- Joined
- Apr 5, 2009
- Messages
- 11,615
- Likes
- 5,772
The Bane of Three Gorges Dam
The travails of the Three Gorges Dam are a cautionary tale for Laos and its Southeast Asian neighbors as they wrestle with the pros and cons of damming the lower Mekong River.
BEIJING—Scientists predicted that when the world's largest hydropower project came online in 2003, it would be an environmental bane. The Three Gorges Dam on the Yangtze River has unfortunately lived up to expectations. For that reason China is embarking on a 10-year mitigation effort that sources say will cost $26.45 billion.
The travails of the Three Gorges Dam are a cautionary tale for Laos and its Southeast Asian neighbors as they wrestle with the pros and cons of damming the lower Mekong River (see main text). Two consequences have proved worse than anticipated: deteriorating water quality and erosion. And the potential for spreading a snail-borne disease apparently wasn't even on planners' radar.
The decision to build the dam in 1992 came after decades of study and fierce internal debate. Benefits such as power generation and flood control are indisputable. But leaders also knew that the costs would be enormous. The newly created 1080-km2 reservoir submerged wholly or in part 13 cities and 466 towns, displacing roughly 1.3 million people, and triggered thousands of landslides. The reservoir wiped out fish spawning areas and raised an impassable barrier to one endangered mammal—the Yangtze finless porpoise—and two species that were in terminal decline: the Chinese river dolphin, or baiji, and the Chinese paddlefish (Science, 1 August 2008, p. 628).
Before the Three Gorges Dam began holding back the river in 2003, local Yangtze water by national standards was suitable for drinking. Not anymore. In the past several years, toxic algal blooms have regularly blighted 22 tributaries. Slower tributary flow due to the reservoir and a surfeit of nutrients from land-use changes are to blame, a team led by Fu Bojie, an ecologist at the Research Centre for Eco-Environmental Sciences of the Chinese Academy of Sciences in Beijing, reported last year in Progress in Physical Geography. A second scourge, they say, is increased heavy metal pollution.
Erosion, too, was underestimated. Because sediments accumulate in the reservoir, water released through the dam's turbines is relatively clear. Sediment-light water scours riverbanks to a degree that "is much higher than the designed and expected levels," Fu's team states. Severe erosion has caused some riverbank sections to collapse.
Another headache is schistosomiasis, known as snail fever in China. As many as 1 million Chinese are infected with the parasitic trematode, transmitted by Oncomelania snails. In endemic areas near lakes and wetlands in the Yangtze River Basin, prevalence hovers around 5%. The Three Gorges Dam increased the snail's habitat—and the infection risk. China's health ministry is improving sanitation and implementing other measures in a bid to reduce the infection rate to less than 1% by 2015.
In May, the State Council announced a massive effort to rein in other potential harms—stabilizing river flow, reinforcing levees, improving water quality—and boost livelihoods of displaced people. "The fact that the government openly acknowledged negative impacts was a significant change toward more openness," says Lars Skov Andersen of the E.U.-China River Basin Management Programme in Wuhan.
Since then, however, few details have come to light. One researcher who studies the new reservoir's impact on plant populations told Science that he has been ordered to deliver his reports to the government and cannot speak publicly about his findings. The official authorized to speak to the media was unavailable before Science went to press.
Secrecy aside, observers are confident that the initiative will have a robust scientific component. Some research lines may break new ground: for instance, probing habitat fragmentation after the reservoir turned dozens of hilltops into islands. But many findings are expected to be a sobering reminder that a big dam can bring unexpected consequences
The travails of the Three Gorges Dam are a cautionary tale for Laos and its Southeast Asian neighbors as they wrestle with the pros and cons of damming the lower Mekong River.
BEIJING—Scientists predicted that when the world's largest hydropower project came online in 2003, it would be an environmental bane. The Three Gorges Dam on the Yangtze River has unfortunately lived up to expectations. For that reason China is embarking on a 10-year mitigation effort that sources say will cost $26.45 billion.
The travails of the Three Gorges Dam are a cautionary tale for Laos and its Southeast Asian neighbors as they wrestle with the pros and cons of damming the lower Mekong River (see main text). Two consequences have proved worse than anticipated: deteriorating water quality and erosion. And the potential for spreading a snail-borne disease apparently wasn't even on planners' radar.
The decision to build the dam in 1992 came after decades of study and fierce internal debate. Benefits such as power generation and flood control are indisputable. But leaders also knew that the costs would be enormous. The newly created 1080-km2 reservoir submerged wholly or in part 13 cities and 466 towns, displacing roughly 1.3 million people, and triggered thousands of landslides. The reservoir wiped out fish spawning areas and raised an impassable barrier to one endangered mammal—the Yangtze finless porpoise—and two species that were in terminal decline: the Chinese river dolphin, or baiji, and the Chinese paddlefish (Science, 1 August 2008, p. 628).
Before the Three Gorges Dam began holding back the river in 2003, local Yangtze water by national standards was suitable for drinking. Not anymore. In the past several years, toxic algal blooms have regularly blighted 22 tributaries. Slower tributary flow due to the reservoir and a surfeit of nutrients from land-use changes are to blame, a team led by Fu Bojie, an ecologist at the Research Centre for Eco-Environmental Sciences of the Chinese Academy of Sciences in Beijing, reported last year in Progress in Physical Geography. A second scourge, they say, is increased heavy metal pollution.
Erosion, too, was underestimated. Because sediments accumulate in the reservoir, water released through the dam's turbines is relatively clear. Sediment-light water scours riverbanks to a degree that "is much higher than the designed and expected levels," Fu's team states. Severe erosion has caused some riverbank sections to collapse.
Another headache is schistosomiasis, known as snail fever in China. As many as 1 million Chinese are infected with the parasitic trematode, transmitted by Oncomelania snails. In endemic areas near lakes and wetlands in the Yangtze River Basin, prevalence hovers around 5%. The Three Gorges Dam increased the snail's habitat—and the infection risk. China's health ministry is improving sanitation and implementing other measures in a bid to reduce the infection rate to less than 1% by 2015.
In May, the State Council announced a massive effort to rein in other potential harms—stabilizing river flow, reinforcing levees, improving water quality—and boost livelihoods of displaced people. "The fact that the government openly acknowledged negative impacts was a significant change toward more openness," says Lars Skov Andersen of the E.U.-China River Basin Management Programme in Wuhan.
Since then, however, few details have come to light. One researcher who studies the new reservoir's impact on plant populations told Science that he has been ordered to deliver his reports to the government and cannot speak publicly about his findings. The official authorized to speak to the media was unavailable before Science went to press.
Secrecy aside, observers are confident that the initiative will have a robust scientific component. Some research lines may break new ground: for instance, probing habitat fragmentation after the reservoir turned dozens of hilltops into islands. But many findings are expected to be a sobering reminder that a big dam can bring unexpected consequences
