Alert: 02/22/2025
A sudden release of water at dams in China will cause the Mekong River to rise 0.50 meters at Chiang Saen, Thailand on February 24.
Spotlight
September flow weak in the upstream, normal in the downstream.
In the Mekong upstream, dam restrictions in China reduced natural flow to Chiang Saen by about 22% during September. Without dam restrictions, natural flow still would have been well below normal, the potential impact of lower than normal rainfall in the upstream portions of the watershed. Farther downstream, normal levels of precipitation throughout the month of Septebmer and relatively lesser impacts from upstream dams maintained the river’s flow to just below normal. At Nakhon Phanom, dam restrictions in China and Laos reduced flow by about 13%. At Stung Treng, even with dam restrictions, Mekong flow achieved a normal level for this time of year.
What Happened Last Week?
- Where’s the Water: Last week saw a large net restriction of water (2.2 billion cubic meters). Major dam restrictions were observed at Huangdeng (PRC, 201 million cubic meters), Xiaowan (PRC, 197 million cubic meters), Nuozhadu (PRC, 150 million cubic meters), Nam Ngum 1 (LAO, 100 million cubic meters), Nam Theun 2 (LAO, 725 million cubic meters), and Ubol Ratana (THA, 417 million cubic meters). Show me the dams.
- River Levels: Levels along the Mekong are much lower than normal for this time of the year mostly due to a combination of low precipitation and upstream dam restrictions. See how this looks.
- Where’s the Water: Last week saw a large net restriction of water (2.2 billion cubic meters). Major dam restrictions were observed at Huangdeng (PRC, 201 million cubic meters), Xiaowan (PRC, 197 million cubic meters), Nuozhadu (PRC, 150 million cubic meters), Nam Ngum 1 (LAO, 100 million cubic meters), Nam Theun 2 (LAO, 725 million cubic meters), and Ubol Ratana (THA, 417 million cubic meters). Show me the dams.
Image of the Week
Late September Floodpulse could be a 2026 peak.
The image shows a total 18,500 square kilometers of Mekong Floodpulse in late September—an impressive increase from early September’s 11,900 square kilometers of flooding. Despite the improvement, MRC monitoring of reverse flow into the Tonle Sap shows 2026’s reverse flow ended on September 27. This suggests that the Tonle Sap Expansion, the main indicator of the Mekong Floodpulse, peaked two-to-three weeks earlier than it has in recent years. Despite this year’s reversal measuring as the highest volume of reverse flow since 2018 according to the MRC, two factors prevented a meaningful expansion of the Tonle Sap Lake: Low lake levels at the start of the wet season and a lack of rain in Cambodia. Reasons for the low lake levels require further study, but high reverse flow with a weak expansion is unusual for the Mekong. Typically, the Mekong Floodpulse peaks just after Tonle Sap reverse flow ends, suggesting that without a lot more rain, the image may represent 2026’s peak floodpulse. In contrast, over the past four years, the Mekong Floodpulse peaked in late October. An early peak suggests an early start to the dry season.
Where is the Water?
How Wet is the Mekong Basin?
- Click or hover over icons on map for more details.
How Much Water is in Reservoirs by Country?
Current volume (billion cubic meters) of usable water across the 45 largest reservoirs in the Mekong Basin.
How Much Water is in the Largest Reservoirs?
- Hover over chart to track reservoir volume for any particular week during the year.
How Strong is the Floodpulse?
Where did River Flow Come From?
How Wet is the Mekong Floodplain?
What Should River Levels Be?
Chiang Saen Gauge (Thailand) [UNDER MAINTENANCE]
Stung Treng Gauge (Cambodia)
Chau Doc Gauge (Vietnam)
For more info, click Natural River Flow Models in the top menu.
How do Dams Impact Different Points along the Mainstream?
How was the Weather Last Week?
- Click on maps to expand and for more details.
For more information, click Compare Maps and Data in the top menu.
Which Dams Impacted the Most?
- Click or hover over icons on map for more details.
Reservoirs with an estimated change of more than 50 million cubic meters (m³) of water over last 7 days.
For more info, click Virtual Gauges in the top menu.
Current Reservoir Volume for 58 Dams
- Hover over reservoir bars to see current or potential volume
For more info, click Virtual Gauges in the top menu.