采用分型算法求解水流运动的二维浅水方程 ,采用“动边界”技术追踪在非恒定流时因水位的变化而引起的计算区域边界的变化 ,建立了天然河道非恒定流的数学模式。通过实例计算说明 ,本模型对河口、湖泊等一类宽阔水域流场的计算非常有效 ,能够满足实际工程的需要。 A two-dimensional shallow water equation for water flow motion was solved by using the sub-type algorithm. The “dynamic boundary” technique was used to track the change of the boundary of the calculation area caused by the water level change in the non-steady flow, and the mathematical model of unsteady flow in the natural river was established. The example shows that this model is very effective for calculating the flow field in a wide area such as estuaries and lakes, and can meet the needs of practical projects.