Mekong River water level rises amid dry season

According to the National Center for Hydro-Meteorological Forecasting, the Mekong Delta region, where the Mekong River reaches the sea, has received a volume of water that is 15-20 percent higher than the average of previous years in April.

For May and June, the levels are expected to increase 20-30 percent year-on-year, the center said.

The water level in the Tien River, a branch of the Mekong, was measured at 1.45 meters last Thursday, which is 0.4 meters higher than the same period last year and 0.5 meters higher than the average of prior years.

On the same day, the water level in the Hau River, the other Mekong branch in the delta, stayed at 1.65 meters, which was 0.5 meters higher than last year and 0.7 meters higher than the average previously.

The water level increase has been ascribed to China releasing water from its hydropower dams along the Mekong River.

According to the Mekong River Commission, the amount of water entering Mekong Delta through the two stations on the Hau and Tien rivers in March increased by 30 percent against the same period last year to 12.3 billion cubic meters.

Nguyen Huu Thien, an independent consultant based in Can Tho, a city in Vietnam’s Mekong Delta, said the increasing water level will help the delta cope with salt intrusion and drought as the region experiences its dry season.

However, in the long term, it may leave negative impacts, he said.Ever since Mekong Delta was formed, generations had depended on the annual floodwaters to inundate their fields before sowing their seeds.

Usually, flooding would start in late July or early August and remain until November or even later, blessing the region with extraordinary fertility as it deposits silt from upstream areas.

However, in recent years, upstream dams and climate change impacts have altered the routine.

According to experts inside and outside Vietnam, those dams hold back water and prevent it from flowing into downstream areas, thus reducing the amount of sediment and fish that are supposed to move from upstream to downstream every annual flood season.

With China releasing dam water during the dry season, Thien said, it would cause disorder because it means that during the flooding season in July, August and September, there would be little or even no floods across Mekong Delta.

The situation will lead to chaos for the ecosystem, he said.

The Mekong has suffered three years of extremely low flow and drought during the wet season. When wet season flow is low, the Mekong’s fisheries and agricultural productivity suffer the most. Low flow and drought are mostly caused by a lack of rainfall, but upstream dams also contribute to wet season droughts by storing significant amounts of water, Brian Eyler, Southeast Asia program director and Mekong Dam Monitor Co-Lead, Stimson Center, told a virtual event February.

He said China has completed 129 dams along the river, 11 of them the largest mainstream dams. Most of the Mekong water, as much as 56 percent, is held in China.