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Fourth year of drought for the Mekong River: the Commission sounds the alarm once again

According to the Mekong River Commission (MRC), the river is entering a fourth year of record drought. This situation would affect the food security of millions of vulnerable inhabitants who depend on farming and fishing practised around the river. Although it is mainly due to the acceleration of climate change and  the increase of warm currents, the role played by the management of the dams upstream is not called into question.

Recognition of a very worrying problem


In a technical report covering the period 2019-2021 made public in January: “Mekong Low Flow and Drought Conditions in 2019-2021”, the MRC confirms that the hydrological regime of the Mekong River Basin has changed considerably since 2015 with a longer dry season and a shorter period of high flow. During the last three decades, the discharges of the Mekong River have reached their lowest level for more than 60 years. 2020 was the driest year in the main branch of the Mekong, with below-normal rainfall in every month months except October.

Source: MRC

However, the situation worsened from 2019, a year marked by drought that greatly affected flow management in 2020 and 2021. Indeed, the drop in water volume in 2019, caused by very low rainfall and a shorter monsoon season, increased the caution of reservoir managers, who drastically increased downstream storage in the upcoming dry season. As a result, the flow regime was disrupted, making power generation from the lower dams particularly instable.

The levels of Lake Tonlé Sap, located in the downstream basin of the Mekong in Cambodia, are very pertinent indicators for observing the effect of a later rainy season and scarce rainfall. Due to its exceptional geological position, the lake is crossed by a regime that alternates according to season. The report emphasises that the reversed discharges, mainly responsible for maintaining the volume in the lake, reached their lowest levels in 60 years in 2020 and 2021. This considerable fall in the levels of the lake, which harbours considerable fish resources, would be a contributing factor for fishing problems reported in the Mekong Delta.

Severe consequences for the living conditions of populations and biodiversity


These years of drought have reduced the food security of the millions of vulnerable inhabitants who depend on fish and agricultural production enabled by a formerly very fertile river. The report estimates that the drought in the Tonle Sap Lake is the cause of significant economic difficulties for the riparian populations.

Tonle Sap Lake at a critical stage of drought – Source: The Phnom Penh Post, Alessandro Marazzi Sassoon

In addition to food production, this situation is an immediate threat to the maintenance of biodiversity in the river basin. After the Amazon River, the Mekong River is home to the greatest aquatic biodiversity and is the largest freshwater fish reservoir in the world. Fish populations are threatened by the low levels of the river and lake, preventing them from migrating or reproducing in good conditions or timing.

The roots of the problem: climate change and El Nino/La Nina


Climate change, and more precisely a shorter and delayed monsoon period, is the main cause of this major disruption. Indeed, the main course of the Mekong River depends on the timing and intensity of monsoons in Southeast Asia, which causes a unique flood peak that is extremely necessary during the wet season.

The study also emphasizes the impact of the El Nino/La Nina phenomenon, a cyclical disruption of the exchange between the atmosphere and the ocean. This meteorological phenomenon causes the warming of the Pacific Ocean, and results in exceptional rainfall or droughts depending on the region. It would be the cause of the drastic decrease in precipitation in the Mekong Basin over the last past years.

However, the report insists that the management of upstream dams is not the main cause of the disruption of the river’s hydrological regime, contrary to what other studies heavily reported in the press may suggest. The authors therefore favor the idea of a unique combination of climate degradation and exceptional drought. However, operation of the various storage dams can help or worsen the situation.

A call to act quickly 


To better cope with future droughts and to increase visibility in terms of agricultural production and energy, the MRC takes the opportunity of this report to formulate recommendations for the six countries bordering the Mekong River:

  • The Commission calls all the Mekong countries to take rapid and drastic action in response to low flows. Created in 1995 by Laos, Cambodia, Vietnam and Thailand, the Mekong River Commission does not include China, even though the country operates eleven dams on the river and that the river has its source in its territory. The Commission thus points out the need for transboundary and coordinated decision making among all stakeholders for the operational management of the river and in particular its reservoirs.


  • Moreover, the Commission insists on the need for a common risk modelling. Such a system applied in real time on the whole Mekong Basin, would allow analysing the impacts of potential decisions taken by the different countries on their respective dams, and thus to better coordinate future flows during dry periods.


  • Finally, the Commission encourages the creation of new reservoirs in the framework of its strategy for 2021-2030. Storage capacity must be improved to better manage the basin for extreme weather events (droughts and floods).


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