Small-scale hydropower (SHP) can generate electricity without the costs of building new dams.
SHP can provide power to remote areas and places where water access is politicized.
The environmental impacts of SPH are unclear and research is ongoing.
How are countries using small-scale hydropower and what are the impacts?
Hydropower, the generation of energy from moving water, provides about 6% of electricity in the U.S. and 14% globally (Office of Energy Efficiency and Renewable Energy n.d., International Hydropower Association 2025). It is considered a low emission and renewable source of power (Department of Energy (DOE) 2018). For more information, see Hydropower.
In the U.S., small-scale hydropower (SHP) is defined as less than 60 megawatts (MW) of capacity (DOE 2018). Other countries’ definitions range from ≤1 MW to ≤50 MW (Zhang et al. 2012). SHP has been the primary type of hydropower developed in the U.S. since the 1980s (Johnson et al. 2025, Johnson & Hadjerioua 2015). SHP can produce energy without the substantial cost of building new dams, and can be developed in remote areas without access to regional or national power grids (Douville et al. 2022, Zhang et al. 2021, Arora et al. 2010).
SHP is primarily generated in four ways (Klein & Fox 2018):
The Federal Energy Regulatory Commission (FERC) regulates and approves hydropower projects in the U.S. (DOE 2018). However, FERC provides license exemptions for SHP projects under a certain power threshold. The threshold to qualify for an exemption varies depending on the project design (Hydropower Regulatory Efficiency Act of 2013).
Installed SHP plants ≤10 MW have a combined capacity of about 79,000 MW worldwide (United Nations Industrial Development Organization (UNIDO) 2023, Figure 1). If SHP was installed at every known feasible location, it would have the potential to generate 221,000 MW. Approximately 64% of potential SHP resources are unused. Europe has installed 54% of its potential SHP capacity. By contrast, Africa has installed 5% of its potential capacity (Korkovelos et al. 2018).
China began developing SHP in the 1980s to increase rural electrification (Zhang et al. 2021). In 2022, China had nearly 42,000 MW of installed SHP, accounting for 53% of the world’s total installed SHP (UNIDO 2023). The next four largest SHP producers (the U.S., Italy, Japan, and Norway) combined had installed 13,830 MW, or 18% of the world’s SHP capacity. In Brazil, 1,600 MW of SHP has been installed, most of which was developed in the last 25 years (UNIDO 2023, Couto & Olden 2018).
As of 2017, India was estimated to have installed over 4,300 MW of SHP, including plants with capacities up to 25 MW (Deloitte 2017). Nepal has focused on micro hydropower, installing plants with <0.1 MW capacity throughout its mountainous rural areas (Bhandari et al. 2018). SHP is an option to develop hydropower in regions like Central Asia, where shared water resources are politically divisive (Azimov & Avezova 2022).
In the U.S., lack of standardized SHP regulations between states, aging and incompatible grid infrastructure, and unknown associated costs can complicate and discourage development (Douville et al. 2022). Increasing transparency and centralizing information for developers about the grid connection process has resulted in greater grid connectivity for other alternative power sources, such as solar.
SHP’s environmental impacts are also less understood than large hydropower’s. The proliferation of SHP has outpaced research on its ecological effects (Couto & Olden 2018). Placing several SHP plants on the same water system may have cumulative effects on water quality and wildlife distribution (Kuriqi et al. 2021, Timpe & Kaplan 2017). Recent studies offer conflicting conclusions, reporting adverse effects on fish migration but potentially beneficial effects on nutrient content (Chen et al. 2025, Chen et al. 2023). Increased testing and monitoring of water systems with SHP installations is needed to better understand the environmental impacts and to develop SHP sustainably (personal communication Couto 2025, Yan et al. 2025, He et al. 2024).
Figure 1. Small hydropower (SHP) capacity by country in 2022. Figure from UNIDO 2023. SHP generates small amounts of power without the cost of building large dams and is used to electrify rural areas. Darker shading on the map indicates more total megawatts (MW) of power generated by SHP plants of ≤10 MW. China, Japan, the U.S., Europe, and Brazil generate the most SHP. Countries in gray had no data.
References:
Arora DS, Busche S, Cowlin S, Engelmeier T, Jaritz H, et al. (2010) Indian renewable energy status report. National Renewable Energy Laboratory. https://docs.nrel.gov/docs/fy11osti/48948.pdf
Azimov U, Avezova N (2022) Sustainable small-scale hydropower solutions in Central Asian countries for local and cross-border energy/water supply. Renewable and Sustainable Energy Reviews. 167: 112726. https://doi.org/10.1016/j.rser.2022.112726
Bhandari R, Saptalena LG, Kusch W (2018) Sustainability assessment of a micro hydropower plant in Nepal. Energy, Sustainability and Society. 8: 3. https://doi.org/10.1186/s13705-018-0147-2
Chen Q, Li Q, Lin Y, Zhang J, Xia J, et al. (2023) River Damming Impacts on Fish Habitat and Associated Conservation Measures. Reviews of Geophysics. 61(4): e2023RG000819. https://doi.org/10.1029/2023RG000819
Chen Q, Chen Y, Lin Y, Zhang J, Ni J, et al. (2025) Does a hydropower reservoir cascade really harm downstream nutrient regimes. Science Bulletin. 69(5): 661-670. https://doi.org/10.1016/j.scib.2024.01.007
Couto TBA, Olden JD (2018) Global proliferation of small hydropower plants – science and policy. Frontiers in Ecology and the Environment. 16(2): 91-100. https://doi.org/10.1002/fee.1746
Couto TBA, Messager ML, Olden JD (2021) Safeguarding migratory fish via strategic planning of future small hydropower in Brazil. Nature Sustainability. 4: 409-416. https://www.nature.com/articles/s41893-020-00665-4
Couto TBA (2025) Lecturer in Conservation Ecology. School of Environmental Sciences, University of East Anglia. Personal communication.
