CJP4W6159-14x20cm.jpg

Hydrology

Upstream flow contributes only a small portion of the total annual flow of the Mekong River. Most of the total flow volume is delivered to the Mekong from tributaries in the Lower Mekong Basin (see Table 1); however, the importance of upstream flow should not be underestimated as dry-season snow melt from China contributes to over 24% of the total flow.

Table 1. Proportional contributions to total Mekong River mean annual flow by river reach, distinguishing those made by the left and right bank tributary systems.

River Reach Left Bank (%) Right Bank (%) Total (%)
China 16 16
China – Chiang Saen 1 3 4
Chiang Saen – Luang Prabang 6 2 8
Luang Prabang – Vientiane 1 2 3
Vientiane – Nakhon Phanom 18 4 22
Nakhon Phanom – Mukdahan 3 1 4
Mukdahan – Pakse 4 6 10
Pakse – Kratie 22 2 24
Tonle Sap 9 9
Total 55 20 100

Flooding

The flood season in the Mekong River Basin lasts from June to November and accounts for 80 to 90% of the total annual flow (MRC 2010). The annual flood season is especially important in the Lower Mekong Basin where it has shaped the environment and its inhabitants.

See the sections on the People and Flood and Drought for more information.

Many of the Mekong’s key ecosystems have developed as a result of seasonal flow fluctuations. The area’s extensive wetland habitats would not exist without the annual flood. Likewise, the life-cycles of many Mekong fish species depend on it. Fish migrate to deep pools in the mainstream to seek refuge during the dry season; later, during the flood season, they migrate back to spawning and nutrient-rich feeding grounds on floodplains.

See the Fisheries section for more information.

Latest News

Mekong River Commission prepares for 3rd Summit and work plan 2018

Yesterday, the Mekong River Commission (MRC) officials met to prepare for the 3rd Summit of prime ministers on 5 April 2018 in Siem Reap to be hosted by the Kingdom of Cambodia.

Op’ed - Improving Navigation Channels While Protecting the Environment

China’s Mekong development plan have stirred debate as potentially becoming an environmental and social peril for downstream Mekong countries

Sister Lakes to Document Learning Processes for Policy Recommendations

In order to amplify what the sister lakes of Cambodia’s Tonle Sap and Thailand’s Songkhla have learnt on community-based lake governance, the two sides agreed today on how and what to document in two upcoming papers they are preparing for policy developme