Preprints
https://doi.org/10.5194/hess-2022-270
https://doi.org/10.5194/hess-2022-270
 
04 Aug 2022
04 Aug 2022
Status: this preprint is currently under review for the journal HESS.

Quantifying the trade-offs in re-operating dams for the environment in the Lower Volta River

Afua Owusu1,2, Jazmin Zatarain Salazar2, Marloes Mul1, Pieter van der Zaag1,3, and Jill Slinger2,4 Afua Owusu et al.
  • 1Land and Water Management Department, IHE Delft Institute for Water Education, Westvest 7, 2611 AX Delft, The Netherlands
  • 2Faculty of Technology, Policy and Management, TU Delft, Jaffalaan 5, 2628 BX Delft, The Netherlands
  • 3Faculty of Civil Engineering and Geosciences, TU Delft, Stevinweg 1, 2628 CN Delft, The Netherlands
  • 4Institute of Water Research, Rhodes University, Drosty Rd, Grahamstown, 6139, South Africa

Abstract. The construction of the Akosombo and Kpong dams in the Lower Volta River Basin in Ghana changed the downstream riverine ecosystem and affected the lives of downstream communities, particularly those who lost their traditional livelihoods. In contrast to the costs borne by those in the vicinity of the river, Ghana as a whole, has enjoyed vast economic benefits from the affordable hydropower, irrigation schemes and lake tourism that developed after construction of the dams. Herein lies the challenge; there exists a trade-off between water for river ecosystems and related services on the one hand, and anthropogenic water demands such hydropower or irrigation on the other. In this study, an Evolutionary Multi-Objective Direct Policy Search (EMODPS) is used to identify the multi-sectorial trade-offs that exist in the Lower Volta River Basin. Three environmental flows, previously determined for the Lower Volta are incorporated separately as an environmental objective. The results highlight the dominance of hydropower production in the Lower Volta, but show that there is room for providing environmental flows under current climatic and water use conditions if firm energy requirement from Akosombo Dam reduces by 12 % to 38 % depending on the environmental flow regime that is implemented. There is uncertainty in climate change effects on runoff in this region, however multiple scenarios are investigated. It is found that climate change leading to increased annual inflows to the Akosombo Dam reduces the trade-off between hydropower and the environment while climate change resulting in lower inflows provide the opportunity to strategically provide dry season environmental flows, that is, reduce flows sufficiently to meet low flow requirements for key ecosystem services such as the clam fishery. This study not only highlights the challenges in balancing anthropogenic water demands and environmental considerations in managing existing dams, but also identifies opportunities for compromise in the Lower Volta River.

Afua Owusu et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2022-270', Anonymous Referee #1, 17 Oct 2022
    • AC2: 'Reply on RC1', Afua Owusu, 27 Oct 2022
  • RC2: 'Comment on hess-2022-270', Kevis Pachos, 19 Oct 2022
    • AC1: 'Reply on RC2', Afua Owusu, 27 Oct 2022

Afua Owusu et al.

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Short summary
The construction of two dams in the Lower Volta River, Ghana affected downstream riverine ecosystems and communities. In contrast, Ghana as a whole has enjoyed vast economic benefits from the dams. Herein lies the challenge; there exists a trade-off between water for river ecosystems and water for anthropogenic water demands such hydropower. In this study, we quantify these trade-offs and show that there is room for providing environmental flows under current and future climatic conditions.