While climate change might lead to higher rainfall in various regions of the United States, certain areas could experience drier conditions and reduced streamflow, resulting in diminished hydropower production.
A recent study evaluating the potential impact of climate change on hydropower generation throughout the continental United States indicates that, with some exceptions in the Southwest, hydropower generation is likely to increase in the future.
The research shows that, in the Pacific Northwest, there will be less winter snowpack in mountains due to warmer temperatures causing more rainfall. This alteration in seasonal water storage presents challenges for water managers and grid operators as they seek to optimize the operation of dams for electricity production.
“We recognize that the climate is changing, and that will directly affect water availability for hydropower,” commented Daniel Broman, a hydro-climatologist with the Department of Energy’s Pacific Northwest National Laboratory and the lead author of the study. “Our research offers a comprehensive overview across the country, which can assist water and energy planners even when they are concentrating on specific regional outlooks.”
The new study was published on August 8 in Environmental Research Letters.
Impact of climate change on hydropower
Hydropower facilities in the United States, numbering 2,250, generate 6% of the country’s electricity. The Pacific Northwest relies heavily on hydropower, which accounts for 60% of the region’s energy needs. Operational strategies for these dams are not solely focused on energy production; they also account for flood management, transportation, irrigation needs, and support for fisheries and ecosystems. Thus, anticipating changes in water availability is crucial for water managers as they strategize for future resource allocation.
To aid in this planning, the DOE periodically publishes the 9505 Assessment, named after Section 9505 of the SECURE Water Act. This report provides an in-depth evaluation of how climate change influences hydropower facilities. The latest report was submitted to Congress in December of 2023.
However, this report only covers 132 federally owned facilities, which account for 46% of the nation’s hydropower capacity, as noted by co-author Nathalie Voisin, the chief scientist for water-energy dynamics at PNNL. To gain a comprehensive understanding of climate change’s effects on hydropower generation nationwide, the researchers included data from an additional 1,412 non-federal facilities.
Partnering with colleagues at DOE’s Oak Ridge National Laboratory, they utilized models to predict how climate change might change the timing and volume of water flow in streams and rivers in the coming decades. The PNNL team processed this water flow data through models that incorporated various water uses, projecting hydropower production for two timeframes: the near term (2020-2039) and the midterm (2040-2059).
The findings revealed that hydropower production is expected to increase by approximately 5% in the near term and 10% in the midterm across the continental U.S. This trend may be linked to projected increases in precipitation as global temperatures rise.
The only region anticipated to experience an average decrease in hydropower generation is some parts of the Southwest, where ongoing drought conditions could lead to a slight reduction in production of about 3-6% in the near term.
Broman emphasized that the unpredictability of climate change means there is a wide range of potential outcomes for hydropower generation. For instance, hydropower production could vary from -5% to +21% during 2020-2039, and from -4% to +28% in the following years.
Seasonal variations could have significant repercussions for water management strategies throughout the country, according to Broman.
Seasonal variations in hydropower production
In winter, the team noted a possible increase of 12% in hydropower production in the near term and an 18% increase in the midterm across the United States. Similarly, higher rainfall in the fall could lead to a near-term rise in hydropower production in the Southeast by anywhere from 5% to 20%, along with smaller increments in the Northeast and Midwest.
However, some of the most dramatic shifts in hydropower production might happen during the summer, particularly in the West. In this region, hydropower generation could see a decrease of 1-5% during summer months, while areas in the East might experience a 1-5% increase during the same period due to higher precipitation.
Traditionally, mountain snowpack in the West has stored water until late spring and summer, providing a reliable source for electricity generation when melted. However, with rising temperatures, there is less snowfall and earlier melt-off, resulting in more electricity produced during the winter months and less available in the following spring and summer.
“Snow acts as a reservoir. When it melts sooner, it alters both the timing and quantity of available water,” Voisin explained. “Because temperatures are on the rise, the availability of hydropower and energy demands may not align as they should.”
Prospects for hydropower
Voisin highlighted that even if hydropower generation dips in specific seasons, it remains a dependable energy source for the power grid. Similar to coal or gas plants, hydropower can be employed flexibly to meet demand, thus enhancing the overall stability of the grid—illustrating its versatility as a renewable energy solution.
Broman and Voisin hope that this detailed multiscale assessment and the supporting data will aid power system operators and water managers in navigating discussions about balancing hydropower flexibility with the diverse benefits provided by water usage.
Given the unpredictable trajectory of climate change, Broman noted that historical data may not accurately predict the realities of the upcoming decades. “Utilities might be evaluating hydropower generation in the context of climate change for their own regions, but the electricity grid spans beyond those regions,” he said.
This research received support from the DOE Office of Energy Efficiency & Renewable Energy’s Water Power Technologies Office, as part of the SECURE Water Act Section 9505 Assessment.
