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Man-made waves deepen Yellow River
(China Daily)
Updated: 2004-06-28 07:38
ZHENGZHOU: The Yellow River, China's second longest, has been deepened by at
least 30 centimetres with the help of artificial waves that have flushed away 10
million tons of sand since a third round of silt-washing operations started last
week.
The work, which started on June 19, created artificial tides in the
Xiaolangdi Reservoir and stirred its sediments to the lower riverbed by an
average 30 to 40 centimetres, according to data provided by the Lijin
hydrological station.
The Lijin hydrological station is the last such station the river water has
to pass before entering the Bohai Sea.
The peak of the artificial floods arrived at the Lijin hydrological station
at 10:24 am Thursday, nearly 48 hours ahead of schedule because the loss of sand
had increased waterflow, hydrological workers said.
Waterflow was 2,500 cubic metres per second and the water course was 340
metres wide, as the peak of the flood - which contained 18 kilograms of sand in
every cubic metre of water - reached the Lijin hydrological station.
The silt-washing operation also raised the water level by 1.2 metres to 13.03
metres, according to hydrological reports.
The peak then flowed into the Bohai Sea at 6:30 pm Thursday. By then, the
silt-washing operation had poured 700 million cubic metres of muddy water into
the sea.
The operation will be a landmark for China to shift from traditional to
modern means in harnessing and exploring the Yellow River, according to Li
Guoying, director of the Yellow River Water Resources Committee.
The committee carried out two sand-washing operations in July 2002 and
September 2003 by discharging currents from the Xiaolangdi Reservoir on the
lower reaches of the river. The two operations washed a total of 187.1 million
tons of sand into the sea.
According to Li, the ongoing third round will rush off silt stored at
Wanjiazhai, Sanmen Gorge and Xiaolangdi reservoirs to clear up the whole water
course and expand in particular the runoff of its lower reaches.
Silt-stirring vessels are in place to churn the densely silted river sections
and sediments of the Xiaolangdi Reservoir, the largest water conservation
project on the Yellow River.
The Xiaolangdi project, which is second only to the Three Gorges Dam on the
Yangtze River in terms of workload, has already prevented some 900 million tons
of silt from flowing into the lower reaches since it started storing water in
October 1999.
But experts say the build-up of silt in the lower reaches of the Yellow River
is still worrying, since 400 million tons silt up on the riverbed every year,
raising the water level by 10 centimetres.
The 5,464-kilometre-long Yellow River originates on the Qinghai-Tibet
Plateau, winds its way through eight provinces and autonomous regions, and
empties into the Bohai Sea in North China.
Once a notorious troublemaker in the Chinese history, the Yellow River used
to breach its embankment twice every three years and change its course every 100
years over the past 2,000 years.
Now the river carries some 1.6 billion tons of silt into the sea annually.
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