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Weekly Dry Season Situation Report in the Lower Mekong River Basin - 23–29 November 2021

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Key Messages

Key messages for this weekly report are presented below.

Rainfall and its forecast

  • During November 23-29, rainfall focused in the areas from Stung Treng in Cambodia to Tan Chau and Chau Doc in Viet Nam, including the 3S area in Cambodia and Viet Nam, varying from 18.20 millimetres (mm) to 54.00 mm.

  • There will be low-average rainfalls for the next 7 days over the Mekong region from 30 Nov to 12 Dec 2021 because there is still a low-pressure dominating the Mekong region.

Water level and its forecast

  • According to MRC’s observed water level at Jinghong showed a slight increase of about 0.04 m from 535.21 m on 23 Nov to 535.25 on 29 Nov 2021 (recorded on 7:00 am), and stayed about 0.49 m lower than its two-average (2020-2021) value. The outflow was up from 796.00 m3/s on 23 Nov to 819.00 m³/s on 22 Nov 2021.

  • Along with the increased outflow from Jinghong upstream, water levels of monitoring stations at Chiang Saen in Thailand also increased about 0.06 m from 23 to 29 Nov 2021. However, from Chiang Khan in Thailand to Paksane in Lao PDR, water levels decreased about 0.55 m from Nov 23 to 29 due to less rainfall in the area and influence of dam operation. Water levels from Nakhon Phanom in Thailand to Pakse in Lao PDR were also decreasing about 0.25 m. Water levels from the stretches of the river from Stung Treng to Kratie and at Kompong Cham in Cambodia, moreover, were decreasing, due to less contributed rainfall from the upstream part (at Pakse and 3S area in Viet Nam).

  • The water volume of the Tonle Sap Lake in 2021 was lower than its LTA but higher than the levels in 2019 and 2020 during the same period from 23 to 29 November 2021, and still considered critical.

  • Over the next seven days, the water levels across most monitoring stations are expected to go down and remain lower than their long-term average value in most stations.

Drought condition and its forecast

  • Drought condition of the LMB from November 20-26 was normal all over the LMB except some moderate drought in northeastern part due to severely dry soil moistures during the beginning of dry season. The region showed no significant threat except some moderate and severe dry soil moistures in the upper and midlle parts of the LMB.

  • For the upcoming thee-month forecast, the LMB is likely to receive from average to above average rainfall from November 2021 to January 2022. There will be some more rain dropping over the southern part of the LMB during November and December 2021 making the condition cooler than normal year, while normal condition is likely taking place in the upper and middle parts of the region during the last two months of the year