the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Quantifying the trade-offs in re-operating dams for the environment in the Lower Volta River
Jazmin Zatarain Salazar
Marloes Mul
Pieter Zaag
Jill Slinger
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.
- Preprint
(1226 KB) -
Supplement
(379 KB) - BibTeX
- EndNote
Afua Owusu et al.
Status: final response (author comments only)
-
RC1: 'Comment on hess-2022-270', Anonymous Referee #1, 17 Oct 2022
The comment was uploaded in the form of a supplement: https://hess.copernicus.org/preprints/hess-2022-270/hess-2022-270-RC1-supplement.pdf
-
AC2: 'Reply on RC1', Afua Owusu, 27 Oct 2022
The authors thank the reviewers for their insightful comments which have proved very helpful in revising the manuscript. Attached are detailed responses to the individual comments raised by each reviewer with new/modified text highlighted. In responding to reviewer 1, the specific comments are addressed before the response to the questions raised in the overall summary.
-
AC2: 'Reply on RC1', Afua Owusu, 27 Oct 2022
-
RC2: 'Comment on hess-2022-270', Kevis Pachos, 19 Oct 2022
lines 365-367: The authors seem to suggest that the flood control objective is performing less well for e-flows2 and 3 (0.83 down from 0.99 in clam e-flows. This is however not shown in Figure 4. Instead Figure 4 suggests the performance of the flood control objective remains the same across all e-flows.
Citation: https://doi.org/10.5194/hess-2022-270-RC2 -
AC1: 'Reply on RC2', Afua Owusu, 27 Oct 2022
The authors are grateful to the reviewer for highlighting the ambiguity in the text. The performance of the flood objective does remain the same, but the performance of the solution decreases for the environment objective for e-flows 2 and 3. The text has been updated to read:Â
The solutions for all e-flow configurations perform well for the flood control objective even though e-flow 2 and 3 prescribe flood releases for two months of the year. As such, comparing clam e-flows to e-flows 2 and 3, there is a reduction (0.99 for clam e-flows vs. 0.83 for e-flows 2 and 3) in the performance of the ‘best environment’ solution for the latter two, as expected, showing that the requirement for floods for two months in a year in those e-flow configurations are not met.
Citation: https://doi.org/10.5194/hess-2022-270-AC1
-
AC1: 'Reply on RC2', Afua Owusu, 27 Oct 2022
Afua Owusu et al.
Afua Owusu et al.
Viewed
HTML | XML | Total | Supplement | BibTeX | EndNote | |
---|---|---|---|---|---|---|
391 | 105 | 13 | 509 | 34 | 5 | 5 |
- HTML: 391
- PDF: 105
- XML: 13
- Total: 509
- Supplement: 34
- BibTeX: 5
- EndNote: 5
Viewed (geographical distribution)
Country | # | Views | % |
---|
Total: | 0 |
HTML: | 0 |
PDF: | 0 |
XML: | 0 |
- 1