This gallery is part of a special National Geographic News series on global water issues.
A meeting among four Southeast Asian countries this week could determine whether construction of the first of up to a dozen controversial dams on the Mekong River can proceed.
The dams are designed to generate electricity for the region, but environmentalists fear they will disrupt the Mekong's delicate freshwater ecology—which supports the endangered giant Mekong catfish and dozens of other critical species—and threaten local communities who rely on the river for food and jobs.
The Xayaburi Dam in northern Laos is the first of 11 proposed dams planned for construction on the lower Mekong River. Nine dams are planned for Laos, and two others are slated for Cambodia.
The approximately 3,000-mile (4,800-kilometer) Mekong River is traditionally separated into two parts on maps: The upper Mekong flows through China, where it is known as the Lancang River, while the lower Mekong runs alongside Myanmar and through Laos, Thailand, Cambodia, and Vietnam before emptying into the South China Sea.
The Xayaburi Dam will take eight years to complete and cost an estimated $3.5 billion. It will generate 1,260 megawatts of electricity, most of which will be sold to Thailand.
According to Trandem, the Laotian government has said it would use the revenues from the dams to further national economic growth and redevelop the country, where the average citizen makes $2,400 per year.
The World’s Largest Freshwater Fishery
In terms of biodiversity, the Mekong River is second only to the Amazon among the world's great rivers. As a home to more than 1,000 fish species, the Mekong supports the world's largest freshwater fishery, and it provides food and income–through fishing, farming, ecotourism, and other jobs–for many of the 65 million people who live in the Lower Mekong basin.
(Related news: “New Mekong Species Photos: Fangless Snake, Bald Bird.”)
The Mekong is unique among the world’s large rivers because "the fish diversity is extremely high, the diversity of migratory species is extremely high, and human dependence upon these species for fisheries is extremely high," said Peter McIntyre, a freshwater conservation expert at the University of Wisconsin-Madison.
"You put all of that together, and putting a large dam in the Mekong is likely to cause major problems."
International Rivers estimates that about 2,100 people would be forced to resettle if the Xayaburi Dam were built and that the livelihoods of another 200,000 people could be impacted directly.
Environmental and Social Costs
Laos has urged neighboring countries to not block the Xayaburi's construction and maintains that the dam will have minimal environmental impacts.
A February 14 note by the Laotian government to other Mekong River member countries said the Xayaburi "relies upon a technologically advanced design to produce the cleanest and renewable electricity with no pollution . . . and a minimum of effects upon the environment in the vicinity."
University of Wisconsin-Madison's McIntyre said he is skeptical of this claim. "There's never been a dam put in place on a large river that didn't have a substantial ecological impact," he said. "That's just a fact."
The Laos government has yet to make its environmental impact assessment (EIA) report for the Xayaburi Dam publicly available, but the Mekong River Commission (MRC)—an intergovernmental group created in 1995 to coordinate water resource issues among Laos, Thailand, Cambodia, and Vietnam—has commissioned its own environmental review of a series of proposed dams on the Mekong mainstream, including the Xayaburi.
The MRC's 198-page Strategic Environmental Assessment (SEA) report, published in October 2010, recommended a 10-year building freeze on all Mekong dam construction projects to allow time for more studies on the dams’ environmental and societal impacts to be conducted.
"My intuition is that if you really account for the full sweep of negative impacts to humans and fish species, it would be hard to justify a dam on the Mekong River," McIntyre said.
Laos recently indicated it would resist the SEA report's recommendations. "We have no reason to believe that the Project should be delayed any further," the Laotian government said in a statement.
Environmental groups and scientists say the risks posed by the dams far outweigh any of their potential benefits.
Biologists have warned the Xayaburi Dam would block the migratory routes of dozens of fish species and could place 41 fish species at risk of extinction, including the critically endangered Mekong giant catfish.
The builders of the Xayaburi Dam have promised to create "fish passages" that would allow fish to continue their migrations.
