Groundwater Potential Assessment Using Electrical Resistivity Method: A Case of Arato Sub-catchment, Enderta Woreda, Mekelle City, Ethiopia
MILAT GOITOM *
Department of Physics, College of Natural and Computational Science University of Kabri Dehar, Kabri Dehar, P.O Box 250, Ethiopia.
FIKADU TAMIRU *
Department of Earth Science, Faculty of Natural and Computational Science, Wollega University, Ethiopia.
*Author to whom correspondence should be addressed.
Abstract
Research for groundwater today has become crucial to obtain quality water from the bedrock. This study was conducted to assess groundwater potential of Arato sub-catchment of Eastern Mekelle city Using Electrical Resistivity Method. Vertical Electrical Sounding was conducted at the site within the area coverage of about 2km2. The schlumberger array was carried out with half current electrode spacing (AB/2) of maximum 500m and profile line spacing of 100m. Data was collected along selected four profiles with four VES points for the three profiles and one profile with three VES points with an interval of about 250m for each VES points. The data acquired from fifteen (15) VES stations using ABEM TERRAMETER (SAS 4000) was tabulated in a table which showed the resistivity, thickness and the number of layers for each VES points. And the data obtained during the survey were interpreted using IPI2WIN and surfer computer software‟s. The curve matching interpretation showed that the VES data‟s were three to six layered formations with error of minimum 0.6% and maximum 3.06%. Pseudo sections were used in order to identify which section had high groundwater potential based on their resistivity distribution and geological parts were done by comparing and evaluating the interpreted VES data‟s with the characterized rock and soil materials from existing borehole indicating different layered formation. From the survey it showed that marl-shale intercalation, fractured limestone and dolerite are dominant rock types ascending with depth. The geological profile sequence in the study area included the top clay soil, marly shale intercalation, highly fractured limestone, fractured limestone and dolerite. From the interpreted geological and geophysical data‟s VES 1, VES 6 and VES 9 showed low resistivity values of 101 ohm-m, 49 ohm-m and 79 ohm-m with depth of 128 m, 187 m and 120 m. Those low resistivity zones showed highly fractured limestone and were concluded as good groundwater aquifer zones. Also from the geo-electric section interpretation it was concluded that profile one, two and three were identified as highly aquifer zones. This showed that the occurrence of groundwater was highly influenced by the geologic forms, such as fracturing and contacts. Lastly borehole investigations were recommended at VES 1, VES 6 and VES 9 with depth from 120 m up to 130 m.
Keywords: Assessment, groundwater potentials, electrical resistivity, Arato Mekele city