Ecological water replenishment is an effective approach to the wetlands suffering water shortage. However, optimizing the replenishment is a tough problem, considering local flow pattern, water exchange and environmental crisis. Therefore, determining the inlet position and the flow rate of water diversion remains an interesting and important topic. This study developed an applicable and reliable method to identify the preferable inlet location and inflow rates of the transferred water, which considers the influence of the factors on environmental risks in receiving water bodies based on numerical results using the lattice Boltzmann method (LBM) in both Lagrangian and Eulerian frameworks. An environmental risk assessment system with comprehensive utilization of water age was established. The Water Transfer Project for the Baiyangdian Lake from the Yellow River is a representative and well-known water replenishment event in China, which served as a case study. The results show that under the static and NNE wind conditions, the north open inlet is a suitable inlet position, while the south one is preferable under the SSW wind condition. Considering the environmental risk of the water transfer, it indicates that higher inflow rate would bring less environmental risk generally and the optimal inflow rate is 20 ${\text{m}}^3/\text{s}$, regardless of the wind conditions and the inlet position. The methods aforementioned played a vital role in optimizing the inlet position of water delivery and selecting the optimal plan of the recharge rate. It could provide a useful reference for ecological restoration and a guarantee for sustainable development of wetlands.