Climatic Extremes under Climate Change Scenario Over Ethiopian River Catchments

Mulugeta, Aregay

dc.contributor.author	Mulugeta, Aregay
dc.date.accessioned	2026-08-21T06:55:33Z
dc.date.available	2026-08-21T06:55:33Z
dc.date.issued	2026-01
dc.identifier.uri	http://ir.bdu.edu.et/handle/123456789/17063
dc.description.abstract	This doctoral research presents a comprehensive analysis of hydroclimatic extremes across Ethiopia’s eight major river basins, addressing critical gaps in understanding compound climate risks in tropical highland regions. The study employs an innovative tripartite framework integrating ground-based observations from 17 WMO-certified meteorological stations and 28 hydrological gauging stations, high-resolution satellite data from TerraClimate (4 km resolution), and ECMWF ERA5 reanalysis data (0.25° resolution) spanning the period 1986-2023. Through the application of advanced statistical methodologies including standardized drought indices (SPI, SPEI, SSI), Mann-Kendall trend analysis, Sen’s slope estimator, and adapted crossing theory for heatwave characterization, the research reveals profound transformations in Ethiopia’s climate system. The investigation demonstrates a statistically significant intensification of meteorological, agricultural, and hydrological droughts across all basins, with frequency increases of 40-60% since the 1980s. The Abay, Awash, andWabi Shebelle basins emerge as particular hotspots, showing the most pronounced drying trends. Large-scale climate teleconnections, particularly ENSO and Indian Ocean Dipole phases, explain 68-85% of interannual drought variability, with basin-specific sensitivity patterns reflecting Ethiopia’s complex physio-graphic diversity. Flood analysis reveals increasing frequency and magnitude of extreme precipitation events, with flood magnitude increasing by 25-40% since the 1980s. The research documents accelerating drought-to-flood transitions, with soil moisture memory effects reducing transition times by 2.3 days per decade, fundamentally challenging conventional water management approaches that treat these phenomena discretely. Thermal extremes analysis identifies unprecedented warming trends, with heatwave frequency increasing by 150% since the 1990s. The research reveals an ”elevation paradox” whereby Ethiopian highlands are warming faster than lowlands, contradicting global patterns and climate model projections. This anomalous warming is driven by reduced cloud cover (Δalbedo = -0.11), expanding foehn winds, and decreasing atmospheric humidity at higher elevations. Climate projections using statistical downscaling of CMIP6 models under SSP scenarios indicate substantial intensification of all climate extremes through 2050, with meteorological and hydrological droughts projected to increase by 50-200%, flood magnitudes by 30-60%, and heatwave duration by 3-5 days per decade. The research particularly highlights growing risks of compound events, including concurrent drought-heatwave conditions and rapid transitions between hydrological extremes. Theoretical contributions include the development of an integrated framework for analyzing compound climate extremes, the identification of elevation-dependent climate responses that challenge conventional climate theory, and documentation of non-stationarity in teleconnection relationships. Methodological advances feature the novel adaptation of crossing theory for tropical highland heatwave analysis and implementation of a hybrid statistical downscaling approach optimized for compound extreme projection. Practical applications include specific recommendations for updating reservoir operation rules, adjusting agricultural calendars, implementing heat health warning systems, and revising infrastructure design standards. The basin-specific characterization of climate risks provides a scientific foundation for targeted adaptation strategies, with the research already informing improved early warning systems in the Awash Basin pilot project achieving 92% accuracy in drought onset detection. This research provides the most comprehensive assessment to date of hydroclimatic extremes in Ethiopia’s river basins, offering both scientific insights for climate resilience planning and methodological frameworks for similar assessments in other tropical highland regions. The findings underscore the urgent need for transformative adaptation approaches that address the interconnected nature of climate risks in one of the world’s most vulnerable regions.	en_US
dc.language.iso	en_US	en_US
dc.subject	Physics	en_US
dc.title	Climatic Extremes under Climate Change Scenario Over Ethiopian River Catchments	en_US
dc.type	Dissartation	en_US