Water Resources
Dams and multi-purpose projects
Weigh the benefits and costs of big dams.
An old tradition. India built clever water works long ago:
- 1st century B.C.: Sringaverapura near Allahabad channelled the flood water of the Ganga;
- Chandragupta Maurya's time: many dams, lakes and irrigation systems;
- irrigation works in Kalinga (Odisha), Nagarjunakonda (Andhra Pradesh), Bennur (Karnataka) and Kolhapur (Maharashtra);
- 11th century: Bhopal Lake, among the biggest man-made lakes of that age;
- 13th-14th century: the Hauz Khas tank in Delhi, built by Alauddin Khalji to supply the Siri Fort area.
What a dam is. A wall built across a river or stream that stops, steers or slows it, usually creating a reservoir (a lake) behind it. A spillway lets extra water pass over or through. Dams are grouped by structure (timber, embankment, masonry), by purpose and by height (low, medium, high).
Multi-purpose projects. Dams were first built to store water for irrigation. Now one dam does many jobs: irrigation, electricity, water for homes and factories, flood control, boating and fun, river transport, and fish breeding.
- Bhakra-Nangal (Satluj-Beas basin): hydel power and irrigation.
- Hirakud (Mahanadi basin): saving water and controlling floods.
- Sardar Sarovar (Narmada, in Gujarat): one of India's largest water projects, covering Maharashtra, Madhya Pradesh, Gujarat and Rajasthan. It brings irrigation to drought-prone and desert areas, including Barmer and Jalore in Rajasthan.
Jawaharlal Nehru called dams the 'temples of modern India': they would join farming and villages with fast-growing industry and cities.
The other side: problems with big dams.
- The river's natural flow changes. Sediment piles up at the bottom of the reservoir, the stream bed gets rockier and fish lose their homes.
- Dams cut a river into pieces, so fish cannot swim up to lay eggs.
- The reservoir drowns plants and soil, which then rot.
- Floods: dams built to stop floods have caused floods, because sediment fills up the reservoir; big dams have also failed to control floods in very heavy rain.
- The flood plains below miss out on silt, a natural fertiliser.
- They have been linked to earthquakes, water-borne diseases, pests and pollution.
- Farmers switch to water-hungry crops, which can make the soil salty (salinisation).
People and quarrels. Big dams often force people to leave their land when the reservoir floods it. They also cause fights between states. Example: in the Krishna-Godavari dispute, Karnataka and Andhra Pradesh object to Maharashtra taking more water at Koyna, because less water would then flow down to their farms and factories.
Helping every farm. The Pradhan Mantri Krishi Sinchayee Yojana aims to give every farm some irrigation. Its two slogans: 'har khet ko pani' (water to every field) and 'per drop more crop' (use less water, grow more).
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