Dams and Landslides

Chinese dam planner says upper Mekong dam impacts “limited”

Grainne Ryder

October 29, 2008

Last month in Vientiane, a spokesman for one of China’s largest dam planning agencies1 assured the Mekong River Commission (which includes the four lower Mekong countries of Lao PDR, Thailand, Cambodia, and Vietnam) that dam-building on the upper Mekong would have only “limited impact” downstream.

Hydro China Corporation’s claim is based on “special research” conducted by a Canadian firm, Duron Environment Scientific Consulting (Note: an internet search yielded no record of this consulting firm), but it conflicts with numerous reports of unusual and often hazardous flow fluctuations, bank erosion, and fisheries decline downstream.

Hydro China’s representative, Dr. Chen Guanfu, said that dam construction so far has had “no obvious impact” on Mekong flows downstream of Yunnan province because the first three dams in operation – Manwan, Dachaoshan, and Jinghong – have no significant storage capacity and the amount of water flowing from Yunnan to downstream countries is just 13.5 percent of the Mekong’s total annual flow anyway. (Note: the Mekong River Commission says China controls 16 percent). When the next two dams, Xiaowan and Nuozhadu, are completed, however, Duron’s research indicates a reduction in flow in the wet season and an increase in the dry season, without any change in the total annual volume of flow.2

In his presentation, Dr. Chen provided no scientific evidence to backup his claims that the first three dams had “no obvious impact,” nor did he acknowledge the experience with large hydro dams elsewhere in China or the lower Mekong countries where even subtle variations in seasonal flows have wiped out migratory fish and destroyed floodplain agriculture downstream.

For example, since completion of the Three Gorges dam on China’s Yangtze River, the harvest of four major carp species has plummeted, according to senior ecologists at the Chinese Academy of Sciences’ Institute of Hydrobiology. Like their Mekong counterparts, Yangtze carp spawn when water levels rise naturally during the monsoon rains. With the Three Gorges dam, however, operators release water from the reservoir in April and May to make room for the summer monsoon rains. According to Chinese and US fisheries researchers quoted in Science magazine, this sudden increase in flow (downstream of the dam) triggers the movement of adult carp from the floodplain lakes to spawning grounds upriver before they have stored enough energy and before eggs have matured. In the fall when dam operators start to hold back water in the reservoir this stimulates carp to migrate back to the floodplains earlier than normal, again reducing their chances to store enough energy for survival. Surveys downstream of the Three Gorges and Gezhouba dams indicate a sharp decline in the number of carp eggs and larvae between 1997 and 2005.

Last year, Chinese officials and experts admitted that the Three Gorges dam would lead to ‘environmental catastrophe’ unless serious efforts were made to combat worsening pollution and more frequent landslides and flooding in the reservoir area.

The dam’s rising waters have already displaced nearly two million people and another four million people living in the reservoir area will be ‘encouraged’ to leave in the next decade as the risk of landslides increases. As well, the impoundment of sediment behind the dam has led to the scouring of river banks downstream and has eroded large islands in the Yangtze delta.

If the Three Gorges experience suggests anything, it is that the downstream effects of the upper Mekong dams will not be limited. Dr. Chen insists that full-scale environmental assessments (EIA) will be done for each project and that each EIA “should be approved by government.” He did not say if this included governments in affected countries downstream.

The Mekong River Commission, meanwhile, is promoting dialogue and information sharing between all six Mekong countries to “ensure that countries’ concerns are addressed as approved projects are implemented.”

But Vietnamese officials remain very concerned that dams on the upper Mekong could have negative and unforeseen consequences for the Mekong delta, where 20 million people rely on Mekong fish for export and water for irrigation.

Vietnam exports more than US$1 billion worth of Mekong catfish a year, according to Nguyen Van Trong, deputy director of Vietnam’s Agricultural Research Institute, who also attended the Vientiane conference last month.


1. China Hydro Corporation is responsible for planning and designing the Lancang/upper Mekong dams. China Huaneng Group, the owner of the Lancang dams and holder of the development ‘rights’ to the Lancang river was not at the meeting in Vientiane. Mekong River Commission meetings tend to be dominated by hydro planners, consultants, and Western donor agencies, thus no actual operating data or cost information is aired.

2. This change in flow patterns is the result of dam operators holding back water at the onset of the rainy season and then releasing water in the dry season to meet their power production targets.

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