Optimal Design of Groundwater Well's Placement and Pumping Rates by Use of a Simulation-Optimization Approach

Improper wells location and excessive groundwater extraction can cause severe damage to aquifers and lead to numerous economic consequences. The purpose of this study is to develop a simulation-optimization model for determination of optimal well's placement and pumping rates, while satisfying the requirement of quantitative and qualitative considerations. The proposed model integrates the groundwater flow simulation model MODFLOW and the Particle Swarm Optimization algorithm. The coupled PSO-MODFLOW model has been applied to the Sarakhs aquifer in the north-east of Iran to minimize the total cost of drilling, transfering and water treatment for supplying the drinking demand of the Sarakhs city. Discharges as well as locations of the pumping wells were taken as the decision variables. Also, the maximum pumping rate and maximum water-table drawdown were incorporated as the problem's constraints. The results show that the proposed approach not only satisfies the constraints but also reduces the total cost of water withdrawal by 5% from 598 million Tomans in the present plan to 572 million Tomans in the optimum plan. Sensitivity analyses indicates that results are not significantly sensitive to changes 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.