Reservoir regulation and reservoir sedimentation make conditions of flow and sediment under the dam change greatly after impoundment of the Three Gorges Project. This paper analyzes change trend and abrupt change situation of incoming water and sediment and studies characteristics of new flow and sediment of Yichang Station after impoundment of the Three Gorges with Mann-Kendall nonparametric rank test method. The result indicates that operation of the Three Gorges Reservoir has leveled runoff process and shortened dry season and extended median water period. After operation of the Three Gorges Reservoir, annual sediment runoff and monthly sediment runoff of some months changed suddenly and sediment runoff reduced sharply in Yichang Station. Sediment entering the middle and the lower reaches of the Yangtze River decreases substantially and it almost can be regarded as clean water discharge. Intorduction After operation of 175m normal water level of the Three Gorges Reservoir, total storage capacity of the reservoir is about 43 billion m3. Most of incoming sediment in the upstream is intercepted and deposited inside the reservoir and clean water and muddy water containing non-bed sand discharges. Change of water and sediment conditions destroys balance of downstream river and causes bed-rebuilding of downstream channels. And this results in a serious of long-term and long distance changes, such as on-way recovery of sand content, undercutting of bed scour, expansion of bank erosion and decline of water table, etc.[1-. Yichang Station controls a drainage area of 1005501km2 in upstream of the Yangtze River and is a major flood source for the middle and the lower reach of the Yangtze River. Thus, water regime information of Yichang Station is significant to flood control of the middle and the lower reach of the Yangtze River, regulation of the Three Gorges Reservoir, construction of water conservancy project all across the Yangtze River, industrial and agricultural production and shipping, etc. On account of this, this article analyzes data about coming water and sediment of Yichang Station to support characteristics of new flow and sediment of Yichang Station after impoundment of the Three Gorges with Mann-Kendall nonparametric rank test method.
Analysis of equilibrium sediment transport in the middle and lower reaches of the Yangtze River after the impoundment of the Three Gorges Reservoir
