Ground Water Resources

Groundwater represents one of the most important water sources in India and accounts for over 400 km³of the annual utilizable resource in the country. Due to the highly variable nature of the climate, groundwater has become a popular alternative for irrigation and domestic water use across India. Reliance on groundwater resources is particularly strong where dry season surface water levels are low or where wet season flows are too disruptive to be easily tapped. In addition to being accessible, groundwater quality is generally excellent in most areas and presents a relatively safe source of drinking water for Indians in rural and urban centres.

The presence and availability of groundwater varies greatly with changes in topography, subsurface geology and the prevailing climate in the region. In some areas, groundwater exists in deep aquifers while in others the water is stored near the surface. The location of the aquifer also affects its recharge rate and its susceptibility to pollution and overuse.

In general, the mountainous and hilly regions in the north and west do not allow adequate infiltration and as a consequence, groundwater is mostly limited to valleys and other lower lying areas. In the peninsular part of the country, the underlying geology limits the formation of large continuous aquifers. Groundwater is therefore scattered where fissures permit adequate storage or is found in shallow depressions near the surface. As a result, the overall yield potential in this region is low although some areas may see medium to high potential depending on the local hydrogeology. Coastal regions are usually rich in groundwater owing to the largely alluvial terrain, but the aquifers risk being easily contaminated by saltwater ingress due to overpumping. The alluvial tract of the Gangetic plain, which extends over 2000 km across central and northern India has the best potential for groundwater extraction in the country. This large area possesses many favourable characteristics for groundwater storage and recharge, and the yield over most of the region has been estimated at moderate to high.

The total annual replenishable ground water resources of the Country have been reassessed as 433 Billion Cubic Meters (BCM) and the net annual ground water availability is estimated as 399 BCM. Existing gross ground water draft as on March 2004 for all uses is 231 BCM per year. The stage of ground water development is 58%. The development of ground water in different areas of the country has not been uniform. Highly intensive development of ground water in certain areas in the country has resulted in over exploitation leading to decline in the levels of ground water and sea water intrusion in coastal areas. There is a continuous growth in dark and overexploited areas in the country.

As per the latest assessment of ground water resources carried out jointly by the Central Ground Water Board (CGWB) and the States, the assessment units are categorized as 'Over exploited'/ 'Critical' and 'Semi-critical' based on the stage of ground water development and the long-term water level declining trend during the past decade (1995-2004). Out of 5723 assessment units (Blocks/ Mandals/Talukas) in the country, 839 units in various States have been categorized as 'Over exploited', i.e., the annual ground water extraction exceeds the annual replenishable resource. In addition 226 units.,11 'Critical', i.e., the stage of ground water development is above 90 per cent and within 100 per cent of annual replenishable resource. There are 550 semi-critical units, where/the stage of ground water development is between 70 per cent and 100 per cent. List of these areas is being circulated to the State Pollution Control Boards and Ministry of Environment and Forests which refer the new industries/projects falling in these areas to the Central Ground Water Authority (CGWA) for obtaining permission.

The CGWA has so far notified 43 over-exploited areas in the country for regulation of ground water development and management. For enforcement of the regulatory directions issued under Section 5 of Environment Protection Act, 1986, concerned Deputy Commissioners/ District Magistrates have been authorized to take necessary action in case of violation of directives of CGWA in the notified areas. For more effective regulation of ground water development and management, Advisory Committees under the Chairmanship of District Collector/ Deputy Commissioners with members drawn from various organizations have been constituted which will render advice in matters pertaining to regulation of ground water development and management.

The CGWA have also notified 65 over-exploited areas in various States, for registration of ground water abstraction structures, which showed a very steep decline in ground water levels and required action for regulation. The CGWA has issued directions to the Chief Secretaries of all States having over-exploited blocks to take all necessary measures to promote/ adopt artificial recharge to ground water/rain water harvesting. The CGWA has also decided to notify 747 more over-exploited areas in the country incompliant of its mandate. As per the provisions under rule 4 of the Environment (Protection) Rules, 1986, objections from the public who are likely to be effected by the directions of the CGWA are regularly sought through public notices in the newspapers. (Source : www.india.gov.in)

Ground Water Potential in River Basins of India (Pro Rata Basis) (Unit: km³/year)