It said the situation will be exacerbated under the impact of climate change and the hydropower dams on the Mekong’s upper course.

Researchers pointed out that the seven dams China built on Mekong’s upper course have led to the reduction of the sediment flows downstream. There are 500 points along the riverbank and the seaside suffering from serious erosion.

Tuoi Tre reported that China has stated it will release water from the Jinghong hydropower dam in Yunnan province from March 15 to April 10, to provide water to help ease the water shortage in downstream countries.

Researchers pointed out that the seven dams China built on Mekong’s upper course have led to the reduction of the sediment flows downstream. There are 500 points along the riverbank and the seaside suffering from serious erosion.

However, experts doubt the water release would help Vietnam’s Mekong Delta escape the drought and saline intrusion which is attacking the area.

According to Nguyen Huu Thien, an independent expert, Mekong River has two big sections. The one running across China, more than 2,000 kilometers, is called Lan Cang, and the other is the Mekong.

Though the river section running through China is long, the width of the basin is quite narrow, so the amount of water is not large.

The section in China makes up 16 percent of total water volume for Mekong Delta, while the section in Myanmar 2 percent. The remaining 82 percent of water volume is in the lower course, of which Laos makes up 35 percent, Thailand 18 percent and Cambodia 18 percent. Meanwhile, 11 percent of water is from the Central Highlands and the rain in Mekong Delta.

“Chinese hydropower dams mostly have impact on the sediment and sand in the Mekong Delta. The amount of water is not the main problem; it only matters in dry years, with little rain,” Thien explained.

According to Thien, most of the water to Mekong Delta is from the lower course (82 percent), while the water in the lower course depends on the climate and weather.

In 2019, when El Nino occurred, the rainfall was very low. This is the biggest reason which explains why Mekong Delta doesn’t have floods and why it is facing serious drought.

There are three possible scenarios for hydropower dams.

First, in the years with normal conditions of floods, hydropower plants store water in flood season and release water in dry seasons, i.e. they ease the floods in flood season and increase the flows in dry season.

Second, in the years with high floods, hydropower plants release water, making the flooding situation more serious.

Third, in dry years, as the rainfall is low, drought and saline intrusion are more serious. Hydropower plants worsen the situation.

Le Ha

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