Drought, Climate Change Threaten Future of US Hydropower

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

The Arizona Dam, which provides electricity to seven states, is not the only US hydropower plant in trouble.

The iconic Hoover Dam, also on the Colorado River, has reduced its water flow and electricity production. California closed the hydroelectric plant at the Oroville Dam for five months due to 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 hydroelectric dams — too much rainfall at once.

The United States has more than 2,100 hydroelectric dams in operation, with locations in nearly every state. They play an important role in their regional power grid. 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 the region and across the US power grid will have to evolve. We study national hydropower production at the system level as engineers. Here are three important things to understand about one of the oldest renewable energy sources in the country in a changing climate.

Hydroelectric Power Plants Can Do Things Other Power Stations Can’t

Hydropower accounts for 6 to 7 percent of all electricity generation in the US, but is an important resource for managing the US power grid.

Because they can be turned on and off quickly, hydroelectric power stations can help control minute-to-minute changes in supply and demand. It can also help the power grid quickly get back on track in the event of a power outage. Hydropower makes up about 40 percent of US grid facilities that can be started without additional power supply during an outage, in part because the only fuel needed to generate power is water stored in a reservoir behind the turbine.

Apart from that, it can also serve as a giant battery for the network. The US has more than 40 pumped hydropower plants, which pump water uphill into reservoirs and then send it through turbines to generate electricity as needed.

So while hydroelectric power represents a small fraction of generation, these dams are integral to keeping the US electricity supply flowing.

Climate Change Affects Hydro Power Differently in Different Regions

Globally, droughts have reduced hydropower generation. How climate change affects hydroelectricity in the US going forward will largely depend on the location of each individual plant.

In areas where melting snow affects river flow, the hydropower potential is expected to increase in winter, when more snow falls as rain, but then decrease in summer when less snow is left to become meltwater. This pattern is expected across much of the western US, along with worsening multi-year droughts that could reduce some hydroelectric production, depending on how much storage capacity the reservoir has.

The Northeast has different challenges. There, extreme rainfall that can cause flooding is expected to increase. More rain could increase the potential for generating electricity, and there is discussion about retrofitting more existing dams to generate hydropower. But since many of the dams there are also used for flood control, the opportunity to generate additional energy from the increased rainfall could be lost if water is released through spillways.

In the southern US, there is expected to be a decrease in rainfall and an intensive drought, which is likely to result in a decrease in hydroelectricity production.

Several Network Operators Face Bigger Challenges

The effect of these changes on the country’s electricity grid will depend on how each part of the grid is managed.

Agencies known as balancing authorities manage electricity supply and demand in their area in real time.

The greatest balancing authority when it comes to hydroelectricity is the Bonneville Power Administration in the Northwest. It can generate about 83,000 megawatt-hours of electricity annually in 59 dams, mainly in Washington, Oregon and Idaho. The Grand Coulee Dam complex alone can generate enough electricity for 1.8 million homes.

Most of these regions share a similar climate and will experience climate change in much the same way in the future. That means that a regional drought or snowless year could hit many of the Bonneville Power Administration’s hydroelectric producers at the same time. Researchers have found that the region’s climate impacts on hydroelectricity present both risks and opportunities for grid operators by increasing summer management challenges but also reducing winter power shortages.

In the Midwest, it’s a different story. Midcontinent Independent Systems Operator (MISO) owns 176 hydroelectric plants in an area 50 percent larger than Bonneville, from northern Minnesota to Louisiana.

Because their hydropower plants are more likely to experience different climates and regional effects at different times, MISO and similar broad operators have the ability to balance the hydropower deficit in one area with generation in another.

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

More Changes Coming

Climate change is not the only factor that will affect the future of hydroelectric power. Competing demands have influenced whether water is allocated for power generation or other uses such as irrigation and drinking.

Water laws and allocations also shift over time and change the way water is managed through reservoirs, affecting hydroelectric power generation. The increase in renewable energy and the potential to use multiple dams and reservoirs for energy storage could also change the equation.

The importance of hydropower across the US power grid means most dams will likely remain, but climate change will change the way these power plants are used and managed.

Caitlin Grady is an assistant professor of civil and environmental engineering and a research associate at the Rock Ethics Institute at Penn State. He received funding from the National Science Foundation and the US Department of Agriculture.

Lauren Dennis is a Ph.D. civil engineering and climate science student at Penn State. He received funding from the National Science Foundation.

This article is republished from Conversation under a Creative Commons license. You can find original article here.

Leave a Comment

%d bloggers like this: