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Weekly Wet Season Situation Report in the Lower Mekong River Basin - 20-26 July 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 took place from Chiang Sean in Thailand to Pakse in Lao PDR, including the lower part in Cambodia and Viet Nam, varying from 3.00 millimetres (mm) to 252.90 mm.

  • There will be significant rainfall for the next 5 days in the Mekong region from 27 July to 01 August 2021 because of low-pressure dominating in the Mekong region.

Water level and its forecast

  • The outflows at Jinghong hydrological station showed slightly decrease over the monitoring period from 20 to 26 July 2021. It was down about 0.17 m from 536.07 metres (m) on July 20 to 535.90 m on July 26. The outflows decreased from 1,375 cubic metres per second (m³/s) on July 20 to 1,261 m³/s on July 26.

  • Amid low flow from Jinghong upstream, the above average rainfall from 20 to 26 July in the LMB has made water levels across most monitoring stations from Chiang Saen in Thailand to Thakhek in Lao PDR increase; and from the stretches of the river between Stung Treng, Kratie and Kompong Cham in Cambodia water levels were also repeatedly increasing and staying higher than their LTA.

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

  • Over the next few days, the water levels across most monitoring stations are expected to rise and are forecasted to stay above their long-term value in some stations.

Drought condition and its forecast

  • Drought conditions of the LMB from July 17 to 23 were normal and wet in all over the region. No drought threat was found during the monitoring week.

  • For the upcoming thee-month forecast, the LMB is likely to receive much below average rainfall in August mainly in the central and southern parts of the region; September is forecasted to be extremely wet in the north, moderately wet and normal in the middle, and normal and moderately dry in southern areas 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.