Tehri Dam

Tehri Dam is the tallest dam in India and the eighth-tallest dam in the world. Located on the Bhagirathi river at the northern edge of Tehri Garhwal district in Uttarakhand, the 260.5 m earth-and-rockfill embankment dam impounds a 3.5 cubic km reservoir (Tehri Lake) and supports a 1,000 MW hydroelectric complex.

The project was sanctioned in 1972 and the foundation stone laid in 1978 — but construction was beset by political controversy over displacement of the historic Tehri town (which sits at the dam site) and ecological concerns about the Bhagirathi headwaters of the Ganga. The Narmada Bachao Andolan-style opposition was led by environmental activist Sundarlal Bahuguna, who maintained a hunger strike for 74 days in 2001-2002 protesting the project.

Multiple Supreme Court cases delayed construction for two decades. The project was finally completed in 2006 with the relocation of 100,000 residents from Old Tehri to New Tehri (a planned town built specifically to receive them). Total cost: ₹11,000 crore in 2006 prices (vs ₹169 crore original 1972 estimate — among India's worst cost overruns).

The embankment dam is built using sloping rolled-fill construction with a central impervious clay core. The foundation is mass concrete on Lesser Himalayan quartzite and phyllite bedrock — a complex geology that required extensive grouting curtains. The 1,000 MW hydroelectric station feeds the Northern Grid, with an additional 1,000 MW Tehri Pumped Storage Plant (Phase II) commissioned in 2024.