Devarabisanahalli Lakebed under threat, says IISc

BENGALURU: Wedged between multinational firms and a mammoth realty project lies the Devarabisanahalli lake in southeast Bengaluru, the latest waterbody in the IT corridor caught in the crosshair of destruction. The 13.7-acre lake located near Intel and Adarsh Palm Retreat in Bellandur is completely covered with macrophytes (hyacinth) and its storage capacity has dropped to 48,863 cubic metres from the original 72,588 cubic metres.

A study conducted by ecologist TV Ramachandra of the Indian Institute of Science proved that the lake is in a precarious condition. “A high concentration of sodium and potassium indicates sewage contamination. Higher turbidity of lake water is due to the presence of silt, clay, organic and inorganic matter and planktonic organisms that makes the water unfit for domestic and industrial purposes,” he said.

When ET visited the lake on Monday, the villagers of Devarabisanahalli and residents of Adarsh Palm Retreat blamed each other for letting sewage into the lake. Residents living around the lake have formed the Devarabisanahalli Lake Group and are actively working with the Ashoka Trust for Research in Ecology and the Environment (ATREE), Friends of Lakes, the IISc and citybased design firm Biome Environmental Solutions. In fact, Ramachandra’s team studied the lake at the request of residents. The Group also includes residents of Adarsh.

The study found that the lake, besides being polluted, holds a large quantity of silt due to “drastic change in land use, thanks to unplanned urbanisation.” The economic value of the silt, Ramachandra said, is anywhere between Rs 5.93 crore and Rs 13 crore. “The sludge at inlets could be used as manure, whereas silt accumulated in other parts of the lake can be used as sand after treatment.”

Residents are in talks with multinational giant Honeywell, which is in the vicinity, to help rejuvenate the lake. “We have prepared a detailed project report considering the entire watershed region. Lakes survive only if there is good amount of groundwater recharging or else they dry up,” said V Ramprasad, convenor of Friends of Lakes, a voluntary group working to protect 22 lakes in the city. The project report involves all stakeholders, including the villagers.

The IISc study found 1.31 acres of the lake being encroached while the Joint Legislative Assembly Committee on Lake Encroachment, headed by legislator KB Koliwad, found a road encroaching just 13.25 guntas.