The long-awaited drainage of China's Tangjiashan "quake lake" started at 7:08 a.m. Saturday, when its water flowed into a manmade sluice channel.
A Xinhua reporter at the commanding center saw water passing the sluice channel via satellite monitor. The flow was rapid, steady and gradually increasing in volume.
The water level at the entry of the sluice channel was 740.37 meters above the sea level.
The channel bifurcated, and some of the water diverged into the separate small channel at 9:30 a.m..
Soldiers of the armed police force are still working at the exit of the sluice channel to expand the channel and make it steepy so that the flow could be speeded up.
The overflow has been estimated to occur Friday night when water level reached the lowest point of the blockage, but it was delayed by a 0.6-meter-high temporary dam erected on Friday afternoon to protect workers dredging the sluice channel.
The swollen lake was formed by a massive landslide following the May 12 earthquake that jolted the country's southwest. It held more than 220 million cubic meters of water and posed a threat to about 1.3 million people downstream.
Some 600 armed police and soldiers worked for six days and nights to dig a 475-meter channel to divert water from the lake.
More than 250,000 people in low-lying areas in Mianyang have been relocated under a plan based on the assumption that a third of the lake volume breached its banks.
Two other plans require the relocation of 1.2 million people if half the lake volume is released or 1.3 million if the barrier fully opened.
The lake is also posing a threat to the Fujiang river bridge on the Baoji-Chengdu Railway, a critical part of the railway network in west China.
Liu Yongzhan, a pontoon bridge army colonel, told Xinhua that his men are ready to protect the bridge by intercepting, bombarding and salvaging large floaters that may be washed down by the flooding.
The swollen quake lake has put China's longest oil pipeline at risk. The pipeline, winding from Lanzhou via Chengdu to Chongqing, was 60 kilometers downstream from the lake.
With a capacity of transferring six million tons of oil each year, the pipeline provides 70 percent of product oil to Sichuan and neighboring Chongqing Municipality.
If the line was cut, refined oil in storage could only supply Sichuan for three days, whereas repair work would take 30 days.
Source: Xinhua
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