Bengaluru: 5 years on, Bellandur Lake to receive rainwater inflow this monsoon

Bengaluru: Rainwater will finally begin flowing back into Bellandur Lake almost five years after the Bangalore Development Authority (BDA) cut off the natural inflow to make way for the lake rejuvenation project.

However, the inflow is likely to carry untreated sewage and effluents as the existing sewage treatment infrastructure upstream of the lake remains inadequate.

Given the high dependence on borewell water in and around Bellandur, known for its high-rise apartment complexes and large commercial establishments, the inflow of rainwater into the 906-acre lake is expected to help recharge groundwater levels that had declined over several summers.

A senior BDA engineer said around 92 per cent of the waterbody has been desilted.

“We have removed about 35 lakh tonnes of silt so far in line with the tender conditions. However, more silt needs to be cleared from nearly 70 acres of the lake. We have sought additional funds for the remaining work,” the engineer said.

Presently, the BDA is constructing a bund (coffer dam) to separate the desilted portions of the lake and ensure inflowing water does not enter areas that are yet to be desilted. “Inlet work on the Koramangala Valley has been completed. Similar work is underway on the Challaghatta Valley as well,” the engineer added.

When DH visited the site on Tuesday, around a dozen earthmovers were operating on the lakebed. Much of the silt removed from the lake had earlier been used to build temporary sewage diversion channels and temporary roads for transporting the silt. The silt has also been dumped along the lake’s periphery and adjoining areas.

Notably, the diversion drain continued to carry sewage, indicating the Bangalore Water Supply and Sewerage Board's (BWSSB) lack of preparedness to treat the sewage that will now flow into the “de-silted” waterbody.

As per the contract, private agency RMN Infrastructure Ltd is required to remove toxic sludge, construct wetlands, build diversion channels for sewage, strengthen embankments, and undertake landscaping and tree plantation, among other works.

The project, which began in 2021, is estimated to cost Rs 350 crore. Some works are still pending.

On the remaining silt, BDA officials said the desilted sludge would be transported to designated locations after drying.

However, some experts remain sceptical about the effectiveness of the BDA’s work.

Environmentalist Yellappa Reddy questioned whether the agency had actually transported 35 lakh tonnes of silt out of the lake. “I see that the silt has been dumped along the lake’s periphery and only a cosmetic touch has been given to the lakebed,” he said, adding that complete desilting of the lake could take decades given the time required for transportation.

“What is needed first is to completely stop the entry of sewage and dumping of garbage,” he said.

A BWSSB officer told DH that the Bellandur STP is currently inadequate to treat all the sewage flowing through the stormwater drain.

“We are building an additional 60 MLD-capacity plant, but it will be ready only after two years,” the officer said.