IDENTIFICATION OF GROUNDWATER POTENTIAL ZONE BY USING GIS AND REMOTESENSING IN SUTEN TO TORA SUB-CATCHMENT, RIFT VALLEY LAKES BASIN, SOUTHERN ETHIOPIA

Abstract

This study was aimed to mapping of Groundwater potential investigation of Suten-Tora sub catchment in the Rift Valley Lakes basin, Southern Ethiopia. Climate, hydro-geological, land use/land cover, soil, lithology, geomorphology and stratigraphic data were collected, analyzed and inferred. The aquifer characteristics from the well completion reports were used to map the Groundwater flow direction. A Groundwater level contour map; which developed from well completion report is revealed that the Groundwater flows from western towards the center and eastern part of the sub-catchment. The results also inferred from the geological formations show that the Suten-Tora Sub-catchment are mainly covered by partially welded pyroclastic flow, Gash Megal rhyolitic lava flows, Guraghe-Anchor basalt, Nazret welded pyroclastic, Lacustrine sediment, Mesozoic sediment, porphyritic rhyolitic lava domes, Wonji basalts, Precambrian basement complex and recent basalt flows. Moreover, there is also a Geological structure in the study area. The linear feature of these structures are characterized by three distinct interconnected fault trends systems are called in NW-SE, NE-SW and N-S which are more or less affect the availability of Groundwater potential. Among the above listed lithological formations lacustrine sediments, Wonji basalt with scoria deposit and pyroclastic are coincide with high Groundwater potential zone. Similarly a moderate Groundwater potential zone is covered by Geological formations; e.g. Chefe Donsa, un-welded to poorly weld pyroclastic and others small formations. In the other way low and very low potential zones are covered by depositions of Nazret pyroclastic, Gash Megal rhyolite and other similar lithological formations. For the delineation of Groundwater potential zones, the weight over analysis of different factors namely: lineament density, lithology, geomorphology, slope, soil texture, drainage density, rainfall and elevation have been analyzed through the Analytical Hierarchal process (AHP) and ArcGIS 10.3 software. The delineated Groundwater potential zone was categories into four classes namely high, moderate, low and very low potential zone. These delineated Groundwater potential zones class called high, Moderate, Low and very low potential zones are covers an area of around 50%, 20%, 16% and 14% of the total sub catchment area respectively. To conclude that; the center and southeastern parts of the sub catchment have high amounts of Groundwater potential. However the western part has les Groundwater potential. Depend on the validation of output accuracy level; the delineation of Groundwater potential zones by using GIS and remote sensing techniques is important method. Finally it has been recommend that ; the well drillers in this study area suggested to use this Groundwater potential zone map as information