A simulation-optimization approach for optimal design of groundwater withdrawal wells' location and pumping rate considering desalination constraints

In this study, a simulation-optimization approach for optimal determination of groundwater withdrawal wells location and pumping rate is developed while incorporating quantitative and water-quality objectives into the objective function simultaneously. The proposed model integrates the groundwater flow simulation model MODFLOW and particle-swarm optimization (PSO) algorithm and is applied to Sarakhs aquifer in Iran as the case study to minimize the total cost of drilling, transfer, and water treatment. Discharges and the location of pumping wells are taken as the decision variables. In addition, the maximum pumping rate and maximum allowable water-table drawdown while meeting the required quality for domestic water are incorporated as the constraints. Results show that the proposed approach not only satisfies the constraints, but also reduces the cost of water withdrawal comparing the existing plan. Sensitivity analysis indicates that results are not significantly sensitive to variation in aquifer's hydraulic conductivity, while the maximum pumping rate directly affects the number of required wells and can, therefore, make a considerable change in the final cost.