Hydropower facilities support electricity grids across the U.S. by remaining dependable and stable, ensuring households and businesses have power when they require it. Currently, hydropower produces 27% of the U.S. utility-scale renewable electricity and nearly 6% of the nation’s overall utility-scale electricity. However, shifting climate conditions, such as altered precipitation trends, earlier snowmelt, and more frequent extreme events, may impact water availability and its flow throughout a watershed (a land area that directs water to rivers, lakes, and oceans). This is especially crucial for managing significant reservoirs, where water serves multiple purposes, including hydropower generation and drinking water supplies.
To aid hydropower owners and operators in ensuring steady and reliable hydropower generation, investigators from Pacific Northwest National Laboratory and Oak Ridge National Laboratory conducted a national study to assess how climate change could influence future hydropower production across the contiguous U.S. This research, detailed in Environmental Research Letters, represents one of the most extensive climate change-informed U.S. hydropower modeling initiatives to date, with data available for 1,544 federal and non-federal hydropower facilities. Collectively, these facilities can generate 86 gigawatts of electricity, sufficient to supply power to nearly 30 million homes.
The study indicates that, on average, U.S. hydropower generation could rise by 5% by 2039 and 10% by 2059 as climate change modifies the nation’s weather patterns and waterways. However, these increases will vary by region and season, and significant reductions in water levels could negatively impact hydropower generation as the risk of regional droughts also escalates.
This research builds upon findings from three assessments regarding the impacts of climate change on federal hydropower, as mandated in Section 9505 of the SECURE Water Act of 2009, which instructed the U.S. Department of Energy to examine the effects of climate change on federal hydropower facilities.
The new study utilizes 96 distinct hydroclimate projection frameworks to encompass more than 85% of total hydropower capacity across the contiguous United States. Its projections for hydropower generation are based on downscaled and bias-corrected future climate forecasts. These forecasts are integrated with hydrologic models, which estimate how watersheds respond to environmental changes, to simulate hydropower operation and production. All research is highly collaborative with the four federal Power Marketing Administrations.
The study further models the compounding effects of hydrologic changes over time, the physical characteristics of each hydropower facility, and the operational constraints and goals of each facility. Throughout this modeling process, various approaches were employed to account for variability in model selection and parameters. The study assumed that all physical and operational characteristics would remain constant, and that no new facilities would be constructed or retired.
According to the research, climate change impacts in one region of the country may differ from those in another region during the year. The West, for instance, may experience declining hydropower generation in the summer and fall as earlier snowmelt increases water availability in late winter and spring. Meanwhile, the East may witness enhanced generation in the fall due to heavier rainfall.
Seasonal forecasting further indicates increased generation in the North and reduced generation in the South. These collective observations underscore much greater uncertainty regarding hydropower generation in California, the Southwest, and the Southeast in comparison to the Pacific Northwest, Northeast, Mid-Atlantic, and Midwest. Some of this uncertainty can be linked to changing snowpack and precipitation events, including winter atmospheric rivers in California and the North American Monsoon in the Southwest. A similar, but slightly narrower, uncertainty applies to fall and winter generation in the Southeast.
The study emphasizes the necessity to continue monitoring shifting seasonal patterns to meet future water and energy demands. The research team intends to keep expanding the dataset to provide regional utilities and power system operators with consistent data to plan for drought scenarios, design long-duration storage, and assess infrastructure improvements to adapt to increasing weather variability. A fourth evaluation on the effects of climate change on federal hydropower facilities is also currently in progress.
