Situated on the Yangtze River in China, the Three Gorges Dam is the largest hydroelectric dam in the world. A Xylem solution at the dam provides data that helps prevent flooding and droughts.
The Three Gorges Dam and its reservoir were designed to protect residents from floods, provide freshwater for agricultural use, and be a source to generate electricity without greenhouse gas emissions.
Construction on the dam started in 1994 and was complete by 2012. The Three Gorges Dam spans 1.4 miles (2.3 kilometers) and is 607 feet (185 meters) tall. In 2014, the dam generated 98.8 TWh of electricity, which was a new world record.
In 2011, however, Southern China was facing the worst drought the country had seen in 50 years. The Three Gorges Dam was criticized by environmentalists, who blamed it for causing the drought by storing water upstream for power generation.
They argued that the annual filling of the Three Gorges Reservoir drastically reduced water levels downstream, causing two of China’s largest freshwater lakes, the Poyang and Dongting, to shrink.
A water monitoring solution for the Yangtze River
Regardless of the drought’s cause, Chinese officials took action. They installed nearly 100 water monitoring sites along the Yangtze River. A H-3553T bubbler from YSI, a Xylem brand, was also installed to gather stage and flow measurements. This data helps officials accurately monitor the water levels of the river above and below the dam.
Monitoring the water levels is important for a number of reasons. The monitoring system provides early warning for future flooding, helps manage droughts, and assists with electricity generation.
Keeping upstream and downstream water in balance
“The sensors from the monitoring sites provide key data that help the Three Gorges Cascade Dispatch Center and Changjiang Water Resources Commission,” says Roger Zhou, Xylem Analytics representative. “The Commission uses the data to build a regional water flow model, which is used for power generation estimation and to calculate the storage capacity of the dam.”
The reservoir holds water at a maximum height of 574 feet (175 meters). If too much water is held in the dam, then there is flooding upstream, but if too much water is released, then there is flooding downstream. So officials analyze the data to determine how much water to discharge.
Monitoring the capacity of the dam is also important when storms are expected.
“If the reservoir is full, there is no room to catch and hold water if there is a flood,” says YSI Water Level Division Product Manager, Tim Jeppsen. “If a big storm is coming, they need to know if there is capacity in the reservoir to prevent flooding below the dam.”
Managing droughts and urban water shortages
Holding too much water in the dam could also cause drought conditions that affect farmers and water transportation.
“Managing the water level data directly affects the lives of millions of people both upstream and downstream from the Three Gorges Dam,” says Jeppsen. “The data also helps officials to redirect the water to cities where residents are experiencing shortages.”
Get more Xylem Analytics news in the magazine Mission: Water.