Kolkata’s historic 72-acre Rabindra Sarobar lake is now at the centre of an environmental emergency, following the detection of abnormally high levels of toxic metallic sediment on its bed — a situation compounded by the fact that the waterbody has not been dredged for over five decades.
Recent tests conducted under the supervision of the West Bengal Pollution Control Board (WBPCB) revealed elevated concentrations of metals like zinc and magnesium in the lakebed’s sediment. Although the overall water quality remains within permissible limits on the surface, officials from the Kolkata Metropolitan Development Authority (KMDA) have raised concerns that the accumulation of toxic metals beneath may be linked to a series of unexplained fish deaths observed over recent years.In response to the findings, authorities have initiated consultations with environmental scientists and aquatic life experts to ascertain the role of these sediments in the declining aquatic health of the Sarobar. KMDA sources confirmed that recommendations are being formulated to determine the viability of large-scale sediment removal, including modern hydro-raking techniques, to restore the lake’s ecological balance.
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Last year, a temporary intervention saw the application of quicklime to neutralise surface toxins, yet the underlying causes remained unaddressed. With urban runoff, untreated waste discharge, and decades of sediment accumulation pressing down on the lakebed, environmentalists argue that short-term fixes are no longer sufficient.Experts from Jadavpur University are currently assessing the depth of the lake — data that hasn’t been accurately recorded in years. The findings will guide the restoration roadmap, likely to be tabled before the National Green Tribunal (NGT) in the coming months.Environmental advocates argue that sedimentation, if left unchecked, could drastically reduce the lake’s depth and disrupt its natural oxygenation cycle, further endangering its biodiversity. The call now is for an integrated lake management plan that not only removes toxins but also prevents their future recurrence through improved urban wastewater regulation and ecosystem regeneration.
Restoration strategies may also include introducing aquatic vegetation capable of oxygen enrichment and heavy metal absorption, a natural solution that has worked in other degraded urban lakes across the country.
Rabindra Sarobar, beyond its ecological value, is deeply tied to the city’s social and cultural life. Home to walkers, rowers, and countless migratory birds, it stands as a rare green lung in a densely packed metropolis. The unfolding crisis has sparked growing civic interest and concern, pressing policymakers to act with urgency and vision.While the causes of the lake’s decline are many, the solution must be singular in its commitment — to sustainability. A revival of Rabindra Sarobar is not just about cleaning a lake, it is about reclaiming Kolkata’s environmental conscience.
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