A satellite image on January 3, 2020, shows Xayaburi Dam sitting astride the Mekong River,
which has turned blue due to drought and other factors reducing sediment, near the town
of Xayaboury, Laos. Photo by Reuters. 

Hydropower dams on the Mekong River are expected to reduce Vietnam’s GDP by 0.3 percentage points due to their impact on fisheries and agriculture. 

A paper titled "Impacts of Mainstream Hydropower Dams on Fisheries and Agriculture in Lower Mekong Basin" on the open access journal Sustainability published by Switzerland’s Multidisciplinary Digital Publishing Institute on March 19 said hydropower dam construction could cause great losses to biodiversity, fisheries and agriculture in the Lower Mekong Basin (LMB).

Specifically, the dams could impact Vietnam's fish population, as well as rice and maize production, which would contribute to a 0.3 percent loss in GDP.

Construction of dams would also increase the vulnerability of communities dependent on fisheries for income and nutrition in Vietnam.

The loss would be caused by several factors, including changes in river flow, water quality and the ways sediment and nutrient are transported. These would be directly harmful to habitats, populations and communities, foraging and breeding behaviors, species interactions and ecosystem functioning, and migration of fishes.

Vietnam and Cambodia could experience severe impacts from these hydrological changes due to their dense populations which depend greatly on fisheries and flood recession agriculture, particularly rice.

Fisheries account for 10-15 percent of Vietnam's GDP, and the losses caused by dam construction could amount 6-9 percent of this sector.

The construction could also severely affect agricultural production in Vietnam through changes to the seasonally inundated floodplains and wetlands close to Tonle Sap Lake and the Mekong Delta. 

It could lead to a decrease of 2.3 percent in rice production in Vietnam, primarily due to changes in sediment loading. Maize production would be reduced by 21 percent.

The economic losses in agricultural and fisheries production could amount to over $1.14 billion, or 0.3 percent of GDP.

The loss would be greater than the benefits accruing from electricity generation, improved irrigation and flood control brought by the dams.

The paper called for less dependence on hydropower generation in developing countries and use of other energy sources to reduce the negative environmental, behavioral, cultural, and socioeconomic effects of large dams.

There are currently 64 dams in the Mekong Basin, including 46 in the LMB which produce 8,650 MW of electricity. Another 11 dams proposed in LMB countries and territories on the Mekong River mainstream are expected to have a capacity of 13,000 MW.

The Mekong Delta, Vietnam's food basket, grows half of its rice and accounts for 90 percent of its rice exports.