But International River's Trandem said no fishery technology currently exists that can guarantee safe passage for the Mekong's numerous fish species.
"Right now, all the evidence points to the fact that fish passages will not work on the Mekong River because you're dealing with such a high volume of fish and such a large number of fish species," Trandem said.
(Read more from National Geographic Emerging Explorer and Fish Biologist Zeb Hogan: “Why We Shouldn’t Dam the World’s Most Productive River.”)
Investors for Xayaburi and the other proposed Mekong dams need look no farther than the Mun River dam in Thailand to see all the things that could go wrong, the nonprofit conservation group WWF has said.
Built in the 1990s, the dam on the Mun River, the Mekong's largest tributary, was a "notable economic failure" that caused massive environmental and social disruptions, WWF said.
At $233 million, the Mun River dam cost investors twice the original estimate, according to WWF, and energy production fell to a third of expected capacity during the dry season. Return on investment dropped from a projected 12 percent to 5 percent. Other environmental groups estimate that more than 20,000 people have been affected by drastic reductions in fish populations upstream of the Mun River dam site and other changes to their livelihoods.
“The lessons of Thailand’s Mun River dam are still fresh: Hasty environmental and social impact studies can lead to a bitter lose-lose situation for both fishermen and dam owners," Suphasuk Pradubsuk, National Policy Coordinator with WWF-Thailand, said in a statement.
Under the Mekong Agreement, the four MRC nations (China and Myanmar are “discussion partners,” but not MRC members) are required to consult with one other on any large construction projects on the main stem of the Mekong River. Countries are supposed to reach an agreement about whether the projects should proceed, and if so, under what conditions.
In October 2010, Laos formally began the six-month MRC approval process for the Xayaburi Dam. A final decision is expected April 22, following a meeting between the four MRC member countries in late March.
However, because no MRC member nation has veto power, construction of the Xayaburi Dam's construction could move forward even if the other countries oppose the project.
"We're not a regulatory body and have no specific enforcement powers, but all countries fully support this prior consultation process and aim to reach a consensus," said MRC chief executive officer Jeremy Bird.
Mekong management is complicated by the fact that the river meanders through no fewer than six countries in Southeast Asia, many of which have had histories of bloody conflict with one another.
Citing a desire to avoid "regional conflict," U.S. Senator Jim Webb, chairman of the Senate Committee on Foreign Relations Subcommittee on East Asian and Pacific Affairs, recently said the U.S. should consider withdrawing funding to the MRC if construction of the dams proceeds. The MRC is funded by Australia, Sweden, the United States, the European Union, and other countries, as well as donors like the Asian Development Bank.
U.S. Secretary of State Hillary Clinton echoed that sentiment last fall during a visit to Vietnam, when she recommended a “pause before major construction continues.”
Brendan Buckley, a paleoclimatologist at the Lamont-Doherty Earth Observatory of Columbia University in New York City, whose team is using tree-ring data to model the climate of the Mekong basin during the last millennium, said he thinks construction of the Mekong dams is inevitable.
Laos and Cambodia "need the standard of living increases that would come from building these kinds of development projects, so they're going to happen," Buckley said.
But whether the dams are built "intelligently with some ecological balance remains to be seen."
Plans for hydropower dams on the lower Mekong River main stem date as far back as the 1950s, but war and political instability in the region, as well as concerns about earlier dam designs, prevented them from being built.
But interest in hydropower dams on the Mekong has seen a resurgence in recent years, said MRC's Bird.
This has been driven in part by concerns about climate change and a shift toward renewable energy sources that have low carbon footprints.
International River's Trandem said the success or failure of the Xayaburi Dam project could determine the fate of the other proposed Mekong dams.
"What happens to the Xayaburi will set the precedent for what happens in the future on the Mekong," Trandem said.
"If the four countries realize that the Xayaburi is not a good idea, it's unlikely that the other [main-stem Mekong] dams in Cambodia and Laos would ever go forward."