Water levels at reservoirs in the western US have hit record lows, diminishing the amount of energy generated at dams. Fossil fuel power plants are filling the gap 鈥� leading to increased greenhouse gas emissions and air pollution during the region鈥檚 megadrought.
On average, about and 50 per cent comes from fossil fuel plants burning gas, coal or oil. The rest is from wind, solar, nuclear power and other sources, such as geothermal energy.
Under drought conditions, the proportions in that mix can change, says at Stanford University in California. Less water in reservoirs means less water to release, leading to reductions in hydropower. The Hoover Dam on the Colorado River, for instance, is generating less than half its usual output because it draws water from a shrinking Lake Mead.
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Qiu and his colleagues analysed the effects of drought on electricity generation in 11 states in the western US, using data collected between 2001 and 2021 on precipitation runoff into reservoirs, electricity generation and resulting emissions.
They found that during the most extreme drought conditions, the amount of electricity generated by fossil fuel plants increased as much as 65 per cent above average at some facilities. During the driest months, plants in California saw average increases of 35 per cent, while the Pacific Northwest and Southwest saw increases of 11 and 9.5 per cent, respectively.
These 鈥渄rought-induced shocks鈥� accounted for 12 per cent of total carbon dioxide emissions from electricity generation over that period, say Qiu. They also accounted for 8 per cent of the sulphur dioxide emissions and 6 per cent of the nitrogen oxide emissions.
Both sulphur dioxide and nitrogen oxide emissions contribute to a harmful type of pollution called PM2.5, which refers to particles between 1 and 2.5 microns in diameter. These tiny particles can penetrate deep intro lung tissues and are responsible for most deaths from air pollution.
鈥淚t鈥檚 not just drought,鈥� says at the Pacific Northwest National Laboratory in Washington state. 鈥淚t also has impacts on air quality.鈥�
While previous used statistical models to show that drought might boost pollution, the current study used measurements from air quality monitors downwind of fossil fuel power plants to confirm that is the case, finding increased PM2.5 pollution, especially within 50 kilometres of the plants. 鈥淚t鈥檚 surprising to actually see this in the real world,鈥� says Qiu.
Drought-induced air pollution has decreased in the US in recent years because many coal-powered plants have been supplanted by natural gas, which produces fewer emissions. Also, more power plants are using scrubbers to reduce pollution. But in countries that use both a large amount of hydropower and coal and oil, such as Madagascar or Honduras, drought-induced shocks would cause more air pollution, says Qiu.
鈥淓ven with a very expansive renewable energy transition this drought-induced fossil problem doesn鈥檛 really go away,鈥� says Qiu. Overall emissions decrease as more renewable sources are added, but ambitious clean energy scenarios show fossil fuel power plants still being used to fill in drought-induced gaps for decades.
搁别蹿别谤别苍肠别:听Earth ArXiv, DOI:
