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How China Turned Off the Tap on the Mekong River

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For three decades, China has been building dams on the upper Basin of the Mekong River, worrying countries downstream that China could one day turn off the tap. New data shows that for six months in 2019, while China received uncommonly high levels of precipitation, its dams held back more water than ever — even as downstream countries suffered through an unprecedented drought. These new findings confirm what many had long suspected: China is impounding much more water than it ever has before and is causing erratic and devastating changes in water levels down stream.

BY Brian Eyler Lead Author · Regan Kwan Data Visualization · Courtney Weatherby Co-author

What We Know

  • New data shows that during a severe drought in the lower Mekong Basin in 2019, China’s upper basin enjoyed high rainfall and snowmelt and China’s upstream dams restricted nearly all of the record rainfall and snowmelt from the downstream. If China’s dams did not restrict flow, portions of the Mekong along the Thai-Lao border would have experienced above average flows from April 2019 to the present instead of suffering through severe drought conditions.
  • This is part of a long pattern that has driven numerous droughts. The increasing frequency of drought in the Lower Basin tracks closely to the way China restricts water upstream during the dry season.
  • China is impounding much more water than it ever has in the past. After the completion of the Nuozhadu dam in 2012, China’s dams collectively impounded considerably more water than the previous 20 year period and also began restricting much more water than they released.
  • China’s dam management is causing erratic and devastating changes in water levels down stream. Sudden unexpected flood events downstream can now be linked to the completion of the Dachaoshan dam and the Nuozhadu dam in 2002 and 2012-2014. Unexpected dam releases caused rapid rises in river level that have devastated communities downstream, causing millions in damage shocking the river’s ecological processes.

For six months in 2019, China's dams held back so much water that they entirely prevented the annual monsoon-driven rise in river level at Chiang Saen, Thailand. This has not happened since modern records have been kept.

Confirming China’s Dams Drive Mekong Drought

From April to September 2019, China’s portion of the upper Mekong received uncommonly high levels of precipitation, yet its dams blocked or restricted more water than ever before - even as downstream countries suffered through an unprecedented drought.

In the 1990s when China built the first dam on the upper Mekong, many speculated that China could use its dams to restrict water from the Mekong downstream, effectively turning off the tap for the countries which rely on the Mekong’s provisions for economic stability and security. Today a total of eleven mega-dams dot China’s upper Mekong reaches and collectively store as much water as the Chesapeake Bay. The frequency and severity of downstream drought has increased over the last two decades, and Thailand, Cambodia, and Vietnam are currently suffering through the worst drought in history.

A new study from Eyes on Earth uses physical river gauge evidence from the Mekong River Commission and remote sensing processes to definitively confirm long held-concerns that the ongoing drought is the result of Chinese water management policy. The Eyes on Earth study shows when China has restricted water from its downstream neighbors, for how long it has restricted this water, and the enormous quantity of water China has restricted over the last three decades.

The report’s most significant finding is that from April to November 2019 China’s portion of the upper Mekong received uncommonly high levels of precipitation, yet its dams blocked or restricted more water than ever as downstream countries suffered through an unprecedented drought. The amount of rainfall and snowmelt in China was enough to keep water levels in much of the Lower Mekong above average between April 2019 and March 2020 if China’s dams were not restricting that water.

Now that these findings are available and can be reported in near-real time, it is incumbent upon stakeholders in Lower Mekong countries to pursue changes to the way China’s upstream dams are operated and negotiate for a more equitable distribution of water resources. Working through the Mekong River Commission, a transboundary river basin organization established by the 1995 Mekong Agreement, to achieve these ends is a best path forward.

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