Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

N. Sundararajan ¹, Y. Srinivas ¹, M. Narasimha Chary ², K. R. Unnikrishnan ³

Affiliations
1 Centre of Exploration Geophysics, Osmania University, Hyderabad - 500 007, IN
2 Atomic Minerals Directorater of Exploration and Research, Department of Atomic Energy, Begumpet, Hyderabad - 500 01 6, IN
3 Centre of Earth Science Studies, Camp Office Elamakara-Post, Cochin - 682 026, IN

Abstract

The groundwater occurrence along the contacts of sandstone outlier in biotite gneiss near Tiruvuru, Krishna district, Andhra Pradesh, was investigated by electrical resistivity survey. The depth and width of such contacts were established from geoelectrical sections drawn based on vertical electrical sounding (VES). Results obtained are correlated with the geology and the bore well data of the area.

Keywords

Groundwater, Resistlivity Survey, Modelling, Geological Contacts, Tiruvuru, Krishna District, Andhra Pradesh.

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S. B. Singh ¹, Jimmy Stephen ¹, Y. Srinivas ¹, U. K. Singh ¹, K. P. Singh ¹

Affiliations
1 National Geophysical Research Institute, Hyderabad - 500 007, IN

Abstract

Delineation of groundwater resources in hard rock terrains is one of the important topics to be treated with a more advanced approach than simple one-dimensional attitude, particularly when looking for deeper water saturated horizons. The present study introduces an integrated geophysical approach to identify structural features such as fractures, weak zones and intrusive dyke bodies, which can control and host potable groundwater at greater depths. The study is conducted in an area of about 8 km² along east coast of Tamil Nadu, which has been identified as a major rainshadow zone. Geophysical measurements were carried out in very closely spaced grids making use of resistivity, magnetic and electromagnetic techniques. The sensitivity of each technique to different rock properties in varying directions has been considered to resolve the problem. A major weak zone running in SW-NE direction is demarcated which is characterised by many intrusive dyke bodies. The conductivity distributions at different depths throw light on many structural features. The varying thickness of weathered rock calculated from the Horizontal Loop Electromagnetic (HLEM) and Deep Resistivity Sounding (DRS) studies for the entire area reflects the extension of weathering associated with dyke emplacements. Geo-electrical sections obtained through DRS studies, concentrated mainly along the weak zone have shown the occurrence of potable groundwater resource controlled by structural features.

Keywords

Integrated geophysics, Groundwater, Hardrock Terrain, Deep Resistivity sounding, Horizontal Loop Electromagnetics (HLEM), Magnetic Method, Tamil Nadu.

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