The impact of neglecting the lakes through encroachment and unscientific rejuvenation processes has been on full display during recent heavy rains, but what is happening inside the lakes is an equally distressing story. As pollutants continue to flow into many lakes, it is wreaking havoc on the aquatic ecosystem.
Hundreds of fish have died in the city in recent years. According to a report released earlier this year, around 35 fish kills have been seen in the city over the past five years, with Jakkur, Kothanur, Panatthur and Haralur lakes identified as vulnerable.
In recent days, fish kill incidents have been reported in all these lakes, including one in Haralur during the second week of September.
Most lake activists and local residents say sewage entering the lakes is the root cause of fish kills.
Lack of proper monitoring by the two authorities concerned, the Bruhat Bengaluru Mahanagara Palike (BBMP) and the Karnataka State Pollution Control Board (KSPCB), is cited as the second cause.
According to a report released earlier this year, around 35 fish kills have been observed in Bengaluru over the past five years, with Jakkur, Kothanur, Panatthur and Haralur lakes identified as vulnerable. | Photo credit: archive photo
“Wastewater does not enter the lake when it is not raining. But when it rains, the sewers overflow and there are two or three entry points from where the sewage mixes with the lake. I’ve been here two years and have seen at least five to six cases of fish kills. We have tried to get the BBMP to take this into account and coordinate with other civic agencies like the BWSSB. They have issued a notice but not much change is happening,” said Nagaraj Udupa, a member of Kothanur Lake Development Association.
Fish kills were reported in Lake Kothanur in June and July. During a visit to the lake, The Hindu saw a lot of solid waste, mostly plastic, floating around the lake.
The same was true at Lake Yelachenahalli. In nearby Lake Chunchghatta, activists had recorded video of fish rising to the surface of the water to breathe.
Experts point out how the ingress of chemicals and sewage reduces dissolved oxygen (DO) levels in lakes.
“Water pollution and nitrification leads to water contamination. When the DO level drops below 4%, the fish die. Chemical oxygen demand (COD) and biological oxygen demand (BOD) levels also increase dramatically when chemicals and untreated industrial effluents enter the water, and they also contribute to reduced DO levels said AN Yellappa Reddy, chairman of the Bangalore Environment Trust. .
He also added that apart from fish, domestic animals, which drink the contaminated water from these lakes, also suffer from some ailments, especially in peri-urban areas. “Ultimately, the products of these animals, like milk, which is also consumed by city dwellers, also pose health risks to humans,” Reddy said.
With him, many lake conservators claim that it is not too late for civic authorities to protect the biodiversity of the lakes and that the most essential thing is strict monitoring.
“The KSPCB produces a monthly water analysis report for all the lakes in the city. Any lake that receives an E rating is not suitable for wildlife and fishing. The BBMP should get these reports from them and the engineer in each area should take action to improve these parameters,” said Raghavendra Pachhapur, Program Manager, ActionAid Association.
The BBMP says the scale of fish kills has declined in recent years and most incidents only occur during the summer.
“In dry weather, if sewage enters the lake, its concentration levels will be high, which could lead to the death of fish. We have created diversion channels to prevent sewage from entering the lakes. But during the rainy season, although some leakage may occur, it gets diluted as the lakes will be full. We have not encountered any major cases of fish kills this rainy season,” said Shashi Kumar, Chief Engineer, Lakes, BBMP.
The lack of civic responsibility is also a cause. Despite many billboards, citizens are dumping solid waste into the lakes. This is why activists believe that until all citizens begin to display proactive behavior and hold officials accountable for the state of water bodies, full-fledged improvement in lakes cannot be seen.
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