HANOI—Vietnamese environmental experts have sharply criticized plans by Laos, China, and Thailand to build a cascade of dams along the upper reaches of the Mekong River, which flows through six countries, including Vietnam.
"If there are such dams on the river, it will change the flow of the river and its quality," said Ky Quang Vinh, head of the Center for Natural Resources and Environment in the southern Vietnamese city of Can Tho.
"For example, it will change the ecosystem and the quantity of water, affecting downstream countries," said Vinh, who has been monitoring water levels recently on the city's Hau river, a major tributary to the 4,350-km (2,700-mile) Mekong.
"They can use the dam system to direct the water flow, which will make downstream countries suffer a shortage of water."
It is like a blood vessel in the human body. When we build dams, it is like a blockage in the veins..."
Nguyen Huu Chiem, Can Tho University
He said a substantial reduction in water levels on the Hau and Tien rivers had rendered them vulnerable to an invasion of salt water from the sea, affecting the ability of the the rivers to support life and agriculture along their banks.
He also blamed upstream dams for lowering the number of microorganisms and seaweed, which help maintain the river's ecosystem.
China is currently constructing eight dams on the river, which flows through its southwestern Yunnan province, where it is known as Lancang Jiang. One of them would be the world's tallest, at 292 m (958 feet).
The dams would provide water storage equal to all the existing reservoirs in Southeast Asia combined.
Meanwhile, Laos has started construction on 23 upstream dams, scheduled for completion by 2010 on the Mekong.
A recent U.N. report said the hydroelectric projects were a means to spur development and lift the country from poverty, noting that Cambodia and Vietnam both have ambitious dam-building plans as well.
But it highlighted the Chinese dam projects as having the biggest impact.
"China's extremely ambitious plan to build a massive cascade of eight dams on the upper half of the Mekong River, as it tumbles through the high gorges of Yunnan province, may pose the single greatest threat to the river," the May 21 report said.
It added that the impact of the proposed dam development include "changes in river flow volume and timing, water quality deterioration, and loss of biodiversity."
China's Foreign Ministry spokesman Ma Zhaoxu said in response that Beijing gave equal attention to the development and environmental protection of cross-border rivers.
'Like a blood vessel'
More than 60 million people depend on the Mekong River—one of the world's longest—for food, water, and transportation.
Yearly wet and dry conditions are important for the production of rice and vegetables.
Experts up and down the Mekong—known as Lancang Jiang in Chinese, Lang Thuong in Vietnamese, and Mae Nam Khong in Lao and Thai—say they fear possible adverse effects on agriculture, the fishing industry, and transportation links of low, and widely fluctuating, water levels.
Nguyen Huu Chiem, head of the environment and natural resources management faculty at Can Tho University, said the Mekong river should be allowed to flow naturally.
"It is like a blood vessel in the human body. When we build dams, it is like a blockage in the veins: It will definitely affect other areas."
But he added: "This is a sensitive matter. There are already some data about water levels in the monsoon and dry seasons of the Mekong river."
"A lot of people think the water level has been affected by upstream dams," Chiem said.
Better understanding sought
The four-country Mekong River Commission (MRC) has launched a detailed environmental impact assessment of the plans for new hydropower projects along the river.
China is not a member of the Commission but provides crucial hydrological data to the MRC under an agreement signed in 2002.
China currently contributes 16 percent of the flow of the Mekong River, according to MRC figures.
MRC chief executive Jeremy Bird said the Mekong is a valuable but fragile resource.
"Before any decisions are made to implement mainstream hydropower schemes in the lower Mekong basin, the four lower Mekong countries have agreed to work together to cultivate a better scientific understanding of the wider development impact," Bird said.
He said private sector proposals for new dams should be guided by principles of economic, environmental, and social sustainability.
"The MRC is faced with perhaps its most important strategic challenge since the Mekong Agreement was signed in 1995 because of increased interest in building hydropower dams in the mainstream of the lower Mekong River Basin," Bird said.
Mekong tributary hydropower turbines currently generate 3,235 MW of electricity.
Projects under construction are likely to double that generating capacity, sparking interest from the private sector in developing the Mekong further.
The Mekong runs through China, Burma, Laos, Thailand, Cambodia, and Vietnam in a 795,000 square km (307,000 square mile) river network.
The network is home to dozens of rare bird and marine species, including the Mekong giant catfish, and already faces threats from pollution, climate change, and the effects of earlier dams that were built in China and have caused water levels to drop sharply on the upper Mekong.
The U.N. report said that for the time being the Mekong's pollution levels are not at "alarming levels," while water shortages and conflicts over water on the Mekong have so far not emerged.
But it said several connected river basins in the Mekong region are under threat, including the Tonle Sap in Cambodia, Nam Khan in Laos, and Sekong-Sesan Srepok in Vietnam and Cambodia, because of increasing development and demand for water.
It also called for countries bordering the Mekong to work more closely together to ensure the Mekong Basin can continue to meet future water needs.
Original reporting by RFA's Vietnamese service. Translated by Hanh Seide. Vietnamese service director: Diem Nguyen. Executive producer: Susan Lavery. Written for the Web in English by Luisetta Mudie. Edited by Sarah Jackson-Han.