Tehri Dam: India's Tallest Dam in the Himalayan Foothills

**Tehri Dam** is the tallest dam in India and one of the tallest in the world, standing **260.5 meters** on the Bhagirathi River — one of the two headstreams of the sacred Ganges — in the Tehri Garhwal district of Uttarakhand. With an installed capacity of **1,000 MW** and an additional 1,000 MW pumped-storage facility, it is a multipurpose project serving hydroelectric power, irrigation, and water supply for Delhi.

Introduction

The dam was one of the most controversial infrastructure projects in Indian history, opposed for decades by environmental activists, seismologists, and local communities who argued that placing a mega-dam in the seismically active Himalayan zone endangered millions of people downstream. Despite these objections, the dam was completed in 2006 after more than 30 years of construction.

Engineering & Structure

• Type: Earth and rockfill dam
• Height: 260.5 meters
• Crest Length: 575 meters
• Volume: 29.05 million m³ of fill

Tehri Dam is an earth and rockfill dam, the tallest of its type in Asia and one of the tallest in the world. Unlike concrete dams, it relies on a massive core of impervious clay flanked by gravel, sand, and rock to hold back the reservoir. The dam's total fill volume of 29.05 million cubic meters creates a structure that is broad at the base (over 1,128 meters wide) and tapers to a 20-meter-wide crest at 575 meters in length.

The decision to build an earth and rockfill dam rather than a concrete structure was driven partly by seismic considerations — earthfill dams are generally more flexible and resilient during earthquakes than rigid concrete dams. Nevertheless, the dam's location in Seismic Zone IV (high risk) remains a subject of intense scientific debate.

Geographic Setting

• River: Bhagirathi River (Ganges headstream)
• Location: Tehri Garhwal, Uttarakhand, India
• Coordinates: 30.38°N, 78.48°E
• Reservoir Area: 52 km²

The Bhagirathi River originates from the Gangotri Glacier at an elevation of 3,892 meters in the Himalayan mountains and flows south through steep gorges before reaching the dam site at approximately 640 meters elevation. At Tehri, the Bhagirathi is joined by the Bhilangna River, and the dam captures the combined flow of both streams. The old town of Tehri, submerged by the reservoir, had been inhabited for centuries at this river confluence.

The surrounding landscape is classic Himalayan foothill terrain — steep, forested slopes of sal and pine, terraced agriculture on gentler hillsides, and narrow river valleys cut through folded sedimentary rock. The region is tectonically active, lying along the Main Central Thrust zone where the Indian plate pushes beneath the Eurasian plate, generating frequent earthquakes.

Hydroelectric Power

• Installed Capacity: 1,000 MW (main) + 1,000 MW (pumped storage)
• Annual Output: ~3.6 TWh (main station)
• Turbines: 4 × 250 MW Francis turbines

Tehri Dam's main power station houses four 250 MW Francis turbines, generating approximately 3.6 terawatt-hours of electricity annually. The downstream Tehri Pumped Storage Hydroelectric Power Plant, with an additional 1,000 MW capacity, uses off-peak electricity to pump water back up to the reservoir, then releases it through turbines during peak demand periods.

The pumped storage facility was completed in 2023 and significantly enhances the project's value to India's grid by providing rapid-response power during peak demand hours. Together, the two facilities make Tehri one of India's most important hydroelectric complexes, serving the northern grid that supplies electricity to Delhi and surrounding states.

Environmental & Social Impact

• People Relocated: ~100,000
• Town Submerged: Old Tehri town
• Seismic Risk: Located in Seismic Zone IV

The Tehri Dam displaced approximately 100,000 people, including the entire population of old Tehri town, which had been a historic hill station and district headquarters. New Tehri was built on a ridge above the reservoir, but many displaced families reported inadequate compensation and difficulty establishing livelihoods in the new location. The social activist Sunderlal Bahuguna led a decades-long protest movement against the dam.

Seismic safety remains the most contentious issue. The dam lies approximately 100 kilometers from the epicenter of the devastating 1991 Uttarkashi earthquake (magnitude 6.8) and 200 kilometers from the 1999 Chamoli earthquake (magnitude 6.6). Engineers maintain that the dam is designed to withstand a magnitude 8.0 earthquake, but critics argue that the consequences of dam failure — a catastrophic flood wave reaching downstream cities including Haridwar, Roorkee, and eventually the Ganges plains — make any risk unacceptable.

Key Facts

• Tehri Dam is the tallest dam in India at 260.5 meters.
• It is an earth and rockfill dam, more flexible against earthquakes than rigid concrete.
• The old town of Tehri, inhabited for centuries, was submerged by the reservoir.
• The combined main and pumped-storage capacity totals 2,000 MW.
• It supplies drinking water to Delhi via a 272 km pipeline.

Fun Facts

• The Bhagirathi River is considered one of the two sacred headstreams of the Ganges; Hindu pilgrims have journeyed to its source at Gangotri for centuries.
• When the reservoir filled, the clock tower of old Tehri was the last structure to disappear beneath the water, becoming a symbol of the town's loss.
• Tehri Lake, formed by the reservoir, has become an unexpected adventure tourism destination, with jet skiing and kayaking at 640 meters elevation in the Himalayan foothills.

Final Thoughts

Tehri Dam embodies the profound tensions between development and risk, displacement and opportunity, that characterize mega-dam construction in seismically active mountain regions. As India's tallest dam and a vital water source for Delhi, it remains both an engineering achievement and a continuing source of controversy.