Analysis on Changes of the Transportation Characteristics of the Bed Load into Three Gorges Reservoir and Their Causes

Zhutuo and Cuntan gauging station are the main reference points into Three Gorges Reservoir. The survey data of gravel bed load in Cuntan station from 1996 to 2001 and Zhutuo station from 1975 to 2001were analyzed. It was found that the bed load transportation has decreased systemically, the sediment granule diameter has become smaller, the sand starting flow velocity has aggrandized and the relation between flow and sand has changed obviously in Cuntan station since 1981 and Zhutuo station since 1991. Finally, it was concluded that the variations be caused by more sediment excavated from the watercourse and more water works block and keep water and soil from running off.