BHAGAT SINGH, RAM NARESH TYAGI, VARSHA SHARMA AND ANIL JINDAL
Abstract
Industrial effluent discharge into freshwater tributaries represents a major environmental challenge in rapidly industrializing regions. This study provides a comprehensive assessment of The physico-chemical characteristics and biological indicators of water quality in the Sirsa tributary of River Sutlej, which flows through the BaddiâBarotiwalaâNalagarh (BBN) pharmaceutical and industrial complex in the Himalayan foothills of Himachal Pradesh, India. Water samples were collected monthly for twelve consecutive months (April 2024 to March 2025) from three strategically selected sites: S1 (Lotic upstream reference zone), S2 (Common Effluent Treatment Plant discharge point at Jagatkhana Bridge), and S3 (Lentic downstream zone at Ghanauli Bridge). Parameters were analyzed using APHA (2005) standard protocols. Statistical analysis included oneway ANOVA with Tukeyâs HSD post-hoc test for inter-site comparisons, Pearson correlation analysis among key physicochemical parameters, and calculation of effect sizes (?²). Results revealed severe pollution at S2â with Chemical Oxygen Demand (COD) ranging from 37.52 to 365.15 mg/l (mean ± SD: 138.99 ± 110.5 mg/l), Dissolved Oxygen (DO) critically depleted to 1.22â2.6 mg/l (1.53 ± 0.65 mg/l), and pH highly acidic (3.2â6.8; 5.00 ± 1.55). All inter-site differences for major parameters were statistically significant (F > 31.0; p < 0.001; ?² > 0.65). Strong negative correlations were observed between DO and BOD (r = â0.82, p < 0.01) and between DO and COD (r = â0.79, p < 0.01). Biological assessment classified S3 site near NH-205 as polysaprobic (Shannon diversity Hâ = 0.36), dominated by Oscillatoria sp., Spirogyra sp., Tubifex sp. and Chironomid larvae. The study demonstrates that inadequately treated industrial effluent has severely compromised the ecological integrity of this tributary, threatening aquatic biodiversity, downstream water use, and public health. Immediate regulatory intervention, infrastructure upgrading, and ecological restoration are urgently required.