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Reduction in silt brings clearer Yangtze River
The amount of silt at the Yangtze River, China's longest, continues to decline, according to a recent survey of hydrological monitoring centres. The latest issue of the "Yangtze River Silt Bulletin" shows the average sand content dropped by 59 per cent in Yichang and 45 per cent at Shashi in 2003. Chen Songsheng, a deputy chief engineer of Hydrological Bureau of the Yangtze River Water Resources Committee (YRWRC), attributed the sustainable dropping of silt at the Yangtze River to water and soil conservation and construction of facilities for holding back silt at major reservoirs. China has built 12,000 reservoirs on the river's upper reaches with a combined water storage capacity of more than 30 billion cubic metres. These facilities play a major role in holding up silt, which poses a severe menace to China's flood control efforts, shipping industry and the lives of people nearby. The Three Gorges Project has blocked 124 million tons of silt since it began to store water in June last year. When China's policy-makers realized that rapid economic and population growth had turned the Yangtze River into a major soil erosion area, they launched a water and soil conservation project in 1988. The project, which cost 2 billion yuan (US$ 240 million), has reduced eroded areas in the Yangtze River Valley by 15 per cent to 500,000 square kilometres. Jialing River, a major tributary of the Yangtze, has only improved 20 per cent of the eroded area in the river valley. Nevertheless, 20 million tons of silt are held back annually. A clearer Yangtze has also helped reduce silt in the Dongting Lake, China's second largest freshwater lake. According to the YRWRC survey, there were 38.3 million tons of silt flowing into the Dongting Lake in 2003. Nearly half of the amount came from the Yangtze River. The rate of silt sediment was 20.5 million tons, accounting for one fifth of the average rate in previous years. The Dongting Lake, next in size to Poyang Lake with a drainage area of 262,000 square kilometres, is located in the northern part of Hunan Province, south of the Yangtze. The lake area has shrunk from 6,000 square kilometres in 1852 to 2,623 square kilometres by 1995 as the result of large-scale land exploitation and silt accumulation. Chinese experts say the lake will play its role of diverting floods on Yangtze River again with a silt reduction and conversion of poor farmland back into lake. |
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