AQUIFER CHARACTERIZATION IN HARD ROCK USING VERTICAL ELECTRICAL RESISTIVITY METHOD: A CASE OF MEGECH CATCHMENT, NORTHWESTERN ETHIOPIA

Abstract

Megech plain is found near Gondar Town in Amhara regional state, Northern Ethiopia. Geographically Megech area is located at UTM(ADINDAN) 315000E-336000E and 1371000N-1399000N with an elevation of 1877 a.m.sl. The current population of the study area is about 15,400 and it will increase to 25,235 after 20 years. Consequently, the current demand of water becomes 11.3 l/s and will increase to about 27.8l/s after 20 years according to GDP of Ethiopia (25 liter per capital demand). Currently they have 6l/s and need additional 5.3l/s and 21.8l/s to satisfy the current and after 20years demand of water. respectively. The geology of Megech catchment is alluvial sediment, aphanitic basalt, amygdaloidal basalt, scoriaceous basalt and welded tuff. The main aim of this study was to assess and classify the aquifer of Megech catchment for extraction of groundwater and minimize the risk of sinking dry boreholes. A total of seventeen VES data have been used for the electrical surveys using Schlumberger electrode array with maximum half-current electrode spacing (AB/2 = 700m). Different maps are prepared from the data and results are presented in slice depth sections, geo electric section, pseudo cross section and single VES data interpretation. Results show that Megech area is characterized by thick deposit with saturated zone such as alluvial sediment and highly fractured and weathered basalt which are water bearing(aquifer) zone. The plain is evaluated as a high groundwater potential area which can be used to extract water for both domestic supply and irrigation purpose.