Two new methods for optimal design of subsurface barrier to control seawater intrusion

Abstract

This research has provided two new methods to control seawater intrusion using a subsurface barrier through development and application of the implicit and explicit simulation-optimization approaches. The objective is to develop implicit and explicit simulation-optimization models for design of a subsurface barrier that controls seawater intrusion. No prior work has been done in which a model for optimal design of a barrier for controlling seawater intrusion is developed. The objective of he seawater intrusion control problem is to minimize the total construction costs while requiring that salt concentrations be held below specified values at two control locations at the end of the design period. An implicit simulation-optimization model is developed for the design of a subsurface barrier to control seawater intrusion. This approach combines a groundwater flow and solute transport simulation model with nonlinear optimization. The more significant development has been simulating a groundwater flow and solute transport model within the genetic algorithm (GA) based optimization method. Both explicit and implicit simulation-optimization models are developed to solve the same problem, and the results are compared. The results indicate that these two models provide a unique solution that may reduce the high construction cost of a barrier. The conclusion drawn from a series of tests performed in support of this work is that the explicit simulation-optimization model using GA performs as well as, if not better than, the implicit simulation-optitimization model employing the gradient-based technique. Development of two methodologies for seawater intrusion control through the implicit and explicit simulation-optimization models is a major achievement of the present study. (Abstract shortened by UMI.)