Mekong River’s Blue Hue Blamed On Upstream Outflow Restrictions, Decreased Rainfall

Water levels in the Mekong River are down to “worrying” levels with some parts of the major Southeast Asian waterway in Laos and Thailand turning blue because of increased algae growth, the Mekong River Commission said in a report Friday.

The report by the MRC – made up of Cambodia, Laos, Thailand and Vietnam – said the lower levels were caused by a lack of rainfall since the beginning of the year, upstream flow changes, hydropower dams in the river’s tributaries and China’s Jinghong Dam holding water back.

“There have been sudden rises and falls in water levels immediately downstream of Jinghong and further down to Vientiane, [Laos], which has been challenging for authorities and communities to prepare for and respond to possible impacts,” said Winai Wangpimool, director of the MRC Secretariat’s Technical Support Division, in the report. 

According to the MRC’s monthly rainfall figures, since November, rainfall has been down 25 percent. The Jinghong dam on Thursday was releasing water at 775 cubic meters per second, nearly half of the usual level of 1,400 cubic meters per second, the MRC said.

At the beginning of January, China’s Ministry of Water Resources told the MRC countries that it would lower outflow at Jinghong between Jan. 5 and 24 to 1,000 cubic meters per second to perform maintenance on powerlines. But the ministry did not communicate the water level before it started restricting flow, nor what water level they would return to on Jan. 25.

In October 2020, Beijing agreed to share data with the MRC, a welcome in the region where 60 million people in Thailand, Laos, Cambodia, and Vietnam depend on the river for agriculture and fishing.

“Continuing this flow pattern could have an impact on river transport, fish migration, agriculture and river weed collection,” Winai said in the report.

“To help the Lower Mekong countries manage risks more effectively, we call on China and the Lower Mekong countries themselves to share their water release plans with us,” he said.

The report said that monitoring stations in Thailand and Laos, water levels have been much lower than usual, while further downstream in Cambodia, levels were higher than the long-term average. In the Vietnam Delta area, water levels fluctuate both above and below the long-term average, but this is a result of daily tidal effects on the seas.

Blue Mekong

The MRC attributed the aquamarine color in northeastern Thailand, a phenomenon last observed in late 2019, to a drop in sediment and increased presence of algae on the riverbed. Under normal conditions, higher volumes of water flowing at faster speeds dump more sediment and flush the system of algae, making the water murky brown.

 ”Just like the situation in 2019, today’s blue-green water phenomenon is likely to spread to other stretches of the Mekong where low flows are experienced,” said So Nam, the MRC Secretariat’s chief environment management officer. 

So Nam said that clearer water could reduce food sources for aquatic insects, fish and invertebrate species, which would in turn affect organisms higher on the food chain. This could harm the fishing industry, from which many rural communities draw their livelihood.

He also said that the bluish color could remain until the next flood season, which usually starts in May, provided that larger reserves of water are released in the Upper Mekong in China and the tributary dams.

Advocates for riparian communities are concerned that excessive damming of the Mekong and its tributaries could lead to long-term negative impacts on the people in the Lower Mekong.

“What we were worried about before the dams were built is actually happening now,” Ormbun Thipsuna, a member of the council of community organizations based in the seven Thai riparian provinces told BenarNews.

“What we can do is a call for no more dams to be built, because the dams will only aggravate the problems for the people of the Mekong River basin,” Ormbun said.

The MRC statement did not include information about recent notifications from China on the water levels, but the Reuters news service reported that Beijing said Jinghong has been releasing 1,000 cubic meters per second since the end of last month, a level which it said was two times the river’s natural flow. Beijing said the MRC should “avoid causing public misunderstanding.”

China has been the target of criticism from the international community for its cascade of 11 mega-dams on the river. The lower Mekong basin experienced severe drought over the past year, with stretches of the river even drying up entirely.