BMC starts groundwork for desilting city’s water lakes

Shelar said the project is still at the survey stage. “Every step is being taken with due technical diligence, alongside efforts to protect the ecological balance and ensure long-term sustainability,” he said

Mumbai: The Brihanmumbai Municipal Corporation (BMC) has started the process to desilt its drinking water lakes, with surveys underway to prepare a Detailed Project Report (DPR) and assess feasibility, guardian minister Ashish Shelar said on Thursday.

BMC starts groundwork for desilting city’s water lakes

For its daily water supply, the city depends on seven reservoirs: Vihar, Tulsi, Tansa, Modak Sagar, Upper Vaitarna, Middle Vaitarna and Bhatsa. These sources provide around 4,000 million litres per day (MLD) against a demand of 4,505 MLD.

None of the lakes have been desilted so far, raising concerns about reduced storage capacity over time. A 2022 report on the National Framework on Sediment Management says sediment build-up reduces reservoir efficiency and can affect long-term water availability.

Shelar said the project is still at the survey stage. “Every step is being taken with due technical diligence, alongside efforts to protect the ecological balance and ensure long-term sustainability,” he said.

While Right to Information responses filed by activists like B N Kumar, director of NatConnect, show that Mumbai’s drinking water lakes have not been desilted for about ten years, an official in the know said desilting has never been attempted on the city’s lakes due to a lack of technical expertise and procedural approvals required from multiple authorities.

“Desilting of drinking water dams are very costly exercises that need strong political will. Hence, most of the big dams across the state have not been desilted,” informs Sanjay Lakhe-Patil, who has actively petitioned issues of dams across the state.

With water demand peaking during summers and concerns recurring despite full reservoirs during monsoon, questions are being raised about the actual storage efficiency of Mumbai’s water system. Congress corporator Ayesha Vanu has sought a scientific survey, third-party audit and a time-bound desilting plan.

According to additional municipal commissioner Abhijit Bangar, the civic body has already conducted preliminary studies, including a bathymetric survey and satellite-based remote sensing. The Maharashtra Engineering Research Institute (MERI) and the state maritime board have assessed Tulsi and Vihar lakes, indicating silt levels of about 16% and 15% respectively.

However, an official said that these levels do not significantly impact water availability, stating that much of the sediment lies in dead stock at the bottom, which cannot be utilised. “Had it been 30-40% siltation levels, then we could have considered it a case of reduced drinking water capacity,” he said. He added that newer reservoirs like Middle Vaitarna, commissioned in 2012, are not yet due for such interventions, while the Maharashtra government manages Upper Vaitarna and Bhatsa.