Evaluation of Sustainability and Determining the Optimal Population Based on Water Resources in Mashhad

The present study at first step aims at evaluating Mashhad’s sustainability of water resources by employing the sustainable urban development models proposed by Haughton then it attempts to determine the optimal of population depending on Water and Sewage Organization of Mashhad to estimate the required amount of water in 2016 by both with and without inclusion of Dousti and Ardak Dams in the calculations. Due to its purposeful nature, this study has used mixed hybrid methodology which is considered as supportive qualitative data for quantitative analyses. The results show that Mashhad plain possesses only 2% of the whole province's groundwater, while 65.97% urban population of province are living on this plain and specifically in the city of Mashhad. Moreover 42% of the required surface water, 92.7% of which belongs to the Dousti Dam located at a distance of 220km from Mashhad, is provided through the surface water and only 30% of domestic sewage is recycled. Therefore, by considering Haughton's theory of urban metabolism into account, Mashhad cannot be regarded as a sustainable city taking its water requirement condition, by including dams of Dousti and Ardak as sources of water supply (dependence out of hinterland), it has a surplus population of 550,459 and by excluding them, 1,192,660 people.