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

RESEARCH ARTICLE The impacts of climate change on hydrological processes of Gilgel Gibe catchment, southwest Ethiopia Zewde Alemayehu TilahunID*, Yechale Kebede Bizuneh, Abren Gelaw Mekonnen Dep’t of Geography & Env’tal Studies, Arba-Minch University, Arba Minch, Ethiopia * zedoalex8@gmail.com Abstract Climate change is a significant driver of water resource availability, affecting the magnitude of surface runoff, aquifer recharge, and river flows. This study investigated the impact of cli- mate change on hydrological processes within the Gilgel Gibe catchment and aimed to determine the level of exposure of water resources to these changes, which is essential for future adaptability planning. To achieve this objective, an ensemble mean of six regional cli- mate models (RCMs) from the coordinated regional climate downscaling experiment (COR- DEX)-Africa was used to simulate future climatic scenarios. The RCMs outputs were then bias corrected using distribution mapping to match observed precipitation and temperature. The Soil and Water Assessment Tool (SWAT) model was used to assess the hydrological impacts of climate change on the catchment. The results indicated that the ensemble mean of the six RCMs projects a decline in precipitation and an increase in temperature under both the RCP4.5 and RCP8.5 representative concentration pathways. Moreover, the increases in both maximum and minimum temperatures are higher for higher emission sce- narios, indicating that RCP8.5 is warmer than RCP4.5. The projected climate change shows

a decrease in surface runoff, groundwater, and water yield, resulting in an overall decline of annual flow. This decline is mainly due to the reduction in seasonal flows driven by climate change scenarios. The changes in precipitation range from -11.2% to -14.3% under RCP4.5 and from -9.2% to -10.0% under RCP8.5, while the changes in temperature range from 1.7˚C to 2.5˚C under RCP4.5 and from 1.8˚C to 3.6˚C under RCP8.5. These changes could lead to reduced water availability for crop production, which could be a chronic issue for sub- sistence agriculture. Additionally, the reduction of surface water and groundwater could fur- ther exacerbate water stress in the downstream areas, affecting the availability of water resources in the catchment. Furthermore, the increasing demands for water, driven by pop- ulation growth and socioeconomic progress, along with the variability in temperature and evaporation demands, will amplify prolonged water scarcity. Therefore, robust climate-resil- ient water management policies are indispensable to manage these risks. In conclusion, this study highlights the importance of considering the impact of climate change on hydro- logical processes and the need for proactive adaptation measures to mitigate the impacts of climate change on water resources. PLOS ONE PLOS ONE | https://doi.org/10.1371/journal.pone.0287314 June 28, 2023 1 / 28 a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Tilahun ZA, Bizuneh YK, Mekonnen AG (2023) The impacts of climate change on hydrological processes of Gilgel Gibe catchment,

southwest Ethiopia. PLoS ONE 18(6): e0287314. https://doi.org/10.1371/journal.pone.0287314 Editor: Salim Heddam, University 20 Aout 1955 skikda, Algeria, ALGERIA Received: August 26, 2022 Accepted: June 2, 2023 Published: June 28, 2023 Peer Review History: PLOS recognizes the benefits of transparency in the peer review process; therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. The editorial history of this article is available here: https://doi.org/10.1371/journal.pone.0287314 Copyright: © 2023 Tilahun et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: The data that support the findings of this study are available from various sources. The Gilgel Gibe catchment digital elevation model (DEM) was extracted from the Shuttle Radar Topography Mission (SRTM) 30 meter resolution