40 per cent of the city's sewage flows into it
On the face of it, vegetable farmers at Ramagondanahalli, near Whitefield, appear to have a good deal: a ready market just a few km away, and Bangalore’s second largest lake in their backyard to meet the year-round irrigation needs.
But with 80 years of insight into life and livelihood in this village on the banks of Varthur lake, Narayanappa will tell you that this water body has quickly gone from being a lifeline for farming communities to a cesspool not just unfit for use, but a distinct health hazard. “Thirty years ago we used nothing but the lake water at home — to drink, to cook and to wash. Now we can use it only to water our crops.”
Mr. Narayanappa attributes the pollution to the influx of “city water” — a theory that is confirmed by a scientific study at the Indian Institute of Science (IISc). Being the last lake downstream of a network of large lakes that dot the city — including Bellandur and Agara — Varthur lake receives 40 per cent of the city’s sewage, says a research paper by the Energy and Wetlands Research Group at IISc.
And in a reflection of the city’s inconsistent and poorly maintained sewerage system, the 500 million litres of sewage that Varthur receives every day is largely untreated, creating a “persistent hyper eutrophic condition,” says the paper ‘Ecological and socio-economic assessment of Varthur Wetland’ published in 2011.
The signs are everywhere. Every few days, a cloud of white foam rises to the surface of the lake, so high that it overflows on to a road-bridge several meters high, a source of mild entertainment to Pavana M., a class eight student, whose school bus takes this route. Seasonally, N. Krishnappa, who draws water from Varthur through a pump for his 10-acre farm, notices that some of his crops wilt inexplicably. On other days the smelly water makes it almost impossible for him to work his field, he says.
Not surprisingly, the IISc. survey found health conditions symptomatic of biological water contamination: dysentery and dermatitis were prevalent in most of the 235 households surveyed.
But the cost of pollution doesn’t end there. It extends to livelihoods. A thriving fishing community has lost indigenous species of fish and is left with only an invasive exotic African catfish; and agricultural productivity, the availability of fodder and fuel wood have taken a beating.
Monetising the impact of Varthur’s pollution on communities that depend on it, the study calculated the enormous loss thus: While “a relatively pristine wetland in Bangalore shows the value of Rs. 10,435/ha/day…Varthur, a sewage fed wetland has a value of Rs.118.9/ha/day."
The pollution in Varthur lake is bound to have a cascading affect, contaminating groundwater and the Dakshina Pinakini downstream, which it finally flows into, explains T.V. Ramachandra, co-author of the paper. “We found in an independent test that borewell water here is high in nitrates, a known carcinogen in high doses,” he says, adding that the percolation of untreated sewage is the obvious source.
An official of the Bangalore Water Supply and Sewerage Board, who did not want to be named, said the board was on the job of creating sewerage lines in this CMC area, but admitted that Varthur’s maladies originate in the very heart of the city.
“We need to first plug the problem of untreated sewage in the core area if we have to save Varthur. A single chief engineer cannot be held responsible for the condition of the lake. There are several areas that need attention: waste water management, the maintenance of sewage lines and the creation of sewage treatment plants.”