Massive fish deaths in Delhi's Najafgarh drain, a tributary of the Yamuna, are raising alarms about the impact of untreated waste and pollution on aquatic life and water quality.
Key Points
- Thousands of fish have died in the Najafgarh drain, near the Dhansa regulator, due to suspected pollution.
- Activists blame untreated residential and industrial waste for the mass fish mortality in the Najafgarh drain.
- Increased temperatures may have lowered dissolved oxygen levels, contributing to the fish deaths.
- The Najafgarh drain, a major source of pollution, flows directly into the Yamuna River.
- Experts warn that mass fish deaths indicate extreme environmental stress and call for immediate action.
Thousands of dead fish have been seen floating on the Najafgarh drain near the Dhansa regulator in the past few days, activists said, pointing to possible inflow of excessive untreated residential effluents and industrial wastes as the probable cause.
Bhim Singh Rawat, a Yamuna activist and member of the South Asia Network on Dams, Rivers and People (SANDRP), said the incident has been observed near Rawta village, on the Delhi-Haryana border.
Untreated Waste And Temperature Impact
"This mass fish mortality can be attributed to excessive inflow of untreated residential effluents as well industrial wastes," Rawat said, adding that all this, paired with an increase in temperature might have caused a drop in the DO (dissolved oxygen) level, leading to fish deaths.
Najafgarh, one of Delhi's most polluted drains, flows directly into the Yamuna, thus raising further concerns about its pollution level.
Rawat said similar incidents have been observed earlier at major points along the Yamuna as well.
Pollution Levels Exceed Safe Limits
A Delhi Pollution Control Committee (DPCC) analysis published in March showed that the biological oxygen demand (BOD) at "Najafgarh Jheel Downsteam" was recorded at 60 mg/l, as compared to the desired standard of 30 mg/l. The report also showed that multiple subdrains of the Najafgarh canal also has BOD levels way above the safe limit.
Fish As Bio-Indicators Of Ecosystem Health
Radhey Shyam Sharma, head of Delhi University's (DU) Department of Environmental Studies, said fish can be taken as an bio-indicator of ecosystem health.
"Mass fish deaths can signify extreme stress on environment. Najafgarh drain already has a very high level of pollution but that problem is compounded by mixture toxicity," Sharma told PTI.
"A particular pollutant can be present at comparative low levels and would not be a problem if present alone. However, when multiple pollutants are present, they might chemically react with each other and lead to mixture toxicity," he explained.
Calling the incident extremely concerning, both called for proper investigation and immediate action to rectify the "imbalance".
"These incidents are a message that we need to take some form of action," Sharma said.
