At China Dialogue, Jiang Gaoming examines the role of human activity in last year’s deadly Zhouqu mudslide:
Zhouqu county, in China’s north-western province of Gansu, was once known for its forests, rich water resources, fertile land and pleasant climate. But after the felling of tens of billions of cubic metres of timber and the construction of huge numbers of hydropower dams, the area’s hills have been left barren and unable to absorb rainfall.
Let’s look at the forests first. The county of Zhouqu has historically been rich in vegetation, with 1,300 species of higher plant alone … Following last August’s devastating mudslide, reporters noted that the hillsides above the Sanyan valley, one of the worst hit areas, were bare of trees and even the brush was sparse. According to local elders, when they were in their teens the valley was covered with large trees. Once the hillsides were stripped, the villagers grazed goats here, worsening the environmental damage. Without the vegetation, heavy rain was able easily to loosen soil and stones, triggering landslides that threatened lives and property below.
In addition to deforestation, widespread construction of hydropower dams has contributed to the area’s vulnerability. The Bailong River, the largest tributary of the Jialing, is 600 kilometres long, 450 kilometres of which flows within the borders of Gansu province. The rapid flow as the river passes down through the mountains makes this an ideal area for building hydropower facilities – and many have been built. But with no thought given to upstream ecologies, such projects have increased the likelihood of mudslides. The Bailong flows through a zone that is prone to earthquakes and the quarrying of stone from the banks of the river to build the dams has further destabilised the hillsides ….
Zhouqu exploited its mountains, its water and its rivers and, in return, suffered a powerful mudslide. This is the national ecological disaster in microcosm.
Hydropower projects have been implicated in other recent disasters, such as the 2008 Wenchuan earthquake: the weight of the water behind large dams can trigger “Reservoir-Induced Seismicity”. A recent interim report by the Chinese Academy of Engineering, covered by Beijing Review, concluded that the Three Gorges reservoir was not to blame for the 2008 quake, though the finger of blame in that case is more often pointed at the relatively nearby Zipingpu reservoir.
The CAE report also claimed that siltation would not choke the Three Gorges as it had the ill-fated Sanmen Xia dam, whose epic tale has been previously featured on CDT.
A silver lining, thin though it is, of natural disasters is the learning opportunity they can offer: last year, the International Commission On Large Dams released a paper on the lessons learned from the Wenchuan earthquake and its effects on dams in the stricken area.