Groundwater Potential Zone Mapping In Ajora-Woybo Watershed, OMO Basin, Southern, Ethiopia, Using GIS, RS & AHP Techniques

Mapping groundwater potential zones is essential for effective well drilling planning. This study focuses on Ajora-Woybo watershed in Southern Ethiopia, which spans 1,787.8 km². The area is experiencing rapid population and livestock growth, leading to increased water demand, while quantity and quality of surface water are declining due to agricultural activities near rivers. The objective of this research was to evaluate groundwater potential zones using geographic information systems, remote sensing, and Analytical Hierarchy Process. Eight thematic layers were utilized for the assessment: geomorphology, lithology, slope, lineament density, soil texture, drainage density, rainfall, and land use/cover. Data for these factors were compiled from remote sensing imagery and various secondary sources, then processed in a geographic information systems environment. The relative weights of the datasets were determined using Analytical Hierarchy Process. The assessment categorized the groundwater potential into four classes: high, moderate, low, and poor. The high potential area, covering 568.4 km², is mainly in the central and northern regions, characterized by flat land and plateau that correspond to volcanic sediment and Nazret group and Dino formation with low slope. Conversely, the poor potential zone spans 152.7 km² in the northeast and southern in mountain peaks. The other classes include low potential (438.1 km²) and moderate potential (628.7 km²). Geomorphology and lithology are sensitive to groundwater occurrence distribution, while land use/cover is less sensitive. The study found 79% agreement between groundwater potential map and observed borehole yield, demonstrating the effectiveness of combining geographic information systems and remote sensing for identifying groundwater zones.