The qanat is one of the traditional water supply systems in semi-arid zones. Today, this sustainable system is under threat from various modern phenomena. Urban sprawl is the most salient factor, which poses a major threat to these water systems (qanats). This study endeavors to explore the effect of urban expansion on the qanat fields as well as the difficulties encountered at city construction and water system junctions in the northeastern city of Mashhad, in Iran. Data analysis reveals that rapid urbanization as well as uncontrolled urban expansion has led to the intersection of city construction and qanats; especially during the last few decades. This phenomenon has resulted in the destruction of 88 qanat fields, water shortage in the city of Mashhad, and the substitution of this sustainable and environment-friendly system with alternative unsustainable water systems such as dams and wells.