VIENTIANE (UCAN): Recorded water levels in the Lower Mekong River Basin [LMB] saw significant increases during the last week of July as a result of heavy rainfall and sudden water releases from dams, the Mekong River Commission [MRC] said on July 29.
However, the commission said river levels across all monitoring stations remain lower than their alarm or danger points with the region experiencing the third year of a drought.
Levels are expected to fall, partly due to reduced outflows from construction work at China’s Jinghong Dam.
River levels were above their long-term averages, mostly at the upper stations, according to MRC data. The region has received about 40 per cent higher than average rainfall in July compared to the same period between 2015 and 2020, it added.
“Due to heavy rainfall, dams in the Lower Mekong including those on the tributary released large amounts of water [between] July 24 and 25, causing water levels to surge quickly,” said Lam Hung Son, head of the MRC Secretariat’s Regional Flood and Drought Management Centre.
He added that it was not immediately clear whether these surges had caused any damage.
“Sudden water releases from tributary dams increasingly pose a challenge to accurate forecasting of river levels,” Lam said, noting that the MRC has installed 67 automatic hydrometeorological stations along the Mekong mainstream and tributaries to collect rainfall and water level data.
Surges of more than six metres were reported at Chiang Khan in Thailand while the Mekong River rose more than four meters in Vientiane
The water level in Thailand’s Chiang Saen, the second uppermost monitoring station in the LMB, increased from 3.10 metres to 6.5 metres from July 20 to 23. However the level receded about a metre between July 24 and 26. The river level was expected to drop further.
The Luang Prabang station in Laos saw its river level rise from 9.92 metres to 12.28 metres from July 22 to 26, although it is forecast to decrease by about 0.35 metres during the five days after that.
In Ban Pakhoung station, five kilometres downstream of the Xayaburi Dam, the station’s water level rose from 10.19 metres to 14.22 metres between July 22 and 26. But the river level at this point was expected to drop by about two meters over the following five days.
Surges of more than six metres were reported at Chiang Khan in Thailand while the Mekong River rose more than four meters in Vientiane.
In Cambodia, water levels in the stretches from Stung Treng to Neak Luong in Prey Veng province were reported to have increased by less than a metre, but were forecast to rise by 2.6 metres towards the beginning of August, the MRC said.
In Vietnam’s Mekong Delta area, encompassing Tan Chau and Chau Doc on the Bassac River, water levels were expected to fluctuate as a result of tidal effects.
The MRC said it had been informed by China’s Ministry of Water Resources that outflows from the Jinghong hydropower station in Yunnan province would drop by as much as 50 per cent due to power grid construction.
“We are expecting a drop in river levels immediately downstream of the Jinghong Dam,” Lam said. “But this will also depend on the amount of rainfall we receive over the coming days.”
