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Vietnam Today

Land subsidence in Mekong Delta a serious concern

Released at: 17:35, 02/06/2017

Land subsidence in Mekong Delta a serious concern

Mr. Tom Kompier (L). Photo: Quynh Nguyen

Subsidence of a few centimeters a year poses a serious threat to the low-lying delta, Dutch-Vietnamese study shows, which is already coping with climate change-related issues.

by Quynh Nguyen

Land subsidence in the Mekong Delta will become increasingly serious, reaching the warning level of more than 4 cm per year over the next ten years, if groundwater extraction is not ended, according to Mr. Tom Kompier, First Secretary, Water & Climate, at the Embassy of the Netherlands in Vietnam, based on a study, called Rise & Fall, from the Netherlands’ Utrecht University, Deltares, an independent institute for applied research in the field of water and subsurface, and Can Tho University, released on June 2.

The study shows that the rate of subsidence has now reached a few centimeters a year, which is a lot higher than the global sea-level rise of a few millimeters a year. This is alarming news for the Mekong Delta, which is only 1-2 meters above sea level.

Salinization, higher floods risk, and coastal erosion increasingly threaten the delta. Unless action is taken, the fertile land, which is home to 20 million people and which produces food for almost 200 million others, faces a major catastrophe.

“This is the first time a delta of this size has been modelled to calculate land subsidence,” said Mr. Philip Minderhoud, a PhD candidate researching land subsidence. “Our study shows that the delta is sinking 1-3 cm per year and that this rate is increasing. In some places, we have even found a loss in elevation of 25-35 cm in the past 25 years.”

Groundwater extraction is not the only cause of land subsidence in the area, according to Mr. Gilles Erkens, a land-subsidence expert at Deltares. “In addition to groundwater extraction from deeper layers, there are other causes, such as compression due to the pressure of loads and the lowering of the shallow water table.”

“Vietnam should stop groundwater extraction as soon as possible,” said Mr. Kompier. “Instead of using groundwater, it should make more investments in renovating canals to help farmers have clean water for cultivation.”

The Rise & Fall research allows Vietnam to include land subsidence in its plans for making this economically important area climate-resilient. The next step will be to extend the model so that it can be used to make forecasts.

In the future, the researchers hope to quantify the different causes of the subsidence observed at the delta’s surface.

Land subsidence is an insidious problem that is often noticed only when actual damage occurs. Other low-lying deltas such as those in Bangladesh, Indonesia, China, and the US can benefit from this study and the results.

“This Mekong Delta study is an important first step in improving our understanding of land subsidence in deltas and developing viable solutions,” said Mr. Esther Stouthamer, the land-subsidence researcher leading the Future Deltas interdisciplinary research program at Utrecht University.

Future Delta focuses on the development and integration of knowledge for global sustainable delta management. Alongside flooding and salinization, land subsidence is one of the main priorities of the program.

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