Alteration of the Fogera Plain flood regime due to Ribb Dam construction, Upper Blue Nile Basin, Ethiopia

Abstract

The Fogera Plain, Ethiopia, is affected by recurrent flooding of the Ribb and Gumara Rivers. A large dam on the Ribb River is under construction for irrigation, but also to reduce flooding. We investigated the effects of the dam on the flood regime of the floodplain wetlands using a combination of hydrodynamic and a rainfall-runoff models. The model was calibrated based on inundation maps retrieved from Landsat images. Pre- and post-dam model comparison for 10 years shows that the dam will reduce the flooding extent by 11%, as it only regulates 23.8% of the upstream watershed. The flood extent and duration necessary to maintain ecologically significant water depths (≥ 0.5 m) show no notable changes. The developed hydrologic and hydrodynamic models can be used to analyze other dam operation and climate change scenarios even though there are uncertainties related to terrain resolution and analysis of hydrological data.

Keywords:

• Dam impact study
• Blue Nile Basin
• Fogera Plain
• Ribb River
• Gumara River
• wetlands ecology

Acknowledgements

The authors acknowledge the Netherlands Fellowship Program (NFP) for the financial support and thank Dr. Seleshi Yalew, Postdoc Researcher at TU Delft, for helping to write the script of Google Earth Engine. We also acknowledge the anonymous reviewers and the editors for their constructive comments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Hydrological and meteorological data used for the study were provided by a third party. Direct requests for these materials may be made to the provider.

Additional information

Notes on contributors

Chalachew A. Mulatu

Chalachew A. Mulatu is lecturer in Bahir Dar University, Ethiopia in the Faculty of Civil and Hydraulic Engineering and PhD student in IHE Delft, the Netherlands. His main research focuses on the hydro-morphological and ecological Implications of dam construction on the downstream river systems. The research mainly focused on the Ribb River, Lake Tana Basin, Ethiopia selected as the case study.

Alessandra Crosato

Alessandra Crosato is an Associate Professor of River Morphology and River Engineering at IHE Delft, the Netherlands. Her research work mainly deals with the development of bars in river channels and river planimetric changes, as well as floating debris in river channels, for which she carries out laboratory experiments and develops process-based mathematical models.

Eddy J. Langendoen

Eddy J. Langendoen is a Research Hydraulic Engineer with the Watershed Physical Processes Research Unit. His research integrates advances from multiple disciplines covering hydrology, hydraulics, sediment transport mechanics, channel erosion, and bioengineering into a unified, predictive framework to assess the impact of in-stream and riparian zone management on channel morphologic adjustment, with specific emphasis on reducing in-stream sediment loads and improving the ecological integrity of degraded stream systems.

Michael M. Moges

Michael M. Moges is Associate Professor of Hydraulic Engineering at in Bahir Dar University, Ethiopia in the Faculty of Civil and Hydraulic Engineering. Currently, he is working in the Ethiopian Ministry of Water Resources as Senior Ministry advisor. His research focuses are River and Reservoir sedimentation, flow modelling in open channels, modelling of sediment transport in rivers, assessment of climate change impacts at a river basin scale, water resources management and modelling.

Michael E. McClain

Michael E. McClain is Chair Professor of Ecohydrology in IHE Delft, the Netherlands. His research focuses on catchment hydrology and water quality, flow-ecology relationships, environmental flows, and land-water interactions. He routinely advises governmental authorities in a science and management context and leads major research and development projects in Africa and South America.