WATER POLITICS

It may not get the same attention as solar panels and wind farms, but few pieces of infrastructure are more crucial for the fate of the planet than China’s cascade of hydroelectric plants.

The sector as a whole could power Japan or Russia. Dams in the three biggest provinces for hydro — Sichuan, Yunnan, and Hubei — alone produce nearly as much electricity as every wind turbine in China, and more than twice as much as all the country’s solar arrays. That makes the vagaries of the weather a crucial variable for global carbon emissions. A drought in 2022 helped drive a resurgence of coal consumption, while heavy rains since last year offered the hope that usage of solid fuel might be finally peaking.

There’s still a slim hope that could be happening. Over the past month, however, hydroelectricity hasn’t been providing the fillip that many (myself included) had hoped.

The proximate cause is a dry spell since August that’s dried up the Yangtze Basin, on which so much of China’s hydro power depends. Rainfall has inundated the country’s northeast, causing flooding, landslides and evacuations but that came at the expense of the southwest, where swathes of Sichuan and Hubei received just a quarter or less of normal precipitation.

Running Dry

The amount of water held in Yangtze Basin reservoirs collapsed in August

The outcome for hydroelectricity has been devastating. Thanks to heavy rains since early last year, 2024 had been shaping up for record strength in China’s dams. That’s now flipped 180 degrees. The Yangtze Basin’s reservoirs typically fill up by about 20 billion cubic meters in August and September, after monsoon rains lash China’s south and west. Even in the devastating drought year of 2022, they gained nearly half that amount. This year, they lost 2.2 million cubic meters. As a result, the monthly slump in hydro generation in September was the sharpest on record: 44 terawatt-hours, enough electricity to power the UK for two months.

That’s worrying on both small and large scales. The most immediate negative effect this year has been a surge in September’s coal generation. It’s the only source of power that can be quickly drummed into service when hydroelectricity fails, since nuclear and renewables are already running flat out and China uses very little gas for electricity.

This makes the pathway to a hoped-for peak in coal consumption this year worryingly narrow. Falling output of cement and pig iron means that the two biggest non-power users of coal have probably consumed about 57 million metric tons less than 2023. The power sector, however, looks to be utilizing about 52 million tons more, so there’s a good chance growth will resume.

Knife Edge

China appears still to be using less coal in 2024 than in 2023, but it’s close

That’s indicative of a bigger problem. China has increased the size of its hydro sector enormously in recent years. In the 2000s, when wind and solar weren’t expected to amount to much, the Yangtze’s dams — above all the Three Gorges, the biggest power plant on the planet — were seen as the key to limiting the country’s carbon footprint.

All that activity, however, is producing remarkably little electrical bang for its buck. China added nearly 20% to the capacity of its large dams between 2018 and 2023 — but generation from all those facilities in the nine months through September was just 12% above the same period in 2019. It’s not clear whether this is because of a one-time sequence of climate anomalies, or a more fundamental problem that will weigh on the sector in years to come. If it’s the latter, China’s decarbonization is going to have to depend less on hydro power, and more on other sources.

The largest issue stretches beyond even China. Hydroelectricity’s ability to provide vast, nation-transforming amounts of cheap, clean energy at a single stroke is hard to beat. At different times, the economies of Brazil, Canada, Russia, Turkey, and Vietnam have all been transformed by the floods of electricity it can generate. Ethiopia, Nepal, Pakistan, and the Democratic Republic of Congo may be the next to use it to get a leg up the ladder of development.

Flooded Market

China produces nearly a third of the world’s hydroelectricity

And yet a warming climate threatens to disrupt the consistent pulse of rainfall that a vibrant hydro sector needs to survive. In Brazil, the biggest user of dam power after China, a multi-year drought has drained reservoirs, withered crops, pushed up inflation, slowed the economy, and left the country more dependent on burning fossil fuels to compensate.

The many other stakeholders in river engineering programs, such as farmers, recreational users and environmentalists, also want a say in how stored water is used — and the fight may grow more bitter as supply becomes less predictable.

Hydroelectricity may be one of our most potent weapons against climate change. Few forms of generation, though, are more vulnerable to the effects of a warming planet. If even China cannot count on hydro-led decarbonization, doubts from other nations will grow.