介绍了能够考虑水文气象过程的饱和-非饱和非稳定地下水流运动数学模型。以全封闭和半封闭式防渗墙为重点研究对象，以长江重要堤防为背景概化得到典型二元和多元结构堤基、堤身断面及土层的饱和非饱和渗流参数；以实测资料为基础概化得到较典型的水文气象过程，提出降雨入渗和蒸发排泄边界处理方式以及初始条件确定方法；提出根据二维模型模拟结果用有无对比法分析防渗墙对地下水动态的影响，根据三维模型模拟结果分析防渗墙端部绕渗对地下水流场动态的影响。模型和参数具有典型性，研究方法合理、有效。

The first paper in the series presents the numerical model for saturated-unsaturated water movement in response to hydrological and meteorological processes. The cut-off walls of closed type and semi-closed type are taken as the main objects to be studied. With the main dyke in lower and middle Yangtze as background, the typical double-layer and multi-layer foundation stratifications, dyke section form, and the hydraulic parameters for the saturated and unsaturated zones are given. The hydrological and meteorological processes are provided according to observed data. The way to deal with the boundary conditions of rainfall infiltration and evaporation is presented. The methods to initiate the water movement for models are suggested. It is suggested to analyze the effects of the cut-off on ground water regime through comparing the 2D numerical simulated results with and without cut-off wall. The 3D numerical simulated results are suggested for analying the effects of the flow around the lateral ends of cut-off on ground water regime. The models and parameters possess typicality. The methods are reasonable and efficient.