(March 28, 2011) A new study warns that plans to raise the Danjiangkou Dam could lead to earthquakes of greater than 4.0 on the Richter Scale. Experts say the dam triggered an earthquake of M 4.7 in 1973.
China’s multi-billion dollar project to divert water from a tributary of the Yangtze to supply parched Beijing with water could trigger earthquakes say seismic experts.
The plan involves raising the Danjiangkou Dam’s reservoir height by 10 metres in order to redirect 9.5 billion cubic metres of water annually 1,000 kilometres to Beijing to ease the city’s water crisis. Writing in the Geophysical Journal International, Sumei Liu, Lihua Xu, and Pradeep Talwani say that raising the reservoir to that height—170 meters above sea level—could trigger earthquakes that exceed magnitude 4 on the Richter scale.
Their startling conclusion comes after reviewing the history of the Danjiangkou Dam, which was completed in the 1960s, in an area with “very low levels of natural seismic activity.” After impoundment began in 1967, the authors report, “the frequency and intensity of seismicity in the area dramatically increased,” culminating in a destructive earthquake with M 4.7 in 1973.
Large reservoirs are known to trigger earthquakes in a phenomenon called “reservoir-induced seismicity.” Interest in RIS has grown since geoscientists began suggesting that the Zipingpu dam in Sichuan province may have triggered the deadly 2008 earthquake that killed 90,000. Of the 102 RIS events that have been recorded world-wide, 16 have occurred in China.
The plan to redirect water from the Danjiangkou Dam to Beijing is part of a $65 billion mega-project to rearrange China’s water basins, called the South-North Water Diversion Project – a plan so ambitious that it dwarfs the Three Gorges dam. Designs call for three different routes to divert water from China’s southern flood plains and western snow-capped mountains northward. The route from the Danjiangkou reservoir is the middle of the three and will channel water from the Han River, a major tributary of the Yangtze in central China.
The reservoir level at Dangjiankou is scheduled to begin rising in 2013. Though RIS is difficult to predict, one pattern indicates that smaller seismic tremors begin immediately as the reservoir rises, followed by deeper, larger magnitude earthquakes on average 4-5 years following maximum impoundment.
The authors of the Geophysical Journal International article are concerned about the “four major Palaeozoic deep regional crustal faults that criss-cross in the reservoir area,” concluding that the induced seismicity that has occurred so far at Danjiangkou was mainly due to water and pore pressure migration along two of those faults. They also noticed a clear relationship between the water levels and the intensity of the earthquakes: the higher the reservoir level, the bigger the ensuing earthquake.
Based on their observations, Talwani et al. anticipate that the increase in the lake level by more than 10 metres to 170 metres above sea level “will be accompanied by seismicity with magnitudes more than M 4.0.”
That news is sure to compound the misery the project is already causing: 330,000 people are in the throes of being resettled to make way for the higher reservoir. But they may be the lucky ones if their new homes are located far enough from the dam where the seismic activity might occur. Those who remain living close to the reservoir could be at greatest risk of landslides and building collapses triggered by seismic events.
Environmentalists won’t be surprised by the scientists’ prediction. For years they have warned that existing large dams should be monitored for RIS and new dams should be avoided because they can cause large earthquakes and large loss of life.
Meanwhile, a rare public opinion survey carried out by Chinese environmentalists last year, showed that Beijing residents would rather opt for conservation and water recycling than large-scale water diversions, arguing that the city should live within its own watershed using pricing and technical innovations to achieve efficient water use.
This latest evidence that Beijing’s failure to manage its own water supplies properly is putting citizens in other parts of the country at risk illustrates the unfairness of the ill-fated water diversion scheme.
Though the project is supposed to be a showpiece for President Hu Jintou’s theories of “scientific development,” it has an origin with dubious scientific merit: In 1952, Chairman Mao reportedly commented that “there’s a lot of water in the south, but not much in the north. If we could borrow some, then everything would be OK.”
When it comes to “scientific development,” China’s leaders would be better served by listening to seismicity scholars and their own people, rather than the musings of the Great Leader.
Patricia Adams is the Executive Director of Probe International.
Read the full article, “International Reservoir-induced seismicity in the Danjiangkou Reservoir: a quantitative analysis,” by Sumei Liu, Lihua Xu, and Pradeep Talwani in the Geophysical Journal International (payment required).
 Pore water pressure refers to the pressure of groundwater held within soil or rock, in gaps between particles (pores).
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