Optimum operation of wells in coastal aquifers

Abstract

The combination of two powerful analysis techniques, simulation and optimisation, produces an engineering design tool that can aid in the formulation of design criteria and assist decision makers in assessing the impacts of design trade-offs. This paper presents a management model with the economic objective of maximising the net benefit derived from a pumped freshwater volume while eliminating the utility cost in coastal aquifers threatened by saltwater intrusion. Because the search space is both discontinuous and extremely wide, and also contains numerous local minima, evolutionary algorithms can be helpful in the search for near-optimal solutions. In this paper, a simulation model of the sharp saltwater–freshwater interface is considered to be time-independent. Moreover, the honey-bee mating optimisation (HBMO) algorithm is applied to a test case and the results are compared with those of a previously developed genetic algorithm (GA) for the same case. The comparison indicates that the HBMO algorithm can be effectively used to obtain near-global optimal solutions for the problem under consideration. The HBMO algorithm is then applied to the management of the coastal aquifer underlying the city of Miami Beach in northeastern Spain. Compared with the GA, the HBMO algorithm results show a significantly better performance and advantages in terms of both the final objective function value (more benefit) obtained and total pumped discharge from the system. Furthermore, the efficiency of the HBMO algorithm in handling non-linear discontinuous groundwater simulation/optimisation problems much more quickly than the GA is a promising point for further use of the algorithm in the field of groundwater optimisation.