Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Safeguarding migratory fish via strategic planning of future small hydropower in Brazil


Small hydropower plants (SHPs) are proliferating globally, but their cumulative threat to blocking migratory fish and the fisheries that these fish sustain has been underappreciated when compared with large hydropower plants (LHPs). Here, we quantified the trade-offs between hydroelectric generation capacity and the impacts on river connectivity for thousands of current and projected future dams across Brazil. SHPs are the main source of river fragmentation, resulting in average connectivity losses of fourfold greater than LHPs. Fragmentation by SHPs is projected to increase by 21% in the future, and two-thirds of the 191 migratory species assessed occupy basins that will experience greater connectivity losses due to SHPs than LHPs. A Pareto frontier analysis identified future dam portfolios that could halve the number of hydropower plants that are required to deliver the same energy-generation capacity compared with the least-favourable solutions, while simultaneously resulting in lower river fragmentation and protecting numerous undammed basins. Our results highlight the need for strategic planning that considers the unprecedented growth and cumulative effects of SHPs.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Temporal trends in river connectivity in Brazil according to changes in DCI over the past century and future projections due to ongoing and planned dam construction.
Fig. 2: Predicted future change in river connectivity.
Fig. 3: Present and projected future river connectivity.
Fig. 4: The effects of SHPs and LHPs on river connectivity.
Fig. 5: Relationship between the generation capacity of each future hydropower project and its effect on river connectivity (DCI) at the basin level.
Fig. 6: Future projections of nationwide river connectivity.

Similar content being viewed by others

Data availability

All of the analyses were based on governmental (ANEEL, IBGE, ICMBio) or open source datasets, such as HydroSHEDS and HydroBASINS. All references are included in the text. A repository with a research compendium including non-reproduceable data sources, intermediate products, scripts and guidance to reproduce the results is available at Figshare ( The output data generated by our analysis are provided in Supplementary Tables 16.

Code availability

The code used to analyse the data and generate figures are available at GitHub ( and


  1. Grill, G. et al. Mapping the world’s free-flowing rivers. Nature 569, 215–221 (2019).

    Article  CAS  Google Scholar 

  2. Zarfl, C., Lumsdon, A. E., Berlekamp, J., Tydecks, L. & Tockner, K. A global boom in hydropower dam construction. Aquat. Sci. 77, 161–170 (2014).

    Article  Google Scholar 

  3. Winemiller, K. O. et al. Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong. Science 351, 128–129 (2016).

    Article  CAS  Google Scholar 

  4. Sabo, J. L. et al. Designing river flows to improve food security futures in the Lower Mekong Basin. Science 358, eaao1053 (2017).

    Article  Google Scholar 

  5. Couto, T. B. A. & Olden, J. D. Global proliferation of small hydropower plants—science and policy. Front. Ecol. Environ. 16, 91–100 (2018).

    Article  Google Scholar 

  6. Premalatha, M., Tabassum-Abbasi, Abbasi, T. & Abbasi, S. A. A critical view on the eco-friendliness of small hydroelectric installations. Sci. Total Environ. 481, 638–643 (2014).

    Article  CAS  Google Scholar 

  7. Kelly-Richards, S., Silber-Coats, N., Crootof, A., Tecklin, D. & Bauer, C. Governing the transition to renewable energy: a review of impacts and policy issues in the small hydropower boom. Energy Policy 101, 251–264 (2017).

    Article  Google Scholar 

  8. Lange, K. et al. Basin-scale effects of small hydropower on biodiversity dynamics. Front. Ecol. Environ. 16, 397–404 (2018).

    Article  Google Scholar 

  9. Kibler, K. M. & Tullos, D. D. Cumulative biophysical impact of small and large hydropower development in Nu River, China. Water Resour. Res. 49, 3104–3118 (2013).

    Article  Google Scholar 

  10. Timpe, K. & Kaplan, D. The changing hydrology of a dammed Amazon. Sci. Adv. 3, e1700611 (2017).

    Article  Google Scholar 

  11. ANEEL Sistema de Informações de Geração da ANEEL - SIGA (Agência Nacional de Energia Elétrica, accessed 8 December 2020);

  12. Athayde, S. et al. Improving policies and instruments to address cumulative impacts of small hydropower in the Amazon. Energy Policy 132, 265–271 (2019).

    Article  Google Scholar 

  13. Anderson, E. P. et al. Fragmentation of Andes-to-Amazon connectivity by hydropower dams. Sci. Adv. 4, eaao1642 (2018).

