STUDY ON SUBSURFACE WATER CONTENT USING ELECTRICAL RESISTIVITY TOMOGRAPHY

Abstract

The main soul of this report is to highlight and discuss the study on subsurface water content with the time in the field near Belra village, Uttarakhand. There are different geophysical methods to see this variation, we performed Electrical Resistivity Tomography (ERT) to see the variation, in this we used different electrode arrays but we have performed the experiments using Wenner and Schlumberger arrays. We applied current through current electrodes and measure potential difference between the electrodes using potential electrode. From this arrangement we get apparent resistivity after that we use Res2Dinv software to calculate inverted electrical resistivity. We obtained resistivity using earth resistivity meter. From this resistivity variation in longitudinally and depth wise we prepared charts to see how resistivity varies with the depth and longitudinally. We found that at shallow depth resistivity is comparatively very large but at deep down resistivity is very low. We performed experiments with two different arrays Wenner and Schlumberger arrays and we get a similar value of the resistivity. We performed experiments on 29th December and 16th January 2021 to see the pattern in variation how subsurface water content changes. We compared the data set results and found that water table falls in that period at shallow depth but as we goes deep down water content is more due to flow of ground water. Resistivity having slight variation till 100 m longitudinally and 8.25 m depth that means there is no change in water content, but as we move beyond 100 m till 8.25 m depth resistivity goes on increasing that means water content is decreasing and when we saw beyond 100 m in deep down i.e. more than 8.25 m depth resistivity is decreasing that means water content is increasing. From the resistivity values we got the subsurface material by resistivity chart and mainly found sandy soil at shallow depth in field near Belra but at deep down we found mostly clays and silt is there.