Periodic characters of sediment load and runoff changes in the Yangtze River basin in the past 40 years, China

Monthly mean sediment load and runoff changes in the past 40 years are analyzed at Pingshan station,Yichang station,Datong station and Hankou station along the mainstream of the Yangtze River basin and Beipei station in the tributary of the Yangtze River basin,with the help of wavelet transform method.The results indicate that:① the wavelet transform method is the proper method for detecting the influences of water reservoirs on transportation of sediment load and runoff changes.The influences of water reservoirs on sediment load are more serious that those on runoff changes; ② Gezhouba dam exerts less influences on runoff changes and sediment load.The down-cut of the riverbed occurrs after the operation of Gezhouba dam,but this influences are not enough to remove the 1-year-period of runoff and sediment load changes; ③ The Three Gorges dam exerts increasing influences on sediment load transportation,removing the 1-year-period sediment load of sediment load changes,but shows no influences on runoff changes.The influences of Three Gorges dam on sediment load are adverse to the distance to the Three Gorges dam; ④ The influences of water reservoirs on sediment load and runoff changes is related to the size of the river catchment.The sensitivity of influences of water reservoirs on sediment load is less in the larger river catchment.