No life on earth can exist without water. Scientists estimate that there is over one billion cubic kilometres of water on this earth, which covers nearly three fourths of the earth's surface in the form of oceans, rivers, lakes, snow, glaciers and groundwater. Though this seems an inordinately huge amount, in actual fact, less than one percent is fresh and usable found in lakes, ponds, rivers and groundwater. Of the remaining, 97% is found in oceans and 2% is locked up in glaciers and ice-caps. Only 1% is available for use..
Water is the basic necessity of life, not only for human beings, but also for plants and animals. Life began in water and it is a basic component of every living cell. Water accounts for 65% of our body weight. If we lost even 12% of it, we would die. About 83% of our blood is water. It helps digest our food, take in oxygen, transport body wastes and control body temperature. We need water in almost every domestic activity, from cooking and washing to bathing and sanitation.
Water, to a large extent, determines climate. Places near large water bodies are cooler because the water bodies act as large sinks for heat, thus moderating the climate of the area. Regions near water bodies generally have milder winters and cooler summers. Water has an even more basic role in climate control through the water cycle. The evaporation of water requires huge amounts of energy, which comes from the sun. When the water vapour falls back to earth as rain, this energy is released. Thus water acts as an energy transfer and storage medium for the climate system.
Food cannot be produced without water. Vegetables are 80-90% water and milk about 87%. Agriculture is the major consumer of water in India, accounting for nearly 93% of the total water. Almost all industrial processes need water which is needed as a solvent, as a medium, as a coolant, as a cleansing agent, etc. Water plays a very important role in disposing of waste, be it domestic sewage or industrial effluents.
Almost all types of power generation require water - from hydel power, where falling water turns turbines to produce power, to nuclear reactors which need huge amounts of water as a coolant. In thermal power generation, next to the fuel, water is the most important resource. For the production of 1 kilowatt of electricity, thermal plants use 140 litres and nuclear plants use 205 litres of water.
The amount of water available for use in India is estimated as 1900 billion cubic metres per year. About 86% of this is the surface run off found in streams, rivers, lakes and ponds. In fact, these are the major sources of water in our country.
India is estimated to have 3,700 mhm. of groundwater, almost 10 times the annual rainfall. Only 10% of the water is being made use of at present, but with lakhs of tubewells being sunk every year to meet the growing water shortage, the water table is declining rapidly.
Tanks are small reservoirs built by constructing earthenware dams. They have been in existence in India since ancient times when tanks were built to store rainfall. But in both British and independent India, these tanks have been sadly neglected. As a result, where tanks irrigated half the cropped area a hundred years ago, today they irrigate hardly 10% of it. In Tamilnadu, man-made earthen reservoirs are known as yeris. There are over 40,000 yeris in Tamilnadu. Their place has been taken by big dams which span the major rivers. While the Indian farmer has benefited from these huge hydel projects, and while hydro electric power is a major source of energy in India, the dams themselves have many detrimental effects on the environment.
The apparent abundance of water is deceptive and we tend to take it for granted. We tend to abuse and overuse it. This has led to water scarcity, for which the reasons are:
Afforestation of barren, hilly slopes on a warfooting should be carried out. Trees withstand drought better than crops. They check dust, replenish streams, provide shade to cattle and man and give fodder for cattle. They provide innumerable uses for man. Denuding the land of trees without compensatory afforestation is a suicidal and short-sighted approach to solving immediate needs.
Ponds and Tanks
Last Modified : 2/12/2020