VietNamNet Bridge - A series of water reservoirs in the upper course of Mekong River could lead to a loss of 90 percent of alluvium in Vietnam’s Mekong River Delta.

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A series of water reservoirs in the upper course of Mekong River could lead to a loss of 90 percent of alluvium in Vietnam’s Mekong River Delta.

According to Ho Long Phi from the HCM City National University’s Water Management and Climate Change Center, the flow and sediment in the delta depends on the flow of the Mekong River basin.

It is expected that 120 irrigation reservoirs will be set up in the future in the Mekong’s upper course, with the total capacity of over 100 billion cubic meters. These include a few on the main stream and others located in many different countries, mostly in Laos, Cambodia and Thailand.

“The water reservoirs in the Mekong River upper course will lead to the loss of 90 percent of sediment in the next 20-30 years,” Phi said.

The loss of alluvium now is 50 percent.

The water reservoirs in the Mekong River upper course will lead to the loss of 90 percent of sediment in the next 20-30 years
Also according to Ho Long Phi, if more reservoirs are set up in the upper course, the decrease in alluvium volume would lead to a lack of fertilizer and worse soil quality.

This will increase the possibility of erosion, because when there is less sediment, the flow tends to erode the riverbanks to offset the decrease, thus causing landslides on river banks. The alluvium cannot compensate for floods, thus making the situation even worse.

Elaborating on the difference between irrigation reservoirs and hydropower dams, Phi said the latter stores water to generate electricity and gives water back, while the former uses water for irrigation and cannot return it. As a result, sediment will be lost in a large quantity.

Phi noted that irrigation reservoirs bring major damages, but people don’t pay much attention to them because they are small and not located on major branches. This explains why people protest hydropower dams, ignoring the damages caused by irrigation reservoirs.

Countries are building more water storage reservoirs because of climate change. Vietnamese scientists have repeatedly warned that the Mekong River Delta would face  drought for dozens of years.

“It would be better not to sit and put high hopes on discussions and negotiations. It is necessary to take action right now and apply necessary measures to adapt to the new circumstances and minimize risks,” an analyst said, adding that the negotiations would not bring what Vietnam wants because every country operates for its own benefit.