27 Environmental Geochemistry and Health (Posters)

We invite presentations on the environmental fate of contaminants and their impact on human and environmental health. Transdisciplinary contributions are encouraged, especially those examining the rock-soil-water-human nexus at all scales with strong public outreach or societal impact.

Sunday, 19 October 2025
8:00 AM - 5:30 PM
HBGCC, Hall 1

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

Paper number: 27-19
Program: Technical Sessions
Time: 8:00 AM – 8:00 AM

Authors

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 Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413382

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.