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Weekly Wet Season Situation Report in the Lower Mekong River Basin - 31 August-6 September 2021

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Situation Report
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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 Chiang Saen in Thailand to Pakse in Lao PDR, including the lower part in Cambodia and Viet Nam, varying from 8.40 millimetres (mm) to 275.50 mm.

  • There will be above-average rainfalls for the next 5 days over the Mekong region from 7 to 12 September 2021 due to 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 slightly increase over the monitoring period from 31 August to 6 September 2021. It was up about 0.03 m from 535.60 metres (m) on August 31 to 535.63 m on September 6. The outflows increased from 1,050 cubic metres per second (m³/s) on August 31 to 1,071 m³/s on September 6.

  • Amid the significant low outflow from Jinghong upstream, water levels across most monitoring stations from Chiang Saen in Thailand to Thakhek in Lao PDR increased during August 31- September 6 due to above-average rainfall in the LMB. However, water levels from Nakhon Phanom in Thailand to Pakse in Lao PDR were staying close to their historical minimum level. Water levels from the stretches of the river from Stung Treng to Kratie and at Kampong Cham in Cambodia, moreover, followed the same trend of the upstream ones and stayed close to their minimum level.

  • The water volume of the Tonle Sap Lake during this reporting period wasslightly higher than that in 2019 and 2020 of the same periods but was still lower than its LTA.

  • Over the next few days, the water levels across most monitoring stations are expected to increase but remain lower than their long-term value in most stations.

Drought condition and its forecast

  • The overall drought conditions from Aug 28 to September 3 showed some drought threat in eastern part of the region covering Borikhamxay and Khammuane of Lao PDR and Sakon Nakhon and Nakhon Phanom of Thailand with severe level. Some other locations in the north were also hit by moderate drought including Phongsaly, Luang Prabang, Xieng Khuang, Xaysomboun, Kalasin, Mukdahan and Savannakhet. However, the condition was not serious.

  • For the upcoming thee-month forecast, the LMB is likely to receive above average rainfall in September and October mainly in the central and southern parts of the region. Like 2020, the forecast shows that October is likely the wettest month of the year. November is forecasted to receive from average to above average rainfall throughout the LMB.