Since the introduction of cities and urbanization, healthy water supplement and urban wastewater treatment have been considered as an important factor to evaluate progress in the urban areas. Tehran as a megacity is facing the lack of water. Tehran water supplement is far from its area; therefore, Tehran-Karaj plain has been considered in this study. So, Tehran water quantity index using the DPSIR model (Driving force, Pressure, Status, Impact and Response) in a period of 3 years (2008-2010) was considered in this paper. Driving forces included population, urbanization, green spaces, and industries. Pressures on urban water included water consumption, water losses, rainfall and evaporation. Then, Tehran water quantity status was investigated based on the existing water in dam reservoirs and groundwater resources. Their impacts on urban area were evaluated and finally, appropriate responses were presented. Some of the presented approaches included industries transmission, improvement of water consumption pattern, improvement of the water treatment plants status and unconventional water resources reuse, identification and rearrangement of subterranean, improvement of irrigation systems operation, and reduction of Tehran urban population.