VPE 511: Environment and Environmental Hygiene (2+1)

WATER RESOURCES

• Water is an elixir of life. It is a renewable and indispensable natural resource. The volume of water on the earth is 1.4 billion cu km of which 93% is sea water, 4.1% is fresh water on land, 0.2% is glaciers and 0.0001% is humidity of air. The amount of underground water is 8 million cu.km.
• Totally 97% of earth’s surface is filled with water. If earth is flat, it will be two feet under water. About 1% of water is needed by man. About 60-65% of water is present in the body of animals and plants. Of the total rainfall, 77% of rain falls on the sea and 23% on land. About 84% of water vapour rise from sea surface whereas 16% from land.

Uses

• Water is used by man for almost all developmental activities such as drinking, irrigation, washing, transportation, waste disposal in the industries and coolant for the thermal power plants.
• It is the water which shapes the earth’s surface and regulates the climate. 70% of water is used for agriculture in the whole world (93% in India and 4% in Kuwait) and 25% of water for industries (70% in Europe and 5% in less developed countries). The per capita use of water in a family of 4 members in the USA is 1000 m³ per year, many time more than in the developing countries.

Abuses

• Man overexploits surface water due to overpopulation. Hence, drought condition prevails. 41% (2.4 billion) of people in the world live under drought condition with very less amount of water. It will increase to 48% (3.5 billion) in 2025 and 9 billion in 2050.
• The withdrawal of ground water is more than its recharge level. So, the sediments in aquifer get compacted and sinking of overlying land surface leads to damage in buildings, fracture in pipes, reversing the flow of sewer canals and tidal flowing takes place. The lowering of water table and intrusion of sea water take place due to mining of ground water.
• If irrigation is done with brackish water, it raises the water table in the ground leading to water-logging and salinity problems. So, agricultural operations will suffer. The surface water is largely used for irrigation (93% in India) , industrial use, public water supply, navigation, hydroelectric generation and thermal power generation.
• The ground water resources in India is estimated at 395.6 billion cubic meters. But we use only 10% of this water. The total requirement of water in India in 2050 would be 1,422 billion cubic metres.