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27-23 Spatial and Seasonal Variability of Precipitation Isotopes in Southwestern Ethiopia’s Omo-Gibe Basin: Linking Hydroclimate Dynamics to Hydropower Sustainability

Session: Environmental Geochemistry and Health (Posters)

Poster Booth No.: 96

Presenting Author:

Zelalem Bedaso

Authors:

Bedaso, Zelalem K.¹, Wu, Shuang-Ye², Zhan, Zhaojun³, Hagos, Yonas Gebreslasie⁴, Kebede, Mulugeta⁵

(1) Earth and Environmental Geosciences, University of Dayton, Dayton, OH, USA, (2) Earth and Environmental Geosciences, University of Dayton, Dayton, OH, USA, (3) Earth and Environmental Geosciences, University of Dayton, Dayton, OH, USA, (4) Earth and Environmental Geosciences, University of Dayton, Dayton, OH, USA, (5) Institute of Geophysics Space Science and Astronomy, Addis Ababa University, Addis Ababa, Ethiopia,

Abstract:

Sustainable water availability is vital for hydropower generation, especially in Ethiopia’s Omo-Gibe River Basin, a key region for the country’s energy supply. This study analyzes daily precipitation isotopes (δ¹⁸O and d-excess) from four stations—Jimma, Hosaena, Jinka, and Omorate—to investigate spatial and seasonal variability, as well as climatic, source, and topographic factors that influence these patterns. Results show δ¹⁸O values are depleted during rainy seasons and enriched during dry periods, indicating seasonal shifts in moisture sources and atmospheric dynamics. Spatially, the amount-weighted mean δ¹⁸O decreases from north to south, with greater variation. Conversely, d-excess does not display a clear seasonal trend but tends to decrease toward the south. Variability in δ¹⁸O is controlled by rainfall type, convective intensity, and moisture source. Higher dry-season d-excess at Jimma suggests the presence of recycled continental moisture, whereas lower values at Hosaena and Jinka point to increased sub-cloud evaporation during low-intensity precipitation. The main moisture sources for the basin include nearby continental regions and the South and North Indian Oceans. The contributions from these sources, along with convective activity along their transport pathways, affect both the isotopic composition of precipitation and rainfall variability, ultimately affecting river flow patterns. Understanding precipitation isotope patterns is essential for hydrological modeling and water resource management, as climate and topography shape river flow and reservoir inflows vital for continuous hydropower production. These insights offer critical constraints for isotope-enabled models, aiding more effective planning and adaptive management of water and energy systems amid climate change across East Africa.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8777

Spatial and Seasonal Variability of Precipitation Isotopes in Southwestern Ethiopia’s Omo-Gibe Basin: Linking Hydroclimate Dynamics to Hydropower Sustainability

Description

Session Format: Poster

Presentation Date: 10/19/2025

Presentation Room: HBGCC, Hall 1

Poster Booth No.: 96

Author Availability: 9:00–11:00 a.m.

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