Under which one of the following rivers has India's first underwater metro rail tunnel been constructed?

India's first underwater metro rail tunnel has been constructed under the Hooghly River in Kolkata [1]. This engineering milestone is part of the East-West Metro Corridor, specifically the Howrah Maidan-Esplanade section. The tunnel connects the twin cities of Kolkata and Howrah, situated on the east and west banks of the river, respectively. The under-river section spans approximately 520 meters and is situated about 13 meters below the riverbed. Inaugurated in March 2024, this project also features the deepest metro station in India at Howrah, located at a depth of 33 meters. The tunnel was constructed using advanced Tunnel Boring Machines (TBMs) to navigate the alluvial soil of the Ganga river system. This development significantly reduces travel time between the two cities and marks a major advancement in India's urban transport infrastructure.

Sources

1. [1] https://www.bbc.com/news/world-asia-india-65773871