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

2.3.1.4 Weather. Daily weather data (1991–2021) were used from nine precipitation and temperature recording stations located within and around the study Catchment (Sekoru, Jimma, Chora, Dedo, Shebe, Omo Nada, Kersa, Seka and Tiro Afeta) (Fig 7). The daily data were collected from the National Meteorological Agency (NMA) of Ethiopia. However, some missing weather elements such as precipitation, maximum and minimum temperature, wind speed, solar radiation and relative humidity data were generated using an ArcSWAT weather generator (WGEN). Moreover, weather data from 1991 and 1992 were used as the model ini- tialization phase (warm up) and not included in the final analysis. 2.3.1.5 Discharge. In Gilgel Gibe catchment drainage system (Fig 8); the Gilgel Gibe catch- ment river discharge gauging stations, Daily discharge data of Gibe near Seka, Bulbul near Serbo, Gilgel Gibe at Abelti, Gilgel Gibe near Asendabo, Gojeb near Shebe, Bidru Awana near Sekoru, Kito near Jimma and Awetu at Jimma gauging stations (Fig 9) for the period 1991 to 2021 were collected Ministry of Water and Energy of Ethiopia (MoWE). These data were used for model calibration and validation. Model calibration was performed for the period from 1993 to 2011, whereas validation was performed for the period from 2012 to 2021. 2.3.1.6 Sensitivity analysis, calibration and validation. Owing to a large number of flow parameters in SWAT, identifying the most sensitive parameters is necessary to improve the calibration of the hydrological model. Model calibration and validation was undertaken auto-

matically using SWAT-CUP (Calibration and Uncertainty Programs). The most sensitive Fig 6. Sub-watersheds of the Gilgel Gibe catchment. https://doi.org/10.1371/journal.pone.0287314.g006 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 10 / 28