Environmental Crisis at Sukhna Lake: Oil Spill and Oxygen Depletion Trigger Fish Mortality
Chandigarh's iconic Sukhna Lake is grappling with a severe environmental crisis, as two allied scientific reports have confirmed a localized oil spillage along its southern shore and critically low levels of dissolved oxygen in the water. These factors are identified as the primary culprits behind the recent spate of fish deaths that have alarmed environmentalists and authorities alike.
Scientific Investigations Uncover Disturbing Findings
The reports, based on comprehensive analyses of water samples and seven dead specimens of bottom-dwelling fish from the Clarias and Tilapia genera, were collected from the lake on January 16, 2026. They were formally submitted last week to the forests and wildlife department by the Chandigarh Pollution Control Committee (CPCC) and the Fish & Fisheries Laboratory of Panjab University's zoology department.
The CPCC report revealed a troubling oil contamination: Over a 200-meter stretch of surface water near the southern shore, ahead of the so-called 'suicide tower', the oil and grease concentration measured 2.8 mg/L, compared to 2.5 mg/L just before the suspect area. "Results clearly establish the presence of oil in collected sample, confirming the contamination of oil in surface water," the CPCC report stated unequivocally.
While the engineering department promptly pumped out the oil spill after its discovery on January 15, this contamination alone does not explain the continuing fish deaths observed on both the southern and northern banks of the lake, both prior to and after the spill incident.
Oxygen Depletion Emerges as Primary Killer
The zoology department's report, authored by associate professor Ravneet Kaur, provides crucial insights into the physiological distress experienced by the aquatic life. The seven fish samples examined showed "acute environmental stress (likely hypoxia)... consistently showed signs of respiratory distress, gill-related damage, tissue softening, haemorrhagic changes, and post-mortem autolysis."
Of the nine water quality parameters analyzed by the zoology department, three critical measurements deviated significantly from permissible limits:
- Dissolved oxygen: Measured at just 3.92 mg/L against the required minimum of 4-5 mg/L
- Free carbon dioxide: Recorded at 13.6 mg/L, exceeding the recommended limit of less than 10 mg/L
- Temperature: Registered at 13.7 degrees Celsius, well below the optimal range of 25-32 degrees Celsius
The report definitively attributed the fish mortality to "oxygen depletion and carbon dioxide build up, common in urban lakes with organic pollution and stagnation."
Underlying Environmental Factors Exacerbating the Crisis
The investigation delineated several interconnected factors contributing to the oxygen depletion and subsequent fish deaths:
"The water level has reduced and a lot of vegetation is visible. Shallow edge areas experience accumulation of organic matter (vegetation) decaying, which increases the biological oxygen demand (BOD)... Both the species of fishes found dead feed at the bottom of waterbodies. Anaerobic decomposition in sediments releases toxic gases, affecting bottom-dwelling or bottom-visiting fish."
Comprehensive Recommendations for Lake Restoration
To create a more sustainable environment for aquatic life in Sukhna Lake, the zoology department presented detailed recommendations to the UT administration, emphasizing the urgent need for vegetation management:
- Maintenance of water level: Stable water levels support aquatic biodiversity, maintain dissolved oxygen concentrations, and reduce stress on fish and plankton communities.
- Removal of excessive vegetation: Dead and decaying vegetation should be controlled through mechanical or manual removal, thus preventing oxygen depletion during decomposition processes.
- Desilting and removal of accumulated organic matter: Desilting should be carried out in a phased manner to remove nutrient-rich sediments and decaying organic matter. This improves water depth, reduces internal nutrient loading, and minimizes the risk of underwater eutrophication and subsequent fish mortality.
Meanwhile, the forests and wildlife department is currently examining additional casualties, including a dead Rock python and approximately a dozen fish found floating together at the regulator-end last Thursday, for comprehensive mortality analysis.
This environmental crisis at Sukhna Lake underscores the delicate balance required to maintain urban water bodies and highlights the urgent need for sustained monitoring and proactive management to prevent future ecological disasters.
