In Science, a Politecnico study explains how to save the Mekong Delta from rising seas

Milan, 6 May 2022 - The Mekong Delta in Vietnam could be almost completely submerged by sea water by the end of the century if urgent action is not taken. In a paper published in the journal Science, an international research team, including the Politecnico di Milano, has identified concrete actions to prevent this economically important and densely populated area from ending up under water.

Most of the 40,000 km2 of the Mekong Delta lies two metres below sea level, and is therefore vulnerable to rising oceans due to global warming. In addition, local practices such as over-pumping of groundwater, extraction of sand used in the construction industry and the rapid development of hydropower threaten the future of Southeast Asia's most productive rice fields. The research team, which includes the Politecnico, argues that only concerted action by the six countries in the Mekong basin (China, Laos, Thailand, Cambodia, Vietnam) and better management of water and sediment within the delta could prevent this outcome.

"It's hard to fathom that a landform the size of the Netherlands and with a comparable population might disappear by the end of the century" - says lead author of the study, Professor Matt Kondolf of the University of California, Berkeley - “However, like any river mouth, the Mekong Delta only continues to survive if it receives a steady supply of sediment from its upstream basin and water flows to spread the deposits across the delta's surface, building up land at a rate equal to or greater than global sea-level rise".

“Hungry for renewable energy, countries in the basin have in recent years developed a number of hydropower plants (whose dams trap sediment and reduce sediment flows downstream) with little regard for the impacts on the water system. What little sediment does reach the lower Mekong is mined for the construction industry in the region, which requires large quantities of sand for land reclamation and building construction" summarizes lead co-author Dr Rafael Schmitt of Stanford University.

There is scientific evidence identifying the processes that threaten the continued existence of the Mekong Delta and how these processes could be controlled and mitigated. The team identified six measures that would significantly increase the survival of delta. Dams could be designed to enable better sediment sediment passage (1), placed strategically to reduce their downstream impacts, or replaced with wind and solar farms, where possible (2). Sediment extraction should be strictly regulated and the use of Mekong sand could be reduced through sustainable building materials (3). Intensive agriculture in the Mekong delta should be reevaluated for sustainability (4) and natural solutions for coastal protection should be implemented on a large scale along the delta’s coasts (5 and 6). All of these measures are feasible and have precedents in other parts of the world.

“Although the scientific community agrees on the effectiveness of these measures, particularly when implemented in unison, there are major obstacles to their implementation” - says Professor Andrea Castelletti, co-author of the study and full professor of Natural Resources Planning and Management at the Politecnico di Milano - “Some of these actions would conflict with the vested interests of certain local actors, such as the sand mining industry and hydroelectric power plants. Measures would require coordination between countries, which would have to agree that sustaining the Mekong Delta is an important regional policy objective”.

Implementation of the measures will require the involvement of national governments and international actors (banks and development agencies), as well as new actors, such as the private sector and civil society. However, the call to action is clear when Professor Kondolf concludes: “A Mekong Delta that will thrive beyond the end of this century is possible, but it will require rapid and concerted action in a basin that has been endangered by competition rather than cooperation between the countries through which the river flows".