How India's longest underground water tunnel will take Narmada water to Vindhya

Madhya Pradesh Chief Minister Mohan Yadav will inspect the site of India's longest underground water conveyance tunnel in Katni on Friday, three days after engineers achieved the final breakthrough in the 11.95-km Sleemanabad tunnel.

Officials said Narmada water will be released into the system after the tunnel boring machine (TBM) is dismantled and removed, marking the start of water transfer to the drought-prone Vindhya region.

The chief minister is also expected to address the media on the project, which marks the completion of the most challenging phase of the 17-year-old Bargi Diversion Project.


Designed to carry Narmada water beneath the Vindhya mountain range into the Son river basin, the tunnel is expected to provide assured irrigation to the drought-prone Vindhya region. The final breakthrough on July 14 completed excavation after engineers overcame nearly two decades of geological and engineering challenges.

Constructed 20-40 metres below the surface, the tunnel passes beneath the Vindhya ridge separating the Narmada and Son river basins. Officials describe it as India's longest underground water tunnel and one of the country's most complex gravity-flow irrigation structures, transporting water without the use of pumps.

The tunnel is the most critical component of the 197-km Bargi Right Bank Main Canal, which has a carrying capacity of 227 cumecs—the highest among canal systems in Madhya Pradesh.

The larger Bargi Diversion Project is expected to provide permanent irrigation to nearly 2.45 lakh hectares across about 1,450 villages in Jabalpur, Katni, Satna, Maihar, Rewa and Panna districts. Officials said the tunnel alone will eventually irrigate around 1.85 lakh hectares in Satna, Maihar, Katni, Rewa and Panna, with phased irrigation planned over the next three rabi seasons.

Construction of the tunnel began in 2008. A Robbins tunnel boring machine commenced excavation in 2011 but managed to excavate only about 1.4 km by 2015 because of difficult geological conditions. To speed up the project, a German-made HK tunnel boring machine was deployed from the opposite end in 2016.

Engineers encountered some of the country's toughest tunnelling conditions, including hard marble, limestone and dolomite formations, unstable slate, residual soil, large underground cavities, groundwater inflows of up to 25,000 litres per minute, sinkholes, carbon dioxide emissions and rapidly changing rock formations that repeatedly damaged the TBM cutter heads.

Officials said the breakthrough was achieved using advanced engineering techniques such as TAM grouting, high-capacity dewatering systems, core drilling and simultaneous excavation from both ends. Doctors were also stationed with tunnelling crews to provide emergency medical assistance during underground operations.

The tunnel passes beneath national highways, railway lines and populated areas without causing structural damage, officials said.

Once the TBM is removed and water is released into the tunnel, work will shift to completing the downstream canal network.

Officials said the project will transform agriculture and the rural economy of the Vindhya region by bringing Narmada waters across the mountain barrier for the first time.

(with TOI inputs)