BENGALURU: A new study has revealed that Bengaluru’s once-pristine lakes are now facing alarming levels of pollution, largely driven by rapid urbanisation, untreated sewage, and industrial effluents. The Lake Health Index study, conducted by Friends of Lake, assessed three major water bodies — Ulsoor, Doddabommasandra, and Shivapura — exposing severe ecological stress and unsafe water quality.
Citizen-led lake health monitoring
The initiative employed trained citizen volunteers to monitor seasonal variations in several water parameters such as pH, colour, odour, and presence of floating garbage. Samples were collected during both pre-monsoon and post-monsoon periods to capture seasonal impacts.
Of the three lakes, Shivapura lake in Peenya emerged as the most severely degraded. Surrounded by dense industrial activity, the lake receives untreated effluents and sewage from nearby slums. The study reported persistently black water, strong sewage odour, and heavy accumulation of floating waste throughout the year. Laboratory tests confirmed high levels of Total Dissolved Solids (TDS) and phosphates, pointing to industrial discharges and chemical runoff.
In contrast, Doddabommasandra lake presented a relatively better picture due to the inflow of treated water from a nearby Sewage Treatment Plant (STP). The lake exhibited clearer water and limited signs of eutrophication. Ulsoor Lake, although not as degraded as Shivapura, showed moderate pollution levels with greenish water and periodic incidents of fish deaths, signalling low dissolved oxygen levels and algal overgrowth.
Pollution spikes after monsoon
Across all three lakes, pollution levels worsened after the monsoon season. According to the report, rainfall flushes accumulated urban waste — including industrial chemicals, sewage, and surface pollutants — into the water bodies. As a result, nitrate and phosphate concentrations rose sharply post-monsoon, increasing the risk of eutrophication.
These nutrient surges promote algal blooms, which deplete oxygen and endanger aquatic organisms. Shivapura Lake’s poor water quality has rendered it unfit for fishing or recreational use, while Doddabommasandra and Ulsoor continue to support limited angling, suggesting a comparatively balanced aquatic ecosystem.
Urbanisation and encroachment choking the lakes
Historically, Bengaluru’s lakes were engineered to harvest rainwater and support agriculture, forming an intricate chain of reservoirs that recharged groundwater and sustained rural livelihoods. However, unchecked urban sprawl, encroachments, and concretisation have transformed many of these lakes into sewage-fed holding ponds.
The study highlighted that land use patterns around lakes directly influence their health. Residential neighbourhoods contribute detergents and nutrients from domestic wastewater, agricultural zones release fertiliser-laden runoff, and industrial areas discharge toxic substances that increase water acidity and solid contamination.
Solid waste dumping, siltation, and fragmented institutional accountability have worsened the situation. The report noted that despite several rejuvenation drives, a lack of coordination among civic agencies, including the Bruhat Bengaluru Mahanagara Palike (BBMP), Karnataka State Pollution Control Board (KSPCB), and Bangalore Water Supply and Sewerage Board (BWSSB), continues to impede meaningful restoration efforts.
The way forward: Ecosystem-based restoration
The Lake Health Index concludes that lakes surrounded by industrial belts and high-density concrete zones exhibit the worst water quality, with multiple parameters exceeding Central Pollution Control Board (CPCB) permissible limits.
To reverse the trend, the study recommends installing efficient Effluent Treatment Plants (ETPs) in industrial areas such as Peenya, strengthening BBMP oversight and imposing strict penalties for untreated sewage discharge, and deploying the proposed citizen lake health mobile app, enabling residents to test water parameters and report violations in real time.
The report stresses that rejuvenation must adopt a holistic, ecosystem-based approach, integrating biodiversity, water chemistry, and land-use management. Piecemeal clean-up drives, it warns, will not restore ecological balance.
As Bengaluru grapples with the dual challenges of urban expansion and water scarcity, safeguarding its lakes is crucial to maintaining groundwater recharge, reducing flood risks, and preserving the city’s fragile environment.