(May 18, 2011) China’s drought has caused the Three Gorges reservoir level to drop precipitously, crippling the mighty Three Gorges Dam. Shipping on the Yangtze River has now halted, power generation has been compromised, and geological hazards are heightened.

By Lisa Peryman, Probe International

Update to this story: Water depth at Three Gorges Dam stood at 154.8 meters on Tuesday afternoon.

China’s worst drought in the past half-century has forced authorities to shutdown a section of the Yangtze River, the central vein of the country and its most important shipping route, to oceangoing vessels.

The dry-up has forced the Yangtze River Waterway Bureau to close a 185-kilometer (115-mile) stretch of the 6,300-kilometre Yangtze from Wuhan in central China, the country’s most populous city, south-west to Yueyang. For now, emergency teams are continuing their work to prevent accidents in the Yangtze’s midsection where the once mighty river is reported to have shrivelled by around 50 metres from last year to an average width of 150 metres.

The brutal spring has left at least two ships grounded, more than 700 ships stranded, made drinking water scarce for hundreds of thousands of people, not to mention livestock, and has brought devastation to farmlands.

The country’s state news agency Xinhua claims the five-month drought has rendered nearly 1,400 reservoirs in Hubei Province, which runs along the middle reaches of the Yangtze River, temporarily unusable. Meanwhile, one-fourth of all small reservoirs contain what officials describe as “dead water” which is off-limits, save for emergency use.

For the second time since it began operation in 2003, officials have been forced to resort to emergency discharges of water from the Three Gorges Dam, to help ease the crisis, although there are claims the giant dam, and the world’s largest, has actually exacerbated the problem by changing the water table in the river’s basin. The river basin is home to one-third of China’s population and is responsible for 40 per cent of the country’s economic growth; it also provides a water highway for 80% of China’s river freight.

But water inflow into the giant dam’s reservoir from the upstream section of the Yangtze River is down 40 percent. The store of water in the reservoir is now further strained by the current release of water at a rate of 7,000 cubic meters per second to ease the downstream drought. If the dam’s reservoir level falls below 155 meters, power output would be compromised, so an inevitable tug of war has begun over the Yangtze’s reduced flow: downstream populations and ships want the reservoir’s water released while Yangtze Power, the owner of the turbines and generators, will want it reserved for power generation.

Truly menacing, though, is the potential for geological disasters. Geoscientists worry that a rapid drawdown in a large reservoir can trigger landslides, and even earthquakes. For example, China’s deadly May 2008 earthquake occurred soon after the Zipingpu dam on a tributary of the Yangtze was drawn down quickly.

The sudden shortfall in water does not surprise dam critics. According to Patricia Adams, Executive Director of Probe International – which has published several books on the Three Gorges dam – large dams are typically state vanity projects financed by governments with deep pockets. As such, dam designers haven’t taken the vagaries of water flows seriously, or considered their consequences.

“Three Gorges is a classic case in which government officials exaggerated the benefits and underestimated the risks,” she says. “What mattered to the Chinese authorities who approved the dam was the prestige of building the world’s largest dam.”

That prestige is surely fading now as the current fiasco plays out on the Yangtze: the world’s largest dam is holding back only a little water while two of its main functions – power generation and shipping – have been stymied by nature.

See Reservoir levels at the Three Gorges Dam: Probe International’s “ticker tape” monitor of Three Gorges reservoir levels.

Further Reading From Probe International

Expect geological trouble at Three Gorges: report

Fragile Three Gorges: Caijing magazine reports

Landslide hits town near China’s Three Gorges dam

Dam on dangerous ground

Quakes jolt Three Gorges area as huge reservoir fills

Three Gorges: Privatizing the profits, socializing the costs

China’s earthquake and early warning system

China’s Three Gorges dam: An environmental catastrophe?

Scientists build case that Zipingpu dam triggered China’s devastating earthquake