China Turns on Tap for Yellow River Silt Trial

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Last updated at: (Beijing Time) Friday, July 05, 2002

China Turns on Tap for Yellow River Silt Trial

A 10-day campaign to flush silt from the middle and lower reaches of the Yellow River was launchedin Zhengzhou on Thursday at the Xiaolangdi Reservoir in central China's Henan Province.

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A 10-day campaign to flush silt from the middle and lower reaches of the Yellow River was launched in Zhengzhou on Thursday at the Xiaolangdi Reservoir in central China's Henan Province.

At 9:00 a.m., when the reservoir's sluice gates opened, powerful jets of water shot out, blasting through the Huayuankou Hydrologic Station at a controlled speed of 2,600 cubic meters per second.

Li Guoying, director of the Yellow River Water Conservancy Committee, said that the experiment was a milestone for China after decades of intensive research.

"The purpose of the experiment is to find the best pressure to send enough water flowing to the lower reaches to flush the silt deposits away," he said.

According to Liu Jixiang, chief engineer of the program, the projected speed of 2,600 cubic meters per second would ensure a sufficient volume of water to flush away the 24.4 million tons of silt deposited over the years on the bed of the river's Tiexie-Lijin segment.

The Yellow River, the second largest in China, has long been plagued by growing siltation. Every year, 1.6 billion tons of silt are swept down to the lower reaches, of which 400 million tons are deposited on the riverbed.

As a result, the river bed rises by 10 centimeters each year causing increased pressure on dam structures. In some places, banks built to withstand floods are higher than nearby townships and flooding poses a great danger to the local population.

To collect data for future silt clearances, the committee will release water at different pressures and monitor the results four times a day.

Construction of the 126-million-yuan Xiaolangdi Reservoir (about 15 million US dollars) began on August 20, 1998. The 5,464-km-long Yellow River runs through nine Chinese provinces and two autonomous regions, emptying into the Bohai Sea, in Shandong Province in east China.

Backgrounder: Uses of Xiaolangdi Reservoir

The Xiaolangdi Reservoir began to be used for a range of purposes such as flood prevention, silt reduction and supplying water to nearby cities for industry and agriculture, when completed at the end of 2001.

Located at the mouth of the last gorge on the lower reaches of the Yellow River, the reservoir is crucial to eliminating river bed siltation.

With a projected capacity of 12.65 billion cubic meters of water, the dam, the largest of its kind on the Yellow River, can hold up to 7.6 billion cubic meters of silt.

If the silt stored in the reservoir reaches 10 billion tons, it is believed that river bed levels in the lower reaches may not rise within the next two decades.

During dry seasons, the reservoir stores water and traps sediment. During flood seasons, it discharges both water and silt.

The idea of using artificial water flows to flush away silt on the middle and lower reaches was first proposed during the 1940s and 1950s.

Currently, over 4.4 billion cubic meters of water is stored in the reservoir, which is enough to guarantee the ongoing silt-clearance experiment.

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