采用饱和非饱和非稳定渗流模型对水布垭面板堆石坝在正常运行、面板局部缺损和面板失效等工况下的渗流场进行了较全面的模拟计算，分析了大坝各分区的水头和比降的分布，确定了垫层、过渡区和主堆石区可能出现的最大比降。这种最大比降对坝体渗透稳定性具有控制意义。据此提出了分区材料允许比降设计指标的建议值，为评价面板堆石坝分区之间水力过渡合理性和渗透稳定性提供了依据。

A transient saturate-unsaturated water flow model is adopted to simulate the seepage field in Shuibuya Concrete Faced Rockfill Dam under different conditions: concrete face functions normally, cracks locally or does not work totally. The distribution of water head and hydraulic gradient in different dam zone is analyzed. The max hydraulic gradient that might appear in the padding zone, transition zone and main rockfill zone is suggested separately, which would control the seepage stability status of the dam. Hereby, the design standard for acceptable seepage gradient of rockfill materials is suggested. This standard can be used to estimate the rationality of hydraulic transition and seepage stability for the dam..