“Why do earthquakes keep happening in that area?” In the wake of China’s 6.1 magnitude quake in Yunnan Province and a number of smaller quakes in the region, questions are once again being asked about the country’s rush to build big dams in its southwestern mountains, an area already vulnerable to seismic hazard.

By Simon Denyer for The Washington Post

BEIJING — As the death toll from an earthquake in southwestern China rose to 589 on Wednesday, it has rekindled a debate about whether the country’s rush to build big dams is to blame for such calamities.

Search-and-rescue teams took advantage of drier weather Wednesday to push into the hard-hit mountain communities after the magnitude 6.1 quake, the country’s deadliest in four years, struck near the city of Zhaotong in Yunnan province.

But questions are once again being asked about China’s rush to build big dams in its southwestern mountains, especially in the wake of a number of smaller quakes since the water level was raised last year at the Xiluodu hydropower station, which lies about 100 miles north of the epicenter of Sunday’s quake.

“Why do earthquakes keep happening in that area?” Wang Yongchen of the environmental group Green Earth Volunteers wrote on his microblogging account. “We can’t afford not to ask the reason why.”

Large reservoirs are known to put pressure on Earth’s crust and can cause quakes, although the link is often hard to establish definitively. China’s dash for hydropower, linked to soaring energy needs, has been the subject of much criticism, especially because many of the dams are being built in regions of “high or very high seismic hazard.”

In May 2008, a debate erupted after a magnitude 8.0 quake struck in Sichuan province, killing nearly 90,000 people, including thousands of children. Some geologists argued that a nearby mega-dam could have been responsible, but government hydro-engineers said reservoirs are more likely to cause small quakes, relieving pressure on Earth’s crust, than large ones.

Yet, now, some government scientists are voicing concern.

Fan Xiao, chief engineer in the Sichuan Geology and Mineral Bureau, said that more than 2,000 small quakes had been detected since the water level increase at the Xiluodu dam in October and that a magnitude 5.3 temblor was observed near the hydropower station in April.

“It all suggested the elevated water levels at the hydro station might have caused an increase in crustal movement,” he said. It was a pattern similar to that observed in Sichuan in 2008, he said.

“We cannot rule out the possibility that this earthquake might be related to the dams in the area,” he said.

There are 25 dams planned or under construction on the Jinsha River, a 1,400-mile tributary of the Yangtze River that runs through Zhaotong.

Independent geologist Yang Yong has been arguing for years that the dams were an environmental disaster and an accident waiting to happen. The area is prone to quakes, with a magnitude 7.0 temblor killing more than 1,400 people in 1974.

There is also the risk of dams breaking during a quake, causing flooding and even higher loss of life, he says.

The official Xinhua News Agency reported this week that a huge lake has formed as a result of landslides caused by Sunday’s earthquake, containing close to 50 million cubic meters of water. The lake is near an under-construction hydropower station and threatens seven other stations downstream, it reported.

Deng Fei, an investigative reporter who leads charity campaigns, said he was concerned by the dam building on the Jinsha when he visited several years ago. “I felt scared at the time,” he posted on his microblogging account. “We are fighting heaven and earth in this way — aren’t we scared of retributions?”

Another Weibo user said he had donated money for previous quake relief efforts but would not do so anymore. “So many houses collapsed after a 6.5-magnitude quake. Who is taking responsibility for the quality of buildings?” he asked. “Are the frequent earthquakes related to the hydro-stations of all sizes being built everywhere? Could you stop lying to the people?”

Fan, the geologist, said that the Xiluodu dam has not yet reached its full capacity and that worse could come in the years ahead. “It’s unlikely the authorities will stop developing hydro projects,” he said, “but what they can do is make the buildings in areas at high risk stronger and quake-resistant.”

Xu Yangjingjing and Gu Jinglu contributed to this report.

Simon Denyer is The Post’s bureau chief in China. He served previously as bureau chief in India and as a Reuters bureau chief in Washington, India and Pakistan.

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