- 05/11/2020 2:46 PM
- 27/12/2020 3:49 PM
- 14/10/2019 10:06 AM
This is due to maintenance work at a hydropower station in China’s Yunnan province
PHNOM PENH--The Mekong River has dropped to perturbing low water levels over the last few weeks with its water color turning blue green, according to the Mekong River Commission (MRC).
Water levels between the Jinghong hydropower station in China’s Yunnan province and the Mekong Delta in Viet Nam have dramatically fallen since early January 2021 due to low rainfall, flow changes upstream, hydropower operations on the Mekong tributaries, and outflow restrictions at the Jinghong dam.
“There have been sudden rises and falls in water levels immediately downstream of the Jinghong station and further down to Vientiane, 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 a press statement on Feb. 12.
The MRC’s monthly rainfall data indicate that, since November 2020, rainfall has been consistently lower than average, dropping by as much as 25 percent, he said in the statement.
The data also show that outflow at the Jinghong station on Feb. 11 was 775 cubic meters per second (m³/s). This represented a 50-percent decline of its normal level of approximately 1,400 m³/s, which was last recorded in December 2020.
According to the statement, the outflow levels at the Jinghong station from Jan. 1 to 7 were stable at 785 m³/s but gradually rose to 1,400 m³/s on Jan. 15, which represented a 1.07-meter rise in water level. From Jan. 15 to 23, the outflow dropped to 740 m³/s before rising to 990 m³/s on Jan. 29. It then fell gradually, reaching 800 m³/s by Feb. 11.
“Continuing this flow pattern could have an impact on river transport, fish migration, agriculture and river weed collection,” Winai stressed. “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.”
In early January, China’s Ministry of Water Resources notified the four Lower Mekong countries that the outflow from the Jinghong station would be restricted to 1,000 m3/s from Jan. 5 to 24 due to maintenance work being done on the power grid transmission lines. However, the Chinese ministry did not specify the water level before the outflow restriction nor the volume that would be restored on Jan. 25, the statement read.
The notification was made following China agreeing in Nov. 2020 to share year-round water level and rainfall data with the MRC. Through this agreement, China had agreed to notify the MRC and its member countries of any abnormal rise or fall in water levels or discharge, and to provide relevant information on factors that might lead to sudden flooding.
The river water gets blue-green hue
In addition to water levels dropping to low levels, the MRC also revealed that the color of the Mekong river water in Thailand’s north-eastern province of Nakhon Phanom has changed to aquamarine—a phenomenon that had occurred once in late 2019.
The MRC’s preliminary analysis of the phenomenon showed that, just like in 2019, several factors have played a role leading to this including the low level of water, a slow drop in river sediments, and the presence of algae at the bottom of the river.
“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.
As he explained, some of the potential impacts of higher-water clarity include changes in the productivity of the river with less food available for aquatic insects, invertebrates and small fishes with this consequently affecting the productivity of aquatic biodiversity, reducing fish catches and threatening the livelihoods of local communities.
The Mekong’s blue-green appearance, Nam said, may continue until flows increase with the onset of the next flood season, which usually begins in late May.
The river may return to normal if large volumes of water are released from storage reservoirs in the upper Mekong, he concluded.