More plateau runoff may not quench downstream thirsts

As Earth's climate grows warmer, increased river runoff on the Qinghai-Tibet Plateau is releasing more fresh water, but it may not quench the growing thirst of millions downstream, according to Chinese research published last week.

Home to the headwaters of more than 10 major Asian rivers, the plateau－known as the roof of the world－has become warmer and wetter due to global climate change. However, an article published on Tuesday in the scientific journal Nature Climate Change said the additional river runoff due to both increased rainfall and melting glaciers may not meet rising water demands from growing populations in South Asia's Indus and Ganges basins.

"A large proportion of the population, which is highly dependent on upstream water resources for their livelihoods, will continue to experience severe water stress even with a wetter climate," said Wang Tao, lead author of the study and a professor at the Chinese Academy of Sciences' Institute of Tibetan Plateau Research.

Previous studies have suggested that if temperatures increase by 2 C globally, the plateau could see temperatures rise by as much as 4 C in coming decades.

To find out how that would affect water supply, Wang's team, using models for estimated rainfall and glacial melt contributions, found the runoff of seven rivers on the plateau would increase by between 1 percent to 7.2 percent by the end of the century.

Although the increased river runoff will provide more water, it will not be able to fully relieve water stress downstream, the study said.

In the next eight decades, a declining population in China, together with more runoff generated from the upper Yangtze and Yellow rivers, will increase per capita water consumption and greatly relieve water stress in those river basins. However, a population surge of over 130 million in the Indus and Ganges basins, where people are highly dependent on upstream water resources, will offset the positive impacts of increased river runoff, aggravating the risk of water shortages.

Wang said demographic data used in the study came from reports by the United Nations Intergovernmental Panel on Climate Change.

The study also stressed the need for policies promoting adaptation in the region.

"We recommend measures such as increasing crop use efficiency and dam regulations in these basins to secure future water, food security and environmental sustainability," said co-author Yao Tandong, also the chief scientist on China's second comprehensive scientific expedition to the plateau and head of Third Pole Environment, an international science program on the region.

Xinhua