DELINEATION OF AQUIFERS BY ELECTRICAL RESISTIVITY METHOD

Abstract

In our life, water play a vital role, especially fresh water is of utmost importance. The main sources of fresh water are lakes, rivers, streams and channels but this water may be contaminated not suites for intended use of water. Ground water is the main source of fresh and pure water; it can be directly used in drinking, agricultural and industrial purposes. So, it becomes of more importance to locate subsurface zones of fresh & pure water and even to locate a pin point (allocation of aquifers) for construction of a tube well either used for drinking, agricultural and industrial purposes. Out of many geophysical methods, direct current (D.C.) resistivity survey is the most extensively used method to delineate aquifers i.e. availability of fresh water under subsurface of specified area. In present work an attempt is tried to identify aquifer layers underneath of selected sites in the study area. Resistivity surveys are conducted. nearby a tube well, whose strata chart is known. These tube well are state public tube wells. These are deep wells and drilled up to around 100 m and installed for agriculture and these have discharge of 150 m3/hour. Resistivity surveys are conducted at 41 sites in Roorkee block and Narsan block (the study area). Schlumberger electrode configuration is used in this work. The data are collected as apparent resistivity for Schlumberger electrode configuration. These data are•interpreted by using IX-1D software, which gives layered model of VES in the graphical and analytical form. The analytical results contain resistivity of layers and their thicknesses and depth of layers from ground level. The results obtained from interpretation of sounding curves of VES are correlated with respective strata chart of nearby tube well. Analyzing result of VES and stratified layers of nearby tube well, geological interpretation of model is carried out. An analysis is also performed that iii how for results obtained from interpretation of VES match with existing data. Results of some sites are very close to actual geological section and of some are approximate to strata charts of state tube wells. This work is an attempt to verify that how closely results can be obtained from D.C. resistivity surveying and with what reliability this method can be used in future to locate water bearing strata from surface investigation and pin point for construction of a new tube well.