Douville T, Severy M, Wall T, Mongird K (2022) Small Hydropower Interconnections. Pacific Northwest National Laboratory. U.S. Department of Energy. https://doi.org/10.2172/1882596
Deloitte (2017) Evaluation of Small Hydro Power (SHP) Programme of MNRE. Government of India Ministry of New & Renewable Energy (MNRE). https://web.archive.org/web/20230726013245/https://mnre.gov.in/img/documents/uploads/7b691718d9194ab68b7d9638bb901a74.pdf
He F, Zarfl C, Tockner K, Olden JD, Campos Z, et al. (2024) Hydropower impacts on riverine biodiversity. Nature Reviews Earth & Environment. 5: 755-772. https://doi.org/10.1038/s43017-024-00596-0
Hydropower Regulatory Efficiency Act of 2013, H.R. 267. 113th Congress. (2013) https://www.congress.gov/bill/113th-congress/house-bill/267
International Hydropower Association (2025) 2025 World Hydropower Outlook. https://www.hydropower.org/publications/2025-world-hydropower-outlook
Johnson K, Hadjerioua B (2015) Small Hydropower in the United States. Oak Ridge National Laboratory. https://info.ornl.gov/sites/publications/files/Pub56556.pdf
Johnson MM, Kao SC, Uria Martinez R (2025) Existing Hydropower Assets (EHA) Plant Database, 2025. Hydrosource, Oak Ridge National Laboratory. https://hydrosource.ornl.gov/data/datasets/eha-plant-2025/
Kao SC, George L, Hansen C, DeNeale ST, Johnson K, et al. (2022) An assessment of hydropower potential at national conduits. Oak Ridge National Laboratory. https://info.ornl.gov/sites/publications/Files/Pub176069.pdf
Klein SJW, Fox ELB (2018) A review of small hydropower performance and cost. Renewable and Sustainable Energy Reviews. 169: 112898. https://doi.org/10.1016/j.rser.2022.112898
Korkovelos A, Mentis D, Siyal SH, Arderne C, Rogner H, et al. (2018) A geospatial assessment of small-scale hydropower potential in sub-Saharan Africa. Energies. 11(11): 3100. https://doi.org/10.3390/en11113100
Kuriqi A, Pinheiro AN, Sordo-Ward A, Bejarano MD, Garrote L (2021) Ecological impacts of run-of-river hydropower plants – current status and future prospects on the brink of energy transition. Renewable and Sustainable Energy Reviews. 142: 110833. https://doi.org/10.1016/j.rser.2021.110833
United Nations Industrial Development Organization (UNIDO) (2023) World Small Hydropower Development Report 2022. https://www.unido.org/sites/default/files/files/2023-05/ENGLISH%20SUMMARY-2022.pdf
U.S. Department of Energy (DOE) (2018) Hydropower Vision: A New Chapter for America’s 1st Renewable Electricity Source. https://www.energy.gov/sites/default/files/2018/02/f49/Hydropower-Vision-021518.pdf
U.S. Department of Energy Office of Energy Efficiency and Renewable Energy (n.d.) Hydropower basics. https://www.energy.gov/eere/water/hydropower-basics
U.S. Energy Information Administration (2021) Hydropower made up 66% of Brazil’s electricity generation in 2020. https://www.eia.gov/todayinenergy/detail.php?id=49436
Timpe K, Kaplan D (2017) The changing hydrology of a dammed Amazon. Science Advances. 3(11): e1700611. https://doi.org/10.1126/sciadv.1700611
Yan X, Zhang S, Chen Q, Zhang J, Feng T, et al. (2025) Establishing eco-environmental monitoring networks for China hydropower reservoirs. The Innovation. 6(6): 100940. https://doi.org/10.1016/j.xinn.2025.100940
Zhang L, Pang M, Bahaj AS, Yang Y, Wang C (2021) Small hydropower development in China: growing challenges and transition strategy. Renewable and Sustainable Energy Reviews. 137: 110653. https://doi.org/10.1016/j.rser.2020.110653
Zhang QF(K) Zhang, Smith B, Zhang W (2012) Small hydropower cost reference model. Oak Ridge National Laboratory. https://info.ornl.gov/sites/publications/files/pub39663.pdf
