The Damodar Valley Corporation, the first multipurpose river valley project of independent India, was modelled on which foreign project?

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.

The correct answer is B, Bhagirathi. The Tehri Dam stands on the Bhagirathi in the Tehri Garhwal district of Uttarakhand, close to the confluence of the Bhagirathi and the Bhilangana, and it is an earth and rock fill dam, the tallest in India at about two hundred and sixty metres. Option A, the Alaknanda, is the other headstream of the Ganga and meets the Bhagirathi at Devprayag to form the Ganga; it carries the Vishnuprayag and Srinagar projects but not Tehri, and it is the strongest distractor because the two streams are always learnt together. Option C, the Sutlej, carries the Bhakra Dam in Himachal Pradesh and the Nathpa Jhakri power project, and Bhakra is the dam most often confused with Tehri in height questions. Option D, the Yamuna, carries barrages at Tajewala and Hathnikund and the Lakhwar project, and is not the river of the Tehri Dam.

The correct answer is B, Mahanadi. The Hirakud Dam lies across the Mahanadi above Sambalpur in Odisha, and counting the main dam together with its earthen dykes it is among the longest dams in the world; it was built chiefly to control the floods that used to devastate coastal Odisha, and it also serves irrigation and power. Option A, the Godavari, is the second longest river of India and carries the Sriram Sagar project and the Polavaram project, not Hirakud. Option C, the Brahmani, also flows through Odisha and carries the Rengali dam, which makes it the sharpest distractor here because the state is the same. Option D, the Subarnarekha, flows through Jharkhand, West Bengal and Odisha and carries the Chandil and Icha projects. Remember the pair Hirakud with Mahanadi as one unit, and the fact that it is a flood control dam first.

The correct answer is B, the Bhakra Dam. Gobind Sagar is the reservoir formed by the Bhakra Dam on the Sutlej in the Bilaspur district of Himachal Pradesh, and it is named after Guru Gobind Singh; the dam is part of the Bhakra Nangal project that serves Punjab, Haryana, Rajasthan and Himachal Pradesh. Option A, the Rihand Dam in Uttar Pradesh, creates Govind Ballabh Pant Sagar, the largest artificial lake in India by volume, and the resemblance between the two names is exactly the trap in this question. Option C, the Pong Dam, stands on the Beas in Himachal Pradesh and creates the Maharana Pratap Sagar reservoir, which is also a Ramsar wetland. Option D, the Nagarjuna Sagar Dam on the Krishna, creates a reservoir of its own name between Telangana and Andhra Pradesh. Learn the reservoir along with each dam and this pair stops being confusing.

The correct answer is C, Tarapur. The Tarapur Atomic Power Station in the Palghar district of Maharashtra was commissioned in 1969 and was the first nuclear power station in India and in Asia to generate electricity commercially; its first two units were boiling water reactors built with American assistance. Option A, Kalpakkam, is the Madras Atomic Power Station in Tamil Nadu, the first station of wholly indigenous design, and it also holds the Indira Gandhi Centre for Atomic Research and the fast breeder reactor programme. Option B, Rawatbhata, is the Rajasthan Atomic Power Station, where the first pressurised heavy water reactor was built in collaboration with Canada, and it is the commonest wrong choice because it too claims a first. Option D, Kudankulam in Tamil Nadu, is the most recent of the four and uses Russian pressurised water reactors of the VVER type.