Conjunctive Use of Surface Water and Groundwater Resources in Abhar River Basin

Conjunctive use of surface and ground-water resources, compared to disjunctive operation of these systems, increases system reliability and decreases water deficits and operational costs. In this study, the two alternatives of groundwater (GWOpt model) operation and conjunctive use of surface and groundwater resources (CONJ model) are considered for Abhar river basin in Iran. In both models, the objective function is minimization of mean groundwater drawdown. The vast amount of calculations needed for distributed parameter optimization models is a major limitation in real systems. However, the above two models are linear and the unit response matrix approach is utilized. The first step in this approach is to calculate the unit response matrices (as the behavior of the groundwater system) using a simulation model, such as MODFLOW. The next step involves incorporating these matrices into the optimization model. The results obtained from the solution of the optimization model indicate that the mean drawdown in the CONJ model is less than that in the GWOpt model. In addition, a decrease of only 6% decrease was observed in the mean drawdown when compared to the simulation model. A decision support system has also been developed that enables the model to be used in real situations.