Integrating Fish-Friendly Hydropower Solutions with the Nature Restoration Policy Through River Barrier Modification

Calvin Stephen, Brian Huxley, John A. Byrne, Patrick Morrissey, Mary Kelly-Quinn and Aonghus McNabola ()
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Calvin Stephen: Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, D02 PN40 Dublin, Ireland
Brian Huxley: School of Biology and Environmental Science, University College Dublin, D04 C1P1 Dublin, Ireland
John A. Byrne: School of Biology and Environmental Science, University College Dublin, D04 C1P1 Dublin, Ireland
Patrick Morrissey: Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, D02 PN40 Dublin, Ireland
Mary Kelly-Quinn: School of Biology and Environmental Science, University College Dublin, D04 C1P1 Dublin, Ireland
Aonghus McNabola: Department of Civil, Structural and Environmental Engineering, Trinity College Dublin, D02 PN40 Dublin, Ireland

Energies, 2025, vol. 18, issue 22, 1-16

Abstract: The recently adopted EU Nature Restoration law emphasises the urgent need to address the ecological impacts of river barriers, which fragment habitats and disrupt natural flows. However, efforts to remove barriers are often constrained by prohibitive costs, regulatory hurdles, and public opposition. In Ireland, barrier removal costs range between EUR 200,000 and EUR 500,000 per structure, representing a substantial financial burden given that more than 73,000 barriers are identified nationwide. Although removal would restore ecological function, it would also eliminate the potential to repurpose these structures for hydropower, thereby reducing opportunities to contribute to the national target of 80% renewable electricity generation by 2030. This study outlines the development of a river barrier modification system to serve the dual purposes of upstream and downstream fish lift over barriers and generation of electricity for local consumption using a fish-friendly pump-as-turbine unit. Under normal flows, the unit generates electricity while during low flows it operates in pumping mode to enable fish passage. A prototype was fabricated and tested at a fish farm using both artificial and live fish. An assessment of the regional potential was also extrapolated from preliminary results suggesting that the BMS offers a cost-effective alternative to full barrier removal, potentially offsetting costs by 50–85% while contributing to both EU restoration targets and national renewable energy goals.

Keywords: barrier removal; fish passage; micro-hydropower; nature restoration; pump-as-turbine; river connectivity (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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