How climate change is driving water scarcity in Asia

Brussels, Aug 26: By the middle of this century, the entire Tibetan Plateau, also known as the "Water Tower" of Asia, will lose a substantial part of its water storage, a study has revealed. The study is the most comprehensive research on the issue to date, and was published in the Natural Climate Change journal.

The Amu Darya basin — which supplies water to central Asia and Afghanistan — shows a decline of 119% in water-supply capacity. The Indus basin — which supplies water to northern India and Pakistan — shows a 79% decline in water-supply capacity. Combined together, this impacts a quarter of the world's human population.

A team of scientists from Penn State, Tsinghua University and the University of Texas at Austin found that climate change in recent decades has led to a severe depletion in terrestrial water storage (TWS), which includes all of the above- and below-ground water, to the tune of 15.8 gigatons per year in certain areas of the Tibetan Plateau.

Based on this pattern, the team has predicted that under a moderate carbon emissions scenario — SSP 2-4.5 emissions, the entire Tibetan Plateau could experience a net loss of about 230 gigatons by the mid-21st century.

"The prognosis is not good," said Michael Mann, professor of atmospheric science at Penn State University.

"In a 'business as usual' scenario, where we fail to meaningfully curtail fossil fuel burning in the decades ahead, we can expect a near collapse — that is, nearly 100% loss — of water availability to downstream regions of the Tibetan Plateau. I was surprised at just how large the predicted decrease is, even under a scenario of modest climate policy," Mann told DW.

Sensitivity to climate change

The Tibetan Plateau's unique high-elevation terrain and atmospheric circulation dominated by monsoons and upper-level westerly winds generate precious freshwater resources in this region. While the area is relatively undisturbed by human activities, it remains an important regulator of the Asian monsoon system. Despite its crucial role in water availability and supply, the region is highly sensitive to climate change.

"Terrestrial water storage across this region is crucial in determining water availability, and it is highly sensitive to climate change," said Di Long, associate professor of hydrologic engineering at Tsinghua University.

The study's findings are particularly important because a detailed look at how climate change has affected the TWS of the Tibetan Plateau had not been conducted before. However, advances in Gravity Recovery and Climate Experiment (GRACE) satellite missions have provided unprecedented opportunities to quantify TWS changes on a large scale.

'Need for bold climate policy'

Earlier, the absence of reliable future projections of TWS limited guidance on policymaking over the climate change hotspot.

"By examining the interactions between climate change and the TWS, this study serves as a basis to guide future research and the management by governments and institutions of improved adaptation strategies," said researcher Di Long.

The Tibetan Plateau is sometimes called "the roof of the world" and it contains a rich network of streams and rivers that supply drinking water to a large portion of Asia.

"Even in a best-case scenario, further losses are likely unavoidable, which will require substantial adaptation to decreasing water resources in this vulnerable, highly populated region of the world," said Mann.

Seven river basin systems were studied in the research, supported by the National Natural Science Foundation of China and the Second Tibetan Plateau Scientific Expedition and Research Program.

The Amu Darya basin, Indus, Ganges–Brahmaputra, Salween–Mekong, Yangtze and Yellow rivers were selected for this analysis because of large populations and water demand in the downstream areas. It was found that in the Ganges–Brahmaputra, Salween–Mekong and Yangtze basins, total water demand in the downstream areas can be met by other factors.

However, in the Amu Darya and Indus basins, the changes in the upstream TWS will seriously threaten downstream water availability.

Geopolitical conflicts facilitate crisis

The issue of dam construction over shared water resources, aggravated by climate change, could result in potential conflicts between the countries. Although the latest study informs about the climate-induced water crisis in West and South Asian countries, several studies in the past have documented the impacts of dam building on rivers originating from the Tibetan Plateau.

The Mekong also springs up from the Tibetan Plateau and flows to the South China Sea through Myanmar, Thailand, Laos, Cambodia, and Vietnam. Around 60 million people depend on the river for fishing, farming and transportation. Hundreds of hydropower dams have been built up and down the river since 2010, and most of them are in China and Laos.

"China's eleven-dam cascade blocks half of the sediment flow in the Mekong — half of the 165 million tons of sediment per year. There is no mitigation that can allow the sediment to flow forward," said Bryan Eyler, Southeast Asia Program Director at the Stimson Center.

"The dam construction on the main stream of the Mekong has been done without any consultation with the downstream countries. Downstream countries don't even know when a new dam has been constructed," Eyler told DW.

A 2020 study from the Lower Mekong Initiative, which used river gauge evidence from the Mekong River Commission and the remote sensing process, suggests that for five months in 2019, China's dams held so much water that they entirely prevented the annual monsoon-driven rise in river level at Chiang Saen in Thailand.

The water shortages could result in geopolitical conflicts. "We fear there will be a full-scale issue in the coming years between India and China with glaciers melting in the Tibetan plateau. Tibet's geography and ecological importance should be understood by India and China both," said Tenzin Lekshey, spokesperson for the Central Tibetan Administration, the Tibetan government-in-exile in India led by the Dalai Lama.

Water could fast emerge as a potential flashpoint between India and China, two of the world's most populous countries. But it has far-reaching consequences for the entire continent.

Source: DW