. This study evaluates potability using a dual index framework, applying two complimentary indices–the Conventional Water Quality Index (CWQI) and an Entropy Weighted Water Quality Index (EWQI). The objective was to compare their diagnostic and identify priority contaminants. Thirty pre monsoon samples (April 2024) were analysed for 10 physicochemical parameters (pH; chloride; total dissolved solids; nitrate; total hardness; iron; calcium; magnesium; sulphate; fluoride), following APHA protocols. CWQI values ranged from 46.96 to 548.81, with over 70% of samples classified as non-potable. EWQI values ranged from 35.90 to 579.86, introducing a differentiated ‘moderate’ category (20% of samples) and classifying nearly half as poor to very poor. Statistical comparison (paired t test, p = 0.18; Bland Altman limits −38.41 to 49.71) indicated no systematic bias between indices. The novelty lies in applying a dual index framework to industrial aquifers, demonstrating that EWQI provides finer resolution in mid-range classes, supporting targeted monitoring. Broader validation across diverse aquifers is recommended before generalising its superiority.