采用率定后的一、二维水流模型，详细计算了各种截流方案下明渠内局部的水流流态，不仅对不同上下口门配合宽度下的水位落差分担关系进行了敏感性分析，还提出了不同截流流量下，在满足给定落差分担关系时上、下游戗堤的进占顺序以及相应的抛投块石粒径。各种方案计算结果表明：当截流流量为12 200 m3/s时，施工方案承担较大风险，宜优化；9 010 m3/s时，现有方案可以较好的满足。同时还反演计算了实际截流不同时刻明渠内的水力条件，计算结果表明：当上游龙口宽度在140 m之前或50 m之后，主要由上戗堤承担截流落差；而此范围之内，由上、下戗堤共同承担截流落差，计算与实测结果较为符合。

Using the developed 1D and 2D flow mathematical models, the water - head distribution relationships between the upstream and downstream closure dikes were analyzed under the different gap widths of upstream and downstream closure dikes. Dike advancing sequences and corresponding closure riprap diameters for different closure discharges were proposed under the given water - head distribution relations. The calculated results of all kinds of closure projects also indicated that the risk of the closure dike advancing sequence is considerably high for the closure discharge of 12 200 m3/s, and it is very favorable for constructing for the closure discharge of 9 010 m3/s. The hydraulic conditions in the open channel during the real closure were calculated through using 1D and 2D flow models. The calculated results showed that the closure water - head was mainly shared by the upstream closure dike as its gap width was greater than 140 m or less than 50 m，and that it was shared by the upstream and lower dikes in this range. This simulated results agreed with the observed data