Article 6C for monitoring purposes

Under Article 6C, during the flood season for monitoring purposes, the daily observed peak water level and derived discharge from 1 July to 31 October are to be compared against the 1:2, 1:10 and 1:20 ARI of the observed flows at the selected hydrological stations. In the cases of the hydrological stations at Phnom Penh (in the Mekong River), Tan Chau (in the Mekong River) and Chau Doc (in the Bassac River), daily observed discharges are not available and, until this can be overcome, daily observed water levels are used. It is suggested that the 1:20 year ARI event be used as the critical threshold, while the 1:2 ARI peak discharges be taken as the quantitative definition of “daily peak flows greater than what naturally occur on the average during the flood season”. There are four zones in this flow framework of increasing flood severity, each involving specific actions:

Zone If the daily water level is … Hydrological conditions Action required
Zone 1 below 1:2 ARI Normal hydrological conditions No need for action.
Zone 2 between 1:2 and 1:10 ARI Stable Need for caution.
Zone 3 between 1:10 and 1:20 ARI Unstable Investigation to be undertaken to identify possible cause(s) and possible mitigation measures. There is a need to be on alert.
Zone 4 above 1:20 ARI Severe Implementation of mitigating measures should be considered.

Location of hydrological stations for monitoring purposes

Hydrological stations
Name Station ID Country
Click on station name to see flow framework for monitoring purposes and associated zones for each station
Chiang Saen 010501 Thailand
Vientiane 011901 Lao PDR
Khong Chiam 013801 Thailand
Pakse 013901 Lao PDR
Stung Treng 014501 Cambodia
Kratie 014901 Cambodia
Chrouy Changvar 019801 Cambodia
Tan Chau 019803 Viet Nam
Chau Doc 039801 Viet Nam


Location of Hydrological Station for Monitoring Purposes
Mekong Mainstream within the Lower Mekong Basin
Lower Mekong Basin boundary