China dams held back Mekong waters during drought: US study

BANGKOK • China's Mekong River dams held back large amounts of water during a damaging drought in downstream countries last year despite China having higher-than-average water levels upstream, said a United States research company.

The Chinese government has disputed the findings, saying there was low rainfall during last year's monsoon season on its portion of the 4,350km river.

The findings by Eyes on Earth, a research and consulting company specialising in water, published in a US-government funded study, could complicate tricky discussions between China and other Mekong countries on how to manage the river that supports 60 million people as it flows past Laos, Myanmar, Thailand and through Cambodia and Vietnam.

Last year's drought, which saw the Lower Mekong at its lowest levels in more than 50 years, devastated farmers and fishermen and saw the massive river recede to expose sandbanks along some stretches while turning from its usual murky brown to bright blue in some other parts because the waters were so shallow.

"If the Chinese are stating that they were not contributing to the drought, the data does not support that position," said Mr Alan Basist, a meteorologist and president of Eyes on Earth, which conducted the study with funding from the US State Department's Lower Mekong Initiative.

Instead, satellite measurements of "surface wetness" in China's Yunnan province, through which the Upper Mekong flows, suggest that the region actually had slightly above-average combined rainfall and snowmelt during the May to October wet season last year.

But water levels measured downstream from China along the Thai-Lao border were at times up to 3m lower than they should have been, the group said in the study.

That suggests China is "not letting the water out during the wet season, even when the restriction of water from China has a severe impact of the drought experienced downstream", Mr Basist said.

The effect of China's 11 dams on the upper Mekong has long been debated, but data has been scarce because China does not release detailed records of how much water the dams are using to fill their reservoirs, which Eyes on Earth says have a combined capacity of more than 47 billion cu m.

China - which has no formal water treaties with the lower Mekong countries - promised to cooperate on management of the river and also to investigate the causes of last year's record drought.

Dismissing the findings, China's Ministry of Foreign Affairs said in a statement to Reuters, referring to the river by its Chinese name: "The explanation that China's dam building on the Lancang River is causing downstream droughts is unreasonable."

The ministry said Yunnan province saw serious drought last year and reservoir volumes at China's dams on the river fell to their historically lowest levels.

"Despite this, China has continued to do its utmost to guarantee reasonable discharge volumes" to countries downstream, it said.


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A version of this article appeared in the print edition of The Straits Times on April 14, 2020, with the headline China dams held back Mekong waters during drought: US study. Subscribe