Clouded by drought: Hydropower essential to U.S. electric grid, but its future is questionable
- July 1, 2022: Vol. 9, Number 7

Clouded by drought: Hydropower essential to U.S. electric grid, but its future is questionable

by Caitlin Grady and Lauren Dennis

The water in Lake Powell, one of the nation’s largest reservoirs, has fallen so low amid the Western drought that federal officials are resorting to emergency measures to avoid shutting down hydroelectric power at the Glen Canyon Dam.

The Arizona dam, which provides electricity to seven states, isn’t the only U.S. hydropower plant in trouble. The iconic Hoover Dam, also on the Colorado River, has reduced its water flow and power production. California shut down a hydropower plant at the Oroville Dam for five months because of low water levels in 2021, and officials have warned the same could happen in 2022.

In the Northeast, a different kind of climate change problem has affected hydropower dams — too much rainfall all at once.

The United States has over 2,100 operational hydroelectric dams, with locations in nearly every state. They play essential roles in their regional power grids. But most were built in the past century under a different climate than they face today.

As global temperatures rise and the climate continues to change, competition for water will increase, and the way hydropower supply is managed within regions and across the power grid in the United States will have to evolve. We study the nation’s hydropower production at a systems level as engineers. Here are three key things to understand about one of the nation’s oldest sources of renewable energy in a changing climate.

Hydropower contributes 6 percent to 7 percent of all power generation in the United States, but it is a crucial resource for managing the U.S. electric grids.

Because it can quickly be turned on and off, hydroelectric power can help control minute-to-minute supply and demand changes. It can also help power grids quickly bounce back when blackouts occur. Hydropower makes up about 40 percent of U.S. electric grid facilities that can be started without an additional power supply during a blackout, in part because the fuel needed to generate power is simply the water held in the reservoir behind the turbine.

So, while hydroelectricity represents a small portion of generation, these dams are integral to keeping the U.S. power supply flowing.

Understanding regional climate effects is increasingly essential for power supply planning and protecting grid security, as balancing authorities work together to keep the lights on.

The importance of hydropower across the U.S. power grid means most dams are likely here to stay, but climate change will change how these plants are used and managed.


This article was written by Caitlin Grady, assistant professor of civil and environmental engineering and research associate in the Rock Ethics Institute at Penn State, and Lauren Dennis, a Ph.D. student in civil engineering and climate science at Penn State. The original version of this article, published by The Conversation, can be read here.

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