Huang Wanli warned that Chongqing harbour would silt up
|On flood control, Professor Huang Wanli strongly questioned the wisdom of building the Three Gorges dam. He warned that Chongqing harbour at the tail end of the Three Gorges reservoir would silt up with coarse pebbles after the reservoir was filled, causing more frequent and severe flooding in the densely populated region of Sichuan province and Chongqing municipality. Prof. Huang pointed to the flood disaster that occurred in Ankang, Shaanxi province, in 1983. The city is located 200 kilometres upstream of the Danjiangkou dam on the Han River, a major Yangtze tributary. After the Danjiangkou dam was built in 1969, coarse pebbles began to accumulate in the river section below Ankang. When major rainstorms hit the region from July 27-31, 1983, the level of the Han River rose precipitously. Ankang was caught in a "pincer attack" from upstream and downstream areas. Due to the heavy rainfall, operators of the Shiquan reservoir upstream of Ankang were forced to release water just as the water level in deep gorges below the city was also rising rapidly.|
The entire city of Ankang was flooded on July 31, 1983,
Statistics compiled by water experts reveal that as many as 36 per cent
of China's reservoirs are poorly constructed or dangerous
Statistics compiled by water experts reveal that as many as 36 per cent of China's reservoirs are poorly constructed or dangerous.
Half of those are medium or large in size, and about 700 of them are in urgent need of repair.
Roughly 10,000 small reservoirs are in the same sorry state.
Such poorly built and dangerous reservoirs are time bombs waiting to explode in the event of a severe flood or other unexpected occurrence.
Unfortunately, Chinese history provides no shortage of lessons on dam failures. One of the worst was the collapse of the Banqiao and Shimantan dams in central China. In August 1975, exceptional rainfall caused devastating floods in the Huai River valley in Henan province. The two medium-sized dams collapsed, along with 60 smaller reservoirs. The tragedy affected 12 million people, and claimed as many as 200,000 lives.
Wang Shucheng, the minister of water resources, has said that 235 dams (233 small, two medium-sized) have collapsed in China since 1991. Of these, 147 burst when flood water overtopped the dams -- 71 of which turned out to have been poorly constructed. Mismanagement was cited as the cause of the other collapses.
China leads the world in terms of number and scale of dam projects, but it has lagged behind developed countries in the safety management of dams and reservoirs. In 1991, the government issued a "regulation on safety management of dams and reservoirs" and another on "methods of management on the downgrading and dismantling of reservoirs" in 2003, but problems have arisen with the implementation of these policies. Moreover, financial and technical difficulties persist with the management of the poorly built and dangerous reservoirs.
A number of hydropower projects have been built in this region
of southwest China without due regard for the danger
When a dam is being planned, the potential impact of seismic activity
is considered. But in a geologically complex area prone to disasters,
this does not mean the dam will be safe