Mapping groundwater potential zones in the Gelda watershed of Ethiopia using GIS and analytical hierarchy process
Résumé
Abstract In Ethiopia, groundwater is critical to ensuring sustainable water security, underpinning domestic needs, agricultural irrigation, and socio-economic progress. This is especially evident in areas where surface water resources are scarce or subject to significant seasonal variability. The groundwater potential (GWP) zones in the Gelda watershed were assessed and delineated using an integrated approach that combined geographic information system (GIS), remote sensing (RS), and the analytic hierarchy process (AHP). Eight key thematic factors influencing GWP rainfall, lineament density, drainage density, slope, land use land cover, Geology, lithology and soil were derived from satellite imagery (Landsat 8, SRTM DEM), CHIRPS rainfall data, geological, soil maps and hydrogeological records. Factor weights were assigned via pairwise comparison matrices in AHP (consistency ratio of 0.043 < 0.1), and layers were standardized and combined using weighted overlay analysis to generate a GWP index map. The map was classified into five zones: very high (2.3%), high (10.2%), moderate (53.6%), low (33.1%), and very low (0.8%). Validation against 80 borehole and spring data points showed strong spatial agreement, with 81% of high-yield sites falling in high to very high zones. Receiver operating characteristic analysis yielded an area under the curve of 0.907, indicating excellent model predictive performance. These findings confirm the robustness of the GIS–RS–AHP framework as a cost-effective, reliable tool for groundwater exploration, borehole siting, and sustainable resource management in data-scarce volcanic highland regions like the Gelda watershed.
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