Mekong Dam Monitor (Update for July 29 - August 4, 2024)

 

Update for July 29 - August 4

Notable changes on the Mekong in the last week. Visit the Monitor home for more, including Burmese, 中文, Khmer, ພາສາລາວ, ไทย, and Tiếng Việt translation.

SPOTLIGHT Dam restrictions lowered river levels to below normal in July Without interference from dams, river levels below Nakhon Phanom would have been above pre-dam average levels in July, suggesting that the Lower Mekong experienced normal precipitation levels for the month of July. Dam restrictions reduced flow 11% below normal at Nakhon Phanom and Pakse and 5% below normal at Stung Treng. Most of these restrictions came from China’s dams and large dams in Laos. Above Vientiane, however, weather conditions were well below normal, particularly in China. At Chiang Saen, July natural flow would have been 20% below normal, but China’s dam restrictions reduced flow to 43% below normal. The Mekong needs normal wet season conditions to produce a strong floodpulse and drive fisheries and agricultural outputs downstream.

IMAGE OF THE WEEK China’s giant Xiaowan Dam filled to the top from July through August China’s Xiaowan Dam is the 2nd largest in the Mekong and holds almost as much water (11 billion cubic meters) as the largest 25 reservoirs in Laos. The dam began to fill in mid-June and the largest increases in reservoir volume were observed after July 14. In total, the reservoir has restricted Mekong flow by 5.82 billion cubic meters since June. It is nearly full. It is important to point out that the reservoir did not drain all of its storage during the 2024 dry season, and in June it started filling from about the middle of its reservoir depth.  These severe restrictions reduce the Mekong floodpulse. This dam alone likely reduced Mekong flow to Chiang Saen by more than 20% since June.

Where is the water? Last week we tracked a significantly large cumulative restriction of flow of 3.7 billion cubic meters of water across 17 dams. Major restrictions came from Xiaowan (PRC, 1 billion cubic meters), Nam Ou 7 (LAO, 100 million cubic meters), Nam Ngum 2 (LAO, 950 million cubic meters), Nam Ngiep 1 (LAO, 321 million cubic meters), Nam Theun 2 (LAO, 164 million cubic meters), Theun Hinboun Expansion (LAO, 698 million cubic meters), and Lower Sesan 2 (CAM, 136 million cubic meters). These huge restrictions have a devastating effect on the Mekong’s fisheries and agricultural outputs, which rely on high river levels throughout the wet season.

Reservoir Storage Over Time

River Levels River levels are once again back to below normal levels throughout the entirety of the basin as a result of lower-than-normal precipitation so far in August and severe dam restrictions upstream

Chiang Saen Gauge Stung Treng Gauge

Weather & Wetness Wet season drought conditions are returning to most of the Mekong Basin. Some peripheral areas such as parts of the 3S Basin and the Cardamom Mountains are experiencing wetter than normal conditions.