To reduce excavation volume,a horizontal diversion connecting at the bottom of the ship lock is typically adopted for the side support hole water delivery system with sidewall ports of the water-saving ship lock.The diversion uniformity of the connecting culvert is the core challenge in the water delivery process of such ship locks.Addressing this issue,based on a water-saving ship lock project in China,a three-dimensional hydraulic numerical simulation method is used to optimize the layout of the connecting culvert.The results show that increasing the interface area between the connecting culvert and the long culvert of lock wall can effectively mitigate the flow oscillations in the lateral culverts.The diversion uniformity of connecting culvert is characterized by K,defined as the ratio of the width on both sides of the horizontal diversion opening to the radius on both sides of the flow splitter.When K=1.064,the flow distribution uniformity in the lateral culverts,the outflow uniformity from the sidewall port,and the hydraulic conditions in chamber are better.The research results can provide technical references for the layout of connecting culverts in similar water-saving ship locks.