The case of the disappearing Mekong delta

What’s happening?

SOURCE: UTRECHT UNIVERSITY. PAPER HERE.

A recent study (written up by the VOA here) exposed yet another potential environmental crisis in Vietnam (and the world). Basically, the Mekong delta is sinking underwater and could disappear entirely by 2100.

What’s driving the subsidence?

This time, the crisis is only partially caused by climate change. The bigger issue is groundwater extraction for agriculture and drinking water. The picture at the right shows the potential impact of increased groundwater extraction. For the past 25 years, groundwater extraction has increased as Vietnam’s population and economy have grown.

I reached out to an author of the paper, Philip Minderhoud, and asked him how much of the disappearance of the delta is due to groundwater extraction, how much to rising sea levels (climate change), or sand extraction or other things?

This is one of the ongoing research questions. But what we see presently is that the land subsidence due to groundwater extraction is on average for the entire delta round ~2.5-4 times higher than the rate of the rising sea level around the Mekong delta (3-4 mm yr). At the coastline, especially in the southern part of the delta, the subsidence rates due to natural compaction of young sediments can also reach subsidence rates up to several centimeters per year. And when the sediment supply in these areas is cut off, the mechanism to buffer these subsidence rates stops and these rates start to add to delta elevation loss.

As for sand extraction, it is more localized according to him, rather than a reason for the general subsidence. [I wrote about sand on February 13, 2019 - scroll down].

SOURCE: ANNE LIN THROUGH UNSPLASH

What does this mean for the people in the region?

Obviously, the Mekong is important. More than 18m people live in the area, and about 200m depend on the area for food. According to the VOA article I linked to above, the Mekong delta is responsible for 50% of the food Vietnam produces. For example, Vietnam is the third largest exporter of rice in the world, much of which is produced in the Mekong. This could all be at risk, and the impact could be severe.

In the short term, there needs to be significant investment in water resources for people in the region to replace groundwater extraction. This probably means piping in water from further away. Minderhoud said that they could be supplied with fresh water from the Mekong river branches, but during dry times or when there is salt-water intrusion, it might not be enough. So the distance might be far and will require money.

Given food security issues and the potential economic loss of agriculture lands disappearing, the cost would be worth it, in my opinion. But it takes foresight, initiative and the will of the government. Particularly when people have to start potentially paying more for water, either through taxes or fees.

Is the government working on this?

It sounds like the government is interested in the research. For example, Minderhoud said that “in Can Tho there was recently a new policy to reduce/stop groundwater extraction in the city, partly because of subsidence.” He didn’t know the specifics, but it does sound like the government is aware of the issue.

Vietnam is already facing the effects of climate change with severe weather events like typhoons, flooding, and drought. According to GermanWatch, Vietnam was the 6th most affected country in the world from the effects of climate change in 2017 alone. These effects have and will likely continue to impact the Mekong Delta more than any other part of the country. I hope that the government starts really investing in infrastructure to deal with this and climate change, such as investing in renewables rather than investing more in coal (more on renewable trends in Vietnam in my post yesterday).