Hydropower Is Drying Up, Further Stressing Energy Grids

SThis Labor Day weekend, the American Southwest is experiencing scorching heat. The heat is the first thing that residents will notice as the summer progresses.

The electric grid is stressed by extreme, long heat waves. Everybody cranks the air conditioners, driving up electricity demand. While the temperatures rise, nuclear, natural gas and coal power plants are less efficient and can produce less heat. The strain on the electric grid this weekend is so worrying that the California Independent System Operator (ISO), which oversees the state’s power system, is asking residents to not charge electric vehicles, to set thermostats to 78°F or higher, and to reduce overall energy use. According to the ISO, this is done in an effort to stop energy scarcity.

One thing that’s certainly not helping this situation is the region’s vanishing hydropower, which makes up nearly a quarter of the region’s electric generation. While the whole Western U.S. is experiencing dry conditions, the Southwest, and California in particular, is experiencing a two-decade megadrought that has severely crimped the state’s hydroelectric sources. As the below chart shows, hydropower has dropped from about 15%-20% of California’s electricity in the early 2000s to only 7.5% last year.

Hydropower can be generated from dammed reservoirs. If the reservoirs are below certain levels, power cannot be produced. Extreme weather can increase the strain on the grid’s energy supply. “If you’re in the middle of a terrible drought and you have way less hydropower than normal, that makes it harder to meet demand,” says Jordan Kern, an assistant professor in the College of Natural Resources at North Carolina State University. “But usually system operators have replacements. There’s going to be electricity that’s produced at natural gas plants. It’s dirtier, it’s more expensive, but it keeps the lights on.”

Continue reading: Colorado River Drought is a cautionary tale about climate

In California, solar and other renewable sources have taken off in the last decade, filling hydropower’s generation void. But renewables don’t have all the benefits of hydropower. According to the 2021 Department of Energy’s report, hydropower contributes greatly to grid reliability. Hydropower operates 24 hours a day and offers more storage options than battery backups. What’s more, hydropower can very rapidly reboot the power grid after a blackout.

A 2019 DOE analysis found that hydropower—despite being only 10% of the country’s total generating capacity—provides about 40% of the country’s so-called “black start” resources that jump-start grid transmission and help switch on other generators following an outage. Solar photovoltaic and wind generators, the report found, “cannot be relied upon” to deliver in that way.

An American government map showing the U.S. since late August 2022. It shows the extreme and extraordinary drought conditions in Western America.

Because of dry conditions that “threaten the availability” of hydropower, the North American Electric Reliability Corporation said in May, all U.S. areas that are part of the Western grid system are “at risk of energy emergencies.” That grid serves 80 million people across 14 states, two Canadian provinces, and a small area of northern Mexico.

Lake Oroville in California was the second largest lake. It fell below the minimum hydropower levels last summer. The Hyatt Power plant had to be shut down. Since the plant was first operational in 1967, it had never been seen before. The same thing could occur to other large reservoirs over the next few years. There’s a 10% chance that Lake Powell could fall below operational levels as soon as next year, and a 30% chance by 2024, according to August projections from the Bureau of Reclamation. The reservoir is situated in Arizona and Utah. It holds water for Glen Canyon Dam. They typically supply power to Wyoming, Utah Colorado, New Mexico Arizona Nevada and Arizona. Right now it is only about 25% full—its lowest-ever level since it was first filled.

Continue reading: China’s Extreme Drought Is Pushing the Country to Rely Even More on Coal

Lake Mead is 28% full. It sits farther down the Colorado River on Nevada’s Arizona border. According to the same Bureau of Reclamation projections, there’s a 23% chance its levels drop to 1,000 feet by 2024, and a 7% chance that they drop to 950 feet by 2026—the point at which water would be too low to flow through the Hoover Dam’s pipes that intake water from the reservoir. The Hoover Dam’s power, which is enough to serve 1.3 million people, is allocated mostly to California, but also Nevada and Arizona. “They may stop being able to produce electricity,” says Kern of the two iconic dam structures. “That is something that people are increasingly concerned about.”

The following chart displays water levels at Western reservoirs. Notably, Lake Mead and Lake Powell are significantly below full and also well below where they’ve been for this time of year, based on a 30-year average, but many others are in similar conditions.

Climate change will make summers longer and more hotter in the United States, which will cause increased stress to the grid. And in many states, losing hydropower means relying more on fossil fuels, which are contributing to climate change and worsening the dry conditions—a vicious, paradoxical cycle.

Similar situations are occurring in other countries that have been affected by drought. Dry conditions in Sichuan Province, China, for example, have hampered hydropower generation—accounting for 80% of the region’s electricity—and caused blackouts. Similar problems have been experienced across Europe in this summer’s power crisis. This is because low water levels made it difficult for hydropower to be generated and also make it hard to cool nuclear reactors and carry coal on rivers.

But conditions aren’t that dire in the U.S. this year. And experts like Jack Schmidt, director of the Center for Colorado River Studies at Utah State University, believes that hydropower shouldn’t be the focus of the wider drought problem. According to Schmidt, the country will find a way to meet its energy needs. But there’s no easy solution if drinking water and irrigation water for agriculture are scarce.

“Water supply is more important than energy,” Schmidt says. “That’s not to say the power isn’t important. Hoover Dam’s power is important. But American society doesn’t crumble if we lose it. It’s not the equivalent of losing water.”

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