In the face of the growing threat to the Mekong Delta, experts believe that the only solution is to restore natural aquifers.
Scientists say that the main cause of the increasingly serious flooding in the area is the overexploitation of aquifers, including ancient rivers, causing subsidence problems.
To settle the matter, it is necessary to control and minimize the underground water and recover natural fresh water sources (surface water).
However, it is not easy to restore natural water sources. It takes 16 days to recover water surface flow, but it takes 1,500 years to do this with underground flow.
Nguyen Van Dat from the HCMC University of Science & Technology, who spent many years researching the flooding and subsidence of land in HCMC and the southeastern province, has suggested a new solution – making use of seawater to fill natural underground water storage.
Dat believes that land subsidence is not only caused by underground water overexploitation, but also by high-rise buildings and urban works. Water-filled aquifers, even with saline water, will be a solid foundation that helps prevent subsidence caused by the weight of urban structures.
The Mekong Delta can take full advantage of the rich seawater sources in the area to fill underground water layers, and revive the ancient rivers which have been overexploited. There are two ways to do this, either transmitting seawater vertically or horizontally.
If applying the former solution, seawater will be blocked by a sea dyke system made of treated slag concrete. The water would be transmitted through a network of composite of soft plastic pipes (60-150 meters, depending on the depth).
If transmitting water horizontally, it would be necessary to install 100×200 mm rectangular grills to prevent salinity. The length of the grills is the same as the water depth. Incoming seawater will encounter the grills and gradually infiltrate into the underground water layer.
Also according to Dat, there is another way to save Mekong Delta from inundation – freshening seawater.
The overexploitation of underground water is attributed to water exhaustion, which causes serious shortage of surface water for people’s daily use and cultivation. People then have to use underground water instead. If seawater can be freshened and provided to people, they would not have to exploit underground water.
Seawater, after being freshened, will be led to the river network of the Mekong Delta, both providing water for daily use, cultivation, and the tourism industry.
Dat stressed that it is necessary to consider seawater in Mekong Delta and rainwater in HCMC as useful natural resources, which can be used to prevent floods and serve many purposes.