    Article  Google Scholar 

  14. McIntyre, P. B. et al. in Conservation of Freshwater Fishes (eds Closs, G. P. et al.) 324–360 (Cambridge Univ. Press, 2015);

  15. Hoeinghaus, D. J. et al. Effects of river impoundment on ecosystem services of large tropical rivers: embodied energy and market value of artisanal fisheries. Conserv. Biol. 23, 1222–1231 (2009).

    Article  Google Scholar 

  16. Leite Lima, M. A., Rosa Carvalho, A., Alexandre Nunes, M., Angelini, R. & Rodrigues da Costa Doria, C. Declining fisheries and increasing prices: the economic cost of tropical rivers impoundment. Fish. Res. 221, 105399 (2020).

    Article  Google Scholar 

  17. Arantes, C. C., Fitzgerald, D. B., Hoeinghaus, D. J. & Winemiller, K. O. Impacts of hydroelectric dams on fishes and fisheries in tropical rivers through the lens of functional traits. Curr. Opin. Environ. Sustain. 37, 28–40 (2019).

    Article  Google Scholar 

  18. Costa-Pereira, R., Correa, S. B. & Galetti, M. Fishing-down within populations harms seed dispersal mutualism. Biotropica 50, 319–325 (2018).

    Article  Google Scholar 

  19. Flecker, A. S. et al. Migratory fishes as material and process subsidies in riverine ecosystems. Am. Fish. Soc. Symp. 73, 559–592 (2010).

    Google Scholar 

  20. Goulding, M. et al. Ecosystem-based management of Amazon fisheries and wetlands. Fish Fish. 20, 138–158 (2019).

    Article  Google Scholar 

  21. Tonkin, J. D. et al. The role of dispersal in river network metacommunities: patterns, processes, and pathways. Freshw. Biol. 63, 141–163 (2018).

    Article  Google Scholar 

  22. Cote, D., Kehler, D. G., Bourne, C. & Wiersma, Y. F. A new measure of longitudinal connectivity for stream networks. Landsc. Ecol. 24, 101–113 (2009).

    Article  Google Scholar 

  23. Brennan, A. S. R. et al. Shifting habitat mosaics and fish production across river basins. Science 364, 783–786 (2019).

    Article  CAS  Google Scholar 

  24. Tickner, D. et al. Managing rivers for multiple benefits—a coherent approach to research, policy and planning. Front. Environ. Sci. 5, 4 (2017).

    Article  Google Scholar 

  25. Jager, H. I., Efroymson, R. A., Opperman, J. J. & Kelly, M. R. Spatial design principles for sustainable hydropower development in river basins. Renew. Sustain. Energy Rev. 45, 808–816 (2015).

    Article  Google Scholar 

  26. Chen, W. & Olden, J. D. Designing flows to resolve human and environmental water needs in a dam-regulated river. Nat. Commun. 8, 2158 (2017).

    Article  Google Scholar 

  27. Schmitt, R. J. P., Bizzi, S., Castelletti, A. & Kondolf, G. M. Improved trade-offs of hydropower and sand connectivity by strategic dam planning in the mekong. Nat. Sustain. 1, 96–104 (2018).

    Article  Google Scholar 

  28. Almeida, R. M. et al. Reducing greenhouse gas emissions of Amazon hydropower with strategic dam planning. Nat. Commun. 10, 4281 (2019).

    Article  Google Scholar 

  29. Ziv, G., Baran, E., Nam, S., Rodriguez-Iturbe, I. & Levin, S. A. Trading-off fish biodiversity, food security, and hydropower in the Mekong River basin. Proc. Natl Acad. Sci. USA 109, 5609–5614 (2012).

    Article  CAS  Google Scholar 

  30. Perkin, J. S. & Gido, K. B. Fragmentation alters stream fish community structure in dendritic ecological networks. Ecol. Appl. 22, 2176–2187 (2012).

    Article  Google Scholar 

  31. Jaeger, K. L., Olden, J. D. & Pelland, N. A. Climate change poised to threaten hydrologic connectivity and endemic fishes in dryland streams. Proc. Natl Acad. Sci. USA 111, 13894–13899 (2014).

    Article  CAS  Google Scholar 

  32. Grill, G., Ouellet Dallaire, C., Fluet Chouinard, E., Sindorf, N. & Lehner, B. Development of new indicators to evaluate river fragmentation and flow regulation at large scales: a case study for the Mekong River basin. Ecol. Indic. 45, 148–159 (2014).

    Article  Google Scholar 

  33. Barbarossa, V. et al. Impacts of current and future large dams on the geographic range connectivity of freshwater fish worldwide. Proc. Natl Acad. Sci. USA 117, 3648–3655 (2020).

