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Evaluating the potential of nature-based solutions to mitigate land use and climate change impacts on the hydrology of the Gefersa and Legedadi watersheds in Ethiopia

Published Article

Africa

Publication date: December 12, 2024

File format: URL

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Addis Ababa relies on the small reservoirs of the Gefersa and Legedadi watersheds, where rapid land‑use change and shifting climate patterns threaten long‑term water security. Using hydrological modeling with multiple land‑use scenarios and extreme climate projections, this study shows expanding urbanization and altered rainfall patterns will intensify dry‑season shortages and increase sediment yield. Simulations reveal that drier seasons become drier and wet seasons wetter under future climates. Integrating nature‑based solutions into watershed management improves dry‑season water availability, supports farming and extends reservoir lifespan. The approach provides a transferable framework for climate‑resilient watershed planning in data‑limited regions.

Subject Tags

  • Watersheds
  • Climate impacts
  • Nature-based solutions

Abstract

Study region

Surface water supply source of Addis Ababa, the capital city of Ethiopia, relies primarily on the small reservoirs in Gefersa and Legedadi water supply systems located upstream of Little and Big Akaki rivers. Thus, Gefersa and Legedadi are the study watersheds of this research.

Study focus

This study evaluates the impacts of land use and climate changes on surface water availability and the benefits of nature-based solutions (NbS) to enhance the water supply and the life of the dams in the Gefersa and Legedadi small watersheds that supply water to Addis Ababa city, Ethiopia. Several land use and climate change scenarios have been developed and integrated into baseline hydrological model to assess their impact on water balance components and sediment yield. Extreme climate change scenarios were developed using the combination of the 5th, 50th and 95th percentiles of future precipitation and temperature changes.

New hydrological insights for the region

The results of the land use change analysis revealed a shift between 2012, 2022 and 2042, with a significant expansion of urban settlements and a decline in forestland and vegetation cover. Under climate change scenario, the simulations project that drier seasons become drier and wet seasons become wetter. Overall, this study highlights the potential benefits of NbS in enhancing water availability, particularly during the dry season, promoting dry season farming and increasing the water supply to meet the water demand. The approach followed in this study can be adapted to other watersheds with access to more recent and good quality datasets for future research.

Citation

Bayissa, Y., Srinivasan, R., Hunink, J., Nyolei, D., Moges, S., de Andrade Costa, D., ... & Tilahun, S. (2025). Evaluating the potential of nature-based solutions to mitigate land use and climate change impacts on the hydrology of the Gefersa and Legedadi watersheds in Ethiopia. Journal of Hydrology: Regional Studies, 57, 102130. https://doi.org/10.1016/j.ejrh.2024.102130

TNC Authors