原文網址：https://www.sutd.edu.sg/Research/Research-News/2020/12/Largest-study-Asia-rivers-unearths-800-years
在評估未來的氣候變遷，並且為水資源管理下定更明智的決策時，這項由新加坡科技設計大學進行的研究將會相當重要。
16個國家，41條河川，62個測站，以及從西元1200年至2012年，總共813年的年度流量，這是新加坡科技設計大學的研究人員耗時兩年得出的數據，目的是要詳加了解亞洲季風區過往的氣候模式。
亞洲季風區擁有許多人口密集的河川流域，包括世界上最大的其中十條河川在內，它為三十多億人提供了水、能量以及食物。因為如此，了解此區過往的氣候模式對我們來說相當重要，這樣才能更加準確地預測水循環的長期變化，以及這些變化對供水造成的影響。
為了重建河川流量的歷史變化，研究人員運用了樹輪的數據。先前Cook等人在2010年發表的研究把亞洲各地的樹輪數據連結起來，創造出一份古代乾旱紀錄，稱為「季風亞洲乾旱年鑑」(Monsoon
Asia Drought Atlas ，MADA)。新加坡科技設計大學的研究人員將MADA輸入他們的河川流量模型當中，接著運用他們研發的新程序來根據水文氣候條件的相似程度，針對各條河川選擇MADA中最有關聯的子集。這道過程讓模型可以從原始的樹輪數據當中，揀選出對河川流量影響最大的氣候因子。
新加坡科技設計大學的博士生Nguyen
Tan Thai Hung是第一作者，他解釋：「我們的結果顯示出亞洲河川的行為模式具有一致性。在相鄰或者接近的流域，大型的乾旱與嚴重的洪水期通常是同時發生。乾旱的範圍有時候大到可以從印度的哥達瓦里河延伸到東南亞的湄公河。這項結果對於水資源管理來說具有重大意義，特別是像泰國這種經濟仰賴多條河川的國家。」
科學家從現代的測量數據已經知道亞洲河川的行為會受到海洋影響。比方說，如果熱帶地區的太平洋因為聖嬰事件而溫度升高，便會改變大氣環流，使得南亞和東南亞的河川可能出現乾旱。然而，新加坡科技設計大學的研究結果卻顯示海洋和河川的關係並非任何時候都一樣。研究人員發現二十世紀前半相較於之前與之後五十年，亞洲河川受到海洋的影響小了許多。
新加坡科技設計大學的副教授Stefano
Galelli是計畫主持人，他說：「研究結果對於政策制定者來說至關重要。我們需要知道過去一千年來河川流量變化的地點與原因，才能制定跟水利設施有關的重大決策。以東協電網為例，這項計畫的構想是把東協各國的水力、火力發電廠以及再生能源電廠，用一個系統互相聯結起來。我們的紀錄顯示出大乾旱曾經同時發生在數個發電廠的所在位置，因此現在我們可以利用這份資訊來設計出一種在這類極端事件發生時，不會受到太多損害的電網。」
Largest study of Asia’s rivers
unearths 800 years of paleoclimate patterns
The SUTD study will be crucial
for assessing future climatic changes and making more informed water management
decisions.
813 years of annual river discharge at 62
stations, 41 rivers in 16 countries, from 1200 to 2012. That is the data that
researchers at the Singapore University of Technology and Design (SUTD)
produced after two years of research in order to better understand past climate
patterns of the Asian Monsoon region.
Home to many populous river basins, including ten of
the world’s biggest rivers, the Asian Monsoon region provides water, energy,
and food for more than three billion people. This makes it crucial for us to
understand past climate patterns so that we can better predict long term
changes in the water cycle and the impact they will have on the water supply.
To reconstruct histories of river discharge, the
researchers relied on tree rings. An earlier study by Cook et al. (2010)
developed an extensive network of tree ring data sites in Asia and created a
paleodrought record called the Monsoon Asia Drought Atlas (MADA). SUTD
researchers used the MADA as an input for their river discharge model. They
developed an innovative procedure to select the most relevant subset of the
MADA for each river based on hydroclimatic similarity. This procedure allowed
the model to extract the most important climate signals that influence river
discharge from the underlying tree ring data.
“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. Sometimes, droughts stretched as
far as from the Godavari in India to the Mekong in Southeast Asia. This has
important implications for water management, especially when a country’s
economy depends on multiple river basins, like in the case of Thailand,”
explained first author Nguyen Tan Thai Hung, a PhD student from SUTD.
Using modern measurements, it has been known that the
behaviour of Asian rivers is influenced by the oceans. For instance, if the
Pacific Ocean becomes warmer in its tropical region in an El Niño event, this
will alter atmospheric circulations and likely cause droughts in South and
Southeast Asian rivers. However, the SUTD study revealed that this ocean-river
connection is not constant over time. The researchers found that 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. One such
example is the development of the ASEAN Power Grid, conceived to interconnect a
system of hydropower, thermoelectric, and renewable energy plants across all
ASEAN countries. 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 principal
investigator Associate Professor Stefano Galelli from SUTD.
原始論文：Hung T. T.
Nguyen, Sean W. D. Turner, Brendan M. Buckley, Stefano Galelli. Coherent
Streamflow Variability in Monsoon Asia Over the Past Eight Centuries—Links to
Oceanic Drivers. Water Resources Research, 2020; 56 (12)
DOI: 10.1029/2020WR027883
引用自：Singapore University of Technology and Design.
"Largest study of Asia's rivers unearths 800 years of paleoclimate
patterns."
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