Abstract：Influenced by the combination of rainfall and reservoir level fluctuation，the determination of groundwater level in landslides is of great importance in assessing the stability of the landslides along reservoir. According to precipitation data from year 1957 to 1988 in Fengjie County in the Three Gorges reservoir area，the probability analysis is conducted by using the extreme distribution and the related rainfall model is developed. Considering the various adjustment of reservoir level in the Three Gorges，its adjustment model is given. In the two models，the rainfall and the change of reservoir level are considered by day in terms of practical situation. A method is then proposed accordingly to study the hydrodynamic field of unsteady fluid flow influenced by this combination. The hydrodynamic field of Baiyi′an landslide is analyzed by this method. Groundwater is calculated in various conditions，and the worst case and its probability are given by comparison.
