Research On Urban Water Resources Carrying Capacity: Theory And Application

Water is a scarce but essential resource to human life, social and economic development and eco-environment. With human population rapid growth and urbanization since 1960s, water scarcity, accompanied by water quality degradation and diversity reduction, has been the second most serious global problem. China is a water-scarce country and will face more serious water scarcity with continued population growth and rapid economic development and urbanization. It is very necessary, and also urgent, to carry out comprehensive studies on water resources carrying capacity (WRCC).State of the arts both of carrying capacity (CC) and WRCC is reviewed thouroughly, and problems are thus pointed out. In dealing with logic problems both in the concept and its application, two parallel concepts, namely CC, which points to normal situation, and threshold carrying capacity (TCC), which points to critical situation, are advocated to replace the current water resources carrying capacity concept. Corresponding research contents and quatification system are presented in light of the two new concepts, which is helpful to solve the instrumental defect and to further future theoretical researches. Economic economics, especially ecosystem services are initially introducted to and integrated with WRCC research. By using utility or value flow as main clue, fundamental aspects of water resources threshold carrying capacity (WRTCC) are studied systematicly. The whole aquatic system and the comprehensive utilities it carried are proposed to be the carrier and the carried respectively, and value judgment criteria based on environmental ethics and threshold statuses based on dynamic analysis by using per capita utility as main objective for WRTCC are proposed. On this basis, urban water resources threshold carrying capacity (UWRTCC) is defined as the maximum per capita utility that a certain urban water system can support in a certain period at a given scientific and technological level, when water management and social economy development are optimized, with its connotation and characteristics presented; and eventually, a new research paradigm, namely ecological economics paradigm is appealed. Indicator system of water resources carrying capacity (WRCC), including the rationale, setting objectives, users, functions and the whole set of method for indicator system establishment, is comprehensively studied. Five criteria are presented, and especially, a framework for preliminary indicator selection is founded based on Drive force-State-Response framework (DSR) and Life Cycle Assessment (LCA). Methods for indicator structurization, quantitatively selection and management are proposed. Based on the above findings, a general WRCC indicator system is founded. Application of WRCC indicator system is presented as well. Comprehensive assessment (CA) of WRCC is studied emphatically. A general process is presented first. Two types of CA of WRCC are identified with respect to the number of objects to be assessed: the one for a certain urban area in a certain period and the other for various urban areas in a certain period, or various periods (including multiple development scenarios) for a certain urban area. Comprehensive models for the whole assessment process and methods for specific steps for two CA cases are presented respectively. For the second case, two solutions are available: one is to use the procedure for the first case for each object and then to compare the results and the other is to use CA for the whole object collection. And the first solution is preferred. Especially, integrated weighting method with respect to important degree, and data contrast to the standard value and data distribution among the values for various bjects is proposed.Based on natural resources and environmental economics, by taking wastewater as a special production sector, a simplified conceptual model of TCC is achieved, on which a calculation model for UWRTCC is established. The case study (Chengdu Metropolitan Area) indicated that the model is feasib...