29 August :The growth of Ground Water Abstraction Structures due to implementation of technically viable schemes have witnessed phenomenal increase in the past six decades. These have been backed by liberal funding and availability of power and diesel, good quality seeds, fertilizers and Government subsidies etc.
As per the 3rd census of Minor Irrigation Schemes during the period 1951-2001, the number of dug wells increased from 3.86 million to 9.62 million, shallow tube wells from 3000 to 8.36 million and public bore wells and tube wells from negligible to 53.02 lakh. The area irrigated by ground water has also seen steady increase from 6.5 million hectare in 1951 to 57.83 million hectare as reported in 3rd census of Minor Irrigation Schemes.
The development of ground water in different part of the country has not been uniform. Highly intensive development of ground water in certain areas in the country has resulted in over-exploitation, which leads to decline in ground water levels and sea water intrusion in coastal areas.
Based on the stage of ground water development and long-term water level declining trend during the past decade (1995-2004), the assessment units are categorized as ‘Over-exploited’, ‘Critical’ and ‘Semi-critical’. Out of 5723 assessment units in Blocks/Mandals/Talukas in the country, 839 units in various states have been categorized as ‘Over-exploited’ in which the annual ground water extraction exceeds the annual availability of ground water resource and significant decline in long-term ground water level trend is observed either in pre-monsoon or post-monsoon or both.
In addition, 226 units are ‘Critical’ i.e. the stage of ground water development is between 90% and 100% and the significant decline is observed in the long-term level trend in both pre-monsoon and post-monsoon periods. There 550 ‘semi-critical’ units where the stage of ground water development is between 70% and 100% and significant decline in long-term water level trend has been reported in either pre-monsoon or post-monsoon.
The major reasons for over-exploitation of ground water resources and consequent environmental impacts are the increasing water demands for agriculture, industrial and drinking purposes; indiscriminate and excessive withdrawals of ground water; rapid pace of organization and increase in cultivation of water intensive crops such as paddy and cash crops.
The factors which contribute to increase in ground water withdrawals include are scanty rainfall in arid and semi-arid regions, limited ground water potential in hard rock areas, excessive dependence on ground water during drought when all other sources shrink and flat rate/free electricity for extracting ground water in certain states.
The increase in energy consumption for extraction of water from progressively deeper levels, drying up of existing wells, sea water ingress in coastal areas and conflicts among users due to water scarcity are the consequences of decline of ground water levels.