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ABSTRACT
We investigated the magnitude of reservoir sedimentation upstream and its sediment-shadow effect on a large downstream-linked lake, Lake Tana (Ethiopia). To better understand the reservoir-induced reductions of fluvial sediment downstream, sediment budgets for two scenarios were developed. The results indicated that reservoir sedimentation is extremely high, with annual storage capacity losses (1–4.2%) exceeding the global average. Consequently, unless mitigation measures are implemented, the reservoirs’ dead storage volume will be filled with sediment in less than 42% of their designed life expectancy. The sediment-trapping conditions created by the reservoirs will also reduce sediment inflow from tributaries into the lake by 15–52%, overbank sedimentation on floodplains by 33–48%, and sediment deposition in Lake Tana by 16–54% annually. Overall, under the current environmental set-up, the ongoing and planned reservoir constructions could extend the expected useful lifetime of Lake Tana from 918 to 2022 years.
Editor A Castellarin; Associate Editor M. Nones
Editor A Castellarin; Associate Editor M. Nones
Acknowledgements
The authors gratefully acknowledge the financial support of Bahir Dar Institute of Technology and VLIR‐UOS through the Global Minds Fund Short Research Stay at UGent and the WASE‐TANA (Water and Sediment Budgets of Lake Tana for Optimization of Land Management and Water Allocation) research projects. The constructive comments and suggestions of the two anonymous reviewers and associate editor on the earlier version of this paper are gratefully acknowledged.
Disclosure statement
No potential conflict of interest was reported by the author(s).