Droughts do more than just dry up our lawns, orchards, pastures and ski slopes.
A new Stanford study reveals a hidden impact of low water: worse air pollution, as we shift from hydropower to fossil fuels to generate energy.
When water levels drop at Shasta, Oroville and other dams, “this creates a drag on our ability to progress towards climate and air quality goals,” said climate scientist Noah Diffenbaugh of Stanford’s School of Earth, Energy & Environmental Sciences and a senior author of the study, published Friday.
California’s drought-induced shift in energy sources led to emission of an additional 51 million tons of carbon dioxide between 2001 and 2015, according to the analysis. That’s like adding 700,000 vehicles per year to our region’s roadways.
A similar trend was seen throughout the U.S. West, according to the research. In 11 states, a shift to fossil fuels dumped an estimated 100 million tons of carbon dioxide into the air – as much pollution as 1.4 million vehicles.
The team also found a drought-driven increase in emissions of sulfur dioxide and nitrogen oxides, air pollutants that can irritate lungs and contribute to acid rain and smog. The study is published in the Dec. 21 issue of the journal Environmental Research Letters.
Hydropower — one of the cleanest and cheapest energy sources — plays an important role in California, representing nearly one-fifth of our total in-state electricity generation in 2017. But it is largely dependent on rainfall to fill reservoirs. Water released from the dams power turbines that generate electricity. When there’s less water in the system, there’s a dramatic drop in hydroelectricity production.
In 2015, the drought pummeled our hydroelectric sector, sending in-state generation down 44 percent. Use of natural gas shot up to 59.9 percent, according to the California Energy Commission. While natural gas is cleaner than coal, it’s dirtier than hydropower. California also increased imports of energy from out-of-state – especially places reliant on coal.
The sources of added pollution varied by state. When hydropower dwindled, California and Idaho increased energy generation from natural gas. Colorado, Wyoming and Montana boosted the burning of coal. Oregon, Washington and Wyoming did both.
During droughts, “we still have electricity demands. It has to get replaced by some other mechanism,” said Diffenbaugh.
Record precipitation and snowpack conditions in early 2017 helped restore the state to above normal hydrological conditions, with major reservoirs filled to capacity. But lower precipitation late in 2017 and 2018 has renewed concerns about drought-like conditions.
As climate change creates a hotter and drier future, the western United States offers an ideal model to better understand the link between droughts and emissions from the power sector, the Stanford team recognized.
“For decades, people have been looking at the impacts of droughts on food security and agriculture,” said postdoctoral researcher Julio Herrera-Estrada, lead author of the study, in a prepared statement. “We’re less aware of exactly how droughts impact the energy sector and pollutant emissions in a quantitative and systematic way.”
The team’s findings could guide efforts to tamp down America’s drought-induced emissions to meet targets established by the landmark U.N. climate agreement in Paris, when nearly 200 nations volunteered a plan to curtail its greenhouse gas emissions by 2030.
And the implications extend far beyond our borders. Other parts of the world depend on hydropower even more than the western U.S.
“What our analysis is showing is that in order to meet those targets, it’s important to consider not only the primary source of energy for energy generation,” said Diffenbaugh, “but also the secondary sources that come on line when droughts happen.”
