Comprehensive knowledge of aquifer system in the hard rock areas is a prerequisite to develop an effective groundwater management strategy. A majority of the geological formations hosting the aquifers are highly variable and complex with scantily available information especially in the hard rock terrain. In such scenarios the worldwide experience has been to acquire continuous data on a regional scale using heliborne geophysical measurements, interpret and integrate them with available geological and ground geophysical information to obtain a reliable knowledge-base on aquifers. The main advantages of the Heliborne geophysical survey is that it is fast, highly data dense, precise and obviously economical. Moreover, it can be conducted in remote as well as inaccessible areas. For mapping the sub-surface, the Heliborne Transient Electromagnetic Method (HTEM) provides the best option as it can efficiently map the sub-surface conductivity variations associated with the groundwater. The HTEM method energizes the ground means of sending a current pulse in the transmitter loop towed below the helicopter. The pulse induces eddy currents in the subsurface geological conductors that in turn produce secondary EM fields, which are recorded by a receiver loop, placed either at the center or in close vicinity of the transmitter loop. The measured response is then analyzed, processed and modeled to create depth images representing subsurface resistivity/conductivity distributions. The resistivity models are calibrated and validated with ground based measurements such as ground geophysics, borehole data etc. and finally results in constructing the geological structures that control the occurrence of groundwater. This advanced technique has been applied in six pilot areas located in Rajasthan, Maharashtra, Bihar, Karnataka, and Tamil Nadu states representing diverse hydrogeological set up. However, this paper presents detailed results from a crystalline hard rock aquifer in Ankasandra watershed, Tumkur district, Karnataka, India.
Advanced Geophysical Investigation including Heliborne TEM in High-Resolution Aquifer Mapping with Special Emphasis on Crystalline Hard Rocks
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Comprehensive knowledge of aquifer system in the hard rock areas is a prerequisite to develop an effective groundwater management strategy. A majority of the geological formations hosting the aquifers are highly variable and complex with scantily available information especially in the hard rock terrain. In such scenarios the worldwide experience has been to acquire continuous data on a regional scale using heliborne geophysical measurements, interpret and integrate them with available geological and ground geophysical information to obtain a reliable knowledge-base on aquifers. The main advantages of the Heliborne geophysical survey is that it is fast, highly data dense, precise and obviously economical. Moreover, it can be conducted in remote as well as inaccessible areas. For mapping the sub-surface, the Heliborne Transient Electromagnetic Method (HTEM) provides the best option as it can efficiently map the sub-surface conductivity variations associated with the groundwater. The HTEM method energizes the ground means of sending a current pulse in the transmitter loop towed below the helicopter. The pulse induces eddy currents in the subsurface geological conductors that in turn produce secondary EM fields, which are recorded by a receiver loop, placed either at the center or in close vicinity of the transmitter loop. The measured response is then analyzed, processed and modeled to create depth images representing subsurface resistivity/conductivity distributions. The resistivity models are calibrated and validated with ground based measurements such as ground geophysics, borehole data etc. and finally results in constructing the geological structures that control the occurrence of groundwater. This advanced technique has been applied in six pilot areas located in Rajasthan, Maharashtra, Bihar, Karnataka, and Tamil Nadu states representing diverse hydrogeological set up. However, this paper presents detailed results from a crystalline hard rock aquifer in Ankasandra watershed, Tumkur district, Karnataka, India.
Publication Mode |
Online |
---|---|
Publication Author |
Subash Chandra, Erugu Nagaiah, N. Veerababu, N. C. Mondal, V. K. Somvanshi, Shakeel Ahmed |
Publication Language |
English |
Publication Type |
Conference Paper |
Publication Year |
2016 |
DOI |
10.17491/cgsi/2016/95954 |
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