Lal, Alvin, and Datta, Bithin (2017) Modelling saltwater intrusion processes and development of a multi-objective strategy for management of coastal aquifers utilizing planned artificial freshwater recharge. Modeling Earth Systems and Environment, 4 (1). pp. 111-126.

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Abstract

The need for freshwater is emerging as the utmost critical resource issue facing humanity. In several arid and semi-arid parts of the world, groundwater resources are being used as an alternative source of freshwater. Excessive and/or unplanned groundwater withdrawals have a negative impact on the aquifer. Groundwater withdrawn from coastal aquifers are susceptible to contamination by saltwater intrusion. This study investigates the efficiency and viability of using artificial freshwater recharge (AFR) to increase fresh groundwater pumping from production wells for beneficial use. A three dimensional (3D), transient, density dependent, finite element based flow and transport model of an illustrative coastal aquifer is implemented using FEMWATER code. First, the effect of AFR on inland encroachment of saline water is quantified for existing scenarios. Specifically, groundwater head and salinity concentration differences at monitoring locations before and after artificial recharge is presented. Second, a multi-objective management model incorporating groundwater pumping and AFR is implemented to control groundwater salinization in an illustrative coastal aquifer system. To avoid computational burden and ensure computational feasibility, the numerical flow and transport simulation model is substituted by the new support vector regression (SVR) predictive models as approximate simulators in the simulation–optimization framework for developing optimal management strategies. The performance evaluation results indicated that the SVR models were adequately trained and were capable of approximating saltwater intrusion processes in the aquifer. Multi-objective genetic algorithm (MOGA) is used to solve the multi-objective optimization problem. The Pareto-optimal front obtained as solution from the SVR–MOGA optimization model presented a set of optimal solutions needed for the sustainable management of the coastal aquifer. The pumping strategies obtained as Pareto optimal solutions with and without freshwater recharge wells showed that saltwater intrusion is sensitive to the AFR. Also, the hydraulic head lenses created by AFR can be used as one practical option to control saltwater intrusion in coastal aquifers. The developed 3D saltwater intrusion model, predictive capability of the developed SVR models and the feasibility of using the proposed linked multi-objective SVR–MOGA optimization model makes the proposed methodology potentially attractive in solving large scale regional saltwater intrusion management problems.

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