Study finds severe pollution in Bengaluru lakes, links urbanisation to water quality decline

A new study assessing the health of Bengaluru’s major lakes, Ulsoor, Doddabommasandra, and Shivapura, has found alarming pollution levels and a strong link between rapid urban growth and lake degradation.

Bengaluru’s once-thriving lakes are choking under the pressure of urbanisation and pollution, according to a new Lake Health Index study covering Ulsoor, Doddabommasandra, and Shivapura lakes. The assessment, conducted using citizen volunteers, tracked changes in water quality during pre-monsoon and post-monsoon periods, examining factors like pH, odour, colour, and floating waste.

Among the three, Shivapura Lake in Peenya was found to be in the worst condition. Surrounded by heavy industries and receiving untreated effluents from nearby factories and slums, the lake’s water remained black and foul-smelling throughout the year, with thick layers of floating garbage. Tests revealed high Total Dissolved Solids (TDS) and phosphate concentrations, confirming severe contamination from industrial discharge and chemical runoff.

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In contrast, Doddabommasandra Lake, which receives treated water from a Sewage Treatment Plant (STP), displayed relatively better clarity and lower pollution levels. Ulsoor Lake, located in the heart of the city, showed moderate pollution marked by greenish water, algal blooms, and occasional fish deaths.

Across all three lakes, the study recorded a sharp increase in pollution levels after the monsoon, attributed to rainwater washing untreated sewage, chemicals, and waste from urban catchments into the water bodies. The post-monsoon samples showed higher levels of nitrate and phosphate, indicating eutrophication, a process that promotes algae growth and reduces oxygen levels, endangering aquatic life.

The report also observed that Shivapura had no fishing activity due to poor water quality, while Ulsoor and Doddabommasandra still supported occasional angling — a sign of slightly better aquatic balance.

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Researchers noted that Bengaluru’s lakes, originally designed to harvest rainwater and support agriculture, have now turned into sewage-fed reservoirs due to encroachments, garbage dumping, untreated inflows, and lack of coordination among civic bodies. The surrounding land use was found to play a key role, residential zones contribute detergents and greywater, farming areas add fertiliser runoff, and industrial belts discharge toxic chemicals.