Geophysics for Aquifer Mapping of India

October 12, 2021 15:00 IST / 09:30 UTC

Aquifer mapping is a holistic approach to ascertain and establish the quantity and quality sustainability of an aquifer on the basis of remote sensing, geological, hydrogeological, geophysical, hydro-chemical including geogenic and anthropogenic contaminations, hydrometeorological and socio-economic studies. The objective is to advance the aquifer awareness by providing comprehensive information of an aquifer including its characteristics at any place, its interaction with surface water systems, its health at a point of time, the future stress it can bear and ways for its conservation and protection required for long-term participatory aquifer management.

In India almost all the variations in hydrogeological and geomorphological conditions are present in the hard rock and sedimentary terrain giving rise to a variety of occurrences of aquifers. There is ample scope to map these aquifers. The groundwater exploration and development in this country through sinking of tube wells, tapping mostly the shallow aquifers and the deeper ones at places started in the mid of the last century. However, a composite aquifer map of the country for different hydrogeological terrain, which is quite essential and useful, could not be prepared till date. Preparation of such maps requires compilation of the existing data and also the generation of data. Generation of data on aquifer disposition through geophysical survey is in practice in India since 1930s and recently modern techniques of data acquisition have been applied. For aquifer mapping CGWB got high density-fast coverage geophysical surveys conducted through CSIR-NGRI in 6 pilot areas of varied hydrogeology using modern technique of heliborne time domain electromagnetics, as also surface geophysical surveys in 15 States by WAPCOS including resistivity imaging in some parts. Besides, for groundwater exploration geophysical applications have been made in diverse hydrogeological terrains of hard rocks, cavernous limestones, coasts, alluvial plains, sedimentary basins, deserts and hills. The objective has been to delineate the weathered and deep fracture zones in granite gneisses, deep aquifers in fractured basaltic flows, saturated cavities in limestones, freshwater aquifers in mainland coastal tract and islands, deep fresh water aquifers in sedimentary basins, inland groundwater salinity, deep buried coast parallel freshwater channels, palaeo-channels of rivers and lost rivers in desert, flood plain aquifers, groundwater pollution and identification of impermeable clay barriers in arsenic contaminated areas, alternative aquifers in water stressed urban areas and assessment of subsurface conditions causing land subsidence in overexploited areas. Also, efficient applications have been made in drought, earthquake, coastal cyclone and Tsunami affected areas. The geophysical methods have also been used in time- lapsed mode for monitoring the quality of groundwater which may form a major input for remediation. The interpretation of subsurface geophysical data is contextual, therefore a variety of issues of resource conservation, protection and augmentation have also been addressed.

The webinar will discuss all the above aspects, delivered by Dr P C Chandra.

Felicitation Ceremony

Sri K C B Raju will be conferred upon life time achievement award for his contributions in the field of Ground Water.

At 91 years of age, Sri Raju is the oldest living hydrologist of our time.

He retired as Director CGWB in 1988. Thereafter he was busy with Vivekananda Institute in Gujrat and dedicatedly did the work of artificial recharge. While in CGWB, he was Director of the Sweden assisted SIDA Project and other regional offices.

Sri Raju is the person who implemented the gradient resistivity profiling technique for the first time in groundwater fracture detection in the world. He may be called as the modern age father of artificial recharge of ground water in India.

Sri Raju joined GSI in 1953 and carried out Groundwater Survey, exploration and development all over country in various Hydrogeological terrains. He was Chief Geologist with Govt. of Assam on deputation between 1971 and 1974 and established Groundwater Division in Directorate of Mines & Geology.

After merger of Ground Water wing of GSI and ETO forming CGWB, he joined CGWB in 1974 and posted as Project Director of SIDA (Swedish Intl. Dev. Agency) assisted multidisciplinary Groundwater Investigation Project in Hard Rock Areas of Noyil, Amaravati and Ponnani River Basins with Headquarters at Coimbatore, to develop methodology for Ground Water Investigations using the latest technology available which included Remote sensing, Geophysics and Nuclear. During this period, 1975-1980, for the first time in the country, the Gradient Resistivity Profiling technique was used to detect the water bearing fractures in Hard Rock Areas. A sub surface dyke was constructed for the first time to prevent ground water running away from a watershed. An International Workshop was conducted for the South Asian Countries under the auspices of UNESCO, SIDA & CGWB . The Project established the occurrence of groundwater between 200 and 300 m.

After completion of the SIDA Project, he was posted as the Director of the Southern Region with Headquarters at Hyderabad in January 1980, which comprises the States of Andhra Pradesh, Tamil Nadu, Karnataka and Kerala besides Union Territories Goa, Pondicherry and Lakshadweep.

He retired from Govt. Of India Service on 31.10.1988.

In Feb 1989, he joined as an Advisor to Sri Vivekananda's Research & Training Institute in Kutch, Gujarat in Water Management till the end of 2014. During this period, developed innovative local Technology to harvest excess annual rain runoff to artificially recharge the deep depleted aquifers of the area to rejuvenate the wells and Tube wells, improve the ground water quality, mitigate the effects of sea water ingress and also to prevent further Ingress of seawater into coastal aquifers. The most effective structures developed are Recharge Tube wells and Subsurface Dykes.

About The Speaker

Dr Prabhat Chandra Chandra, a professional groundwater geophysicist, was born in Varanasi, India in 1950. He received B.Sc. and M.Sc degrees in Geology and Geophysics from Banaras Hindu University (BHU) in 1970 and 1972 with Master NL Sharma Gold Medal in Geology and first rank in Geophysics.

Soon after, Dr Chandra started his career as a groundwater geophysicist at CSIR-National Geophysical Research Institute, Hyderabad (NGRI) India and in 1978 joined Central Ground Water Board (CGWB), Govt. of India. His doctoral thesis is on groundwater geophysics. He superannuated in December 2010 at the age of 60 as Director, CGWB.

During his 38 years professional career he got ample opportunity to work on a variety of groundwater issues almost in all the hydrogeological terrains of India including hard rock, coastal tracts, limestone, basalts, alluvium, desert, island and hilly tracts. In view of the scarcity of groundwater in hard rock he took up the challenging geophysical investigations of delineating fracture zones in hard rocks which cover 2/3rd part of the country. There are several papers and reports to his credit.

He got trained in groundwater management through Indo-British Fellowship from UK and visited World Water Week, Sweden and Hydro Geophysics Group (HGG), Aarhus University Denmark for presentations on groundwater geophysics.

After superannuation he worked as Consultant to The World Bank, New Delhi and Expert to CSIR-NGRI along with the experts from U.S. Geological Survey (USGS) and HGG, Aarhus University, Denmark for aquifer mapping in pilot projects through heliborne geophysical surveys and as Advisor to WAPCOS Ltd. Govt. of India for aquifer mapping in several States of India through surface and borehole geophysical surveys.

Dr Chandra has published a book ‘Groundwater Geophysics in Hard Rock’ based on his vast experience in delineating the fracture zones in hard rocks, subsurface characterization and locating high yielding well sites