Land subsidence submerging the Mekong Delta

Land subsidence submerging the Mekong Delta

Land Subsidence

Land subsidence submerging the Mekong Delta

The Mekong Delta in Vietnam is a fertile and economically important area in Southeast Asia that is also known as Vietnam's 'rice bowl'. It is one of the largest deltas in the world. The area is subsiding at a rate of 1-4 centimetres a year, and the Vietnamese are increasingly feeling the impact: more flooding and the increasing salinisation of groundwater and surface water. If Vietnam does nothing and continues down the same road, parts of the delta will subside by almost a metre in the next thirty years, putting most of the area below sea level.

A rapidly increasing population and economic development are driving a rapid increase in water consumption. The extraction of groundwater for drinking water, agriculture, and fish and shrimp farms is largely responsible for the severe subsidence in this low-lying area.

Our role in the Mekong Delta and the results

In 2016, we built our first 3D groundwater model that can calculate land subsidence for the entire Mekong Delta. The model is based on 25 years of geological and geotechnical data and groundwater levels, and it has been calibrated using satellite data. It shows that groundwater extraction is a major driver of subsidence in the Mekong Delta. It is the first time that a delta of this size has been modelled to calculate land subsidence. Vietnam can use this research to include land subsidence in their plans to make this economically important area climate-robust. The next step will be to extend the model so that it can be used to make forecasts. We will also install an extensometer to measure the vertical movement of the land in detail and at different depths. In that way, we can work out the underlying causes for the subsidence we see at the surface level. Because, alongside the extraction of groundwater from the deeper subsurface, there are more factors that cause land subsidence, examples being compression due to loading, the lowering of the water table, and the oxidation of peat.

In Vietnam, people are increasingly aware of the fact that land subsidence represents a problem. Our research fits in very well with the plans that Vietnam is now developing to make the delta climate-robust. Our research is a first step on the way to developing approaches to slow down land subsidence.
Philip Minderhoud
Deltares expert land subsidence
If we know what causes the subsidence in the Mekong delta and understand the process better, we can then develop approaches to tackle land subsidence.
Hung Van Pham
Director of Center for water resources technologies for the South of Viet Nam

For this project Deltares has collaborated with the following partners:

  • TNO
  • Universiteit Utrecht
  • Dai Hoc Can Tho

Want to know more about this project?

Philip Minderhoud
Expert land subsidence