A hydro-geophysical investigation of groundwater by electrical profiling

Abstract

Groundwater is water that exists in the pore spaces and fractures in rocks and sediments beneath the earth’s surface. The Electrical Resistivity method was used for the hydro-geophysical investigation of groundwater resources in coconut garden of Horticulture College so as to discover a sustainable source of water, to meet the various requirements of the campus. The main objectives of the present project were to conduct hydro-geophysical investigation of groundwater potential and to obtain aquifer distribution within the study area in order to delineate possible sites for drilling tube wells for irrigation water supply. A special technique called ‘Resistivity Scanning’ is found to successfully delineate the fractured geometry of formation. This technique will provide an insight into the nature of subsurface formations. Wenner configuration of electrode arrangement is mostly practiced for the resistivity observations. Resistivity observations were taken with vertical electrical sounding (VES). An estimate of the resistivity and thickness of various subsurface layers at a location could be obtained by successively increasing electrode spacing. The inverse of the resistance measured 1/R was plotted against Wenner electrode separation on a linear graph. Even thin layers at deeper layers could be detected. IGIS signal stacking resistivity meter model SSR-MP-ATS was used. From the eight locations under consideration, none of the locations could serve as potential groundwater sources. By the analysis of 2 -D cross-section of strip resistivity ,to identify site favourable for recharge structure, we can arrive at the conclusion that a continuous soil layer of average depth 10 m was observed at the top.Major portion of area was occupied by a continuous layer of crystalline rock formation which extended up to 80m depth. Beyond crystalline rock, there was a layer of continuous metamorphic formation which could not provide sufficient water. By this study, all possible sites in the coconut garden were explored for the presence of ground water. The project could come to a conclusion that, potential areas for sustainable water supply were not available in the coconut garden.