Thousands of dead fish, swarms of maggots and a stench that has lingered for days have turned Doddagubbi Lake in Bengaluru into a stark reminder of the risks polluted runoff poses to urban water bodies.
Nearly a week after the mass fish kill, the 125-acre lake in Bengaluru’s Mahadevapura Assembly constituency remains at the centre of a dispute over responsibility for the deaths and the delay in removing the carcasses.
Villagers allege that neither the Greater Bengaluru Authority (GBA) nor the Minor Irrigation Department has taken responsibility for addressing the situation. Meanwhile, the Karnataka State Pollution Control Board (KSPCB) has said it will issue notices to Bengaluru Solid Waste Management Limited (BSWML), as leachate from a nearby dumping yard is suspected of contributing to the contamination.
The incident raises a larger question for a city whose lakes face mounting pressure from expanding settlements, waste disposal and drainage networks: what happens when rainwater carries pollution into a lake, and the damage goes unaddressed?
Thousands of fish, one suspected cause
The first explanation for the deaths points to a problem beneath the water’s surface.
B Chikkanna, deputy director of the Fisheries Department in Mahadevapura ward, told Hindustan Times on Sunday that the initial assessment indicated the fish had died from asphyxiation caused by low levels of dissolved oxygen in the lake.
“Prima facie, the fishes died due to asphyxiation. Due to the rains, a large quantity of rainwater mixed with polluted water from Mittaganahalli GBA dumping yard entered Doddagubbi Lake, causing a shortage of oxygen,” Chikkanna told the newspaper.
The Fisheries Department has begun an inquiry and collected water samples to investigate the deaths. The results will be crucial in establishing the precise cause and identifying the source of contamination.
As BSWML and Minor Irrigation Department fail to clear dead fish, Doddagubbi lake is now infested with Maggots. @NewIndianXpress,@XpressBengaluru,@ramupatil_TNIE,@mg_chetan,@aknisreekarthik,@krishnabgowda,@DKShivakumar,@RLR_BTM https://t.co/F32LNINQ33
— Yacoob (@yacoobExpress) October 9, 2026
The suspected sequence of events points to a familiar urban environmental problem. Rainwater that should replenish a lake can also carry pollutants from surrounding land, waste facilities and drainage channels. When this runoff contains high levels of organic waste, the resulting decomposition can reduce the oxygen available to aquatic life.
While oxygen depletion is the Fisheries Department’s preliminary explanation, investigators must establish what caused oxygen levels to fall and how the pollutants entered the lake.
Why oxygen matters to a lake
Dissolved oxygen is the oxygen present in water that fish and other aquatic organisms need to survive. When levels drop sharply, fish may be unable to obtain enough oxygen, leading to mass deaths.
Research on Bengaluru’s lakes has documented similar incidents.
In a 2016 report titled Recurring Fish Mortality Episodes in Bangalore Lakes: Sign of Irresponsible and Fragmented Governance, researchers T V Ramachandra, Sincy Varghese, Asulabha K S and Sudarshan Bhat of the Indian Institute of Science’s Energy and Wetlands Research Group examined fish deaths in Ulsoor and Devarabisanahalli lakes.
Their analysis of water and fish samples linked the deaths to asphyxiation following a sudden decline in dissolved oxygen, associated with the sustained inflow of untreated sewage.
Sewage increases the organic load in a water body. As microorganisms break down this material, they consume oxygen, potentially leaving too little for fish and other aquatic organisms. Higher temperatures can intensify these biological processes.
The findings offer scientific context for understanding the suspected oxygen depletion at Doddagubbi, although the lake’s own test results are needed to establish whether the same mechanism was at work.
A study of Bellandur Lake, published in the Journal of Environmental Biology in July 2003, also documented the effects of urban pollution. Researchers J S Chandrashekar, K Lenin Babu and R K Somashekar of Bangalore University’s Department of Environmental Sciences reported high biochemical oxygen demand — a measure of the oxygen microorganisms need to break down organic matter — and warned that continued pollution could leave the lake ecologically inactive.
Together, these studies show why identifying the source of pollution matters as much as responding to visible fish deaths. A lake’s ability to support aquatic life can be compromised long before a mass fish kill makes the damage apparent.
When a dumping yard meets a lake
Leachate is the contaminated liquid formed when water passes through waste, picking up dissolved and suspended substances. Depending on the type of waste and conditions at the site, it can contain organic pollutants, salts, metals and other potentially harmful compounds.
If leachate escapes into nearby drains, ponds or lakes, it can affect water quality and aquatic ecosystems.
A study published in the International Journal of Geo-Engineering on 12 December 2018 examined the potential effects of leachate leakage from the Mavallipura municipal solid waste landfill near Bengaluru.
Researchers B P Naveen, J Sumalatha and R K Malik investigated the landfill’s leachate and surrounding water bodies. Their work documented concerns about runoff entering nearby ponds and open wells and assessed how contaminants could move through soil and spread into surrounding water resources.
The research highlights why landfill drainage and leachate containment are particularly important during periods of rainfall. However, it does not establish that the same process caused the fish deaths at Doddagubbi. That question must be answered through local water sampling and an investigation of the drainage pathways.
The damage does not end with the fish
With dead fish reportedly left uncollected for days, decomposition has produced a foul odour and attracted maggots. What began as a suspected water-quality emergency has become a sanitation concern for nearby communities.
If leachate escapes into nearby drains, ponds or lakes, it can affect water quality and aquatic ecosystems. Photograph: (The Hindu)
The consequences of leaving the carcasses in place extend beyond the smell. Decomposing organic matter can increase the oxygen demand in the water, while the continued presence of dead fish can complicate efforts to restore the affected area. The extent of any additional deterioration in Doddagubbi Lake’s water quality has not yet been established.
Investigators must determine the source of contamination, but the immediate response need not wait for every question to be settled. The carcasses need to be removed and disposed of safely, the water needs to be tested, and the route through which pollutants may have entered the lake needs to be identified.
What happens after the carcasses are cleared?
Removing the dead fish would address the most immediate and visible problem. It would not, by itself, prevent another fish kill.
That requires identifying and stopping the source of pollution, assessing the lake’s water quality and monitoring dissolved oxygen levels. Authorities must also examine the drains that carry rainwater into the lake, check whether polluted runoff is entering through them, and ensure that nearby waste facilities contain and manage leachate effectively.
Research into fish deaths at Ulsoor and Devarabisanahalli lakes in 2016, along with the 2003 study of Bellandur Lake, highlights the consequences of sustained pollution and inadequate management of urban water bodies.
The ongoing investigation will determine whether a similar chain of events unfolded at Doddagubbi. Until the sampling results establish the cause, the suspected link to the nearby dumping yard remains an allegation that needs to be investigated.
Doddagubbi’s case highlights the need to look beyond the immediate crisis. Clearing the carcasses is essential, but protecting the lake in the long term will depend on identifying the source of contamination, preventing further pollution and ensuring that the agencies responsible take action.
The fish deaths have made the damage visible. The challenge now is to address the underlying problem before another incident occurs.
