(i) our population is increasing rapidly.
(ii) due to lack of sufficient vegetation cover on ground, only a little rain water seeps into the ground and gets stored as ground water.
(iii) the high yielding varieties of crops require much more water for irrigation.
(iv) discharge of untreated sewage and industrial wastes into rivers and lakes reduces the availability of usable water.
(v) the changing life-style of people, especially in urban areas, is consuming more water.
Rivers are another important source of water. Rivers get their water supply from the melting of snow lying on the peaks of snow mountains (or glaciers) as well as from rains. The management of river-water is done by constructing dams on rivers.
In order to make proper use of river water, dams are constructed across the rivers to regulate the flow of water. In our country dams have been built across many rivers. The large reservoir of a dam stores a huge amount of water (brought in by the flowing river). This stored water is then allowed to flow downstream at the desired rate. Bhakra Dam is one such dam which has been built across the river Satluj in the state of Punjab our country. Dams built across the rivers are big storehouses of river water.
1. Water from a dam is used for irrigation in fields rough a network of canals. Dams ensure round the ear water supply to the crop fields and help raise agricultural production. For example, Indira Gandhi anal originating from Bhakra Dam has brought greenery to considerable areas of Rajasthan.
2. Water from a dam is supplied to the people in towns and cities through pipelines after suitable treatment. In this way, construction of dams ensures continuous water supply in the region.
3. The falling water (or flowing water) from the dam is used for generating electricity. The water rushing down the dam turns turbines which run electric generators. The electricity thus produced is called hydroelectricity.
The construction of high-rise dams for the management of river water and generation of electricity has certain problems associated with it. The public opposition to the construction of large dams on rivers is mainly due to the following three problems likely to be created by them: