In which of the following locations can you build large dams to generate hydel power?
- A.Hilly terrains
- B.Desert areas
- C.Plains
- D.Oceans
Show answer
Correct answer: A. Hilly terrains
Explanation
The correct answer is A, hilly terrains. Hydel or hydroelectric power depends on head, the vertical distance through which water falls on to the turbine, and on a narrow valley in hard rock where a tall dam can hold a deep reservoir. Hills supply both, which is why the great hydro stations of the country stand in the Himalaya and the Western Ghats, at Tehri, Nathpa Jhakri, Koyna and Idukki. Option B, desert areas, is wrong because a desert has neither perennial flow nor the gradient needed, and high evaporation would empty a reservoir. Option C, plains, is wrong because the gradient there is too gentle to give useful head; plains carry barrages for irrigation and navigation, such as Farakka, rather than high dams. Option D, oceans, is wrong because a dam needs a river channel to close; the sea is used for tidal and wave power, which is a different technology altogether.