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Weekly Dry Season Situation Report in the Lower Mekong River Basin - 9-15 November 2021

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Key Messages

Key messages for this weekly report are presented below.

Rainfall and its forecast

  • Rainfall focused in the areas from Kratie in Cambodia to Tan Chau and Chau Doc in Viet Nam, including the 3S area in Cambodia and Viet Nam, varying from 1.40 millimetres (mm) to 197.00 mm.

  • There will be average rainfalls for the next 7 days over the Mekong region from 16 to 22 November 2021 because there is still a low-pressure dominating the Mekong region.

Water level and its forecast

  • According to MRC’s observed water level data, the outflows at Jinghong hydrological station showed water level changes over the monitoring period from 9 to 15 November 2021. Water levels at this station increased about 0.55 metres (m) from 535.26 m on 2 Nov to 535.81 on 8 Nov 2021 (recorded on 7:00 am) and stayed about 0.56 m higher than its two-year-average (2020-2021) value. The outflow rose from 825.00 m3/s on 9 Nov to 1197.00 m³/s on 15 Nov 2021.

  • Amid the increased outflow from Jinghong upstream, water levels of monitoring stations at Chiang Saen in Thailand decreased about 0.10 m from 9 to 15 Nov 2021. However, from Chiang Khan in Thailand to Vientiane in Lao PDR, water levels will increase about 0.50 m from 16 to 22 Nov 2021 due to some rainfall in the area and influence of dam operation. Water levels from Nakhon Phanom in Thailand to Pakse in Lao PDR, on the other hand, were decreasing. Water levels from the stretches of the river from Stung Treng to Kratie and at Kompong Cham in Cambodia, moreover, were drastically 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 9 to 15 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 conditions from November 6 to 12 were normal all over the LMB. The region showed no drought threat except some moderate and severe dry soil moistures in the upper part 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.