Environmental protection efforts by
Sichuan Province in southwest China pay off, and the ancient
Dujiangyan irrigation system will soon require dredging and
maintenance only once every 20-30 years, instead of once a year.
Li
Junzhu, a senior engineer in charge of the dam's maintenance, said
Saturday it will no longer be necessary to block the inner canal to
dredge and remove silt on an annual basis due to the marked
reduction in silt accumulation.
The Dujiangyan irrigation system traditionally underwent dredging
and maintenance on an annual basis, a rule set by its builder Li
Bing, an official of the Qin Kingdom during the Warring States
period (475 BC-221 BC).
Between 1974 and 1992, according to Liu Zhenghui, an engineer from
the Dujiangyan Administrative Bureau, the system's inner canal was
dammed for dredging every four to five years on average. The
system's last maintenance took place ten years ago.
"This is largely due to fewer floods on the Minjiang River, better
water quality and less silt in the water control project area," he
said.
Water and soil conservation efforts in the Minjiang source area
over the past decade have contributed to reducing the amount of
silt in the river.
With regard to soil conservation, deforestation was prohibited in
mid-1990s, and some farm land was converted into woodlands.
Another major factor behind the silt reduction is the scientific
and management of the irrigation system, said Peng Shuming,
director of the Dujiangyan Administrative Bureau.
Currently, a large water conservancy project is being built
upstream from the Dujiangyan irrigation system, which will help
protect the ancient irrigation system from the threat of
floods.
The 2,250-year-old irrigation system, on the upper reaches of the
Minjiang River, a major tributary of the Yangtze River, is
considered the oldest functioning irrigation system in the world.
Restoration of the system to its original form got underway
Wednesday and is expected to be completed in 42 days.
(Xinhua News Agency November 16, 2002)