As Earth's climate continues to grow warmer, increased river runoff in the Qinghai-Tibet Plateau, known as the roof of the world, has provided more fresh water, but may not quench the growing thirst of millions downstream.
Home to headwaters of over 10 major Asian rivers, the plateau has become warmer and wetter under the impact of global climate change. However, an article published Tuesday in the scientific journal Nature Climate Change says that the more river runoff brought on by both increased rainfall and glacier melting may not meet rising water demands from the growing population in regions of the Indus and the Ganges.
"A large proportion of the population living 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 Institute of Tibetan Plateau Research, Chinese Academy of Sciences.
Previous studies have suggested that if temperatures increase 2 degrees Celsius globally as indicated by the Paris Conference on Climate Change in 2015, the plateau could see a temperature hike as high as 4 degrees Celsius in coming decades.
To find out how the water supply would change under such a scenario, Wang's team, using earth system models for estimated rainfalls and glacier melting contributions, quantified the runoff of seven rivers on the plateau and found it would increase 1 percent to 7.2 percent by the end of the 21st century.
Although the increased river runoff will provide more water, it is not able to fully relieve the downstream water stress, the study said.
In next eight decades, the future population decline, together with more runoff generated from the upper Yangtze and Yellow Rivers, will increase per capita water consumption and greatly relieve local water stress, while a population surge of over 130 million in the areas of Indus and Ganges basins with their populations highly dependent on upstream water resources will offset the positive impacts of increased river runoff, aggravating the risk of water shortage.
Demographic data used in the study comes from reports by the United Nations Intergovernmental Panel on Climate Change, according to Wang.
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 lead of the Third Pole Environment, an international science program of the region.