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Urban water resources are the basis for the formation and development of cities and the source of urban water supply. However, with the acceleration of urbanization and the explosion of urban populations, the contradiction between water supply and demand in some areas, especially in big cities, has become increasingly prominent. It is simply not sufficient to rely on local conventional water resources to meet urban water demand, and a single source water supply mode has a higher vulnerability, resulting in greater safety risks in urban or regional water supply systems. Therefore, giving full play to the water supply capacity and carrying out multi-source water supplies are necessary and urgent. This paper gives an overview of the optimal allocation of multi-source for urban water supply concerning variation tendency, modeling methods and facing challenges. Based on the variation tendency of water consumption and water supply pattern in China, Tianjin is taken as a typical city for systematically outlining water supply changes and cause analysis. Subsequently, the modeling methods for proposing the optimal allocation scheme are summarized, which are composed of defining the topological relation, constructing the mathematical model and seeking the optimal solution. Ultimately, the current and emerging challenges are discussed including emergency operation of multi-source water supply and joint operation of water quality and quantity. These summaries and prospects provide a valuable reference for giving full play to the multi-source water supply capacity and carrying out relevant research so as to propose the optimal allocation scheme in urban multi-source water supply systems. [ABSTRACT FROM AUTHOR]

To ease the growing water crisis, Tianjin has pioneered the implementation of the most stringent water management system in China. Presently, Tianjin achieves the highest industrial water efficiency in China. In 2010, Tianjin was named the first “Water-Saving Society Construction Demonstration City” by the Chinese central government. To provide a theoretical basis and supporting data for the construction of “national water-saving cities”, a decomposition method is adopted to quantitatively analyze changing industrial water use in Tianjin. Data are decomposed using a refined Laspeyres model, highlighting changes associated with industrial restructuring, followed by detailed sectoral analysis. There are two distinct stages of industrial water use: before 2008, industrial water use decreased, driven predominantly by technological advances; after 2008, higher industrial output led to greater industrial water use that overshadowed the water savings achieved by technological development. Nevertheless, water efficiency showed limited improvement, despite the increasing industrial scale and output of certain industrial sectors. The findings show that in Tianjin, reduced industrial water use is not the primary objective, but an associated combination of industrial development and structural adjustment. [ABSTRACT FROM AUTHOR]