Asia: 800 years of river variability revealed by tree rings

Asia: 800 years of river variability revealed by tree rings


Thanks to the analysis of tree rings, researchers from the University of Technology and Design in Singapore were able to reconstruct the fluctuations in the flow of Asian rivers over the last 8 centuries. Results published in the journal Water Resources Research that will better inform decision-making in the area of Water Management – a major challenge for South Asian countries.

The South Asian region is home to 10 of the world’s largest rivers. In this part of the globe where nearly 2 billion people depend directly on Water Resources, any decrease in river flow can have dramatic socio-economic and health impacts. Also, it appears necessary to understand how these sources fluctuate from the decadal to multisecular scale. This is in order to better inform decision-making in the field of water management. Especially in times of climate change.

Streams that fluctuate consistently

The data obtained by the researchers show how the annual flow of 41 rivers spread over 16 countries in the region fluctuated between 1200 and 2012. “Our results show that Asia’s rivers are behaving consistently. Large droughts and large rainfall periods often occurred simultaneously in adjacent or neighboring basins, ” says Nguyen Tan Thai Hung, lead author of the study. “Sometimes droughts stretched from the Godavari in India to the Mekong in Southeast Asia. This has important implications for water management, especially when the economy of a country depends on several river basins, as in the case of Thailand “.

This large-scale variability is closely related to monsoon variability. For example, when the Pacific experiences El Nino events, rainfall tends to be in deficit in South Asia. Conversely for La Nina events. However, scientists have shown that this relationship is not stationary over time. Indeed, the relationship is – for example-not visible during the first part of the 20th century. The variability of Asian rivers actually depends on multiple factors including the Pacific, but also the Atlantic and Indian Ocean. The continental surface also plays an important role because it warms up more or less quickly depending on the state of the soil – abnormally wet, dry, etc. finally, major volcanic eruptions also induce a signature on the rainfall regime.

The case of ASEAN Power Grid

“This research is of great importance to policy makers. We need to know where and why river flows have changed over the last millennium to make big decisions about water-dependent infrastructure , ” says Stefano Galelli, co-author of the paper. “One such example is the development of the ASEAN Power Grid, a network designed to interconnect a system of Hydro, thermoelectric and renewable energy plants in all countries of the Association of Southeast Asian nations. Our records show that mega-droughts have hit several power generation sites simultaneously. So we can now use this information to design a less vulnerable network during extreme events .”