‘Asian water tower’ is facing a worsening supply imbalance, study finds
- Caused by global warming and atmospheric circulation changes, it could lead to disputes between nations downstream of the Third Pole
- The region – including the Tibetan Plateau and surrounding Hindu Kush Himalayan mountain ranges – delivers water to almost 2 billion people
Global warming and atmospheric circulation changes will worsen water stress in nations downstream of the Third Pole – including India, Bangladesh and Nepal – where about 90 per cent of water is used for irrigation, according to a new study.
It said more demand for water and a worsening imbalance in water resources in the region could increase the potential for disputes and conflict between countries that share transboundary river basins.
The team, led by researchers from the Chinese Academy of Sciences, called for more cooperation among those nations to develop new water use strategies.
The Third Pole – which includes the Tibetan Plateau and the surrounding Hindu Kush Himalayan mountain ranges – has the most glaciers outside the Arctic and Antarctica and is known as the “Asian water tower”.
The region is the source of the 10 major rivers in Asia and delivers water to almost 2 billion people – about a quarter of the world’s population.
“Therefore, it is a global hotspot for investigating how climate change and socio-economic change conspire and change water supply and demand in the future,” said Walter Immerzeel, study co-author and a professor at Utrecht University in the Netherlands.
The researchers found that the annual temperature over the Third Pole increased by 0.44 degrees Celsius per decade from 1979 to 2020 – twice the global average rate.
Moreover, despite a slight overall increase in annual precipitation in the region, there was a clear imbalance between the region’s northern and southern areas.
According to the study, significant increases in precipitation were observed in the basins to the north of the region – including the Salween, Mekong, Yangtze and Yellow river basins.
However, the exorheic basins of the Asian water tower – including the Brahmaputra, Ganges and Indus river basins that ultimately run into the ocean – saw a significant decrease in annual precipitation from 1980 to 2018.
The researchers said the precipitation change was caused by two atmospheric circulation patterns – the strengthening of westerlies and a weakening Indian monsoon – as well as rapid temperature warming.
The imbalance in the Third Pole is also reflected in its glaciers, lakes and rivers, according to the study.
It said the northern endorheic basins – which do not flow to other external bodies of water – saw lower losses of solid water like snow and glaciers as a result of the westerlies. They saw larger gains in liquid water such as lakes and rivers.
But the southern exorheic basins had substantial losses of solid water and smaller gains in liquid water.
The study said considerable glacier mass loss had been observed in the monsoon-influenced Himalayan ranges in the south. But glaciers remained stable or even expanded in regions dominated by westerlies, including parts of China’s Pamir and Kunlun mountains, where precipitation had increased.
Climate change is expected to worsen the imbalance between solid and liquid water states in the region in the future, according to the researchers.
If that situation continues – and as demand for water in the region grows – water stress in the downstream countries is also expected to rise.
“This imbalance is expected to pose a great challenge to the supply-demand balance of water resources in downstream regions,” Yao Tandong, lead author of the study and a researcher with the Chinese Academy of Sciences, said in a statement.
Immerzeel from Utrecht University said changes could add to tensions in an “already sensitive geopolitical situation”.
“Water diplomacy and new agreements that account for changes in seasonal water availability would help this process,” he said.
Lonnie Thompson, another study co-author and distinguished university professor at The Ohio State University, said part of the process of adapting to the consequences of climate change involved water conservation at regional or local levels.
“A key component of adaptation and preparation for future challenges is education,” he said. “International communication and discussions are most important for reducing the risk of future disputes as we all must deal with unprecedented, global-scale climatic and environmental changes.”