How Western Droughts Increased Carbon Emissions

In the early 20th century, as the United States developed the West, the federal government built hundreds of hydroelectric dams on major rivers in the region. These dams have destroyed riverine ecosystems and flooded indigenous land, but have also provided an affordable and abundant source of renewable energy for tens of millions of people. Hydroelectricity now satisfies about a quarter of the region’s energy needs.

But the hydroelectric fleet in the West has taken a major hit over the past 20 years as a series of devastating droughts hit the area. When large rivers dry up, less water flows through the turbines of hydroelectric dams, and as a result, the dams produce less electricity. At the same time, the heat waves that often accompany dry spells lead to higher energy demand, as people ramp up their air conditioning. This is bad news for grid operators, who must find an alternative source of electricity just as dams are failing.

This decline in hydropower leads to a significant increase in fossil fuel emissions, according to a new study published last week in the Proceedings of the National Academy of Sciences, a leading scientific journal. After examining power generation across the West between 2001 and 2021, the study authors found that coal- and gas-fired plants increased their activity during the dry months to replace lost hydropower, bringing to higher carbon emissions and more local air pollution. While that discovery was expected, the scale of the increase in fossil fuel emissions surprised researchers.

The effect on power mix is ​​actually quite large, said Minghao Qiu, a postdoctoral scholar at Stanford University who is the study’s lead author.

All told, the decline of hydroelectricity caused an additional 121 million tons of carbon emissions between 2001 and 2021, roughly as if 1.3 million more cars had been on the road during the same period. The magnitude of the change varied from grid to grid and from power plant to power plant, but everywhere it was sizable. Fossil fuel emissions rose 11% in the Northwest during the driest months and a whopping 30% in California. In some plants, generation has increased up to 65% of normal levels during dry spells.

During drier years, this increase has had staggering consequences for the climate: in 2001, for example, a decline in hydroelectricity caused fossil-fuel-fired power plants in the West to emit 27 million tons more carbon dioxide than they otherwise would have, or about 10% of their total emissions that year.

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Since coal and natural gas tend to be more expensive to produce than hydroelectricity, the drought likely led to higher energy costs for customers in the West. But the study also argues that the decline in hydroelectric power generation has been accompanied by large costs to the environment and public health, amounting to more than $20 billion so far this century. Not only has increased carbon emissions caused by droughts caused future warming that will lead to more climate disasters, but the air pollution around fossil fuel plants has also made nearby residents ill, which will later lead to higher public health costs.

In 2001, for example, California’s natural gas plants scaled up to offset a drought-induced decline in hydroelectricity across the region, leading to a more than 40 percent increase in emissions of toxic chemicals such as carbon dioxide. sulfur dioxide and nitric oxide.

These adverse health effects have not always occurred in the same places where a drought has occurred. When the hydroelectric fleet in a state like Washington faltered, grid operators imported electricity from other states, carrying electrons on long transmission cables that criss-cross the region. This replacement energy came from coal-fired plants in Montana and gas-fired plants in California, and people close to those distant facilities bore the health care costs as those plants burned more fossil fuels. The study found that more than half of the increase in fossil fuel production from 2001 to 2021 occurred in states that weren’t experiencing droughts.

A climate shock in one place can really wreak havoc in distant places, because the energy grid is so connected, Qiu told Grist.

In an interesting twist, the study found that even a rapid buildup of renewables may not solve the problem of increased pollution during dry spells. Western states are racing to build more solar and wind power, and the Biden administration is pushing to build more of these facilities on the region’s abundant public land. But Qius’s study found that fossil-fuel plants will continue to provide backup energy when other sources such as hydroelectricity fall short, as they can ramp up at short notice, unlike renewables which depend on the amount of sun and wind available. To reduce fossil fuel emissions during droughts, states and the federal government must work on developing better storage options, such as upgraded batteries, to conserve the extra energy produced by renewables, according to Qiu.

We’re looking at generators that ramp up their generation while there’s increased demand due to a heat wave or decreased supply due to drought, he told Grist. If there is a future drought, it will still be fossil fuel power plants that will ramp up their output to fill that electricity gap.

Update: This story has been updated to include a cumulative figure for carbon emissions attributable to loss of hydroelectricity.