The lower reaches of the Yellow
River, a famous "suspended river" with a riverbed four to six
meters higher than the surrounding fields, is symbolized as "a
sword hanging above the heads of local residents." Continuous
droughts and increasing silt deposits in the riverbed in past 10
years have built up another "suspended river," which, three to five
meters higher than the base of the first one, adds greater pressure
to the work of flood control.
According to Hong Shangchi, deputy
general engineer of the Yellow River Conservancy Commission the
river course becomes remarkably broad when the Yellow River flows
into the lower reaches. Of the total area of 4,200 square
kilometers of the river course, 84 percent is beach land and only
the narrow sunken part in the middle serves as riverbed.
In a normal year, 30 percent of the
silt brought down by the Yellow River is dumped into the riverbed
while 70 percent of it is deposited in the beach land. The river
course used to be at a condition of higher beach land and lower
riverbed.
However, during the past 10 years,
the Yellow River has been short of water for most of the time. As a
result, 90 percent of its silt has been deposited in the riverbed.
The beach land, then, has had less sedimentation due to less
exchange of water and sand. Another "suspended river" higher than
the original riverbed has thus been formed in the river course.
Currently, a 300-kilometer-long "second-level suspended river" lies
on riverbed of the Yellow River's lower reaches.
Some experts from the Yellow River
Conservancy Commission pointed out that under the condition of the
"second-level suspended river," once big floods occur, it will
cause great changes in the river's flow. The main stream of the
Yellow River may flow wildly and hit the embankment directly,
greatly increasing the risk of flooding and the breaching of dykes.
Therefore, the control of the "second-level suspended river" has
become an extremely urgent task in harnessing the Yellow
River.
A trial project of controlling the
"suspended river" in the lower reaches of the Yellow River was
started on June 6 in Puyang, central China's Henan
Province. Builders will dredge a six-kilometer-long river
section ranging from Nanxiaodi to Penglou of Puyang in order to
increase the flood discharging capacity of the riverbed. The
project will hopefully help accumulate experience for more powerful
and effective control of the "second-level suspended river" in the
future.
(China.org.cn by Wang Qian, July 24,
2003)