Simulation of seawater intrusion and optimization of cutoff wall schemes based on surrogate model

In the present study, a 3-D variable density mathematical model for seawater intrusion (SI) was built in Longkou City, China. Based on the model, a cutoff wall construction scheme suitable for the study area was proposed, and the mathematical model was used to simulate and predict the effects of the cutoff wall. By introducing the seawater desalination technology into the construction of the cutoff wall, the optimization model was built with the minimum cost as the objective function, and the simulation model was embedded into the optimization model for calculation. To reduce the huge amounts of computations caused by calling the simulation model repeatedly, a surrogate model of the simulation model was built using the Kriging method. The optimal control plan was obtained by solving the optimization model. The results show the following: 1. The 3-D variable density groundwater intrusion model built with calibration and verification is a reliable method of risk assessment of SI. 2. The surrogate model can significantly reduce the computational load while ensuring accuracy. 3. Using the optimization model based on the surrogate model, the optimal solution can be quickly yielded for the design of the cutoff wall, and it is an effective way for the risk management of SI.