Assessment of water crisis is made on the basis of per capita per year availability of water.
If per capita per year availability of water in a country is less than 1,000 cubic meters per year, such areas are considered to be suffering from water crisis.
At present, about 26 countries where more than 24 crore population of the world resides, come in this category. Maximum countries suffering from water crisis are in Africa while nine countries are in the Near East.
Two-third part of India also suffers from water crisis. Even the Cherapunji area, which is famous for maximum rainfall in the world, is suffering from water crisis. Due to fast deforestation, rain water of hills cannot be stored and most of the surface water flows away to saline seas. Due to mining of soap stone, deforestation has taken place on a large scale.
Maximum exploitation of water in India is being made for irrigation in agriculture. At the world level, 69 per cent of pure water is used for agricultural purposes, 23 per cent for industries and 8 per cent for domestic consumption. During the last four decades, due to revolutionary changes in agriculture, demand for water has increased and this demand is being met from fresh water. Unscientific methods too were adopted for selfish motives, which required more water.
In Maharashtra, tube wells were installed in such a large number in fields of sugarcane and sugar mills that about 2,000 wells of Talgaon became dry on that account. About 23,000 villages are affected by this problem due to exploitation of groundwater in agriculture, resulting in scarcity of drinking water in the area. Similarly, the situation in Rajasthan is also grave.
Out of the total area (3, 42,239 sq. km), 63 per cent (2, 15,142 sq. km) is groundwater probability area. About 29 per cent of this is located in western Rajasthan, which is of saline nature, while 8 per cent is hilly area. Due to excessive exploitation of groundwater in this area, the water level has gone down to the extent of 5 to 10 metres. Consequently, where sufficient water was available for agriculture two decades ago in the 1980s, water crisis is being faced today.
Due to decreasing water resources in the country, availability of per capita water has also reduced. At the time of independence of the country, availability of per capita water was 5,326 cubic metre per year which reduced to 2,267 cubic metre in 1991. The demand increased relatively with time.
In 1990, per capita demand for water was 550 cubic km, which increased by 75 cubic km in the year 2000 and it is estimated to be 1,050 cubic km by the year 2025. The main reason is increasing population and quantitative as well as qualitative deterioration of water. India gets 4,006 cubic km water from snow and rainfall but due to uneven distribution of water, on one side Cherapunji gets 11,000 mm rainfall annually while, Rajasthan gets only 150 mm rainfall annually.
Thus, most of the water received from rainfall flows away unused. Surface water sources of rivers, ponds, lakes, wells, baoris etc. have only 1,869 cubic km water, out of which only 690 cubic km water becomes available for different uses. This also includes 360 cubic km underground water which is used for irrigation.
During the last decade, more than 85 per cent water was used for irrigation but in the coming two decades it would reduce to 60-70 per cent. For the remaining purposes only 15 per cent water is being presently used, which is likely to increase to 27 per cent by the year 2025. Thus, by the year 2010, water crisis would be visible in the whole country.
Among the river basins of the country, maximum water is available in Brahmaputra Basin. Here, per capita water available is 18,081 cubic km whereas, it is only 360 cubic metre in Sabarmati, 366 cubic metre in Pennar and Kanyakumari. Availability of water in Brahmaputra basin is sufficient but it is not used in such proportion and most of the water flows waste. It is interesting to note that the tradition of conservation of such water has been in practice since the ancient times.
Yamuna canal and Agra canal were constructed in the 16th century, which carried water of Himalayas to Punjab, Rajasthan and Uttar Pradesh. In the 19th century, Kurnool, Kuddappa and Periyar Begad canals were constructed. Thus, wherever there is excess water in the country, it is taken to water scarcity areas. For this purpose, it is proposed to form a National Water Grid in India.