Climate change risks drowning Mekong Delta

Most of the 40,000 km2 delta is less than 2 meters above sea level, and thus at risk of being submerged by climate-change related sea level rise. Further risk factors include over-pumping of groundwater and unsustainable sand mining for construction, as well as rapid hydropower development upstream.  

Only concerted action of the six countries in the upstream Mekong basin, located on the Southeast Asian mainland, and better management of water and sediments within the delta could reduce the risk, argues an interdisciplinary research team in the journal Science. Authors include Susanne Schmeier, Associate Professor of Water Law and Diplomacy at IHE Delft.

“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,” said lead author Matt Kondolf, Professor of Landscape Architecture and Environmental Planning at University of California, Berkley. “Yet, like any river delta, the Mekong Delta can only exist if it receives a constant sediment supply from its upstream basin and water flows to spread that sediment across the delta surface build land at a rate that is equal or greater than global sea level rise.”  

Rapid and urgent action is needed, Schmeier added.

“Efforts by national governments, regional organizations and international actors, such as development agencies and banks, as well as the private sector and civil society, are all needed if the Mekong delta is to have a chance,” she added. “We need basin-wide transboundary, fast and concerted cooperation among all partners.”

In the Mekong, water and sediment flows are increasingly endangered. Countries in the basin develop renewable hydropower, which has system-scale impacts as dams trap sediment and reduce downstream sediment flows. Sand minding that feeds a burgeoning real estate sector and land reclamation compounds the problem.

In the delta itself, high dikes built to control floods and enable high-intensity agriculture prevents flood waters from overflowing onto the delta surface and deposit fertile sediment. In addition, unsustainable groundwater use makes the delta surface sink several centimetres a year.

The authors identify measures that would significantly increase the lifetime of the delta. Dams could be designed to enable better sediment passage, placed in a strategic way that reduces their downstream impacts, or replaced by wind and solar farms where possible. Sediment mining should be strictly regulated, and use of Mekong sand could be reduced through sustainable building materials and recycling.

Intensive agriculture in the Mekong Delta should be reevaluated for its sustainability, and natural solutions for coastal protections should be implemented on a large scale along the delta’s coasts. All these measures are feasible and have global precedents.  

However, they face opposition by stakeholders such as the sand mining industry, and they require cross-country coordination that can be difficult to achieve.

Countries would also need to agree that the sustenance of the Mekong delta is an important regional policy objective. In Vietnam, where most of the delta is located, some recent policies try to counter some symptoms of a sinking delta, but there is little acknowledgement of the existential risk to the delta, nor ambition to work on truly systemic solutions.  

About IHE Delft Institute for Water Education

IHE Delft is the largest international graduate water education facility in the world and is based in Delft, the Netherlands. Since 1957 the Institute has provided water education and training to professionals from over 160 countries, the vast majority from Africa, Asia and Latin America. Also, numerous research and institutional strengthening projects are carried out in partnership to strengthen capacity in the water sector worldwide. Through our overarching work on capacity development, IHE Delft aims to make a tangible contribution to achieving all Sustainable Development Goals in which water is key.