Asia’s ‘water tower’ is in trouble, and Chinese scientists are sounding the alarm

Accelerated glacier melt on the Tibetan Plateau is threatening water quality for 2 billion people, Chinese researchers say
Scientists call for urgent joint research to determine impact on water quality from warmer temperatures

Science

Echo Xie

Published: 9:30pm, 11 Nov 2022

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Global warming is slowly turning one of the world’s most important sources of fresh water into toxic mud, but scientists say they do not yet know how bad the problem is.

The Tibetan Plateau and its surrounding mountain regions, known in environmental circles as the “Asian water tower”, is the source of Asia’s 10 major rivers, delivering water to almost 2 billion people – about a quarter of the world’s population.

But Chinese researchers have called for urgent action to improve the water quality in both the upstream and downstream areas of the region, which they believe will rapidly deteriorate as global temperatures rise.

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In an article published in the journal Nature Reviews Earth & Environment on October 11, researchers from the Chinese Academy of Sciences said climate change would accelerate glacier melt, increasing upstream flows of sediments and other contaminants that will compromise water quality downstream.

They suggest better monitoring of the problem by creating a research network based on water quality data, as well as joint actions by upstream and downstream countries to mitigate the issue.

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The Asian water tower is home to most glaciers outside the Arctic and Antarctica and is highly sensitive to climate change.

From 1979 to 2020, the average temperature in the region increased by 0.44 degrees Celsius per decade – twice the global average rate, according to a study published in the journal in June.

Most studies of the region have focused on water quantity, however water quality assessments are becoming increasingly important for local and downstream livelihoods, according to the researchers.

“The entire volume of water in the Asian water tower will increase under climate change and chemicals in the water will be carried to the downstream rivers, but not much attention has been paid to this area,” said a co-author of the study in an interview with the Post on Friday.

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According to the study, global warming has caused glacier melt and permafrost thawing in the region. As a result, sediment fluxes (the flows caused by melting) in the headwaters have increased during the past six decades.

The total sediment flux in the Asian water tower is projected to more than double by 2050 under an extreme climate change scenario, according to a study published in Science in October 2021.

Along with changes in water volume, upstream water brings chemicals, including arsenic, calcium and magnesium, to downstream rivers, according to the authors.

As a result, downstream water quality will not only be increasingly impacted by human activities and climate change, but also by the changes in upstream water quality.

The authors called for joint research from upstream and downstream countries to better understand the issue.

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“There are relatively few monitoring sites in the Tibetan Plateau region and most of them are observing the hydrology. We don’t have systemic and long-term monitoring on the water quality,” said the researcher, who requested anonymity because he was not authorised to talk to the media.

“The most important thing is to build a joint monitoring network for upstream and downstream water quality to carry out long-term observation. We also need to develop advanced earth system models to understand water quality changes in the long term.”

The study concluded: “We advocate for the creation of a research network that collects and stores basin-scale, cross-border, standardised data of surface and groundwater quality, glacier run-off geochemistry, permafrost degradation, and pollutant release.”

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