Hydrogeology of the Indian Himalayas: A review

Present paper highlights the recent advances made in the hydrogeological sciences in the Hindu Kush Himalayan region based on the data collected from 25000 borewells drilled in different hydrostratigraphic zones identified by Arya, 1996 to solve the drinking water and meet the growing industrial and agricultural requirements in the hills states of northwest Indian Himalayas. Success stories where groundwater resources has changed the socio economic status of the people residing in the high altitude cold mountain deserts of Ladakh will be highlighted.
Historical development of groundwater resources in Himalayas and need of traditional methods of exploration will be emphasised in comparison to the modern geophysical and remote sensing methods, to systematically explore and develop the groundwater resources.
Borehole data from the wells drilled on the snouts of highland glaciers in the cold mountain deserts of Ladakh at an altitude of more then 11000 feet above the mean and encountering of artesian conditions at 14230 feet at Chushul will be used to know the extent of glacial melt and rate of recharging taking place. Impact of global warming on the hydrogeological system in the mountain will be studied. Preliminary investigations have revealed that global warming is a natural phenomenon and man and his activities after the industrial revolution in 16th century had little role to enhance the already receding glaciers most of them have already become extinct in the Lesser Himalayan region during those times. Borehole data will also be used to infer the paleo mountain flooding activities in the past which led to the extinction of major habitations and civilisations which flourished in the valleys along the foot hills in the past. This flooding seems to be acyclic event (?) which can trigger even today once the hydrostratic pressure due to global warming increases the volume of water stored in the paleochannels in these nountains.
Case studies will be highlighted where groundwater levels in the borewells drilled along the major faults and contact boundaries in these Himalayan regions has been used as a tool to monitor the crustal movements and earthquakes Inspite of the fact detailed quantitative analysis has been carried in the last 15 years, qualitative analysis and dating of these groundwater resources in remote corners of Himalayas is still a challenge and hardly any scientific documentation has been done. Lastly model will be projected to show the occurrence, movement and development of groundwater resources in entire Hindu Kush Himalayan region and its importancein the overall economic and sustainable development in remote inaccessible areas.