Optimal control of seawater intrusion in coastal aquifers

Abstract

Seawater intrusion is one of the most serious environmental problems in many coastal regions all over the world. This is because mixing a small quantity of seawater with groundwater makes it unsuitable for use and can result in abandonment of aquifers. Therefore, seawater intrusion should be prevented or at least controlled to protect groundwater resources. This paper presents a new method for optimal control of seawater intrusion. The proposed method is based on a combination of abstraction of saline water near shoreline and recharge of aquifer using surface ponds. The source of water for the surface pond could be treated waste water or excess of desalinated brackish water (if any), etc. The variable density flow and solute transport model, SUTRA, is integrated with a Genetic Algorithm optimization tool in order to investigate the efficacy of different scenarios of the seawater intrusion control in an unconfined costal aquifer. The locations of the pond and the abstraction well in relation to the shoreline, depth of abstraction well and the rates of abstraction and recharge are considered as the main decision variables of the optimization model, which aims to minimize the costs of construction and operation of the abstraction wells and recharge ponds as well as the salt concentrations in the aquifer. Comparison is made between the results of the proposed method and other methods of seawater intrusion control. The results indicate that the proposed method is efficient in controlling seawater intrusion. This proposed strategy can be considered as a powerful tool for cost-effective management of seawater intrusion in coastal aquifers.