In the largest study of Asian rivers, 800 years of paleoclimate patterns were shown in

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The study by the University of Technology and Design of Singapore will be critical for assessing future climate change and making more informed decisions on water management.

813 years of annual discharge of rivers at 62 stations, 41 rivers in 16 countries, between 1200 and 2012.

This is the data researchers at the University of Technology and Design of Singapore (SUTD) produced to better understand past climate patterns of the Asian monsoon region after two years of research.

The Asian monsoon region is home to many populous river basins, including ten of the largest rivers in the world (Figure 1), and provides more than three billion people with water, energy, and food.

Therefore, in order to better predict long-term changes in the hydrological cycle and their impacts on water supply, it is critical for us to understand past climate patterns.

The researchers relied upon tree rings to reconstruct the history of river discharge.

Cook et al. (2010) developed an extensive network of tree-ring information in Asia in an earlier study and created a paleodrought dataset called the Monsoon Asia Drought Atlas (MADA). The MADA was used by the SUTD researchers as an input to their river runoff model.

They developed an innovative procedure based on hydroclimatic similarity to select the most relevant subset of the MADA for each river.

This procedure enabled the model to extract from the underlying tree-ring data the most relevant climate signals affecting river discharge.

Our findings show that rivers in Asia behave according to a coherent pattern. In adjacent or nearby catchments, large droughts and large pluvial periods often occurred simultaneously. Droughts sometimes even extended from the Godavari in India to the Mekong in Southeast Asia (Figure 2).

This has important implications for water management, particularly when the economy of a country, as in the case of Thailand, relies on multiple river basins,” explains first author Nguyen Tan Thai Hung, a PhD student at SUTD.

It is known, through modern measurements, that the behavior of Asian rivers is affected by the oceans.

For instance, when the Pacific Ocean warms during an El Niño event in its tropical region, it alters atmospheric circulation and is likely to cause droughts in the rivers of South and Southeast Asia. The SUTD study, however, showed that this connection is not constant over time between the ocean and rivers.

The researchers found that in the first half of the 20th century, rivers in Asia were much less affected by the oceans than in the 50 years before and the 50 years after. This research is of great importance to policymakers; in order to make important decisions about water-dependent infrastructure, we need to know where and why river discharge has changed over the last millennium. One such example is the development of the ASEAN Power Grid, which aims to interconnect a system across ASEAN of hydropower, thermoelectric, and renewable energy facilities.

T. Nguyen and Sean W.

D.

Oh, Turner, Brendan M.

Buckley, and Stefano Galelli, Water Resources Research.DOI: 10.1029/2020WR027883, September 26, 2020.
Acknowledgments: The President’s Graduate Fellowship of the University of Technology and Design of Singapore supports Hung Nguyen.

For their insightful comments, we are grateful to Edward Cook, Caroline Ummenhofer, Nerilie Abram, Nathalie Goodkin, Xun Sun, Murray Peel, Rory Nathan, and Robert Wasson.

For their constructive reviews, we thank Michelle Ho, Justin Maxwell, Valerie Trouet, two anonymous reviewers, and the Associate Editor.

We would like to thank Thanh Dang, Mukund Rao, Christoph Libisch-Lehner, Rosanne D’Arrigo, Donghoon Lee, and Caroline Leland for the Mekong, Brahmaputra, Angat, Citarum, Han, and Yeruu river river data.

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