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Water Resources

Only 2.5 per cent of the entire volume of water available in the world is in the form of freshwater. Almost 70 per cent of the freshwater occurs in the form of ice sheets in Antarctica, Greenland and the mountainous glaciers and ice covers. Rest occurs in ground water. In India, freshwater is obtained from precipitation, surface run-off and ground water which are continuously replenished by the hydrological cycle. Water is a renewable resource.

Water scarcity is a major problem in most of the countries of the world. By 2025, it is predicted that nearly two billion people will live in acute water shortage. India ranks 133 in the world in terms of availability of water per person per year. Scarcity of water occurs mostly in regions of drought and low rainfall. Rajasthan has tremendous shortage of water. The variation in seasonal and annual precipitation causes water scarcity. Anthropological factors such as over-exploitation, excessive and often wasteful use, and unequal access to water among different social groups lead to scarcity of water. Water scarcity in Indian cities is due to the large and growing population, the resultant demand for water in greater proportion and its unequal access.

Greater demands of water occur because of the following reasons:

  1. To increase the food crop production, expansion of agricultural area has taken place. This has expanded the need for irrigation to dry areas, as well as in areas of water scarcity. This has stressed the availability of water. As a result, the underground water table has fallen sharply.
  2. Extension of industries requires more power. The increased demand of water to produce hydro-electricity exerts more pressure on the water resources.

Increased urbanisation in the industrialised cities has led to a large-scale construction of housing societies and colonies. Most of these communities have arranged for extracting out the groundwater through pumping devices. These are gradually depleting the groundwater table. The pollution of the underground water with release of domestic and industrial effluents, pesticides and chemical fertilisers from the agricultural fields has deteriorated the quality of water. In many cases, such water poses health hazard for human consumption. The water of many major rivers of India like Ganga and Yamuna is of very poor quality and represents open sewers in sections.

Irrigation is the method of supplying water to the agricultural fields when the natural supply of water falls short. Indian agriculture depends on the monsoon rainfall for its water requirements. Since monsoon rainfall is seasonal in nature, irrigation in India is much needed to ensure the year long supply of water for agriculture.

Depending on the source of water, irrigation can be of the following types:

  1. Well irrigation: This is suitable even in dry areas. Wells are of two types, open wells and tube wells. This type of irrigation accounts for over 51 per cent of total irrigated area in India, mostly in North Indian plains and eastern coastal plains. This type of irrigation is also practiced in Rajasthan, Gujarat, Madhya Pradesh, Karnataka, Andhra Pradesh and Tamil Nadu.
  2. Tank irrigation: Bunds are constructed across small streams which store water. This type of irrigation is mainly found in the rocky terrain of peninsular India. It serves only 8 per cent of the total irrigated land. It is mostly found in Karnataka, Andhra Pradesh, Tamil Nadu, Maharashtra, Madhya Pradesh and Orissa. However, there are two major problems associated with this type of irrigation:
    1. Silting up of the tanks occurs leading to decreased capacity to store water.
    2. Since they mostly depend on rain water, they contain water during the rainy seasons; they dry up in the hot summer when water is actually required in the fields.
  3. Canal irrigation: It is practiced mostly in North India where the rivers are perennial. Canals serve 39 per cent of the irrigated area. These are constructed and controlled by the government who invests the huge capital required for their construction. Canals are mostly of two types
    1. non-perennial (inundation) canals and (b) perennial canals. Canals draw water from the rivers or reservoirs associated with dams and barrages across the river’s flow and these canals distribute water to the agricultural fields.

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