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Maharashtra State is covered by nearly 90 % of Mesozoic and early Tertiary volcanic rocks, characterised by a thick sequence of a multi-layered, hard, compact basalt (Deccan Trap), often crossed by dykes and sills and intersected by deep faults. Its thickness is around 2000 meters in the Bombay area, The most promising groundwater conditions are in depressions; stream banks; inter-lava flows; in areas where basalt is intersected by dykes; and wherever the rock is deeply weathered or highly fractured.
Ground water development took place in the past 40 years with nearly two hundred thousand of low yielding boreholes drilled by the government and by the private sector. In addition, there are several hundred thousands of large diameter hand-dug wells used mainly for irrigated agriculture. The high density of these water sources indicates the existence of a huge shallow groundwater body actively recharged during the monsoon time by direct rainwater percolation and by infiltration from small and large water courses.
Aquifers are generally shallow, represented by weathered and fractured basalt located mainly in depressions, river sides, and flat areas. Deeper aquifers may occur; they are in most cases connected with inter-lava flows and exceptionally with granular rock type, faults and dykes.
In the past thirty years much attention has been paid to drought prone semi-arid areas. Groundwater availability has increased in many places thanks to the construction of numerous "percolation tanks" and other water holding structures. Much attention is now being paid to recharge augmentation by introducing appropriate technology for watershed management. Thanks to such efforts, in several areas, low yielding boreholes and seasonal open hand dug wells located in hard rock terrain are now supplying permanent water for human consumption and for irrigation of cash crops.
Several studies have also been carried out in Maharashtra State to assess the importance of hydro-fracturing and borehole blasting to increase storage capacity of poorly fractured basalt.
The intensive groundwater development of the past decades has surely alleviated the widespread poverty of hundreds of millions of rural people by contributing to the success of the "green revolution".
The Author is working since last 19 years in Maharashtra State in his self-financed project of drilling drinking water wells for remote villages and hamlets populated by Adivasis, the tribal people of India, considered to be the "poorest of the poor"; he also promoted the use of appropriate pumping technology through the low cost ?bucket pump', manufactured and maintained locally.
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