IDENTIFICATION OF GROUNDWATER POTENTIAL ZONES USING GIS AND REMOTE SENSING: THE CASE OF MEGECH WATERSHED, ETHIOPIA

Abstract

Groundwater is one of the water resources which plays an important role in water supply in many countries including Ethiopia. Identifying and delineating the groundwater potential zones is very important for development plans, policies and sustainable utilization of the groundwater resources in the area of interest. However, there were only limited studies conducted on groundwater potential of the Megech watershed. This study is mainly aimed to identify and map the groundwater potential zones of Megech watershed. A total of nine thematic layers including geology, lineament density, slope, geomorphology, soil, LULC, rainfall, drainage density and elevation were used to map the groundwater potential zones of Megech watershed in GIS environment. Weights and rates were assigned for each thematic layer and for each thematic layer classes respectively using the PriEsT AHP tool. ArcGIS overlay analysis was conducted to obtain the groundwater potential map. The percentage of influence to the output map of the study area in view of groundwater potential was computed using PriEsT software package having geology/lithology 30%, lineament density 23%, slope 15%, geomorphology 10%, soil 7%, LULC 6%, rainfall 4%, drainage density 3% and finally elevation 2%. The first four thematic layers (geology, lineament density, slope and geomorphology) were found to be the dominant factors as portrayed in the map removal analysis. There were three groundwater potential zones identified and mapped in the study area namely low, moderate and high. The qualitative results were also compared with an independent set of 79 groundwater point data to validate the results. The validation analysis showed 75% agreement between the groundwater point data classes and the groundwater potential zones identified.