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

General weather patterns:

From 7 to 13 Jan 2020, 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 3 months from Jan to Mar 2020, the cold appears because the influentially high-pressure air mass areas prevail over Thailand for the whole month. However, at some periods, coldly high-pressure air masses from China will meet hot air masses already prevailing over LMB. Figures 1 presented the weather map for 7 and 13 Jan 2020.

General behavior of the Mekong River:

This week from 7 to 13 Jan 2020, water levels from Chiang Sean were continued to decrease, varied from -0.03 m to -0.18 m due to the test the equipment of hydropower station at Jinghong, China. Water levels at these stations were below its Long-term -Average (LTA). However, water level at Luang Prabang and Chiang Khan are likely impacted by hydropower dam at Xayaburi, in which they fluctuated, varied from -0.05 m to -0.30 m. Water levels at stations at the middle part of LMB from Vientiane to Pakse were also decreased based on the trend inflows from upstream, drawn water levels stay below their LTA and even 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 low and stay closely to their minimum levels. For the 2 tidal stations at Tan Chau and Chau Doc, water levels increased followed the same trends as minimum levels in January 2020. 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 7 to 13 Jan 2020 at Chiang Sean station were decreased since 6 Jan 2020, according to an official notification from China’s Ministry of Water Resources which copied to the Mekong River Commission Secretariat on 31st Dec 2019. The decrease of water levels was resulted from the test of equipment of hydropower station at Jinghong, China. At this station water levels decreased from -0.03 m to -0.18 m. However, at Luang Prabang station, water levels were fluctuated close to its historical maximum levels. Water levels at this station sometime decreased in between - 0.05 m to -0.30 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 MRC Weekly Dry Season Situation Report: 7-13 Jan 2020 Page 2 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 7 to 13 Jan 2020 at Chiang Khan station were likely also nominated by upstream hydropower dam of Xayaburi, which was noted that water levels decreased, varied from -0.02 to -0.10 m. The current observed water levels at Vientiane and Nong Khai stations are stay below their historical LTA and reached to their Minimum levels.

For stations from Nakhon Phanom to Pakse

Water levels from 7 to 13 Jan 2020 at Khong Chiam to Pakse stations were slightly increased, varied from 0.02 to 0.10 m. 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 7 to 13 Jan 2020 at Stung Treng, Kratie and Kompong Cham were continued to decrease, varied from -0.02 m to -0.06 m. The current water levels at Kompong Cham, Chaktomuk Koh Khel, Phnom Penh Port, Neak Luong and Prekdam on the Tonle Sap were found close to their historical minimum levels (1980-2018).

Tan Chau and Chau Doc

Water levels from 7 to 13 Jan 2020at the 2 tidal stations at Tan Chau and Chau Doc were increased, fluctuating followed over their LTAs, due to the tidal effect from the sea.
According to the Japan Meteorological Agency (JMA), Sea surface temperature (SST) variability in the tropics Neutral, which has no major impact.