    Article  CAS  Google Scholar 

  34. Instituto Chico Mendes de Conservação da Biodiversidade Livro Vermelho da Fauna Brasileira Ameaçada de Extinção Vol. VI, Peixes (ICMBio/MMA, 2018).

  35. Carolsfield, J., Harvey, B., Ross, C. & Baer, A. Migratory Fishes of South America: Biology, Fisheries and Conservation Status (World Fisheries Trust, World Bank, IDRC, 2003);

  36. Ferreira, J. H. I., Camacho, J. R., Malagoli, J. A. & Guimarães, S. C. J. Assessment of the potential of small hydropower development in Brazil. Renew. Sustain. Energy Rev. 56, 380–387 (2016).

    Article  Google Scholar 

  37. Programas de Governo: Proinfa (Eletrobras, 2019);

  38. Latrubesse, E. M. et al. Damming the rivers of the Amazon Basin. Nature 546, 363–369 (2017).

    Article  CAS  Google Scholar 

  39. Fearnside, P. M. Amazon dams and waterways: Brazil’s Tapajós Basin plans. Ambio 44, 426–439 (2015).

    Article  Google Scholar 

  40. Farinosi, F. et al. Future climate and land use change impacts on river flows in the Tapajós Basin in the Brazilian Amazon. Earth’s Future 7, 993–1017 (2019).

    Article  Google Scholar 

  41. Almeida, J. D. E. Between distinct voracities: the hydro-energetic machine and the Iyakaliti’s response. Tapiti 12, 93–98 (2014).

    Google Scholar 

  42. Baigún, C., Minotti, P. & Oldani, N. Assessment of sábalo (Prochilodus lineatus) fisheries in the lower Paraná river basin (Argentina) based on hydrological, biological, and fishery indicators. Neotrop. Ichthyol. 11, 199–210 (2013).

    Article  Google Scholar 

  43. Brown, P. H., Tullos, D., Tilt, B., Magee, D. & Wolf, A. T. Modeling the costs and benefits of dam construction from a multidisciplinary perspective. J. Environ. Manage. 90, S303–S311 (2009).

    Article  Google Scholar 

  44. Petheram, C. & McMahon, T. A. Dams, dam costs and damnable cost overruns. J. Hydrol. X 3, 100026 (2019).

    Article  Google Scholar 

  45. Poff, N. L. et al. Sustainable water management under future uncertainty with eco-engineering decision scaling. Nat. Clim. Change 6, 25–34 (2016).

    Article  Google Scholar 

  46. CEPEL Manual for Hydropower Inventory Studies of River Basins English version (Ministry of Mines and Energy, 2007).

  47. Duarte, C. G., Dibo, A. P. A., Siqueira-Gay, J. & Sánchez, L. E. Practitioners’ perceptions of the Brazilian environmental impact assessment system: results from a survey. Impact Assess. Proj. A. 35, 293–309 (2017).

    Article  Google Scholar 

  48. Da Serra Costa, F. et al. Hydropower inventory studies of river basins in Brazil. Int. J. Hydropower Dams 18, 31–36 (2011).

    Google Scholar 

  49. Opperman, J. et al. Connected and Flowing: A Renewable Future for Rivers, Climate and People (WWF and The Nature Conservancy, 2019).

  50. Lehner, B., Verdin, K. & Jarvis, A. New global hydrography derived from spaceborne elevation data. EOS Trans. 89, 93–94 (2008).

    Article  Google Scholar 

  51. Lehner, B. & Grill, G. Global river hydrography and network routing: baseline data and new approaches to study the world’s large river systems. Hydrol. Process. 27, 2171–2186 (2013).

    Article  Google Scholar 

  52. Sistema de Informações Geográficas do Setor Elétrico—SIGEL (ANEEL, 2018).

  53. Potencial dos Recursos Energéticos no Horizonte 2050 (Empresa de Pesquisa Energética, 2018).

  54. Base Cartográfica Contínua 1:250,000 (IBGE, 2019);

  55. Vera-Escalona, I., Senthivasan, S., Habit, E. & Ruzzante, D. E. Past, present, and future of a freshwater fish metapopulation in a threatened landscape. Conserv. Biol. 32, 849–859 (2018).

    Article  Google Scholar 

  56. Reis, R. E. et al. Fish biodiversity and conservation in South America. J. Fish. Biol. 89, 12–47 (2016).

    Article  CAS  Google Scholar 

  57. Comte, L. & Olden, J. D. Evidence for dispersal syndromes in freshwater fishes. Proc. R. Soc. B 285, 20172214 (2018).

    Article  Google Scholar 

  58. Comte, L. & Olden, J. D. Fish dispersal in flowing waters: a synthesis of movement- and genetic-based studies. Fish Fish. 19, 1063–1077 (2018).

