Three Gorges “Reservoir Watch”

Reservoir levels at the Three Gorges Dam: Why we are tracking them.

Although the Three Gorges Dam is a multitasking giant designed to generate electricity, control floods and promote navigation, it has difficulty meeting these design goals simultaneously. In the dam’s operations, these three functions tend to conflict with each other. When the dam’s water levels are lowered in anticipation of containing surging floodwaters, power generation suffers. So too does navigation upstream. When water is retained in the reservoir to generate maximum power, downstream areas are deprived of water and ships are beached. When floodwaters do come, water is retained in the reservoir to protect downstream populations, causing flooding for upstream populations instead. This is especially so for the Three Gorges Dam where silt deposits in the slow-moving waters of the reservoir are raising the river bed and the dam’s reservoir to a higher level than announced, placingupstream populations at risk of flooding.

For the millions of people living upstream and downstream of theThree Gorges Dam,the management of the dam’s reservoir level directly affects their security and livelihoods. But the risks don’t end there.

Landslides are triggered by a rising and falling reservoir after water permeates the surrounding soil, loosens it and induces large and small land masses to slide down into the reservoir. According to Chinese and US Geological Survey experts, thousands of landslides in the geologically young Three Gorges area could be triggered in this way. Some already have, with deadly consequences.

Seismologists have also detected that earthquakes induced by large reservoirs, like Three Gorges, occur after a dam has operated at its maximum operating level (called the Normal Pool Level or NPL) and goes into drawdown – with the largest reservoir-induced seismic events occurring within 4 to 5 years after reaching the NPL. Scientists now believe that this process at the Zipingpu dam in Sichuan may have triggered the May 12, 2008 earthquake that killed 90,000 Chinese citizens and are poring over data to determine the dynamic effect of the dam’s reservoir levels on seismic activity leading up to and including the enormous M7.9 earthquake.

The Three Gorges reservoir levels are important for reasons of public safety. But they also serve as an important indicator of the dam’s failure to deliver its promised goals: insufficient water cannot generate the electricity revenues to cover the cost of dam construction, or facilitate shipping upstream to the port of Chongqing. Threateningly high water levels caused by high inflows indicate that the dam cannot contain floodwaters, as promised.

For these reasons, and in order to produce a clear-eyed analysis of the costs and benefits of the Three Gorges Dam, we are tracking the daily Three Gorges reservoir level here.