Pollution rises in Bengaluru lakes post monsoon: Study

BENGALURU: A new lake health study, covering three major water bodies in Bengaluru -- Ulsoor, Doddabommasandra and Shivapura has revealed dangerous levels of pollution and a clear link between rapid urbanisation and deteriorating water quality. The study Lake Health Index by Friends of Lake, a group working on lake rejuvenation and protection -- used citizen volunteers to track seasonal changes in water parameters such as pH, colour, odour, floating garbage and others. Samples were collected during the pre-monsoon and post-monsoon cycles. Of the three water bodies, Shivapura lake in Peenya, surrounded by heavy industries and receiving untreated effluents and sewage from neighbouring slums, showed the most severe degradation. The lake had black water throughout the year, strong sewage odour and extensive floating garbage accumulation. High levels of Total Dissolved Solids and phosphates indicate heavy industrial discharge and runoff. In contrast, Doddabommasandra lake supplied with treated water through a Sewage Treatment Plant (STP) showed better water clarity and fewer signs of eutrophication. Ulsoor Lake showed moderate pollution with greenish water and occasional fish deaths. Across all three lakes, pollution levels worsened post-monsoon. The study attributes this to rainfall flushing industrial chemicals, sewage and surface pollutants into the lakes, especially from concretised urban catchments. Nutrient levels nitrate and phosphate increased sharply after monsoon, indicating eutrophication risk. Higher nutrient loads encourage algal blooms, reduce dissolved oxygen and endanger aquatic life. Shivapuras water quality was so poor that no fishing activity was seen, while Ulsoor and Doddabommasandra continued to support occasional angling a sign of healthier aquatic balance. The report notes that Bengalurus lakes, historically built to harvest rainwater and support agriculture, are now reduced to sewage-fed holding ponds. Encroachment, solid waste dumping, untreated sewage inflow and lack of accountability among agencies have prevented meaningful restoration. The study also highlights that surrounding land use has direct impact such as residential areas adding detergents and nutrients; farming zones contributing fertiliser runoff; and industrial belts driving spikes in acidity and toxic solids. The report concludes that lakes surrounded by industrial activity and dense concretised development show the most severe degradation, with most parameters exceeding permissible limits. The study emphasises that lake revival cannot be piecemeal it must consider the entire ecosystem, including biodiversity, water chemistry and land use patterns. Key recommendations include, installing efficient effluent treatment plants (ETPs) in industrial belt lakes like Shivapura; strengthening erstwhile BBMP oversight and enforcing penalties for untreated sewage discharge; rolling out the proposed citizen lake health app and allowing residents to test basic water parameters and report violations.