'Mega-droughts' of the past have often simultaneously hit sites that are currently home to power production along Asian rivers, says the largest study of the continent's river systems which may help predict long term changes in the region's water cycle.
The study, published in the journal Water Resources Research, noted that the findings have important implications for water management and power production, especially when a country's economy depends on multiple river basins.
"Our records show that 'mega-droughts' have hit multiple power production sites simultaneously, so we can now use this information to design a grid that is less vulnerable during extreme events," said study co-author Stefano Galelli from Singapore University of Technology and Design (SUTD).
According to the research, rivers in Asia behave in a coherent pattern, with droughts stretching as far as from the Godavari in India to the Mekong in Southeast Asia, explained study first author Nguyen Tan Thai Hung from SUTD.
As the region is home to many populous river basins which provide water, energy, and food for more than three billion people, the scientists said it is crucial to understand past climate patterns in the Asian Monsoon region in order to better predict long term changes in the water cycle and its impact on the water supply.
Following two years of analysing tree rings to reconstruct the courses of streams in the continent, the scientists produced data on 813 years (from 1200 to 2012) of annual river discharge at 62 stations in 41 rivers flowing through 16 countries, including India.
The researchers also obtained data from a previously published study of an extensive network of tree ring data sites in Asia and prehistoric drought record called the Monsoon Asia Drought Atlas (MADA).
Based on an analysis of the underlying tree ring data, the scientists extracted the most important climate signals that influence river discharge in the continent.
While earlier research had already found that droughts in Asian rivers are influenced by temperatures of the Pacific, Indian, and Atlantic Oceans, the new study revealed that this ocean-river connection is not constant over time.
According to the researchers, rivers in Asia were much less influenced by the oceans in the first half of the 20th century compared to the 50 years before, and 50 years after that period.
"This research is of great importance to policy makers -- we need to know where and why river discharge changed during the past millennium to make big decisions on water-dependent infrastructure," Galelli added.