Analysis of influence of large-scale water conservancy project on variation characteristics of water and sediment in middle and lower reaches of Yangtze River

After impoundment of the Three Gorges Dam,the runoff and sediment discharge of downstream are directly affected. According to the hydrological data in Datong and Yichang station for 1988 to2012 year,the paper used correlation analysis method and non-parametric Mann-Kendall test to comparatively analyzed runoff and sediment discharge characteristics and its variation rule in time and space in Datong and Yichang station of Yangtze River Basin. It was found that due to the water storage fluctuations,the annual runoff in Yichang and Datong stations of Three Gorges Dam reservoir,but there do not appear significant trend change; and sediment began to decline from 1980's,the decrease trend of sediment discharge is clear in 2003 after completion of the Three Gorges Dam. The impact of the Three Gorges dam downstream on water and sediment of downstream hydrological stations decreases with the increase of distance away from Three Gorges Dam,the change of water and sand in the upstream of Yichang station is more significant than that in the downstream of Datong station.