Conjunctive Use of Surface- and Ground-water Considering the Effects of the Wastewater Collection Plan (Case Study: Tehran, Karaj and Shahryar Plains)

The increase in population and the expansion of agricultural and industrial water needs in Tehran-Karaj region has created a complex system of resources extraction and supply that necessitates the need to manage the water resources in this region. The purpose of this study is to analyze the water resources management in the current and future situations, the effect of wastewater allocation on supplying demands, and also to provide strategies for consumption reduction and management. These objectives are investigated in five different scenarios. For Groundwater simulation MODFLOW model is used and WEAP model is employed for water resources planning. In all scenarios, the first priority is given to the drinking and industrial demands which are supplied above 99% in all scenarios. The results showed that considering the implementation of future projects and increasing demands, the sustainability of resources was reduced in the last years of simulation which indicated a shortage of water resources against demands. According to the results, if no wastewater is allocated, the annual agricultural demand should be reduced by 40%, in order to keep the water shortage below 10%. If wastewater is allocated along with a 30% reduction in agricultural demand, the percentage of supply would exceed 90% and the water resources of the basin are in better condition in terms of sustainability and vulnerability.