Open Access

ARTICLE

Evaluation of Projected Change in Climate Extreme Events through CMIP6 Models over Omo Gibe River Basin, Ethiopia

Fetene Muluken Chanie^1,2, Mulugeta Genanu Kebede^3,4,*, Yared Godine Demeke², Zelalem Bedaso⁵

1 Department of Meteorological Data and Climatology, Ethiopian Meteorology Institute, Addis Ababa, Ethiopia
2 Meteorology and Hydrology Faculty, Water Technology Institute, Arba Minch University, Arba Minch, Ethiopia
3 Ethiopian Disaster Risk Management Commission, National Early Warning and Response Coordination Center, Addis Ababa, Ethiopia
4 Institute of Geophysics, Space Science, and Astronomy, Center for Space and Atmospheric Research (CSAR), Addis Ababa University, Addis Ababa, Ethiopia
5 Department of Geology and Environmental Geosciences, University of Dayton, 300 College Park, Dayton, OH, USA

* Corresponding Author: Mulugeta Genanu Kebede. Email:

(This article belongs to the Special Issue: Resource and Environmental Information Modeling)

Revue Internationale de Géomatique 2026, 35, 131-160. https://doi.org/10.32604/rig.2026.076765

Received 26 November 2025; Accepted 25 February 2026; Issue published 19 March 2026

Abstract

Extreme climate and weather conditions pose significant risks to public health, economic stability, and the quality of both built and natural environments. This study evaluates projected changes in climate extreme events over the Omo-Gibe River Basin (OGRB), Ethiopia, using 12 CMIP6 Global Climate Models (GCMs). Additionally, rainfall-runoff simulations were assessed using the HEC-HMS hydrological model. Due to the region’s susceptibility to extreme hydro-meteorological events like floods and droughts, gaining insight into future climate variability is essential for managing water resources effectively and reducing disaster risks. This analysis examines extreme precipitation and temperature indices under two future climate scenarios, SSP2-4.5 and SSP5-8.5, across the short-term (2023–2053) and mid-term (2054–2084) periods. Daily precipitation and temperature observations from 1984 to 2014, provided by the Ethiopian Meteorology Institute, were utilized for model validation. Bias correction was applied using the distribution mapping method to enhance the accuracy of CMIP6 simulations. Model performance was assessed using statistical evaluation metrics, including the coefficient of determination (R²), mean bias error (MBE), root mean square error (RMSE), and categorical indices such as the probability of detection (POD), false alarm ratio (FAR), and critical success index (CSI). Results indicate a significant increase in extreme precipitation indices such as R95pTOT (up to +8.73 mm/year) and PRCPTOT (+7.49 mm/year) in specific clusters, while consecutive dry days (CDD) show decreasing trends. Temperature extremes are projected to rise, with TXn and TNn increasing by approximately 0.03°C per year. Bias correction substantially improved model performance, reducing mean precipitation bias by approximately 60% and lowering RMSE for extreme indices such as R95pTOT and Rx1day by about 40% relative to the raw simulations. The projections also indicate a decline in consecutive dry days (CDD), with reductions of about 9 days under both SSP2-4.5 and SSP5-8.5 compared to the historical period. Streamflow simulations using the HEC-HMS model reveal a projected increase of 36.3%–92.8% in annual discharge by 2073, with shifting seasonal peaks. These findings highlight the growing risk of extreme climate events in the basin, necessitating adaptive water resource management strategies and improved climate resilience planning.

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Supplementary Material

Supplementary Material File

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