Yellamappa Setty lake in Krishnarajapuram was once the largest lake in Bangalore; now, it is the third largest.
Divided by the NH 4, which runs through the water body, one side has dried up, diminishing its size. Today, it is the place where much domestic and industrial sewage is drained.
This lake is at the tail-end of one of Bangalore's three major water systems. Originating at Bantkondanahalli lake, water flows through Yelahanka, Nagawara and Kalkere to Yellamappa Setty, from where it goes to Krishnagiri district in Tamil Nadu.
“We are at the end of the system, in a low lying area into which water can drain. So, the city's sewage, which gets mixed with flowing water, gets stagnated in our lake,” says Narayanappa, who mans the fish contractor's store near the lake. “Then, there is the industrial sewage, which has always been a problem in this area.”
Something fishy
Lakes in Bangalore are contracted out for fishing every five years in a bid to regulate uncontrolled fishing. Cauveryappan has held the lease to fish in Yellamappa Setty lake since 2010. “There are three more years for the lease to expire, but already we do not catch any fish,” Narayanappa says. “We bring it all the way from Doddabellapur lake.”
“This lake only has catfish, which has eaten up all the other varieties such as catla, prawns, rohu and thilapia,” he rues.
This may be the result of seeding lakes manually with fish, according to T.V. Ramachandra of the Centre for Ecological Studies. “Catfish were introduced because they can breathe despite the lake getting covered by algal bloom, which usually spells death to aquatic life, by draining the water underneath of oxygen,” he explains. “Catfish periodically surface and gulp air and that is sufficient for their survival, whereas they prey on other types of fish underwater.”
According to Afroz, a tailor living and working in the lane adjoining the lake, the local population would anyway not consume fish from the Yellamappa Setty lake because they saw how pollutants killed many fish, frogs and birds that ate the fish, about five years ago.
“But we still buy the fish that is brought from other lakes and sold here, because our traditional diet is full of freshwater fish recipes. This was after all a place where there was confluence of various water sources from the hillocks and hence, a rich aquatic life.”
Harmful green cover
“Algal bloom itself is an organic reaction to effluents mixing in the lake in the presence of sunlight,” says M.B. Krishna, an ornithologist. He remembers when the lake used to be a haunt for a wide range of birds and birdwatchers. A group of ornithologists in the city pooled their resources and undertook a research project on this and other lakes in the early nineties.
“We discovered that there were drastic variations in the pH levels of water at different points within Yellamappa Setty lake,” Krishna says. “Organic effluents from fertilizer, pharmaceutical and other chemical factories were affecting the acidity or alkalinity of the water alarmingly.”
Ramachandra's recent project on the possibility of extracting biofuel from algae revealed that the algae in Yellamappa Setty lake were of a composition that indicated high level of organic effluents from industries. “These toxins which enter the body of fish kill birds that consume them and are carcinogenic to people who eat them,” Ramachandra says.
Krishna's research team also noticed a visible decline in the population of birds. “A fish's body has fat that acts as a solvent to the toxins; birds, which have a high metabolic rate and require very high amounts of energy to fly, consume a lot of fish, and are the first to be hit when a lake and its aquatic life is polluted,” he explains. “That is exactly what happened at Yellamappa Setty lake.”
He also recalls that another research project in his university found that the fish themselves, thilapia in this case, had contracted cancer, by absorbing toxins in their body.
A correlation analysis done as part of his research showed that toxins present in fish did not affect the amount of fishing or consumption of fish by people. Now, it has come to a stage that people reject any catch from Yellamappa Setty lake.
