BEIJING -- A growing threat of landslides on ground surrounding the massive Three Gorges Dam reservoir could force the government to relocate 100,000 more residents of the area, from which 46,000 were moved earlier, an expert with China's land and resources ministry said this week.
The official, Liu Yuan, told China National Radio on Monday that rising water levels in the reservoir had made adjacent land increasingly unstable. Since the reservoir reached its high-water mark in 2010, landslides and other accidents have risen 70 percent.
"Due to the complexity and uncertainty of the problems, the pattern of geological disaster cannot be accurately predicted," he said. "It's difficult to know what's going on."
Mr. Liu runs the ministry's Three Gorges Geological Disaster Prevention Office.
The dam, the world's largest hydroelectric project, has been a target of criticism by environmentalists and some geologists since before the reservoir began to inundate a long stretch of the Yangtze River, long regarded as one of the world's scenic wonders, in 2003. A massive landslide occurred that year, followed by others, but only in 2007 did the government admit that the rising waters were causing instability and that a catastrophe could occur unless preventive steps were taken.
Officials have recorded 430 landslides and nearly 2,900 smaller geological accidents along the lakeshore, and 5,386 other potentially dangerous sites are being monitored, Mr. Liu said.
Major slides not only imperil people living along the shore, but can create huge, dangerous waves. The 2003 landslide generated a 65-foot wave that killed at least 14 people. A 2007 slide on a Yangtze tributary near the reservoir buried a bus, killing 31.
The government relocated 1.4 million people to build the dam and reservoir, which is comparatively narrow but longer than Lake Superior in North America. The latest proposed relocation affects residents along hundreds of miles of twisting lakeshore from Jiangjin, in the Chongqing municipality, to the dam's location at Yichang, in Hubei Province.
Since the reservoir began filling with water, officials have experimented with different water levels, from 445 feet to 575 feet deep, which is the proposed eventual depth. Geologic incidents have become more frequent as the amount of water has increased.
Landslides can be expected within three to five years after the reservoir reaches its maximum depth, Mr. Liu said.
The slides are caused in part by the government's seasonal raising and lowering of the lake's water level to cope with floods, according to an examination of the dam's problems in a 2008 article in Scientific American magazine. At high levels, water seeps into soil atop the Yangtze's steep cliffs, making it prone to slides. At low levels, the reduction in water pressure on the land renders the moist soil even more unstable.
Other experts say the sheer weight of the massive lake has increased the threat of earthquakes in the fault-prone region.
Li Bobo contributed research.world
This article originally appeared in The New York Times.