Water crisis has been caused due to growing population and increase in demand of food-grains and also subsequent Green Revolution in the late sixties.
After 1970, groundwater has been exploited very fast by digging wells in every hectare and drawing out water by huge machines.
It has definitely been a sorrowful and unscientific event. On the other hand, recharging of groundwater by rainfall has not been proportionate to its speed of exploitation, because quantity and duration of rainfall has continuously reduced due to deteriorating ecology.
In the absence of forest cover, rain water drains away or it evaporates and vanishes, whereas previously groundwater was recharged more by blockage of rain water in the roots of trees. Dry leaves and branches of trees made a sponge on the surface of the earth which increased the capacity of the earth to absorb more water.
At present it is not so possible due to destruction of forests. A large part of the country has become prey to dark zone from the point of view of groundwater due to over exploitation, because, as compared to recharge of groundwater, its exploitation is on the higher side.
To assess the development level of groundwater reservoir, the following accepted formula is used:
Level of Groundwater Development = Annual Net Groundwater Use\Net Groundwater Reservoir × 100 Available for Irrigation. When the quantity of groundwater available for irrigation is 85 per cent of total (annual) groundwater reservoir, it is called Grey Zone. To assess the rate of groundwater development, average of total increase in use of groundwater during last 5 to 10 years is found out. This average is called rate of groundwater development.
By knowing the level of groundwater development, the possibility of quantity and direction of groundwater development for future can be assessed. To be saved from the stage of over exploitation of groundwater, it is divided into four categories on the basis of exploitation of groundwater:
According to the above classification, areas where level of groundwater development is more than 85 per cent, groundwater exploitation should be completely banned. Similarly, in Grey Areas, groundwater use should be balanced.
The object of balancing means that the stage of 85 per cent level of groundwater development should not reach through planned development.’ White Zones’ are those areas where the rate of groundwater exploitation is less than 65 per cent and groundwater is available in sufficient quantity.
In ‘Grey Zone’, the rate of groundwater exploitation ranges between 65 to 85 per cent and it is in transit zone. Areas where groundwater exploitation is more than 85 percent are ‘Dark Zones’ where groundwater exploitation is playing with nature, because in a few days existing humidity of the earth would finish and the whole biomass would also reach at the brink of extinction.