Keywords: EC logs, hard rock aquifers, India, vertical disparity, electrical conductivity, groundwater, water bearing fractures, granitic aquifers
Vertical disparity in electrical conductivity of groundwater: inferring water-bearing fractures in granitic aquifer
A detailed study was conducted in hard rock terrain for delineating water-bearing fractures using electrical conductivity (EC) logs. The EC logs of groundwater were taken both in pre- and post-monsoon seasons of the year 2001; in 25 borewells in a small granitic watershed at an interval of 1 m right from the water table (though narrow spacing wherever required) till the depth to bottom of the well. The EC values in various borewells have showed the changes, which were attributed to the presence of water bearing fractures zone(s). In addition, the results were compared with a number of studies carried out in the area viz., lithologs of the wells from the drilling data, sub-surface geophysical logging and also with an additional experiment of injected flow tests in the same borewells. A clear correlation is found among the anomalies and hence, it is to delineate the fractures at a desired depth using EC logs and nevertheless supported by geological information.