Study to Evaluate Impact of Brahmaputra Underwater Tunnel on River Dolphins

The NHIDCL is funding a significant study to assess the environmental impact of the upcoming Brahmaputra underwater tunnel on Ganges River dolphins and aquatic life. The research, titled ‘Beneath the Brahmaputra,’ will involve acoustic monitoring and habitat assessments to evaluate the effects of construction noise and vibrations. Led by Dr. Vishnupriya Kolipakam, the study aims to provide insights into the ecological responses during different phases of the project. With recent dolphin population estimates highlighting the importance of conservation, this study is crucial for ensuring the protection of these aquatic mammals. The project is expected to cost nearly Rs 12,000 crore and will include a 15.79-km underwater tunnel.

By Narendra Chaudhary Sep 23, 2026, 10:56 IST

Impact Assessment of Underwater Tunnel Construction

AT Photo: River dolphin in India

Guwahati, Sept 23: The National Highways & Infrastructure Development Corporation Limited (NHIDCL) is set to finance a research project aimed at understanding the potential effects of the forthcoming Brahmaputra underwater tunnel on Ganges River dolphins and the surrounding aquatic ecosystem.

The initiative, titled ‘Beneath the Brahmaputra,’ will utilize acoustic monitoring, habitat evaluations, and dolphin tagging to assess the ecological impact and propose mitigation strategies for safer infrastructure development.

This research will focus on the ecological responses to the construction of the underwater tunnel, particularly examining how noise and vibrations from the project may affect aquatic life and biodiversity.

Dr. Vishnupriya Kolipakam will lead the study.

According to project scientist Sunny Deori, the research team has already conducted a site visit and anticipates commencing the pre-construction phase of the study by mid-October.

“We expect to provide a preliminary report by March,” she stated.

The study is structured in three phases: pre-construction, construction, and post-construction (recovery phase).

Recent estimates indicate that the Brahmaputra river system and its tributaries in Assam are home to 635 dolphins, underscoring the importance of conservation efforts for this species.

The Brahmaputra offers a stable, unobstructed, and relatively undisturbed natural habitat, which supports a healthy population trend compared to historical counts. While the main river shows stable dolphin numbers, tributaries like the Subansiri have seen significant declines, and there have been no recent dolphin sightings in the Barak.

The NHIDCL has recently issued a tender for the construction of a four-lane twin-tube underwater road and rail tunnel, along with associated four-lane approach roads and railway infrastructure in one of the tubes.

The estimated civil cost for this project is Rs 11,982.36 crore, with a projected construction timeline of five years.

The total greenfield alignment will span approximately 33.77 km, which includes a substantial 15.79-km twin-tube underwater tunnel.