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Water-related development in the basin


Mekong farmers have been irrigating farmland since the first century. Today, thousands of farmers throughout the basin are producing a second and some a third rice crop per year in around 12 500 irrigation schemes. Farmers in the Mekong river basin produce enough rice to feed 300 million people per year (MRC, 2010b). Rice is the principal livelihood of people in the region (CDRI, 2008).

Today, 70 percent of the basin’s population rely on agriculture for their livelihoods and an increasing population in the region is putting pressure on food security. Agriculture is vital to raising standards of living, improving livelihoods and poverty mitigation in the basin. It is currently the most dominant water-related sector, for both subsistence agriculture and export, particularly in Thailand and Viet Nam where it generates thousands of millions of annual revenue in United States dollars. Agriculture in Cambodia and Lao People’s Democratic Republic is currently less intensively developed (MRC, 2009). It has been estimaed that demand for agricultural products from the basin will increase from 20 to 50 percent in the next 30 years. Agriculture, along with fishing and forestry, employs 85 percent of the people living in the basin (MRC, 2010b).

The total area equipped for irrigation in the Mekong river basin is estimated to be around 4.3 million ha, of which Viet Nam accounts for 42 percent, Thailand 30 percent, China 12 percent, Cambodia 8 percent, Lao People´s Democratic Republic 7 percent and Myanmar 2 percent. Area actually irrigated is estimated at 3.6 million ha. The equipped area irrigated by surface water accounts for 98 percent while groundwater accounts for 2 percent.

In the Lower Basin, the dry-season irrigated area of about 1.2 million ha is less than 10 percent of the total agricultural area (15 million ha) (MRC, 2010).

The Mekong Delta is one of the most productive regions in the world. Often referred to as Viet Nam’s ‘rice bowl’, the Delta produces more than 16 million tonnes of rice annually for domestic consumption and export in addition to highly productive shrimp farms, orchards and market gardens. Every year, annual floods enrich the delta soils and bring millions of fish to spawn. Sediments carried from far upstream replace the land lost through natural erosion (MRC, 2010b).

Expansion of the present level of agriculture in the basin is limited by the availability of water in the dry season. Proposed dam development, especially reservoir dams upstream, could give a boost to the agricultural sector by redistributing some river flows from the wet to the dry season (MRC, 2009). There are plans to increase dry season irrigation by 50 percent (from 1.2 to 1.8 million ha) over the next 20 years, with Lao People’s Democratic Republic planning to expand irrigation in the dry season from less than 100 000 ha to over 300 000 ha. Major irrigation expansion is being studied in Cambodia, linked to investments in flood control in the undeveloped Cambodian delta, and linked to hydropower development elsewhere (MRC, 2010).

Total water withdrawal in the Mekong river basin is estimated at 62 km3, or 13 percent of the Mekong’s average annual discharge, of which Viet Nam accounts for approximately 52 percent, Thailand 29 percent, China 9 percent, Lao People´s Democratic Republic 5 percent, Cambodia 3 percent, and Myanmar 2 percent. Irrigation withdrawal accounts for 56 km3, or 90.5 percent of the total.

Existing reservoir storage capacity is insufficient to redistribute water significantly between seasons. Groundwater use in the basin is modest except in China, northeast Thailand and Viet Nam where surface water is scarce during the dry season. Sustainable groundwater development potential requires careful assessment. Surface water and groundwater account for 97 percent and 3 percent of total withdrawals in the Mekong river basin respectively.

The Watershed Management Project aims to put individuals and communities in charge of protecting catchments to ensure clean water. Sometimes, this may involve changing agricultural techniques or sanitation habits, which contaminate nearby water sources. The programme began its third and final phase in 2008 (MRC, 2009).

Dams and hydropower

The Mekong river basin has become one of the most active regions in the world for hydropower development (MRC, 2009c). The total potential for feasible hydropower projects in the four Lower Basin countries is approximately 30 000 MW, more than enough to meet the expected demand in the coming decade. This includes 13 000 MW on the Mekong’s mainstream, and the remaining on its tributaries, of which 13 000 MW are in Lao People’s Democratic Republic, 2 200 MW in Cambodia and 2 000 MW in Viet Nam (WEPA, 2010).

As shown in Table 2, hydropower projects with a total installed capacity of 2 612 MW are already in operation in the Lower Basin, while projects with a further 3 574 MW are currently under construction. All of these projects are located on the tributaries, not on the mainstream. Nearly half of them enable some degree of seasonal regulation of streamflow. Much of the electricity produced is used to power cities and industries outside the basin (MRC, 2010b).

Table 3 shows the existing large dams with details on height and capacity, where information was available. Thirteen hydropower dams have a capacity of more than 10 MW.

The governments of Cambodia, Lao People’s Democratic Republic and Thailand are now actively considering building dams on the mainstream Mekong river, as well as on tributaries. Private sector interest in tributary development in Viet Nam also remains high (MRC, 2009). Over the next 20 years, further Lower Basin dams are planned, including twelve mainstream projects. Ten of these are dams planned across the river channel (eight in Lao People’s Democratic Republic, two of which are on the Lao-Thailand mainstream, and two in Cambodia), one will be partial damming (Don Sahong) and one a diversion project (Thakho) in Lao People’s Democratic Republic. Thirty tributary dams are planned, mostly in Lao People’s Democratic Republic. All mainstream dams are classified as “run-of-river”, with limited storage capacity and regulation potential. Many tributary dams include significant reservoirs, adding 21 000 million m3 of storage (MRC, 2010).

There is also huge hydropower potential in the Upper Basin. In Yunnan Province (China), total hydropower potential is an estimated 23 000 MW (WEPA, 2010). China is completing its hydropower cascade on the Lancang mainstream. The Manwan, Dachaoshan, Jinghong and Xiaowan dams are currently operational and the Nuozhadu dam will be completed in 2014. The Xiaowan and the Nuozhadu dams, with 15 043 and 22 400 million m3 of storage, may cause significant seasonal redistribution of flow from the wet season to the dry season and further reduce sediment transport in the Mekong mainstream, providing both opportunities and risks to downstream countries (MRC, 2010).

Table 4 shows the major existing and planned mainstream hydropower projects in the Upper Basin in China. While the first three dams constructed have limited capacity to regulate flows, Xiaowan and Nuozhadu (under construction) have major storage capacity and therefore significant influence on the seasonal distribution of flow entering the Lower Basin (MRC, 2009c).

Navigation is important but largely undeveloped as an integrated transport sector. River-related tourism is important for national revenue and local income generation (MRC, 2010).

There are increasing opportunities for the private sector and foreign state-owned companies in the development of water and related resources, such as hydropower, navigation, large-scale irrigation, and industry (mining, forestry, and tourism). In many of these areas, private sector investment now exceeds that of the public sector. In comparison with conventional public sector driven developments, private sector developments are more opportunity-driven with relatively short planning cycles and assessment processes. While private sector participation is welcomed, it needs to be open to public scrutiny and sensitive to civil society concerns. This will require effective regulatory systems, including enabling legislation and regulations and enforcement capacity, as well as strong and empowered water resource management agencies (MRC, 2010).


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