Water, as you know, is the most essential component of life. Our water resources are limited, though apparently, water is available in an abundant quantity. There is scarcity of usable quality of water in large parts of the world. You will be quite amazed to know that only 2.7% of the total water resources of the earth consist of fresh water, fit for drinking, irrigation and such other purposes. Water flowing in the streams and rivers is only 0.0001% of the total water resource on the earth, i.e., one bucket in 10,000 buckets! Fresh water lakes contain only 0.009% of total water. Ground water upto a depth of about 150 metres accounts for only 0.625%. Water found in the frozen state as snow on high mountains, which cannot be directly used, accounts for about 2.15%.
The total volume of water found in underground reservoirs, called aquifers, which can be pumped out is estimated to bi: 42.3 x 1010%cbic metres, of which only a quarter is being used, and the rest can be utilised in future for irrigation, industries and homes etc. The hydrological map of India given here shows that there are many regions of the country, such as parts of Andhra Pradesh and Tamil Nadu, which have a low ground water potential.
That is, the amount of ground water is in small quantity in these regions. From the above, we can cee that water which is required for various purposes like irrigation, navigation, generation of hydro-electricity and domestic and industrial needs is rather scarce. It is, therefore, necessary that water resources should be exploited judiciously.