Hydropower decline due to climate change may increase price tag to decarbonize the grid

A new study warns that current plans to achieve zero emissions on the grid by 2050 vastly underestimate the required investments in generation and transmission infrastructure. The reason: These plans do not account for climate change’s impacts on water resources.

Specifically, changes in water availability caused by climate change could decrease hydropower generation by up to 23% by the year 2050, while electricity demand could increase by 2%. Both these phenomena would come together in summer to compound impacts on the grid.

To adapt to these impacts, the Western United States would need to build up to 139 gigawatts of power capacity between 2030 and 2050—equivalent to nearly three times California’s peak power demand, or up to 13 gigawatts in transmission capacity during the same time period. The total additional investment would come with a price tag of up to $150 billion.

That is the conclusion of a study published Nov. 25 in Nature Communications and co-authored by a team of Canadian and U.S. researchers, including at the University of California San Diego.

In this study, researchers took into account the vulnerability of the Western United States to water-related climate change impacts, such as rising temperatures, changing patterns in rainfall and declining snowpack. They built simulations that link the region’s water and electricity systems. They then evaluated how the region could adapt to a range of potential climate change futures from 2030 to 2050, while still trying to transition to a grid powered by carbon-free energy sources.

“Our results suggest that if [the West] ignores climate change impacts and associated water sector dynamics in planning, the grid will have insufficient resources to maintain system reliability and meet decarbonization goals,” the researchers write.

Loss of hydropower no matter the scenario

Under the models researchers used, the Pacific Northwest would experience some increases in rainfall, while the Southwest would continue to experience drying and droughts. As a result, key water basins in the region, such as the Colorado River, would keep shrinking.

Hydropower, which constitutes 20% of average energy generation in the West, will decline in response to these conditions. The models indicate that a mix of renewable power sources, such as wind and solar, will be necessary to offset these hydropower shortfalls. In climate scenarios with lower hydropower shortfalls and lower increases in energy consumption, wind power would mostly fill the gap. In scenarios with greater shortfalls, solar power would play a large role in filling the gap, complemented by flexible battery storage and geothermal power.

Meanwhile, increased need for cooling buildings would drive up electricity demand, which would be especially high in the Southwest—California, Nevada, Arizona and New Mexico. In the Pacific Northwest—Oregon and Washington—decreased electricity use for heating could partially offset increased electricity use for cooling.

The electricity demand related to water consumption is expected to increase in the Mountain region—Colorado, Montana, Wyoming, Idaho and Utah. Agricultural water needs, and associated electricity use for groundwater pumping, would also keep increasing in California’s Central Valley.

“Without explicitly quantifying how climate change and water interdependencies may together affect future electricity supply and demand, grid planners may significantly underestimate the magnitude and type of resources needed to achieve decarbonization goals and maintain grid reliability,” the researchers write.

Next steps

Next steps in the research would include evaluating how programs that seek to make demand more flexible and responsive could offset shortfalls in supply. Also, researchers would like to explore the role of transitions in the electricity sector, such as widespread electrification of buildings and transportation systems, and their synergies with the operation of the grid. More study is needed to understand how extended and more intense droughts would impact water and electricity systems in the West.

“Finally, we need to understand and overcome the significant political barriers to transmission expansion across the West, which may make capacity additions difficult to achieve in practice,” the researchers write.