The impacts of climate change on hydrological processes of Gilgel Gibe catchment, southwest Ethiopia

2. Study area and research methods 2.1 Description of the study area 2.1.1 Location. The study area of this research is Gilgel Gibe Catchment, located in the upstream of the Omo Gibe basin in Jimma zone of Oromia National Regional State, located approximately 260 km southwest of Addis Ababa. The geographical coordinates of the catch- ment are approximately 7036’0’’ - 800’0’’ N latitude and 36036’0’’ - 37034’0’’E longitude, as shown in Fig 1 (ArcGIS 10.5). The catchment encompasses an area of approximately 514,103.4 ha, with elevations ranging from 1,096 to 3,341 m above sea level. The catchment spans across several districts, including Sekoru, Tiro Afeta, Kersa, Seka Chekorsa, Omo Nada, Dedo, Shebe Sembo, and Chora in Jimma zone, as well as Jimma special town. The Gilgel Gibe River is the main river of the catchment and is intersected by the Gilgel Gibe hydroelectric dam. 2.1.2 Soil. The topography of the Gilgel Gibe catchment ranges from flatlands in the valley bottom to steep slopes in the surrounding mountain ranges. The catchment is dominated by various soil types according to FAO/UNESCO [32], including Chromic Vertisols, Chromic Vertisols/Eutric Fluvisols, Dystric Nitoso, Chromic Vertisols/Eutric Nitosols, Dystric Nitosols, Dystric Nitosols/Orthic Acrisols, Eutric Nitosols/Chromic Vertisols, Lithosols/Eutric Cambi- sols, Orthic Acrisols/Dystric Nitosols, and Pellic Vertisols (Fig 2). 2.1.3 Climate. Despite being located in the tropical zone, Ethiopia exhibits a diverse range

of climates due to several factors. Altitude, rift valley, and the Inter-Tropical Convergence Fig 1. Location and elevation map of study area. https://doi.org/10.1371/journal.pone.0287314.g001 PLOS ONE The impacts of climate change on hydrological processes of gilgel gibe catchment PLOS ONE | https://doi.org/10.1371/journal.pone.0287314 June 28, 2023 4 / 28