Optimization of Conjunctive Use of Surface Water, Groundwater and Wastewater Resources in Hashtgerd Plain

A study is undertaken to exploit the contrast between disjunctive use and conjunctive use of multiple resources comprising: surface water, groundwater and wastewater. The primary aim is the increase in system reliability but decrease in water deficits and operational costs. Groundwater budget is studied by two alternatives models of (GMS) and conjunctive use of water resources (PSO) are considered for Hashtgerd basin in Iran. In both models, the objective function is minimization of mean groundwater drawdown. The first step in this approach is estimation of the hydrodynamic parameters and groundwater budget in steady and unsteady conditions using a simulation by GMS model. The next step involves incorporating these amount of groundwater budget into the optimization model. The results of the simulation model indicate that groundwater budget of Hashtgerd plain is negative, which reservoir storage loss is almost 17 MCM per year (2011-12). The results of the optimization model indicate that the most increases of the aquifer storge are in November, April and Februry, respectively, and the discharg of groundwaters in all zones of basin is located at the borderline for sixty percent of months. According to conditions in the plain and the results of the optimization model, the groundwater shoudn,t been withdrawal more than presented values when the reservoir storge changes is zero, then the maximum use of surface water and wastewater Could avoid more groundwater declination. Eventually the best solution to mange water resources to avoid over abstraction is the hybrid use of all water resources within each zone.