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Chinese dams withhold water, worsen 2019 drought in Mekong Delta: researchers

Chinese dams withhold water, worsen 2019 drought in Mekong Delta: researchers

Saturday, May 30, 2020, 08:08 GMT+7
Chinese dams withhold water, worsen 2019 drought in Mekong Delta: researchers
Alan Basist, director of Eyes on Earth, Inc., is seen in a supplied photo.

A new study by Alan Basist, director of Eyes on Earth, Inc., and Claude Williams from Global Environmental Satellite Applications, Inc. is drawing serious attention for its firm conclusion: the severe lack of water in the Lower Mekong during the 2019 rainy season was largely influenced by the restriction of water by dams on the Lancang River, as the Mekong is known in China.

Using satellite data from 1992 to 2019 and the river gauge at Chiang Sean, Thailand, the researchers developed a model to better understand the operation of dams in China, data which the country has never willingly disclosed.

Tuoi Tre News interviewed Basist, the study’s lead author, and Brian Eyler, director of Stimson’s Southeast Asia program, about the implications of the findings.

Can you tell us about the start of your research?

Alan Basist: We came up with the idea of doing a research project on monitoring the amount of water that comes out of the upper basin using the Chiang Sean gate station at the Thailand entrance of the Golden Triangle.

Our model was extremely accurate and it became evident that the satellite was beginning to predict a natural flow in 2019 that was fairly normal or slightly greater than normal.

We found that there was clearly a substantial amount of water missing based upon the wetness index and our model of how much water should have been flowing from the upper basin.

We couldn’t help but wonder, “Where’s the water?”

The whole purpose of our technology and applying it in this situation is to promote transparency about how much water is in the basin.

If countries can determine the basin’s baseline water flow, they can have a more honest discussion as to how the water should be distributed so that the river can be shared.  

As researchers, we try not to be involved in policy or politics. We only wanted to understand the scientific integrity of the data, and how the data can be used to promote transparency and equitable distribution of water resources among the countries that share a river basin.

The Mekong River Commission had issued a commentary note on your research. Do you agree with them?

Alan Basist: The Mekong River Commission encouraged us to do this study at the very beginning. They provided us with the data.

In December 2019, when I presented the results of our findings through March 2019 and demonstrated how successful our model was in Hanoi, a representative from the Mekong River Commission came up to me and asked if I could extend the study to include the 2019 drought.

I was a little surprised about their criticism because I thought we were in agreement with the study. Some of their criticisms are very real.

I mean, I could have referenced some more of the Mekong River Commission's work, more of the history, more of the previous studies.

When I said that the drought was largely impacted by the flow from the Upper Mekong, I could have stated more clearly that the major cause of the drought was the dryness in Thailand.

However, the lack of water coming from the Upper Mekong only compounded the drought. It wasn't the original cause of the drought.

Yes, I could have said that more clearly in our report. I also could have explained more clearly what exactly the wetness index is and how sophisticated it is for monitoring all the different sources of liquid water in the basin.

It's a very effective way to model. It may be a simple model, but it's only a simple model because the variables are very complicated. It’s a quadratic relationship.

Their criticism was that the model was too simple. I don't think they understood that it was the same quadratic formula that they used in their model.

I still want to continue to work with the Mekong River Commission and see their criticism as an opportunity to improve our report.

At the same time, the findings in the report are very good and I stand behind them.

This study focused on a particular time during the severe drought year and it showed the damaging impacts. What would the impact of Chinese dams on the Mekong Delta be on Vietnam during a normal year?

Brian Eyler: Regardless of the year, China's upstream dams have an impact on the Mekong Delta.

Their biggest collective impact is of sediment removal from the Mekong system because 60 percent of the sediment in the Mekong’s mainstream should come from China.

Sediment is critically important for agricultural production in the Mekong Delta as floods and some irrigation projects will distribute sediment across the delta during the monsoon season.

Sediment is also critical for making the delta resilient against the threat of climate change.

When sediment is missing and unevenly distributed across the delta floodplain, the delta becomes geologically weakened and more susceptible to erosion and falling into the ocean, especially during times of severe storms and encroaching sea level rise.

China’s dams have removed more than half of the sediment from the Mekong mainstream.

Brian Eyler, director of Stimson’s Southeast Asia program, is seen in a supplied photo.
Brian Eyler, director of Stimson’s Southeast Asia program, is seen in a supplied photo.

China may restrict flow through its dam system, but do you know what happens to that water? Where does it wind up?

Brian Eyler: China’s water restrictions most likely keep its reservoirs full. Five dams have been built over the past five years in the Upper Mekong, all with large reservoirs, and water likely stays in those areas.

China's Mekong dams are not commonly used for hydropower production. If hydropower is not being generated, then most of the water simply is not used, it is stored for future use.

Those upstream dams act like banks that allow China to save water for the future at the expense of downstream countries.

China has been releasing more water on average during the dry season which raises the level of the river on average during the dry season, but river gauges in the Mekong Delta suggest that water doesn’t make it to Vietnam.

I see no evidence of China diverting water from the Mekong into other river basins in China.

To date, doing this is technically impossible, but this is not to say those impossibilities cannot be overcome in the future as water resource allocations in China deplete year on year.

Can water be used as a ‘weapon’ to control the Lower Mekong region, such as limiting the flow of water in the drought season and releasing excessive amounts in years with heavy floods?

Brian Eyler: Until this report came out, I would have answered the question of “can water be used as a ‘weapon’ to control the Lower Mekong region?” with “no,”  but scientific evidence has since changed my mind.

Last year, China held so much water back during the monsoon season, which was unseasonably dry, that it broke the mainstream monsoon rise of the river.

Whether China did this on purpose as a kind of weapon remains to be explained.

I have my doubts and believe the action to be a function of poor communication or a lack of coordination between dam operators and Beijing, but those actions reveal that China’s restrictions have the power to cut deeply into the viability of the Mekong mainstream.

Also, the report identifies sudden releases of water that are related to new dams coming online.

Again, the downstream consequences of these sudden releases were probably not premeditated in China, but the consequences surely felt like weapons to the communities in northern Thailand and Laos whose livelihoods were damaged by these sudden releases.

Numerous times their fields were suddenly flooded and tractors and livestock swept away into the river by unexpected flooding caused by sudden, unannounced releases.

In the Mekong, the impoverished farmer or fisher is always impacted both first and worst.

Chinese dams could complicate tricky discussions between China and other Mekong countries. How can the governments of the involved countries, as well as concerned parties, discuss this issue and push for greater transparency and cooperation from China?

Brian Eyler: Eyes on Earth's methods can be easily replicated at a relatively low cost. This means an alternative form of transparency over what is happening on the Mekong upstream has appeared.

If local stakeholders, whether they be governmental or non-governmental, adopt these methods or press for near-real time reporting from Eyes on Earth or another research institution, then these findings could become commonly held knowledge and used for the betterment of the Mekong at large.

The MRC should take these methods and findings and determine their value, both to monitoring the Mekong and with its discussions with China's Lancang Mekong Cooperation Mechanism.

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Hong Van / Tuoi Tre News


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