The climate of the Mekong River Basin ranges from temperate to tropical. In the Upper Mekong Basin, some of the taller peaks of the Tibetan Plateau are glaciated. In fact, much of this part of the Basin is snow-covered in winter. Melting snow from the Tibetan Plateau feeds the Mekong River’s dry-season flow, especially in the middle reaches. In the relatively lower elevations of the Yunnan province of China, the climate of the Mekong River Basin changes and the temperature gradually increases.
June to October is the wet season in the Lower Mekong Basin (LMB); with the exception of two brief transition periods (see Figure 1 below), the rest of the year in the LMB is the dry season. The wet season results from the flow of moisture-laden air from the Indian Ocean in the summer. During the rest of the year, high-pressure systems over the Asian continent give rise to the dry season in the LMB.
The climate of the Lower Mekong Basin (LMB), which is almost always hot and often humid, is classified as tropical monsoonal. In the warmest months of March and April, average temperature ranges from 30°C to 38°C. Cooler temperatures prevail from November to February. At higher elevations in the Lao People’s Democratic Republic (PDR), winter temperature averages 15°C.
The distribution of mean annual rainfall over the Basin follows a distinct east-to-west gradient. In the LMB, the rain-soaked uplands in the Lao PDR and Cambodia receive the most precipitation (3,000 mm) and the semi-arid Khorat Plateau in northeast Thailand the least (1,000 to 1,600 mm). The Upper Mekong Basin is similar to the LMB in that rainfall is regulated by the global monsoon system. In the Upper Basin, annual rainfall can be as little as 600 mm in the Tibetan Plateau and as much as 1,700 mm in the mountains of Yunnan.
Countries in the LMB are among the most vulnerable locations in the world with respect to climate change. While the future impact of climate change is difficult to forecast, projections for the Mekong River Basin for the next 20 to 30 years, based on a downgraded global climate model, are as follows:
Find out more on climate change in the Mekong River Basin.
Hoanh C.T., Guttman H., Droogers P. and Aerts J. 2003. Water, climate, food and environment in the Mekong Basin in South East Asia. Institute for Environmental Studies, Free University of Amsterdam, Amsterdam, Netherlands.
MRC 2010. State of the Basin Report 2010. Mekong River Commission
MRC 2005. Overview of the Hydrology of the Mekong Basin. Mekong River Commission.
A delegation of Chinese hydrological experts visited national Mekong committees in Cambodia and Thailand from 24 to 31 May 2017. Led by Mr Kuang Jian
The forum provided an opportunity for hydropower developers and specialists, government, research institutes, development partners and other regional and international organizations to discuss about hydropower planning and development in the Mekong Basin.
The Lower Mekong Basin is at greater risk to climate change with extreme weather events such as typhoons and heat waves and is also more vulnerable to floods and droughts that can affect people’s livelihoods and reduce agricultural productivity