WUHAN (BLOOMBERG) – Wan Jinjun, a 62-year-old retiree who has swum the Yangtze River almost every day for the past decade in Wuhan, said he’s never seen a drought like this before.

An extreme summer has taken a toll on Asia’s longest river, which flows about 6,300km through China and feeds farms that provide much of the country’s food and massive hydroelectric stations, including the Three Gorges Dam – the world’s biggest power plant.

A year ago, water lapped almost as high as the riverbank where Wan swims. Now, the level is at the lowest for this time of year since records began in 1865, exposing swathes of sand, rock and oozing brown mud that reeks of rotting fish.

“And it keeps going down,” said Wan, who last week needed to descend almost 100 steps – usually hidden beneath the water-line – to cool off on a sweltering 40 deg C day.

Yangtze’s retreating water levels have snarled electricity generation at many key hydropower plants, sparking energy chaos across many parts of the country.

Mega cities including Shanghai are turning off lights, escalators and cutting back on air conditioning. Tesla has warned of disruptions in the supply chain for its Shanghai plant, and others such as Toyota and Contemporary Amperex Technology, the world’s top maker of batteries for electric vehicles, have shuttered factories.

Though the energy crunch is far less severe than in 2021 – when a coal shortage led to nationwide power cuts – it’s adding to challenges authorities are facing in reviving an economy already battered by frequent Covid-19 lockdowns and a property crisis.

And the timing comes months before President Xi Jinping is set to seek an unprecedented third term. China’s top officials, including Mr Xi and Premier Li Keqiang, had earlier vowed to prevent such repeats.

The southwestern province of Sichuan, enduring the region’s worst drought since the 1960s, is by far the hardest hit given its high dependence on hydropower. While dam generation plunged by half in the region, a gruelling heatwave has sent electricity demand surging by about a quarter.

That’s added pressure on an energy network that serves a population about the size of Germany and supplies to industrial hubs that are home to factories of suppliers to Tesla.

Hydropower is China’s largest source of clean energy, accounting for about 18 per cent of the country’s power generation in 2020, according to BloombergNEF. The country also has the world’s largest fleet of solar panels and wind turbines, and is super-charging investment in renewables as it tries to reduce reliance on imported fuel. Chinese firms invested US$98 billion (S$136 billion) in clean energy in the first half of 2022, more than double the amount in the same period in 2021.

Sichuan’s power shortage shows that hydropower, usually seen as the most stable renewable source, is still not as reliable as coal, according to Wei Hanyang, an analyst with BloombergNEF.

That raises questions about how smoothly China can shift away from its reliance on fossil fuels, given that wind and solar are even less stable, said Wei.