Class 10 Geography
Water: Some Facts and Figures:
- Out of total volume of water on earth; 97.5% exists in oceans and seas.
- About 2.5% of total water is available as freshwater.
- 70% of total freshwater is present as frozen ice in icebergs and glaciers.
- A little less than 30% of total freshwater is stored as groundwater.
- India receives about 4% of global precipitation.
- India ranks 133rd in the world in terms of water availability per person per annum.
- The total renewable water resources in India are estimated at 1,897 sq km per annum.
- It is predicted that large parts of India will join regions with absolute water scarcity; by 2025.
- Overexploitation of water, excessive use and unequal access to water among different social groups are the main causes of water scarcity.
- A large population needs ever more water for various purposes. Large scale farming also needs lot of water for irrigation. While demand has been increasing, the process of natural recharge of groundwater has suffered because of several reasons.
- Large scale deforestation has disturbed the natural recharge of groundwater at many places. Construction of concrete buildings, factories and roads has also made the ground less impervious to rainwater. This has almost totally stopped the percolation of rainwater to recharge groundwater.
- Excess use of chemical fertilisers and insecticides has contaminated groundwater at many places. The contamination is at such a high level that water has become unfit for human consumption.
- Sewage and effluents are being discharged into rivers and ponds; without being treated. This has turned most of the rivers into filthy drains.
Water Resource Management
India had a long tradition of building various structures to manage water resources. Irrigation systems were built as early as during the Mauryan Empire.
At present, many multipurpose dam projects had been built in India. These dams serve many purposes. They prevent flood by checking the flow of water. The water from the dams is used through a system of canals to irrigate far flung areas. Dams are also used for electricity generation. Moreover, drinking water is also supplied from the dams.
But dams have caused a lot of people being displaced from their ancestral lands. Additionally, a vast tract of land gets submerged in the catchment area of dam. This results in large scale environmental consequences. Due to these reasons, many movement groups have begun protesting against building of large dams. Narmada Bachao Andolan is an example of one such movement.
Most of the rainwater just flows off without percolating down the ground. This can be prevented by using rainwater harvesting. Rainwater can be collected for future use or can be channelized to recharge groundwater. Rooftop rainwater harvesting is ideal to be applied at small scale. Many infrastructure projects; like Metro rail and flyovers have also started making provisions for rainwater harvesting.