Author(s): Dechun Liu; Miaolin Wang; Lijuan Guo
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Keywords: Pebble bed load; Sediment measurement; Sediment runoff characteristic; Three Gorges Project
Abstract: Detailed and accurate data are needed for researching the problem of Three Gorges Reservoir sedimentation. Measurements of gravel and cobble load transport in the Three Gorges Reach were started in early 1960 at Cuntan Station on the stem channel of the upper Yangtze River. From the beginning of the year 1974, measurement work was conducted successively at Zhutuo, Wanxian and Fengjie Stations. This paper presents the measuring method of gravel and cobble load, including the sampler, sampling and measuring frequency, arrangement of sampling verticals and sampling duration, as well as information reorganization and so on, and analyzes sediment runoff characteristic and its changes in the stem of the upper Yangtze River reaches. Results of the analysis indicate: (1) Pebble load in the stem channel of the upper reaches of the Yangtze River is not large, and approximately accounts for only 0.05% -0.09% of the total sediment load of suspended bed-material load in the same reaches and period; (2) Pebble load increased a little between Cuntan and Wanxian, and a slight decrease between Zhutuo and Cuntan, Wanxian and Fengjie; (3) Grain-size distribution of the pebble load shows a trend of decrease in particle size along the reaches downstream, and its variation basically agrees with the Sternbeg formula; (4) In the last 10-20 years, pebble load in the main stream of the upper Yangtze River has decreased by 22% -58%, and its median particle diameter D50 has been reduced by approximate 0.005m-0.013m. According to the investigation, that is caused by sand mining in the river channel and sand diversion by irrigation works.
Year: 2004