    Article  Google Scholar 

  59. Boletim Estatístico da Pesca e Aquicultura (Ministério da Pesca e Aquicultura, 2011).

  60. Freire, K. M. F., Machado, M. L. & Crepaldi, D. Overview of inland recreational fisheries in Brazil. Fisheries 37, 484–494 (2012).

    Article  Google Scholar 

  61. Brönmark, C. et al. There and back again: migration in freshwater fishes. Can. J. Zool. 92, 467–479 (2013).

    Article  Google Scholar 

  62. Noonan, M. J., Grant, J. W. A. & Jackson, C. D. A quantitative assessment of fish passage efficiency. Fish Fish. 13, 450–464 (2012).

    Article  Google Scholar 

  63. Pompeu, P. S., Agostinho, A. & Pelicice, F. M. Existing and future challenges: the concept of successful fish passage in South America. River Res. Appl. 28, 504–512 (2012).

    Article  Google Scholar 

  64. Santos, J. M. et al. Ecohydraulics of pool-type fishways: getting past the barriers. Ecol. Eng. 48, 38–50 (2012).

    Article  Google Scholar 

  65. Januchowski-Hartley, S. R., Jézéquel, C. & Tedesco, P. A. Modelling built infrastructure heights to evaluate common assumptions in aquatic conservation. J. Environ. Manage. 232, 131–137 (2019).

    Article  Google Scholar 

  66. Agostinho, A. A. et al. Fish ladder of Lajeado Dam: migrations on one-way routes? Neotrop. Ichthyol. 5, 121–130 (2007).

    Article  Google Scholar 

  67. Farah-Pérez, A., Umaña-Villalobos, G., Picado-Barboza, J. & Anderson, E. P. An analysis of river fragmentation by dams and river dewatering in Costa Rica. River Res. Appl. 1442–1448 (2020).

  68. Torrente-Vilara, G., Zuanon, J., Leprieur, F., Oberdorff, T. & Tedesco, P. A. Effects of natural rapids and waterfalls on fish assemblage structure in the Madeira River (Amazon Basin). Ecol. Freshw. Fish 20, 588–597 (2011).

    Article  Google Scholar 

  69. Roocks, P. Computing Pareto frontiers and database preferences with the rPref package. R J. 8, 393–404 (2016).

    Article  Google Scholar 

  70. World Energy Outlook (International Energy Agency, 2018).

Download references


We thank J. Zuanon and R. Reis for validating our migratory species list and ICMBio for sharing their dataset on fish species occurrence; D. Li, D. Martins and J. Rocha for the assistance with the analysis. J.D.O. was supported by a H. Mason Keeler Endowed Professorship from the School of Aquatic and Fishery Sciences, University of Washington, who also supported T.B.A.C.; T.B.A.C. received the CNPq/Science Without Borders Fellowship (203991/2014-1), and research grants from Rufford Foundation and National Geographic Society.

Author information

Authors and Affiliations



T.B.A.C. and J.D.O. designed the study, and all of the authors led the writing. T.B.A.C. and M.L.M. worked on the data acquisition, processing and analysis in R, and M.L.M. coded the spatial analysis in Python.

Corresponding author

Correspondence to Thiago B. A. Couto.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Sustainability thanks Mauricio Arias and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Supplementary information

Supplementary Information

Supplementary Figs. 1–10, Methods and references.

Reporting Summary

Supplementary Table 1

Estimates of river connectivity loss (DCIp) in the occurrence range of the 365 fish species considered migratory.

Supplementary Table 2

Projected effect of each future hydropower project on river connectivity (DCIp).

Supplementary Table 3

Projected nationwide connectivity loss (DCIp) and generation capacity gains for the favourable future hydropower dam portfolios.

Supplementary Table 4

Estimates of river connectivity loss (DCIi) in the occurrence range of the 365 fish species considered migratory. The DCIi is an estimate of river connectivity loss for migratory fish populations that are predominantly composed of external immigrants from downstream basins (see Supplementary Methods).

Supplementary Table 5

Projected effect of each future hydropower project on river connectivity (DCIi).

Supplementary Table 6

Projected nationwide connectivity loss (DCIi) and generation capacity gains for the favourable future hydropower dam portfolios.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Couto, T.B.A., Messager, M.L. & Olden, J.D. Safeguarding migratory fish via strategic planning of future small hydropower in Brazil. Nat Sustain 4, 409–416 (2021).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing Anthropocene

Sign up for the Nature Briefing: Anthropocene newsletter — what matters in anthropocene research, free to your inbox weekly.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing: Anthropocene