The Tehri dam is the highest dam in India and one of the highest in the World. The Tehri dam withholds a reservoir of capacity ` 4 . 0 km^(3)` and surface area `52 km^(2)` . It is used for irrigation, municipal water supply and the generation of 1000 MW of hydro electricity. The Tehri Dam has been the object of protests. Environment activist Shri Sunder Lal Bahuguna led the "Anti Tehri Dam Movement" from 1980s to 2014. The protest was against the displacement of town inhabitants and environmental consequences of the weak ecosystem. The relocation of more than 1,00,000 people from the area has led to protracted legal battles over resettlement rights and ultimately resulted in the delayed completion of the project.
How is hydropower harnessed ?

Explanation

**Step-by-Step Solution:**

1. **Understanding Hydropower**: Hydropower is the energy derived from the movement of water, typically from rivers or reservoirs. It is harnessed by converting the energy of flowing or falling water into electricity.

2. **Constructing a Dam**: To harness hydropower, a dam is constructed across a river. This dam creates a reservoir, which stores a large volume of water. In the case of the Tehri Dam, it has a reservoir capacity of 4.0 km³.

3. **Potential Energy**: When water is stored in the reservoir, it possesses potential energy due to its height above the turbine. The higher the water level, the more potential energy it has.

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