Optimum operation of recharge basins

Mathematical models based on nonlinear programming are developed for operating recharge-basin systems (also referred to as soil-aquifer treatment systems). The objective of these optimization models is to determine the operation policy (loading schedules) that maximizes the infiltration volume subject to constraints for continuity, infiltration, ground-water flow, and the physical constraints describing the recharge basins. Two basic physical processes that are involved in the recharge-basin systems are the infiltration process and the soil-moisture-redistribution process. The infiltration process is modeled using both the Philip’s and the Green-Ampt infiltration models, and the soil-moisture redistribution process is modeled using Darcy’s equation as well as a kinematic-wave model. An improvement on the developed models is to consider the final moisture content at the end of each cycle time as a decision variable; which also allows the total cycle time to become a decision variable. In the modified applications, the objective is changed to maximizing the infiltration rate instead of maximizing the infiltration volume. Several hypothetical applications are presented to illustrate the modeling procedure.