Weekly Dry Season Situation Report for the Mekong River Basin – Prepared on: 31/12/2019, covering the week 24th to 30th December 2019

Weather Patterns, General Behaviors of the Mekong River and Outlook Situation

General weather patterns:

From 24 to 30 Dec 2019, there was no rainfall in the LMB. Based on the weather outlook bulletins and maps issued by the Thailand Meteorology Department (TMD) were used to verify the weather condition in the LMB. They stated that for the next 2 months from December 2019 to February 2020, the total rain of northern, northeastern, eastern and central parts including within the area of Bangkok Metropolitan and Vicinity would be reached about 20% to 30% below normal condition. They stated that some westerly wind waves from Myanmar may pass the Upper Thailand causing the area to meet thunder rain, gusty wind at some areas and possibly falling hail. Figures 1 & 2 presented the weather map for 25 and 30 December 2019.

General behavior of the Mekong River:

This week from 24 to 30 Dec 2019, water levels from Chiang Sean were increased due to the inflow from China, varied from 0.03 m to 0.11 m which could draw water levels at this station upper than its LTA. However, water level trend at Luang Prabang and Chiang Khan are likely impacted by hydropower dam at Xayaburi, in which they fluctuated, varied from 0.02 m to 0.08 m. Water levels at stations at the middle part of LMB from Vientiane to Pakse were slightly increased but the water levels were close to their minimum levels. Follow the same trend of water levels from upstream, stations at Stung Treng, Kratie, Chaktomuk on the Bassac, Phnom Penh Port and Neak Luong were also close to their minimum levels. For the 2 tidal stations at Tan Chau and Chau Doc, water levels increased the same trends as minimum levels in December 2019. The actual water levels at most of the key station are staying below their LTAs and even Min Levels (see its hydrograph in Annex B).

For stations from Chiang Saen and Luang Prabang

Water levels from 24 to 30 Dec 2019 at Chiang Sean station were increased, due to the inflow from Jinghong (as observed during the wet season from June to October). At this station water levels decreased from 0.03 m to 0.11 m. However, at Luang Prabang station, water levels were fluctuated and stay close to its historical Maximum Levels. Water levels at this station sometime increased rapidly in 0.35 m, due to the reservoir operation of upstream and downstream at Xayaburi. It was observed that the Luang Prabang stations is likely nominated by hydro power dam operation upstream (tributaries) and downstream (Xayaburi) in which water levels always fluctuated above their LTAs, during the impounding reservoir at Xayaburi from end of October 2018 to May 2019.

For stations from Chiang Khan, Vientiane-Nong Khai and Paksane

Water levels from 24 to 30 Dec 2019 at Chiang Khan station were likely also nominated by upstream hydropower dam of Xayaburi, which was noted that water levels fluctuated from 0.02 to 0.08 m. The current observed water levels at Chiang Khan, Vientiane/Nong Khai and Paksane stations are close to their historical minimum levels.

For stations from Nakhon Phanom to Pakse

Water levels from 24 to 30 Dec 2019 at Khong Chiam to Pakse stations were found slightly decreased, varied from 0.02 to 0.04m. The current water levels at these stations area still below their minimum historical levels.

For stations from Stung Treng to Kompong Cham/ Phnom Penh to Koh Khel/Neak Luong

Water levels from 24 to 30 Dec 2019 at Stung Treng, Kratie and Kompong Cham were continued to slightly decrease, varied from 0.02 m to 0.08 m. The current water levels at Stung Trend, Kratie,

Kompong Cham, Chaktomuk Koh Khel, Phnom Penh Port and Neak Luong were close to their historical minimum levels (1980-2018). For Prekdam on the Tonle Sap, water levels are stayed above its Minimum levels.

Tan Chau and Chau Doc

Water levels from 24 to 30 Dec 2019 at the 2 tidal stations at Tan Chau and Chau Doc were slightly decreased, follows the same trends of their minimum levels due to the tidal effect from the sea. Water levels were kept the same trends as minimum levels since early December 2019 and the actual water levels are stayed below their LTAs

According to the Japan Meteorological Agency (JMA), Sea surface temperature (SST) variability in the tropics Neutral, which has no major impact.

Source: Mekong River Commission

Posted in Legal January 4, 2020