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Weekly Wet Season Situation Report in the Lower Mekong River Basin - 7-13 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 4.10 millimetres (mm) to 328.80 mm.

  • There will be above-average rainfalls for the next 5 days over the Mekong region from 14 to 18 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 significantly decrease over the monitoring period from 7 to 13 September 2021. It dropped about 0.78 m from 535.98 m on 10 Sept to 535.20 on 13 Sept 2021. The outflows decreased from 1,318 cubic metres per second (m³/s) on Sept 10 to 790 m³/s on Sept 13, 2021.

  • Amid the significant low outflow from Jinghong upstream, water levels of monitoring stations at Chiang Saen in Thailand also decreased about 0.55 m from 7 to 13 September 2021. From Chiang Khan in Thailand to Vientiane in Lao PDR, water levels decreased during 7-13 September due to below-average rainfall in the area. However, water levels from Nakhon Phanom in Thailand to Pakse in Lao PDR were increasing.
    Water levels from the stretches of the river from Stung Treng to Kratie and at Kampong Cham in Cambodia were also increasing, following the same trend of the upstream flow and staying lower than their LTA.

  • The water volume of the Tonle Sap Lake is lower than its LTA but higher than the levels in 2019 and 2020 during the same period.

  • 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

  • During the monitoring week from September 4 to 9, the LMB was experiencing some moderate and severe meteorological and agricultural droughts. However, the conditions were not serious enough to post any threat for agriculture and water use in the region. The overall drought conditions through combined drought index shows normal conditions for the entire LMB.

  • 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.