Study on the Channel Condition Changes of the End Portion Rapids in Early Action Days of Three Gorge Reservoir

The action mode of Three Gorges Reservoir has been 175-155-145m mode from September 2008. The channel conditions of perennial reservoir have been improved markedly in dry season for the depth becoming larger and the velocity becoming lower. But the ships still sail difficultly on the rapids of reservoir end in flood period.Through theory analysis and mathematical model creation, it studies the rapids of the Three Gorges Reservoir region, especially the changing of channel conditions in flood period.The main conclusions are as follows:i) Using the calculating method hydraulic parameter of rapids abating and selecting the representative ship to calculate the navigable hydraulic parameter of 3000 tons ships.ii)Creating two-dimensional mathematical model of stream to simulate and calculate the flow conditions of rapids and comparing the different flow conditions between nature and 145m watering. The calculating results of mathematical model and the realities fit together well.iii)Comparing and analyzing the calculation results and nature data of different rapids of the Three Gorges Reservoir end, it shows that the improvement of rapids were different in 175-155-145m action mode. Guanyin rapid has the maximum improvement and the next one is Heshang papid. There is a little improvement in Huangcao rapid and no change in Tongluo rapid.