NEW DELHI: An irreversible decline in freshwater storage projected in parts of Asia due to climate change could impact 2 billion people living downstream of the Tibetan Plateau as it could pose a serious threat to water supplies to India, Afghanistan, and Pakistan by mid-century, according to the satellite-based assessment of water changes in Tibetan Plateau.
Terrestrial water storage over the Tibetan Plateau, a major global water tower, is crucial in determining water transport and availability to a large downstream Asian population. The assessment over the last two decades (2002-2020) and projection for 2021-2060 are based on measurements of water mass in glaciers, lakes, and below-ground sources, combined with machine-learning techniques to provide a benchmark of observed TWS (Terrestrial Water storage) changes, reflecting competing effects of glacier retreat, lake expansion, and subsurface water loss.
Research led by scientists at Penn State, Tsinghua University, and the University of Texas at Austin projects that climate change, under a scenario of weak climate policy, will cause irreversible declines in freshwater storage in the region, constituting a serious threat to the water supply for central Asia, Afghanistan, Northern India, Kashmir, and Pakistan by the middle of the century.
“In a business as usual scenario, where we fail to meaningfully curtail fossil fuel burning in the decades ahead, we can expect a substantial — 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,” said Michael Mann, distinguished professor of atmospheric science at Penn State. The research is published in the journal Nature Climate Change.
According to the researchers, despite its importance, the impacts of climate change on past and future terrestrial water storage (TWS) — which includes all the above- and below-ground water — in the Tibetan Plateau have largely been underexplored.
The team found that climate change in recent decades has led to a severe depletion in TWS (-15.8 gigatons/year) in certain areas of the Tibetan Plateau and substantial increases in TWS (5.6 gigatons/year) in others, likely due to the competing effects of glacier retreat, degradation of seasonally frozen ground, and lake expansion.
The team’s projections for future TWS under a moderate carbon emissions scenario — specifically, the mid-range emissions scenario — suggest that the entire Tibetan Plateau could experience a net loss of about 230 gigatons by the mid-21st century (2031 to 2060) relative to an early 21st century (2002 to 2030) baseline.
More specifically, excess water loss projections for the Amu Darya basin — which supplies water to central Asia and Afghanistan — and the Indus basin — which supplies water to Northern India, Kashmir, and Pakistan — indicate a decline of 119 per cent and 79 per cent in water-supply capacity, respectively.