China has the world’s largest unused profitable hydropower potential, which if developed could meet 30 per cent of China’s electricity needs, a new global assessment has found.
A team of researchers from Britain, China, Singapore, Spain, Sweden, Thailand and the United States studied data from nearly 3 million rivers around the world to determine the total amount of unused hydropower potential.
Their findings, published in the peer-reviewed journal Nature Water on Tuesday, showed China’s potential development sites lie mainly in the mountainous areas in the south – Tibet, Sichuan, Yunnan and Guizhou.
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While hydropower was a renewable and “relatively cost-effective” energy source, it “fundamentally changes the natural discharge of rivers, disturbs freshwater ecosystems and may contribute to local species extinctions”, the researchers said.
To limit potential impacts on the environment and societies, the team excluded areas considered heritage sites, biodiversity hotspots, forests, settlements of more than 50,000 people, and earthquake-prone regions from their assessment.
They found that Asia and Africa together accounted for 85 per cent of the world’s unused profitable hydropower – equivalent to 5.27 trillion kilowatt-hours per year.
Most of the Asian locations were in China, Myanmar, India, Pakistan and Nepal, while the African locations included the Democratic Republic of the Congo, Ethiopia and Zambia in Africa, where hydropower development is still in its infancy.
“Many countries in Asia and Africa also have not maximised their profitable hydropower potentials,” the team said.
“The Himalayas, Asia’s water tower, have the greatest potential [two-thirds of the global total] for hydropower expansion, and many planned reservoirs are already under construction in the region.”
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China, which leads the world with the highest amount of existing hydropower production, is home to some of the world’s largest hydroelectric dams, including the Three Gorges Dam on the Yangtze River, and the Baihetan and Xiluodu dams on the Jinsha River.
Beijing is planning to build a mega dam in Tibet’s Medog county, upstream from India, which is expected to generate more than three times the amount of electricity produced by the Three Gorges Dam.
The region is also home to one of the largest rivers in the world – the Brahmaputra, or Yarlung Tsangpo, which flows through China, India, Bhutan and Bangladesh. The scientists said cooperation between the countries must improve to better manage river flow and reduce conflicts.
In Europe, hydropower potential was “extremely exploited”, with developed hydropower strongly exceeding its full profitable potential, the researchers found.
“Considering that Europe has 1.2 million instream barriers, efforts are currently being made to remove many dams to restore river ecosystems,” the researchers said in the article.
According to the International Energy Agency, hydropower supplied one-sixth of total global electricity generated in 2020, making it the single largest source of low-carbon power.
Global hydropower capacity would need to double by 2050 to put the world on a pathway to net-zero emissions by 2050, according to a road map set out by the IEA in 2021.
Co-lead author Zeng Zhenzhong, an associate professor at the school of environmental science and engineering at Southern University of Science and Technology (SUSTech) in Shenzhen, said the new assessment showed that the IEA target was achievable.
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Zeng also said dams had a role to play in easing drought.
“China’s nationwide drought last year was very rare. Poyang Lake [the country’s largest freshwater lake] also dried up, affecting farming,” he said.
“The Three Gorges Dam released water to relieve the drought downstream, bringing up the water levels there, including Poyang Lake. It played a key role in moderating downriver. Without the dam, the drought could have been even more severe.”
The team took the middle ground by considering the benefits as well as the environmental and societal impacts of building hydropower plants, according to Xu Rongrong, another co-lead author and a research assistant professor at SUSTech.
“Some smaller reservoirs are mismanaged. They cut off the downstream water flow, damaging the ecosystem,” he said.
“In the study, we required hydropower stations to maintain environmental flows to retain habitats for freshwater animals, although it can partly reduce electricity production. It balances the need for power generation and environmental protection.”
David Dudgeon, emeritus professor of ecology and biodiversity at the University of Hong Kong, who was not involved in the study, said “environmental flow” – the annual flow of freshwater downstream from dams on which animals depend – was key for the health of those ecosystems, which depended on upstream water flows.
But Dudgeon said determining needs for the amount of water to be released was a complex process and a fixed allocation might not be effective, given different climates and the variety of animals in the world’s rivers.
“With appropriate safeguards, hydropower dams can be viable and valuable sources of energy, like in parts of Africa where there are currently few dams, especially if the spatial planning of dams ensures the connectivity of some river tributaries allowing connectivity and fish migration,” Dudgeon said.
“But in many places, new dams will be damaging to freshwater biodiversity and ecosystem services for humans, such as fisheries.
“In the Himalayas, for example, it could have limited long-term viability, particularly in view of regional geological instability, glacial melting and changes in precipitation that will take place as a result of climate disruption by humans.”
More from South China Morning Post:
- China is at the centre of Asia’s struggle for water security
- China’s coal plants consumed a city’s worth of extra water every day during summer drought, alarming climate analysts
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