The annually 'replenishable' groundwater resources of the country have been assessed as 432 billion cubic meter (BCM). After keeping a provision of 71 BCM per year for domestic and industrial use, 361 BCM/y is available for irrigation. The Ganga basin has the highest potential followed by Godavari basin and Brahmputra basin. The Indo-Gangatic alluvial plain with an area of around 25,000 km2 is one of the largest groundwater reservoirs in the world.

In addition to replinishable resources, the country is blessed with enormous groundwater resources below the lowest level of groundwater fluctuation, termed as 'in-storage' groundwater resource. The in-storage groundwater resources upto the depth of 450 meters in alluvium and 100 meters in hard rock terrain have been estimated as 10812 BCM.

Groundwater Pollution in India

Apart from reported cases by different institutions, groundwater quality concerns in India was realized way-back in mid eighties with a systematic study of groundwater quality and identification of 'problematic zones' by Central Pollution Control Board with reference to pollution. These (problem) areas due to their complex industrial scenario and increasing dependence on natural resources have been witness to excessive exploitation of groundwater for domestic and industrial uses. With pollution control enforcement activities gaining momentum there were observed cases of indiscriminate waste disposal, subsurface discharge of effluent and inappropriate wastewater management by industries. This has led to severe stress on groundwater, in terms of ' quantitative imbalance' as well as 'quality deterioration'. In consideration of the potential of pollution in these problem areas, Central Pollution Control Board has initiated groundwater quality monitoring in these areas. As an integral part of such studies groundwater status shall be brought out with suggested measures for pollution control ( see Table - 6).

Status of Groundwater in major Indian cities/towns

With only twenty five percent population living in urban areas, India has cities, amongst the biggest in the world. Indian urban centers are posed with problem of over-exploitation of groundwater due to increasing dependence on it as other fresh-water resources are dwindling fast. The poor urban infrastructure having no systematic provision of sewage or solid waste management, unplanned growth, un-organized land-use and poor drainage system further compound the groundwater quality concerns.

The very process of urbanization in Indian cities, has led to phenomenal decrease of natural (groundwater) recharge due to paving and soil compaction, thus promoting imbalance in over-all groundwater budget .