Subhechcha Ganguly 
Kolkata Metro Railway is set to implement a significant eco-friendly upgrade on its Blue Line, the oldest metro corridor in India, by replacing traditional water-cooled chillers with air-cooled systems—an initiative expected to conserve approximately 180 million litres of groundwater annually. This volume is equivalent to the capacity of over 70 Olympic-sized swimming pools.
Commissioned on October 24, 1984, the Blue Line originally spanned 3.4 km between Esplanade and Bhowanipore (now Netaji Bhavan). Today, it stretches 31.3 km between Kavi Subhash and Dakshineshwar. Out of the 15 underground stations along the route, 11 will undergo the cooling system transformation.
“In a bid to preserve groundwater, we are introducing a new cooling system in the Blue Line. Switching from water-cooled to air-cooled chillers will significantly reduce our dependency on groundwater,” said a senior Metro Railway official.
The project, backed by a ₹150 crore allocation from the Union government, is scheduled to begin in 2026 and be completed by 2029. Tenders have already been opened and are currently under evaluation.
Experts view this move as a crucial step toward environmental sustainability. A 2022 study published in Springer Nature highlighted that Kolkata is experiencing groundwater depletion at an alarming rate—up to 33 cm annually at the city’s core—triggering gradual land subsidence.
While some experts, including IIT Kharagpur’s Professor Abhijit Mukherjee, acknowledge that the saved water may seem modest for a metropolitan city, they emphasise that every conservation effort contributes positively to long-term sustainability.
