Revealing Eight Centuries of Asia’s River Patterns

In the largest study of Asia’s rivers to date, researchers tracked eight centuries worth of annual river discharge to unearth insights on past climate patterns.

AsianScientist (Feb. 2, 2021) – After two intense years of research, a team from Singapore has tracked 813 years of annual river discharge from 62 stations at 41 rivers across 16 countries in Asia. Their findings, representing the largest study yet of Asia’s rivers, were published in Water Resources Research.

Home to ten of the world’s biggest rivers, the Asian monsoon region provides water, energy and food for over three billion people. But as South Asia’s great glaciers shrink due to climate change, the region as a whole now faces a looming water crisis. To better predict potential changes in the water cycle and their impact on the water supply, it is crucial to understand past climate patterns.

Interestingly, researchers often rely on indirect measures like tree rings to reconstruct histories of river discharge. This is because tree growth is often driven by the same climate-related factors as river discharge, including precipitation and evapotranspiration. Previously, scientists from National Taiwan University and Columbia University had assembled an extensive network of tree ring data sites in Asia called the Monsoon Asia Drought Atlas (MADA).

Using MADA as the basis of their river discharge model, researchers from the Singapore University of Technology and Design (SUTD) selected the most relevant MADA subset for 41 major river basins in Asia. By doing so, their model managed to extract important climate signals influencing river discharge from the tree ring data across over 800 years—from 1200 to 2012.

A map of the Asian Monsoon region, with the river basins involved in this study highlighted. Rivers considered as past of the world’s 30 biggest have names indicated in blue. Photo credit: Singapore University of Technology and Design.

“Our results reveal that rivers in Asia behave in a coherent pattern. Large droughts and major pluvial periods have often occurred simultaneously in adjacent or nearby basins,” explained first author Mr. Nguyen Tan Thai Hung. “Sometimes, droughts stretched as far as from the Godavari in India to the Mekong in Southeast Asia.”

Their study also revealed that contrary to popular belief, the oceans have not always influenced the behavior of Asian rivers. Nowadays, when El Niño warms the Pacific Ocean in the tropical regions, the altered atmospheric circulation makes droughts more likely in South and Southeast Asian rivers. However, the SUTD team found that rivers in Asia were much less influenced by the oceans in the first half of the 20th century compared to 50 years before and 50 years after.

The team’s research ultimately holds great importance for policymakers across the region. For instance, currently in development is the ASEAN Power Grid, an interconnected system of hydropower, thermoelectric and renewable energy plants across all ASEAN countries.

According to principal investigator Associate Professor Stefano Galelli, their records show that mega-droughts have previously hit multiple power production sites at the same time. Armed with this information, researchers and policymakers can now design grids that are less vulnerable during extreme events.

“We need to know where and why river discharge changed during the past millennium to make big decisions on water-dependent infrastructure,” concluded Galelli.

The article can be found at: Nguyen et al. (2020) Coherent Streamflow Variability in Monsoon Asia Over the Past Eight Centuries—Links to Oceanic Drivers.


Source: Singapore University of Technology and Design; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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