Evolution Analysis of Inflow Runoff of Three Gorges Reservoir

Based on the inflow runoff of Three Gorges Reservoir and average annual precipitation of the upper reaches of the Yangtze River,the variations of annual runoff,monthly runoff and the runoff in storage period have been comparatively analyzed by using statistical method.The results show that the phenomenon of reduced inflow is to be normal cyclical fluctuation;because of the regulation of a large reservoirs in the upper reaches of the Yangtze River,the annual distribution of runoff has been changed since 1990;if taking average flow of the designed storage stage as a benchmark,the water storage period of Three Gorges reservoir must move up to early September under the conditions of runoff series from 1991 to 2009.