In China, 1 million people are at risk from glacier-melt flooding, a disaster threat set to grow with global warming
More than 1 million people in China are at risk from glacial lake outburst floods that occur when water is suddenly released from a lake fed by a glacier melt, according to a new study.
The exposed populations live in western China throughout the mountainous regions of Xinjiang, Tibet, Qinghai, Sichuan and Yunnan, with the areas east of Xinjiang's capital, Urumqi, and Yunnan's capital, Kunming, deemed the most dangerous.
The global study by researchers in Britain and New Zealand found that across the world, 15 million people who live within 50km (31 miles) of a glacial lake could be under threat from floods, a risk that will grow amid changes to the climate.
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More than half of them are found in four countries: India, Pakistan and China - which has the largest concentration of glaciers and ice caps outside the polar regions - as well as Peru, home to a section of the Andes Mountains.
"The continued ice loss and expansion of glacial lakes due to climate change therefore represents a globally important natural hazard that requires urgent attention if future loss of life from GLOF [glacial lake outburst floods] is to be minimised," the team said in an article published in the peer-reviewed journal Nature Communications on Wednesday.
Such floods often happen with little warning when a natural dam containing a glacial lake fails. The sudden flush of water can kill people and damage property, infrastructure and farms.
China's Tibet autonomous region has had at least 27 glacial lake outbursts since the 1930s. In 1981, a flood at Cirenmaco killed 200 people and washed away the China-Nepal Friendship Bridge.
Another lake in the southeastern Qinghai-Tibetan Plateau, Jiwenco, failed in June 2020, destroying buildings, roads, bridges and farmlands along the flow path.
Author Tom Robinson, a senior lecturer at the University of Canterbury in New Zealand who researches disaster risk and resilience, said people exposed to GLOFs in China were likely to be highly vulnerable to the effects of flooding because the regions were remote and rural.
The team's analysis found that four glacial basins in China were among the 50 most dangerous in the world.
"As well as the Heihe River basin [the second largest inland river basin in northwestern China] and Jinsha River basin [in the upper stretches of the Yangtze River], several of the river basins close to Urumqi appear to be particularly dangerous," Robinson said.
He said climate change could cause lakes that are not of concern now to become worrying in the future, while new and potentially dangerous lakes might form.
"As the climate continues to warm, glacier retreat will form larger and more numerous lakes," he said. "At the same time, lakes are likely to become more exposed to GLOF 'triggers', such as a large landslide or ice avalanche entering the lake, displacing water and causing the natural dam that impounds the lake to fail."
He said limiting climate change and keeping global warming under 1.5 degrees Celsius compared with pre-industrial levels would be key to helping slow the growth of glacial lakes.
But a certain amount of ice loss was already "locked in", meaning even "if we stopped all emissions today, GLOF hazard will continue to increase for several decades", he said.
Early warning systems could help communities far downstream evacuate but they are not as effective for people living within 5km to 10km of glacial lakes who would not be given enough time to flee to safety before the flood arrives.
For people living in high-risk areas, Robinson said governments could "try to encourage them to live on the edges of the valleys where they are less likely to be impacted and can more easily evacuate if required", while reserving areas close to the river for agriculture only.
Installing sluice gates to manually lower lake levels and control the flow of water was also a possible solution, but the gates would be expensive to build and maintain, he said.
"None of these options will work on their own, and what is appropriate and works in one location may not work in another, so it's really now about looking at the local-level and finding the appropriate measures for the threatened populations," Robinson said.
This article originally appeared on the South China Morning Post (SCMP).
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